Browsing by Author "Cockrum, Rebecca"
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- Assessing Availability and Utilization of Essential Amino Acids in Dairy Cattle Using Stable Isotope Based ApproachHuang, Xinbei (Virginia Tech, 2020-02-19)Determining the AA availability and metabolism in ruminant is a big challenge due to the rumen fermentation and complicated post absorption utilization. Current techniques used for direct determination of AA absorption and metabolism are laborious and expensive with large variation. The objectives of this project were to investigate AA availability of rumen undegradable protein, develop a stable isotope technique for determination of microbial protein and to evaluate the metabolism of amino acids in mammary glands of dairy cattle using stable isotope-based approaches. In the first experiment, seven heifers (258 ± 28 kg BW) were randomly chosen and assigned to 8 treatment sequences in a 7 x 8, incomplete, Latin square design. Treatments were a basal diet (BD), and 10% (DM basis) of BD replaced by corn silage (CS), grass hay (GH), alfalfa hay (AH), dried distillers grain (DDGS), soybean hulls (SH), wet brewers grain (BG), or corn grain (CG). Individual essential AA availabilities for corn silage, grass hay, alfalfa hay, dried distillers grain, soyhulls, brewers grain and corn grain were 33.4, 29.9, 34.1, 40.6, 28.8, 41.2, and 36.5% of the essential AA in each of the respective ingredients when a loss of 8.27% to splanchnic utilization during first pass was assumed; however, availability varied across individual essential AA. In the second experiment, twelve cows were blocked into 3 groups according to days in milk and randomly assigned to 4 treatments in a repeated 4 x 4 Latin square design with 2 factors to evaluate the essential AA availability from microbial protein and rumen undegradable protein under different rumen fermentation conditions. The 4 treatments were high rumen undegradable protein and high starch (HPHS), low rumen undegradable protein and high starch (LPHS), high rumen undegradable protein and low starch (HPLS) and low rumen undegradable protein and low starch (LPLS). Microbial protein synthesis calculated from purine derivatives was positively associated with rumen degradable protein, which was consistent with total microbial AA entry derived from the isotope dilution model indicating that the isotope based approach was representative. The individual essential AA availability from microbial protein was determined by isotope technique, whereas the PD method was just total PD absorption reflecting CP absorption. The metabolizable AA estimates from NDS nutritional model was similar to results from isotope dilution models, but with smaller difference among treatments. The microbial protein estimated from White's model showed the same trend among treatments compared to isotope dilution model, which may imply it represents the rumen fermentation better. The average essential AA digestibility for microbial AA was 82%, which varied across individual AA and treatments. In the third experiment, four cows (78 ± 10 DIM) were used to study the effects of jugular infusion of 2 groups of AA on essential AA uptake and metabolism by mammary glands in a 4 x 4 Latin square design. Treatments were jugular infusion of saline (CON), methionine plus lysine plus histidine (MKH), isoleucine plus leucine (IL), or MKH plus IL (MKH+IL). The MKH increased milk protein yield in high producing dairy cows. The IL infusion increased milk and milk lactose yields. The production response was associated with a change in mammary plasma flow together with changes in AA uptake and metabolism in mammary gland. Mammary uptake of essential AA was 135 % of milk protein output. Efflux of EAA from the mammary to blood was 13-61% of influx, which was high for BCAA but low for Met and Lys. Changes in influx and efflux resulted in net uptake difference of infused essential AA that were responsive to varying supplies resulting in maintenance of homeostasis. The proportion of AA catabolized and used for milk protein was affected by EAA infusion, which demonstrated plasticity of mammary gland in AA metabolism. Overall, results suggested essential AA availability from rumen undegraded protein and microbial protein varied across individual AA and diets and can be affected by rumen fermentation. After absorption, EAA transport into mammary tissue was bi-directional and their metabolism was affected by AA supply and energy. Using a single coefficient to represent all AA digestibility in MCP or feed ingredient and an integrated efficiency of MP-AA converted into milk protein is inaccurate.
- Assessing Intestinal Absorption of Amino Acids Utilizing an Isotope Based ApproachEstes, Kari Ann (Virginia Tech, 2017-01-30)The purpose of this research was to further test a stable isotope based approach as a more reliable in vivo method to determine amino acid bioavailability from a variety of ingredients. The method was used to assess feather meal (FM), blood meal (BM), soybean meal (SBM), and a rumen protected amino acid (RPAA). An abomasal infusion of raw EAAs (isoleucine, leucine and methionine) and an abomasal infusion of sodium caseinate were used as control treatments to test the accuracy of the technique. The isotope-based results were then compared to in situ, in vitro and in vivo test results. The isotope-based technique provided AA bioavailability values for five non-essential AA and seven essential AA. The raw EAA infusion had the greatest AA recovery in plasma with an estimated absorbed RUP value of 93.4± 7.35% followed by the casein infusion (86.7 ± 4.81%), SBM (54.8 ± 5.19%), FM (52.7 ± 4.81%) and BM (47.5 ± 4.81%). The RPAA treatment had the lowest bioavailability at 9.9 ± 12.73%. Numerically, SBM supplied the most absorbable EAA of the 4 feed ingredients, but was not significantly different from that of BM and FM. Simply based on the control treatments in this research (raw EAA and casein), this isotope method was a more accurate method in determining AA bioavailability values with relatively low standard errors. Ingredients are exposed to all aspects of natural digestive processes and the method is able to determine AA appearance in the blood with no use of in situ or in vitro measurements.
- Clearance of Biodegradable Polymer and Polyethylene Films from the Rumens of Holstein Bull CalvesGalyon, Hailey; Vibostok, Samuel; Duncan, Jane; Ferreira, Gonzalo; Whittington, Abby; Havens, Kirk; McDevitt, Jason; Cockrum, Rebecca (MDPI, 2023-03-03)Due to the occurrence of plastic impaction in ruminants and its deleterious effects on health and production, it is necessary to determine the suitability of biodegradable polymers to replace polyethylene-based agricultural plastics, such as hay netting. The objectives of this study were to evaluate the clearance of a polyhydroxyalkanoate (PHA) and poly(butylene succinate-co-adipate) (PBSA) melt-blend polymer from the rumen when fed to cattle and subsequent animal health. Twelve Holstein bull calves were dosed with an encapsulated 13.6 g of PBSA:PHA (Blend), 13.6 g of low-density polyethylene (LDPE), or four empty gelatin capsules (Control) for 30 d. The feed intake, body weight, and body temperature were evaluated, and hemograms were run on d 0 and d 30. On d 31, calves were euthanized to evaluate gross rumen measurements and pathology, papillae length, and polymer residues in rumen contents. No calves presented any signs related to plastic impaction. The feed intake; body weight; rectal temperature; hematological parameters; gross rumen measurements and pathology; and rumen pH and temperature were not affected by treatments. Calves dosed with LDPE had 27 g of undegraded polymer retained in the rumen while Blend calves had only 2 g of fragmented polymers that were 10% of their original size. Agricultural plastics developed from PBSA:PHA may be a suitable alternative to LDPE-based products in the case of animal ingestion and may reduce the incidence of plastic impaction.
