School of Animal Sciences

Permanent URI for this community

https://hdl.handle.net/10919/111086

The School of Animal Sciences merged Dairy Science and Animal and Poultry Science in 2022.

Browse

Now showing 1 - 20 of 69

AgroSeek: a system for computational analysis of environmental metagenomic data and associated metadata
Liang, Xiao; Akers, Kyle; Keenum, Ishi M.; Wind, Lauren L.; Gupta, Suraj; Chen, Chaoqi; Aldaihani, Reem; Pruden, Amy; Zhang, Liqing; Knowlton, Katharine F.; Xia, Kang; Heath, Lenwood S. (2021-03-10)
Background Metagenomics is gaining attention as a powerful tool for identifying how agricultural management practices influence human and animal health, especially in terms of potential to contribute to the spread of antibiotic resistance. However, the ability to compare the distribution and prevalence of antibiotic resistance genes (ARGs) across multiple studies and environments is currently impossible without a complete re-analysis of published datasets. This challenge must be addressed for metagenomics to realize its potential for helping guide effective policy and practice measures relevant to agricultural ecosystems, for example, identifying critical control points for mitigating the spread of antibiotic resistance. Results Here we introduce AgroSeek, a centralized web-based system that provides computational tools for analysis and comparison of metagenomic data sets tailored specifically to researchers and other users in the agricultural sector interested in tracking and mitigating the spread of ARGs. AgroSeek draws from rich, user-provided metagenomic data and metadata to facilitate analysis, comparison, and prediction in a user-friendly fashion. Further, AgroSeek draws from publicly-contributed data sets to provide a point of comparison and context for data analysis. To incorporate metadata into our analysis and comparison procedures, we provide flexible metadata templates, including user-customized metadata attributes to facilitate data sharing, while maintaining the metadata in a comparable fashion for the broader user community and to support large-scale comparative and predictive analysis. Conclusion AgroSeek provides an easy-to-use tool for environmental metagenomic analysis and comparison, based on both gene annotations and associated metadata, with this initial demonstration focusing on control of antibiotic resistance in agricultural ecosystems. Agroseek creates a space for metagenomic data sharing and collaboration to assist policy makers, stakeholders, and the public in decision-making. AgroSeek is publicly-available at https://agroseek.cs.vt.edu/ .
Amino Acid Metabolomic Profiles in Bovine Mammary Epithelial Cells under Essential Amino Acid Restriction
López-Diez, Laura; Calle-Velásquez, Camilo; Hanigan, Mark D.; Ruiz-Cortés, Zulma Tatiana (MDPI, 2021-05-07)
Mammary epithelial cells (MECs) in culture are a useful model for elucidating mammary gland metabolism and changes that occur under different nutrient disponibility. MECs were exposed to different treatments: 100% EAA for 8 h and 24 h restriction (R); 2% EAA for 8 h and 24 h R; 2% EAA for 8 h and 24 h + 100% EAA for 8 h and 24 h restriction + re-feeding (R + RF). Western blotting and protein quantification was performed. The Kyoto Encyclopedia of Genes and Genomes (KEGG) software identified the amino acids (AAs) and signaling pathways. The chi-squared test, multiple classification analysis, and analysis of variance were used for the purification and identification of data. Intracellular casein levels were not affected. The KEGG analysis revealed that the important pathways of metabolism of AAs, which were involved in processes related to metabolism and biosynthesis of phenylalanine, tyrosine, and tryptophan (fumarate, acetyl-CoA, and tricarboxylic acid (TCA) cycle), were affected by both R and R + RF treatments, mainly through the glutamic-oxaloacetic transaminase-2 enzyme. Additionally, metabolic processes mediated by the mitochondrial malate dehydrogenase, S-adenosylmethionine synthetase, and asparagine synthase proteins positively regulated the carbohydrate pathway, pyruvate, and TCA cycles, as well as the metabolism of alanine, aspartate, and glutamate metabolism (carbohydrate and TCA cycle). We hypothesized that MECs have the capacity to utilize alternative pathways that ensure the availability of substrates for composing milk proteins.
Antibiotic resistance genes in the faeces of dairy cows following short-term therapeutic and prophylactic antibiotic administration
Feng, Xin; Chambers, Lindsey R.; Knowlton, Katharine F. (2019-12-06)
The objective of the research was to quantify three antibiotic resistance genes (tetQ, cfxA and mefA) in the faeces of dairy cows following therapeutic and prophylactic antibiotic treatments. Manure collected from dairy cows treated with either no antibiotic, pirlimycin hydrochloride (PIRL), ceftiofur crystalline free acid (CCFA) or cephapirin benzathine (CEPH) were submitted to quantitative PCR analysis. No treatment effects on the abundance of the tetQ and cfxA were observed. There was a trend for the abundance of the mefA to be increased in cows treated with PIRL (P = 0.07). Overall, the results showed no difference of measured three ARGs from cows receiving different antibiotics. Considering the limited scope of our investigation, further investigation is needed to provide more information on ARGs excretion from cows that received therapeutic and prophylactic antibiotic treatment.