- Dairy Pipeline September 2020Alward, Kayla; Cockrum, Rebecca; Martel, Cynthia; Mountain, Travis P. (Virginia Cooperative Extension, 2020-09-08)This issue discusses reducing the negative effects of intramammary antibiotic infusions on gut function and performance in cows. And what’s behind a credit score?
- Dairy Pipeline. April 2017Callan, Peter L.; Cayford, Eleonor Marilyn; Cockrum, Rebecca; Petersson-Wolfe, Christina S. (Virginia Cooperative Extension, 2017-03-30)This issue includes an article examining inbreeding depression problems in dairy cattle, and an ongoing genomic evaluation effort compared to the traditional use of pedigrees. There is also an article highlighting the International Dairy Federation World Summit
- Dairy Pipeline. January/February 2019Owens, Connor E.; Cockrum, Rebecca; Martel, Cynthia (Virginia Cooperative Extension, 2019-01-30)This issue has two articles. The first article focuses on criteria used in evaluation of fertility in dairy cows. The second article discusses how the Virginia Cooperative Extension program can help farmers.
- Digestibility Kinetics of Polyhydroxyalkanoate and Poly(butylene succinate-co-adipate) after In Vitro Fermentation in Rumen FluidGalyon, Hailey; Vibostok, Samuel; Duncan, Jane; Ferreira, Gonzalo; Whittington, Abby; Havens, Kirk; McDevitt, Jason; Cockrum, Rebecca (MDPI, 2022-05-21)Using polyhydroxyalkanoate (PHA) materials for ruminal boluses could allow for longer sustained release of drugs and hormones that would reduce administration time and unneeded animal discomfort caused by continuous administration. The objective of this study was to determine ruminal degradability and kinetics of biodegradable polymers and blends. A proprietary PHA-based polymer, poly(butylene succinate-co-adipate) (PBSA), PBSA:PHA melt blends, and forage controls were incubated in rumen fluid for up to 240 h. Mass loss was measured after each incubation time, and digestion kinetic parameters were estimated. Thermogravimetric, differential scanning calorimetry, and intrinsic viscosity analyses were conducted on incubated samples. Generally, across treatments, mass loss was significant by 96 h with a minimum increase of 0.25% compared to 0 h but did not change thereafter. Degradation kinetics demonstrated that polymer treatments were still in the exponential degradation phase at 240 h with a maximum disappearance rate of 0.0031 %/h. Melting temperature increased, onset thermal degradation temperature decreased, and intrinsic viscosity decreased with incubation time, indicating structural changes to the polymers. Based on these preliminary findings, the first stage of degradation occurs within 24 h and PHA degrades slowly. However, further ruminal degradation studies of biodegradable polymers are warranted to elucidate maximum degradation and its characteristics.
- Factors affecting the quality and function of the bovine periovulatory follicleHarl, Audra Whitney (Virginia Tech, 2018-11-15)For many cattle operations, profitability depends on the success of reproductive management programs. Opportunities for improving fertility exist within the numerous challenges related to reproductive management. Non-conventional, creative tools for reproductive management could help producers overcome these challenges. In an effort to produce information that could be used to improve reproductive performance of cattle, the following studies were undertaken. The objectives of these studies were threefold: to determine whether GnRH administered as an epidural injection causes ovulation in healthy cows and heifers, to evaluate whether the follicular environment (specifically, follicle fluid) surrounding the oocyte during the maturation phase affects the ability of the cumulus-oocyte complex to progress through early embryonic development, and to investigate the relative effects of estradiol and progesterone on oocyte maturation and early embryo development. Ability of GnRH to elicit an ovulatory response when administered as an epidural was evaluated in crossbred angus cows and heifers. The preliminary study evaluated this route of administration in crossbred angus cows. Animals were assigned randomly to either intramuscular or epidural administration, and ovaries were visualized via transrectal ultrasound every 6 h until ovulation of the dominant follicle. Results indicated that epidural administration of GnRH was able to trigger an ovulatory response, but timing of ovulation was not measured. The main experiment evaluated incidence of ovulation, time to ovulation, and ovulatory follicle size in crossbred angus heifers administered GnRH either epidurally or intramuscularly. Heifers were randomly assigned to treatment and ovaries were visualized every 4 h via transrectal ultrasound until ovulation of the dominant follicle. Results indicated that epidural administration of GnRH was able to elicit an ovulatory response in heifers, and the timing of ovulation and ovulatory follicle size was not different between administration route. Further investigation is needed to determine if characteristics of the ovulatory response (such as the luteinizing hormone surge) and circulating concentrations of GnRH are altered by epidural administration, which may impact fertility. GnRH administration is standard practice in many estrous synchronization programs. For fixed-time artificial insemination programs, the detection of estrus prior to insemination has been shown to improve conception and decrease early embryonic loss. The impact of behavioral estrus expression on the oocyte and early embryo were evaluated. Oocytes were matured in vitro in follicle fluid collected from synchronized cows who were classified as having expressed behavioral estrus or not expressing estrus. Embryo cleavage was not affected by estrus expression, but there was a tendency for improved blastocyst development in embryos matured in follicle fluid from animals who had expressed estrus. Cell number was not affected by estrus expression, but future research is needed as to the effect on oocyte acquisition of competence and early embryonic development. Despite the progress that has been made in culture conditions for in vitro produced embryos, developmental capacity following fertilization is limited at best, with only around one-third of oocytes placed into maturation resulting in viable embryos. During in vivo maturation, the oocyte undergoes final maturation within the follicle, surrounded by a changing microenvironment of estradiol and progesterone. Although the effects of steroids on oocyte development in vitro have been studied on an individual basis, a direct comparison between the ratio of estrogen and progesterone relative to follicle size has not been investigated Effects of steroid hormones estradiol and progesterone on oocyte maturation and early embryonic development were evaluated. Oocytes were matured in vitro in media supplemented with either estradiol, progesterone, or a combination of estradiol and progesterone. Oocytes were fertilized after maturation and cultured for 7 d until development to blastocyst stage. Addition of estradiol alone did not support oocyte maturation or early embryonic development in vitro, and a combination of estradiol and progesterone exhibited an inhibitory effect on oocyte maturation and early embryonic development. Addition of progesterone alone resulted in improved development when compared with estradiol alone or a combination of estradiol and progesterone. These results indicate that efficiency of reproductive management programs is controlled by multi-faceted factors and opportunities for improvement of reproductive outcomes exist in all of these factors. Although ovulation can be elicited via epidural administration, the impact of this ovulatory trigger on fertility requires further investigation. Display of estrus after synchronization for fixed-time artificial insemination improves conception and decreases early embryonic loss and has a may improve blastocyst development. This effect on early embryo development could be the focus of future research, further improving fertility and possibly the efficacy of in vitro embryo production. Steroid hormones play crucial roles in oocyte competency and the addition of progesterone during in vitro maturation improves development compared with estradiol alone or a combination of estradiol and progesterone.
- Genetic and Maternal Factors Underlying Early Milk Production and Their Influence on Calf HealthNin-Velez, Alexandra Irma (Virginia Tech, 2020-09-11)The quality of early milk produced by dams is affected by various factors (i.e. breed, age, parity, environment, nutrition, management). The impact of these factors on the quality of milk then have subsequent effects on calf health and development. Producers are responsible for following guidelines in order to ensure that they feed calves optimal quality milk in order to produce a healthy animal. They can also regulate factors such as environment and nutrition of the dam in order to produce better quality early milk. However, even after maximizing these factors there is still high mortality rate among pre-weaned calves, therefore, other factors such as mode of birth and genetics need to be studied to determine impacts on early milk quality and make further improvements to calf health and decrease mortality. Two experiments were conducted in order to study the effects of maternal and genetic factors on early milk production and to determine relationships that exist with calf health. The objective of the first study was to determine the effects that the mode of delivery had on early milk composition, and on the rumen microbiome of calves. We hypothesized that mode of birth would impact early milk composition, and, in turn, influence the microbial phyla in the calf gut. The second study had three objectives: 1) establish phenotypic relationships between colostrum composition traits, milk production traits, and calf health, 2) determine impact of breed and season on colostrum production and 3) ) elucidate the genetic parameters (i.e. heritability, genotypic, and phenotypic correlations) among colostrum production and milk production We hypothesized that colostrum composition and production differ among breeds and by season and that individual components influence calf health. Additionally, we hypothesized that colostrum quality traits (i.e. Brix score and volume) are heritable. For the first study Charolaise (CHAR; n = 23) and Angus (ANG; n = 15) dams were divided into two experimental groups; dams underwent vaginal (VD; n= 25) or cesarean (CD; n= 13) deliveries. Early milk samples were collected and quantified for protein, lactose, somatic cell count, and fatty acid concentrations. After parturition calves were separated based on dams experimental group. Rumen fluid was collected from calves on d 1, 3, and 28 post-partum. Extracted DNA from fluid were used for metagenomic sequencing (ANG calves, n=11; CHAR calves, n=13). Samples were run on the HiSeq 2500 platform as paired end reads according to Ilumina's standard sequencing protocol. A regression analysis was done in SAS using PROC GLM and regressing mode of birth on milk components for d 1,3, and 28. After, milk components found to be significantly impacted by mode of birth were regressed against microbial counts. Results showed that VD dams were more likely to have increased (P 0.05) protein, solids non-fat, and lactose on d 1 and 3, but decreased (P < 0.05) urea concentrations. Similarly, short, medium, and long-chain fatty acids were increased (P 0.05) in VD d 3 milk. Changes in true protein elicited a decrease (P 0.05) in rumen fluid Actinobacteria and Proteobacteria; whereas, both solids non-fat and lactose were associated with an increased (P 0.05) response in d 1 transition milk. No significant results for d 28 of sampling were observed. Based on our results we suggest that mode of birth influences protein concentrations in early milk. However, only a slight impact on the overall dynamics of the calf rumen was observed with the microbiome remaining relatively stable on the phyla level in response to changes in protein concentration. The second study looked into relationships between colostrum composition traits, management practices, and calf health, as well as determined heritability and genetic correlations for colostrum quality traits. Values for test-day milk, protein, fat, and somatic cell count (SCS) for Holstein (HO, n= 250) and Jersey (JE, n=289) cows were obtained from the Animal Genomic and Improvement laboratory server at the USDA. Brix score, colostrum weight, dam age, parity, and 3-month season of calving were also recorded. After, colostrum samples from JE cows were sent to DHIA where compositional measurements were obtained (i.e. true protein, fat, lactose, SCS, solid non-fats). Lactoferrin concentration for JE colostrum samples was also determined via ELISA. Calf blood samples were collected within 72 h post-partum and total serum protein (TSP) quantified to determine success of passive immunity transfer. Additionally, farm staff were instructed to record colostrum source for 1st feeding (i.e. dam, mix, other), freshness for 1st feeding (frozen vs fresh), Brix score of colostrum fed, volume of colostrum fed, and birth weight. A PROC Mixed with LSMEANS was performed in SAS to determine relationships between colostrum components, test day components, and quality traits for season, breed, and the interaction between season and breed. Also, PROC Mixed with LSMEANS was used to determine relationships of calf health with environment, management, and colostrum components. Additionally, a Pearson correlation was used to determine relationships between colostrum components and quality traits. Results for Holstein and Jersey showed that both colostrum Brix and volume (P < 0.001) differed by breed. Colostrum volume (P < 0.001), lactose (P < 0.001), and lactoferrin (P = 0.002) varied significantly by season. Additionally, test day milk (P = 0.046), fat (P = 0.012), and protein (P = 0.003) varied significantly by season. Moreover, a significant season and breed interaction (P = 0.028) was observed solely for colostrum volume. Calf health models indicated that TSP, colostrum total protein and solid non-fats impacted incidence of respiratory illness, but no factor significantly impacted incidence of scours. Results for Pearson correlation indicated strong correlations between true protein and solid non-fats and Brix (r = 0.99; 0.86). Lactoferrin also had moderate negative correlations with volume and lactose (r = -0.35; -0.33). Heritability and repeatability's were calculated using BLUPF90 family of programs. A single-trait repeatability animal model was used and included a 1-vector phenotype (Brix or Colostrum weight), fixed effects (i.e. calving year, parity, 3-month season of calving, and age at calving), additive genetic variance, random permanent environment effects, and random residual effects. A series of bivariate models were used to calculate genetic correlations of Brix score and colostrum weight with test-day compositional traits. Heritability estimates results for Holstein cow Brix and colostrum weight, were 0.25 and 0.15. Jersey cow heritability estimates were 0.36 and 0.47 respectively. We also observed some significant genetic correlations with Holstein Brix score and test-day milk (-0.23), fat (0.54), and SCS (0.29) having moderate correlations. Holstein colostrum weight had a strong correlation with test-day milk (0.96). Jerseys had strong genetic correlation of Brix score with colostrum weight (-0.98). Low to moderately heritability was observed for Brix score and colostrum weight in both breeds making them receptive to genetic selection in order to improve breeding programs. In conclusion, mode of birth significantly impacted colostrum composition which had subsequent effects on abundance of rumen microbiota. Colostrum Brix and volume were impacted by breed, season, and interaction, and calf incidence of disease was impacted by colostrum composition and environment. Additionally, two factors influencing colostrum quality (Brix score and colostrum weight) were found to be low to moderately heritable and have moderate to strong genetic correlations to compositional traits. Strong significant relationships were also found between colostrum compositional traits and colostrum quality traits. Therefore, incorporating quality traits into breeding programs has the potential to influence compositional traits which, in turn, can impact calf health and development by the interactions that exist between composition and microbial abundance in the rumen.