Bayesian QTL mapping using skewed Student-tdistributions
von Rohr, Peter; Hoeschele, Ina (2002-01-15)
In most QTL mapping studies, phenotypes are assumed to follow normal distributions. Deviations from this assumption may lead to detection of false positive QTL. To improve the robustness of Bayesian QTL mapping methods, the normal distribution for residuals is replaced with a skewed Student-t distribution. The latter distribution is able to account for both heavy tails and skewness, and both components are each controlled by a single parameter. The Bayesian QTL mapping method using a skewed Student-t distribution is evaluated with simulated data sets under five different scenarios of residual error distributions and QTL effects.
Can consumers’ willingness to pay incentivize adoption of environmental impact reducing technologies in meat animal production?
White, Robin R.; Brady, Michael (2014-12)
This study develops a model estimating consumer willingness to pay (WTP) for environmental meat attributes and uses a multi-objective nutritional optimizer to explore the extent to which WTP can offset on-farm costs of reducing water use. Data for the WTP model are sourced from a literature survey of the Agricola and Google Scholar databases yielding 46 studies estimating WTP for pure and impure (organic, grass-fed, natural) environmental meat attributes. Bayesian analysis is used to estimate 3 models varying in independent variables. Models are evaluated by the correlation coefficient (R2), root mean squared error of prediction (RMSPE) and posterior model probability. The most probable model is then used to estimate a confidence range of WTP for pure environmental beef. Impure environmental labels result in higher WTP than pure labels. Non-hypothetical WTP for pure environmental labeling for North American consumers ranges from 6.7% to 32.6%. A case study is conducted to identify the expected reduction in water use that can be funded from capturing WTP through labeling. A multi-objective nutritional optimizer is used to identify ideal management of beef cattle to reduce whole-system water use in three regions of the United States. Cost increases from management are varied over the predicted range in WTP and combined with the probability of a consumer purchasing beef at each WTP value to identify the theoretical effect on expected environmental impact reduction. A 10% premium is the ideal WTP, resulting in water use reductions between 24.4 L and 41.4 L.
Challenges in enriching milk fat with polyunsaturated fatty acids
Lanier, Jennifer S.; Corl, Benjamin A. (Biomed Central, 2015-06-12)
Milk fatty acid composition is determined by several factors including diet. The milk fatty acid profile of dairy cows is low in polyunsaturated fatty acids, especially those of the n-3 series. Efforts to change and influence fatty acid profile with longer chain polyunsaturated fatty acids have proven challenging. Several barriers prevent easy transfer of dietary polyunsaturated fatty acids to milk fat including rumen biohydrogenation and fatty acid esterification. The potential for cellular uptake and differences in fatty acid incorporation into milk fat might also have an effect, though this has received less research effort. Given physiological impediments to enriching milk fat with polyunsaturated fatty acids, manipulating the genome of the cow might provide a greater increase than diet alone, but this too may be challenged by the physiology of the cow.
Choosing the Right Liquid Feed for Your Calves
Yohe, Taylor (Virginia Tech. Department of Dairy Science, 2017-02-16)
The primary messages of this presentation are that there are any good options for liquid diets to feed calves. One should stay away from unpasteurized waste milk! Pasteurized waste milk is a decent option, and it is, at the moment, unaffected by VFD. Feeding as close to whole milk with lower fat is the best option, and MR with high protein (25-28%) and low to mid fat (10-20% depending on season) with digestible nutrients is also a good option.
Combined effects of composting and antibiotic administration on cattle manure–borne antibiotic resistance genes
Keenum, Ishi M.; Williams, Robert K.; Ray, Partha P.; Garner, Emily; Knowlton, Katharine F.; Pruden, Amy (2021-04-01)