- Long-term in situ ruminal degradation of biodegradable polymers in Holstein dairy cattleGalyon, Hailey; Vibostok, Samuel; Duncan, Jane; Ferreira, Gonzalo; Whittington, Abby; Cockrum, Rebecca (American Dairy Science Association, 2022-12-22)Using biodegradable materials such as polyhydroxyalkanoates (PHA) and poly(butylene succinate-co-adipate) (PBSA) to develop single-use agricultural plastics like bale netting may reduce the negative effects of plastic accumulation in the rumens of cattle. The objective of this research was to assess the long-term degradation of PHA, PBSA, and a PBSA:PHA blend (Blend) compared with a low-density polyethylene (LDPE) control. Polyhydroxyalkanoate, PBSA, Blend, and LDPE films were incubated in the rumens of 3 cannulated, nonlactating Holsteins for up to 150 d. In situ disappearance (ISD) and residue length were assessed after every incubation time. Data were analyzed with PROC MIXED in SAS and adjusted by Tukey's method to determine least squares differences between polymer treatments, incubation time, and their interaction. By 30 d, PHA achieved 100% degradation, with initiation occurring at 14 d indicated by ISD and a reduction in residue length. Poly(butylene succinate-co-adipate) and Blend did not achieve any significant ISD, but fragmentation of PBSA occurred at 60 d and fragmentation of Blend at just 1 d, likely due to abiotic hydrolysis. Low-density polyethylene achieved no ISD, and residue length did not change over incubation time. We propose that a PBSA:PHA blend is a valid alternative to polyethylene single-use agricultural plastic products based on its fragmentation within 1 d of incubation.
- Modeling Nitrogen and Energy Metabolism in the BovineLi, Mengmeng (Virginia Tech, 2019-01-30)The objectives of this research were to: 1) evaluate the accuracy of the Molly cow model predictions of ruminal metabolism and nutrient digestion when simulating dairy and beef cattle diets, 2) advance representations of N recycling between blood and the gut and urinary N excretion in the model, 3) improve the representation of pH and to refit parameters related to ruminal metabolism and nutrient digestion in the model, 4) investigate how ruminal pH affects the microbial community, expression of carbohydrate-active enzyme transcripts (CAZymes), fiber degradation, and short chain fatty acid (SCFA) concentrations. To achieve the first objective, a total of 229 studies (n = 938 treatments) including dairy and beef cattle data, published from 1972 through 2016, were collected from the literature and used to assess the model accuracy and precision based on root mean squared errors (RMSE) and concordance correlation coefficients (CCC). Only slight mean and slope bias were exhibited for ruminal outflow of NDF, starch, lipid, total N, and non-ammonia N, and for fecal output of protein, NDF, lipid, and starch. However, ruminal pH was poorly simulated and contributed to problems in ruminal nutrient degradation and VFA production predictions. To achieve the second objective, representations including ruminal ammonia outflow, intestinal urea entry, microbial protein synthesis in the hindgut, and fecal urea N excretion, were added in the model. Total urea entry, gut urea entry, and urinary urea elimination rates collected from 15 published urea kinetics studies were used to derive related parameters. Significant improvements in predictions of variables describing ruminal N metabolism, blood urea metabolism and urinary N secretion were exhibited after the modifications. To achieve the third objective, a dataset assembled from the literature containing 284 peer reviewed studies with 1223 treatment means was used to derive parameter estimates for ruminal metabolism and nutrient digestions. After refitting the parameters, the model is even more robust in representing ruminal nutrient degradation compared to the initial model. Adding ammonia concentration as a driver to the pH equation increased the precision of predicted ruminal pH, and thereby, the precision of predicted VFA concentrations due to an improved representation of pH regulation of VFA production rates. To achieve the fourth objective, six cannulated Holstein heifers with an initial BW of 362 ± 22 kg (mean ± SD) were subjected to 2 treatments in a cross-over design. The treatments were 10 days of intraruminal infusions of both 1) distilled water (Control), and 2) a dilute blend of hydrochloric and phosphoric acids to achieve a pH reduction of 0.5 units (LpH). Statistical analyses indicated 19 bacterial genera and 4 protozoal genera were affected by low ruminal pH. We observed significant correlations between 54 microbes (43 bacterial and 11 protozoal genera) and 25 enzymes, of which 8 key enzymes participated in reactions leading to SCFA production, suggesting that the ruminal microbial community alters fiber catalysis and fermentation in response to altered pH through a shift in carbohydrate-active enzyme transcripts (CAZymes) expression. Overall, after the modifications and reparameterizations, 19.7 to 37.5% of RMSE with essentially no slope bias and minor mean bias were exhibited for of ruminal and fecal outflow of ADF, NDF, fat, and protein, suggesting the model is properly to represent nutrient degradation and digestion in the bovine. Considering ruminal microbes and CAZymes in predicting ruminal volatile fatty acid concentrations could explain more variance of observations.
- Nutrient Impacts on Rumen Growth and DevelopmentYohe, Taylor Timothy (Virginia Tech, 2018-04-19)Our collective knowledge of calf nutrition has evolved over the past 100+ years, but there are still areas of improvement that merit further scientific inquiry. The work described herein explored different aspects of calf nutrition with a central focus on rumen growth and development. The first study performed used 8 Holstein bull calves to determine if calf starters differing in starch and neutral detergent fiber (NDF) content would affect calf growth, intake, rumen metabolites, blood metabolites, and gross rumen measurements when fed along with milk replacer (MR). The experiment used completely pelleted calf starters consisting of ground and pelleted barley, wheat, and corn grains. Besides the high-starch starter resulting in lower rumen pH, the hypothesis that completely pelleted calf starter diets differing in NDF and starch level would alter intake, growth, rumen metabolism, and rumen measurements was not supported. However, calves fed the high-NDF starter were $5.71 less expensive per calf to raise. Findings suggest a form of feed effect in today's calf starter diets that might be of physiological and economic importance. The second study tested custom-built rumen infusion, sampling, and evacuation devices. The main objectives were to build and confirm the successful use of the devices in one Holstein bull calf at 62 days of age, which determined a liquid passage rate out of the rumen at 40.2% of ruminal fluid/h. The third and final study examined the effects of form of diet (MR only, n = 5; MR and starter, n = 6) on rumen growth and development. More specifically, isocaloric and isonitrogenous diets were fed to neonatal and ruminally cannulated Holstein calves for 6 week. The hypothesis of MR and starter calves having altered gross rumen measurements, epithelial stem and progenitor cell number, and epithelial proliferation status was supported, but hypothesized changes in volatile fatty acid (VFA) transporter abundance and VFA absorption rate were not supported. These results indicate that form of diet, even one that promotes rumen growth, does not equate to enhanced ability to absorb VFA, but there is an effect on rumen stem and progenitor cells as well as epithelial proliferation.
- Nutritional and genetic characterization of dairy cows managed on pasture-based systems, identifying key aspects to improve their performanceMorales Ramirez, Alvaro Gonzalo (Virginia Tech, 2023-01-25)Understanding the particularities of pasture inclusion on cows' diets and their subsequent impact on the digestive processes, together with possible differences in the nutrient utilization of cows managed under grazing conditions, are challenges that must be elucidated in order to design strategies to improve the cows' productive performance. The objectives of this dissertation were: 1) to review the existing literature on ration formulation for dairy cows in pasture-based systems, identifying limitations and potential improvement areas, 2) to evaluate the adequacy of the Molly model predictions of ruminal fermentation, nutrient digestion, and performance from cows consuming fresh ryegrass-based diets, identifying mechanisms that could be used to direct further model improvements, 3) to evaluate the model predictions of milk, fat and protein production using data from Holstein-Friesian and Jersey cows from Chile managed under pasture-based systems, identifying mechanisms that could be used to direct further model improvements, 4) to identify the different dairy breeds and their crosses that are used in the Chilean dairy population, determining if there are specific breed and heterosis effects on productive and some functional traits, and 5) to characterize the ruminal degradation dynamics of crude protein (CP) and individual amino acids (AA) from ryegrass (Lolium perenne) at vegetative stage, generating information to improve the ration formulation in dairy cows in pasture-based systems. From the literature revision in objective 1, different factors that could help to create a more specific classification of dairy pasture-based systems were identified. Maximizing grass inclusion seems to leads to an oversimplification of diets, potentially limiting the performance of medium and high producing cows. Despite the low N use efficiencies reached in pasture-based systems, there is a lack of information in studies that delve into the ruminal degradation of CP and AA, as well as their intestinal absorption, and subsequent post-absorptive utilization. Advances in the understanding of these areas could help to create strategies to face this problem. There is evidence suggesting that cows can perform different under different productive systems, but various breeds, strains, and crossbreds are used in pasture-based systems, being needed first a better characterization of them. To achieve the second objective, a total of 25 studies (n = 115 treatments) including dairy cows consuming ryegrass predominant diets, published from 1970 through 2020, were collected from the literature and used to assess the model accuracy and precision based on root mean squared errors and concordance correlation coefficients (CCC). Predictions of protein and fiber digestion and fiber and organic matter fecal excretion were improved after model reparameterization, while body weight and body condition score predictions were improved after model modifications and reparameterization. Although digestion of nutrient was better represented by the new set of parameters derived, the accuracies of milk, protein, and fat production remained low (CCC of 0.13, 0.12, and 018, respectively), with moderate slope bias. To achieve the third objective, a dataset including 180 group cows' diets (153 from Holstein Friesian and 27 from Jersey cows) from 18 commercial dairy farms with different inclusion of ryegrass was compiled. Chemical composition of feeds ingredients, group intakes and animal performance records, were provided by the Chilean cooperative Colun. Separately model mammary reparameterization of Holstein Friesian and Jersey cows' data, improved both milk production (CCC values of 0.69 and 0.90, respectively) and milk solids predictions (CCC values of 0.68 and 0.92 for milk protein and 0.65 and 0.80 for milk fat, for Holstein Friesian and Jersey cows, respectively). This indicates that there seems to be some differences in mammary cells and cells activity between breeds evaluated, translated into different lactation curves and milk solids synthesis patters. To achieve the fourth objective, a dataset considering 1,429,132 records from 586,624 cows that calved between 1998 and 2018 was compiled. Pedigree information, milk, milk protein, and milk fat, as well as somatic cell score and calving interval records were provided by the Chilean cooperative COOPRINSEM. The proportion of each breed according to the different country origin (strain) was calculated for all the animals, being identified eight genetic strains with enough information to perform separated genetic evaluations: Chilean Friesian, French Holstein-Friesian, US-Holstein, US-Jersey, French Montbeliarde, New Zealander Holstein-Friesian, Swedish Red and White, and British Friesian. Four different genetic models, increasing in complexity (considering breed or strain classification, crossbreeding proportion, and heterosis effects) were tested. Specific effects for some genetic strains, as well as heterosis effects between some strains with Chilean Friesian were identified, so these effects should be considered when performing genetic evaluations in the Chilean dairy population. Also, they can be used to direct future selection programs. To achieve the last objective, an in situ study using three cannulated cows was carried out at the Agricultural Research Station of the Austral University of Chile (Valdivia, Chile). Samples from a perennial ryegrass pasture were collected during winter, spring and summer at vegetative stage. Duplicate bags were ruminally incubated for 4, 8, 12, 24, and 96 h. CP and AA profile of original samples and from incubation residues were determined. Ryegrass samples presented a high crude protein content (averaging 25.8%), however, the RUP content was ~15 to 20% of CP. Significant differences were observed for ryegrass CP and individual AA ruminal degradation kinetics, this seems to be associated to some specific AA.
- On-farm strategies for the prevention and detection of Gram-specific clinical mastitis in dairy cowsSteele, Nicole (Virginia Tech, 2019-04-17)Controlling mastitis in dairy herds relies on good prevention and detection methods. This dissertation describes two areas of research relating to mastitis control. In the first objective, the efficacy of 2 vaccines against Escherichia coli mastitis in mid-lactation dairy cows was evaluated. Secondly, in a series of 3 studies, milk and activity sensor data were used to derive models for clinical mastitis (CM) detection, and models were tested for their ability to indicate the causative pathogen type. Primiparous and multiparous animals were vaccinated with 1 of 2 commercially available J5 vaccines (V1 or V2) or served as unvaccinated controls (CTL). Intramammary challenge with E. coli approximately 84 d later resulted in few treatment differences in the clinical and behavioral responses, except that vaccinated cows exhibited fever (≥ 39.4 °C) 3 h earlier and laid down for longer periods than CTL. Although vaccinated cows had similar severity and duration of CM, V1 cows produced more serum IgG1 and IgG2 than V2 cows. Our results indicated that the effects of vaccination were diminished in mid-lactation, and that antibodies are not the limiting factor in defending against induced E. coli mastitis. Multiple regression models, incorporating the slope changes in relevant milk and activity sensor data, were developed to indicate all CM cases (ACM), or specifically, CM due to Gram-negative (GN) or Gram-positive (GP) bacteria. Gram-specific models had greater detection accuracy (> 80%) than the ACM model (75%) when evaluated using the model training dataset, but independent evaluation demonstrated reduced sensitivity (Se) of detecting CM by all models (GN, 62%, ACM, 56%, and GP, 32% Se). Data in the 3 d prior to CM were more important in detecting GN pathogens, whereas the best GP models incorporated changes more than 1 week prior to CM detection. Still, model performance was imperfect. Next, models were rederived from a dataset that better reflected the infection distribution of the herds its use was intended for. However, the Se of detecting CM in real-time, across 2 farms, was < 21% for all models, and categorization by Gram-status had no benefit. An insufficient number of CM cases was considered to contribute to the poor detection performance of models and limited repeatability across farms. Consequently, models derived in this study were inadequate for implementation as mastitis detection tools. In the future, development of new sensors and application of more sophisticated algorithms to the field of mastitis detection may improve the accuracy of models using sensor data.
- Phenotypic and microbial influences on dairy heifer fertility and calf gut microbial developmentOwens, Connor E. (Virginia Tech, 2020-10-12)Pregnancy loss and calf death can cost dairy producers more than $230 million annually. While methods involving nutrition, climate, and health management to mitigate pregnancy loss and calf death have been developed, one potential influence that has not been well examined is the reproductive microbiome. I hypothesized that the microbiome of the reproductive tract would influence heifer fertility and calf gut microbial development. The objectives of this dissertation were: 1) to examine differences in phenotypes related to reproductive physiology in virgin Holstein heifers based on outcome of first insemination, 2) to characterize the uterine microbiome of virgin Holstein heifers before insemination and examine associations between uterine microbial composition and fertility related phenotypes, insemination outcome, and season of breeding, and 3) to characterize the various maternal and calf fecal microbiomes and predicted metagenomes during peri-partum and post-partum periods and examine the influence of the maternal microbiome on calf gut development during the pre-weaning phase. In the first experiment, virgin Holstein heifers (n = 52) were enrolled over 12 periods, on period per month. On -3 d before insemination, heifers were weighed and the uterus was flushed. Flush pH and glucose concentration were measured. Blood was collected from coccygeal vessels on d -3, 15, 18, 21, 24, 27, and 30 relative to insemination and serum progesterone concentration was measured. Ultrasound measurements of dominant follicle diameter and corpus luteum volume. Insemination outcome was determined on d 30 using ultrasound and pregnancy was checked on d 42, 56, 70, and 84. Heifers were clustered based on outcome of insemination at d 30 (not pregnant, NP30, n = 24; pregnant, PS30, n = 28), d 84 (not pregnant, NP84, n = 24; pregnant but lost before d 84, PL84, n = 2; successfully pregnant through d 84, PS84, n = 26). Differences in phenotypes were assessed based on insemination outcome at d 30 and d 84. Weight was greater in NP30 heifer than PS30 heifers. Progesterone was greater in PS30 and PS84 heifers than NP30 or NP84 heifers on d -3 and 18 to 30 and CL volume was greater in PS30 and PS84 heifers than NP30 and NP84 heifers on d 21 and 30. To summarize, traits related to pregnancy maintenance were different in virgin Holstein heifers based on first insemination outcomes and might be able to be used to predict heifer reproductive performance. Uterine flushes were examined in a subset of heifers (n = 28) based on insemination outcome and period. This subset was also clustered based on season (spring, n = 3; summer, n = 12; fall, n = 8; winter, n = 5). From this subset of heifers, DNA was extracted from uterine flush and 16S amplicons of the V4 region underwent 250 paired-end sequencing via Illumina NovaSeq 6000. Filtered reads were clustered into operational taxonomic units using a 97% similarity and assigned taxonomy using the SSURNA Silva reference version 132. Alpha and beta diversity were measured and differences in alpha and beta diversity measurements were analyzed based on insemination outcome at d 30 or d 84 and season of breeding. Differential abundance analyses were performed at the phylum and genus taxonomic ranks based on insemination outcome at d 30 or d 84 and season of breeding. Bacterial richness was reduced in PL84 heifers than NP84 and PS84 heifers and reduced in heifers bred in spring than those bred in other seasons. Bacterial community structure was different based on insemination outcome at d 30 and d 84 using unweighted Unifrac distances and was different based on season of breeding using weighted Unifrac distances. We observed an increase of Bacteroidetes in PS30 and PS84 heifers compared to NP30 and NP84 heifers. Ureaplasma and Ruminococcus had an increased abundance in PS30 and PS84 heifers than NP30 and NP84 heifers, while Afipia and Gardnerella had an increased abundance in NP30 and NP84 heifers than PS30 and PS84 heifers. Prevotella and Ruminococcus had a reduced abundance in summer bred heifers than winter bred heifers. Proteobacteria had a moderate negative correlation with -3 d progesterone (rp = -0.42) and Actinobacteria had a moderate negative correlation with fetal growth rate (rp = -0.66). Uterine microbiome of virgin Holstein heifers differed based on insemination outcomes and season of breeding and might be a new phenotype to indicate heifer fertility. In the second experiment, multiparous Holstein cows (n = 12) were placed in individual box stalls 14 d before expected calving. Sterile swabs were used to collect samples from the posterior vagina of the dam approximately 24 h before calving, dam feces, dam oral cavity, and colostrum within 1 h after calving, and cotyledonary placenta within 6 h after calving. Calves (n = 12; bulls = 8, heifers = 4) were isolated immediately after parturition to prevent environmental contamination. Colostrum was fed to calves using a clean bottle that was assigned to the calf for the duration of the study. Calves were individually housed for 60 d until weaning. Sterile swabs were used to collect calf fecal samples at birth, 24 h, 7 d, 42 d, and 60 d of age. A subset of calf-dam pairs (n = 6; bulls = 3, heifers = 3) were selected and DNA was extracted from all samples. Amplicons covering V4-V5 16S rDNA regions were generated using extracted DNA and sequenced using 300 bp paired end sequencing via Illumina MiSeq. Sequences were aligned into operational taxonomic units using the 97% Greengenes reference database. Spearman correlations were performed between maternal and calf fecal microbiomes. Negative binomial regression models were created for genera in calf fecal samples at each time point using genera in maternal microbiomes. Metagenomes were predicted, collapsed into gene pathways and differences in predicted metagenomes were analyzed within STAMP (Statistical Analysis of Metagenomic Profiles). We determined that Bacteroidetes dominated the calf fecal microbiome at all time points (relative abundance ≥ 42.55%) except for 24 h post-calving, where Proteobacteria were the dominant phylum (relative abundance = 85.10%). Colostrum and placenta had low diversity within samples and clustered independently from fecal samples. Each maternal microbiome was a significant predictor for calf fecal microbiome during at least 2 time points. Genes for infectious disease and neurodegenerative disease were greater in colostrum and 24 h calf fecal samples compared to other samples. Results indicated that no one maternal microbiome was a major influence on calf fecal microbiome inoculation and development. Instead, calf fecal microbial development stems from various maternal microbial sources. Overall, the reproductive microbiome was predictive of heifer pregnancy outcomes and calf fecal microbial development. The virgin heifer uterine microbiome could be used to predict fertility and adaptation to heat stress, but further research including a larger group of pregnancy loss is needed. Maternal microbiomes from the reproductive tract, colostrum, oral cavity, and feces could all be used to predict calf microbial development, but more research including other maternal microbiomes and environmental microbial contributions is needed. However, the results from this dissertation indicate reproductive microbiome composition is a trait that might be predictive of dairy cattle performance.
- Photoperiod and Temperature-Humidity Index during the Dry-Period Impact Colostrum and Milk Production in Dairy CattleAlward, Kayla Jean (Virginia Tech, 2023-06-26)Colostrum quality is critical to calf health as colostrum provides immunoglobulins (Ig) that are critical for a calf's immune system. Despite close management of factors known to affect colostrum production, 23% of dairy cows are still producing inadequate volume or quality of colostrum, which causes calf death and poor performance. Therefore, the objectives of this dissertation are to investigate factors that affect colostrum production and methods to improve colostrum yield and quality. Based on previous literature showing that photoperiod impacts milk yield post-calving in dry cows and that light intensity and temperature-humidity index (THI) impact colostral Ig content, I hypothesized that photoperiod and THI during the dry period impact colostrum yield and quantity in Holstein and Jersey cows. The first study evaluated the isolated effect of photoperiod on colostrum production. Dry cows were housed in a temperature-controlled barn and exposed to either short-day photoperiod (SDPP) of 8 h of light per day or long-day photoperiod (LDPP) of 16 h of light per day for the entire dry period until calving. Altered photoperiod had no effect on colostrum yield, Ig content or other components of colostrum. However, Jersey cows had a higher Brix score, fat, protein, IgA and IgM. After calving, milk production was not affected by photoperiod treatment, likely due to cows being exposed to an irregular lighting scheme. The second study evaluated the combined effects of photoperiod and THI during the dry period on colostrum production and broke cows into a bottom (1), middle (2) and top (3) third based on their photoperiod exposure. Holstein cows produced more colostrum than Jersey cows in each photoperiod category. For both breeds, photoperiod category 1 cows produced less colostrum than cows in photoperiod category 2 and 3. Brix score did not differ by breed but differed by farm and photoperiod category with farm 1, photoperiod category 3 cows having increased Brix score compared to farm 2, photoperiod category 1 and 2 cows. Colostrum components for Jersey cows did not differ by photoperiod category. However, colostrum volume, Brix score, protein and SNF were all impacted by THI and (or) photoperiod variables in predictive modeling. This indicates that colostrum yield and quality in Holstein and Jersey cows are similarly impacted by both photoperiod exposure and THI exposure during the last two months of pregnancy. Therefore, farmers can utilize short-day photoperiod during the dry period during times of moderate THI to improve milk production post-calving without negatively impacting colostrum production. However, future studies are needed to tease out THI and photoperiod impact on colostrum on a large scale in order to improve dry cow management and colostrum production.
- The Relationship between Residual Feed Intake, Dry Matter Intake, and Reproductive Performance in Holstein Dairy CowsCayford, Eleonor Marilyn (Virginia Tech, 2017-05-22)Feed represents a large portion of input costs for dairy operations. Decreasing the feed consumed, measured here as dry matter intake (DMI), would therefore be advantageous to producers. However, this decrease could result in cows that do not supply the necessary energy to maintain high production, growth, and reproduction. Measures of feed efficiency try to capture important energy expenditures to ensure that cows consume less while maintaining production. Feed efficiency in this study is measured in residual feed intake (RFI), which is calculated as the difference between DMI and expected DMI based on production and growth measures. However, the RFI model does not capture the energy stores required for reproduction; therefore, selection for RFI may lead to reduced reproductive performance. In this thesis, I explored the phenotypic and genetic relationships between RFI, DMI, and reproductive performance as measured by number of services (NS), days open (DO), and days to first calving (DFC). First, ANOVA tests and phenotypic correlations determined the phenotypic relationship between the traits. Then, heritability and genetic correlations were used to estimate the genetic parameters. Phenotypically, results indicated mixed relationships between traits. Heritability estimates were low for reproductive traits and moderate for DMI and RFI. There was no unfavorable genetic relationship between DMI or RFI with any of the reproductive traits. Therefore, neither selection for DMI nor RFI will unfavorably impact reproduction.
- Ruminal Degradation of Polyhydroxyalkanoate and Poly(butylene succinate-co-adipate)Galyon, Hailey Roselea (Virginia Tech, 2022-06-21)The occurrence of plastic impaction in ruminants is a growing concern. As indiscriminate feeders, cattle may consume plastic foreign materials incorporated into their diets and it is currently estimated that 20% of cattle contain plastic foreign materials in their rumen. These materials are indigestible and accumulate for the lifetime of the animal. As these materials accumulate, they may reduce feed efficiency and production by erosion and ulceration of rumen epithelium, stunting of papillae, blockage of the reticulo-omasal orifice, and leaching of toxic heavy metals. It is necessary to reduce the incidences of plastic impaction in domestic ruminants. Using polyhydroxyalkanoate (PHA) and poly(butylene succinate-co-adipate) (PBSA) biodegradable materials for feed storage products such as bale netting could reduce the incidences and effects of polyethylene-based plastic impaction in ruminants. The objectives of these studies were to evaluate the degradability of PHA and PBSA materials in the reticulorumen via in vitro, in situ, and in vivo methods. Our hypothesis was that these materials would degrade in the rumen and that a melt-blend of PHA and PBSA may degrade faster than its individual components. An in vitro study incubated a proprietary PHA-based polymer, PBSA, and PBSA:PHA melt blend nurdles, and forage controls in rumen fluid for up to 240h in DaisyII Incubators. Mass loss was measured, and digestion kinetic parameters were estimated. Thermogravimetric and differential scanning calorimetry analyses were conducted on incubated samples. Results indicated that the first stage of degradation occurs within 24h and PHA degrades slowly. Degradation kinetics demonstrated that polymer treatments were still in the exponential degradation phase at 240h with a maximum disappearance rate of 0.0031%/h, and mass loss was less than 2% for all polymers. Melting temperature increased and onset thermal degradation temperature decreased with incubation time, indicating structural changes to the polymers starting at 24h. Further in situ degradation, however, indicated these biodegradable materials degrade at more accelerated rates in the rumen. Polyhydroxyalkanote, PBSA, PBSA:PHA blend, and low-density polyethylene (LDPE) films were incubated in the rumens of three cannulated, non-lactating Holsteins for 0, 1, 14, 30, 60, 90, 120, and 150d. In situ disappearance (ISD) and residue length were assessed after every incubation time. Polyhydroxyalkanoate achieved 100% degradation by 30d, with initiation occurring at 14d indicated by ISD and a reduction in residue length. The fractional rate of disappearance of PHA was 7.84%/d. Poly(butylene succinate-co¬-adipate) and Blend did not achieve any significant ISD, yet fragmentation of PBSA occurred at 60d and the blend at just 1d likely due to abiotic hydrolysis. Low-density polyethylene achieved no ISD and residue length did not change over incubation time. From these results, we proposed a PBSA:PHA blend is a valid alternative to polyethylene single-use agricultural plastic products based on its fragmentation within 1d of incubation. Administration of PBSA:PHA film boluses compared to LDPE films and a control further supported this dissemination. Holstein bull calves (n = 12, 62 ± 9d, 74.9 ± 8.0kg) were randomly allocated to one of three daily bolus treatments: 13.6g of PBSA:PHA in 4 gelatin capsules (Blend), 13.6g of LDPE in 4 gelatin capsules (LDPE), or 4 empty gelatin capsules (Control) for 30d. Hemograms were conducted on blood samples collected on d0 and d30. On d31, animals were sacrificed to evaluate gross rumen measurements and pathology, determine papillae length, and characterize polymer residues present in rumen contents. Feed intake, body weight, body temperature, and general health were determined throughout the study. No animals presented any symptoms related to plastic impaction and animal health was not particularly affected by treatment. Daily grain and hay intake, body weight, rectal temperature, hematological parameters, gross rumen measurements and pathology, and rumen pH and temperature were not affected by treatment. There was evidence that degradation of PBSA:PHA may release byproducts that support rumen functionality. Methylene blue reduction time of Blend calves tended to be decreased by 30% compared to LDPE calves, and caudal ventral papillae length of Blend calves were 50% longer than those of Control animals. Though studies are needed to specifically elucidate the production of byproducts due to degradation of PBSA:PHA and their correlations. Polymer accumulation and residue length differed among treatments. Calves dosed with LDPE retained 6.7% of the dosed polymer, undegraded, while Blend calves retained 0.4% of the dosed polymer. The polymer residues in Blend calves were 10% of their original size. Single-use agricultural plastics developed from PBSA:PHA may be a suitable alternative to LDPE-based products in the case of ingestion in ruminants due to no acute health inflictions, fragmentation of polymers with 1d, and improved clearance from the reticulorumen. As such, utilization of these materials may reduce the incidences of plastic impaction in ruminants in commercial operations. Further long-term feeding studies are needed to evaluate specific byproduct production of PBSA:PHA and their potential influences on rumen function and animal health and production in normal commercial conditions.
- Sources of Variation in the Microbiome of Pre-Weaned Dairy CalvesHuffard, Haley Garrett (Virginia Tech, 2019-09-20)This study investigated the microbial colonization and maternal influences on the neonatal calf gut microbiome. Microbiome samples were collected from dams (n = 6) and calves (n = 6) using sterile flocked swabs. The vaginal, oral, and fecal bacterial communities were examined from the dam and the fecal community of calves was examined from birth to 60 d of age. Microbial communities varied by anatomical location and age of the calf. Metagenomic analysis 16s ribosomal DNA revealed ten phyla associated with microbiomes of the dam and the same ten phyla associated with calf feces at various time points: Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, Cyanobacteria, Verrucomicrobia, Spirochaetes, Tenericutes, Fibrobacteres, and Lentisphaerae. Overall, the calf meconium and fecal microbiome is influenced by a combination of the maternal vagina, oral, and fecal microbiomes. Further studies will be needed to identify the transference mechanisms of maternal microbes to offspring and the associated host-microbial interactions.
- Transcriptional profiles of cumulus-oocyte complexes related to developmental competence in bovine oocytesWalker, Bailey Nicole (Virginia Tech, 2021-01-05)During folliculogenesis, oocytes and cumulus cells undergo many morphological and physiological changes. Transcriptome data were produced from single oocytes and corresponding cumulus cells (CC) to infer the differences in the transcript abundance from fully grown versus growing phase oocytes and surrounding CC. Using cow ovaries from an abattoir, COC were collected from follicles ranging from 3 to 8 mm in diameter. Cumulus-oocyte complexes were incubated in the supravital stain brilliant cresyl blue (BCB) as a means of separating oocytes based on the growth phase. Fully developed oocytes remained stained and were categorized as BCB+, whereas oocytes in the growing phase were colorless and were categorized as BCB-. Following the classification, COC were used for in vitro embryo production. Blastocyst yield from COC classified as BCB+, BCB- and unstained controls were 20%, 14% and 16.5%, respectively (P=0.18). Transcriptome data were also produced from oocytes and cumulus cells from BCB+ and BCB- COC. Transcripts from one long non-coding gene were differentially abundant in fully grown oocytes compared to oocytes in the growing phase. Eleven protein-coding genes were differentially expressed in cumulus cells collected from COC containing growing and fully grown oocytes. The results indicate no significant variation of transcript abundance of protein-coding genes in oocytes and limited regulation of transcript abundance in cumulus cells relative to the oocyte's growth phase in mid to large antral follicles.