Background Research is needed to delineate the relative and combined effects of different antibiotic administration and manure management practices in either amplifying or attenuating the potential for antibiotic resistance to spread. Here, we carried out a comprehensive parallel examination of the effects of small-scale (> 55 °C × 3 days) static and turned composting of manures from dairy and beef cattle collected during standard antibiotic administration (cephapirin/pirlimycin or sulfamethazine/chlortetracycline/tylosin, respectively), versus from untreated cattle, on “resistomes” (total antibiotic resistance genes (ARGs) determined via shotgun metagenomic sequencing), bacterial microbiota, and indicator ARGs enumerated via quantitative polymerase chain reaction. To gain insight into the role of the thermophilic phase, compost was also externally heated to > 55 °C × 15 days. Results Progression of composting with time and succession of the corresponding bacterial microbiota was the overarching driver of the resistome composition (ANOSIM; R = 0.424, p = 0.001, respectively) in all composts at the small-scale. Reduction in relative abundance (16S rRNA gene normalized) of total ARGs in finished compost (day 42) versus day 0 was noted across all conditions (ANOSIM; R = 0.728, p = 0.001), except when externally heated. Sul1, intI1, beta-lactam ARGs, and plasmid-associated genes increased in all finished composts as compared with the initial condition. External heating more effectively reduced certain clinically relevant ARGs (blaOXA, blaCARB), fecal coliforms, and resistome risk scores, which take into account putative pathogen annotations. When manure was collected during antibiotic administration, taxonomic composition of the compost was distinct according to nonmetric multidimensional analysis and tet(W) decayed faster in the dairy manure with antibiotic condition and slower in the beef manure with antibiotic condition. Conclusions This comprehensive, integrated study revealed that composting had a dominant effect on corresponding resistome composition, while little difference was noted as a function of collecting manure during antibiotic administration. Reduction in total ARGs, tet(W), and resistome risk suggested that composting reduced some potential for antibiotic resistance to spread, but the increase and persistence of other indicators of antibiotic resistance were concerning. Results indicate that composting guidelines intended for pathogen reduction do not necessarily provide a comprehensive barrier to ARGs or their mobility prior to land application and additional mitigation measures should be considered.
Dairy Science Research at Virginia Tech
Ferreira, Gonzalo (Virginia Tech. Department of Dairy Science, 2017-02-16)
VT Dairy Complex - Research Summary: • 3 intensive metabolic trials - 4 feeding trials - 2 in vitro digestibility trials - 3 rumen development trials - 2 animal behavior and welfare trials - 2 antibiotic resistance trials - 1 mammary gland physiology trial
Development and Validation of a UPLC-MS/MS Method to Monitor Cephapirin Excretion in Dairy Cows following Intramammary Infusion
Ray, Partha; Knowlton, Katharine F.; Shang, Chao; Xia, Kang (PLOS, 2014-11-06)
Cephapirin, a cephalosporin antibiotic, is used by the majority of dairy farms in the US. Fecal and urinary excretion of cephapirin could introduce this compound into the environment when manure is land applied as fertilizer, and may cause development of bacterial resistance to antibiotics critical for human health. The environmental loading of cephapirin by the livestock industry remains un-assessed, largely due to a lack of appropriate analytical methods. Therefore, this study aimed to develop and validate a cephapirin quantification method to capture the temporal pattern of cephapirin excretion in dairy cows following intramammary infusion. The method includes an extraction with phosphate buffer and methanol, solid-phase extraction (SPE) clean-up, and quantification using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The LOQ values of the developed method were 4.02 µg kg−1 and 0.96 µg L−1 for feces and urine, respectively. This robust method recovered >60% and >80% cephapirin from spiked blank fecal and urine samples, respectively, with acceptable intra- and inter-day variation (<10%). Using this method, we detected trace amounts (µg kg−1) of cephapirin in dairy cow feces, and cephapirin in urine was detected at very high concentrations (133 to 480 µg L−1). Cephapirin was primarily excreted via urine and its urinary excretion was influenced by day (P = 0.03). Peak excretion (2.69 mg) was on day 1 following intramammary infusion and decreased sharply thereafter (0.19, 0.19, 0.08, and 0.17 mg on day 2, 3, 4, and 5, respectively) reflecting a quadratic pattern of excretion (Quadratic: P = 0.03). The described method for quantification of cephapirin in bovine feces and urine is sensitive, accurate, and robust and allowed to monitor the pattern of cephapirin excretion in dairy cows. This data will help develop manure segregation and treatment methods to minimize the risk of antibiotic loading to the environment from dairy farms.
Diet shifts provoke complex and variable changes in the metabolic networks of the ruminal microbiome
Wolff, Sara M.; Ellison, Melinda J.; Hao, Yue; Cockrum, Rebecca R.; Austin, Kathy J.; Baraboo, Michael; Burch, Katherine; Lee, Hyuk Jin; Maurer, Taylor; Patil, Rocky; Ravelo, Andrea; Taxis, Tasia M.; Truong, Huan; Lamberson, William R.; Cammack, Kristi M.; Conant, Gavin C. (2017-06-08)
Background: Grazing mammals rely on their ruminal microbial symbionts to convert plant structural biomass into metabolites they can assimilate. To explore how this complex metabolic system adapts to the host animal's diet, we inferred a microbiome-level metabolic network from shotgun metagenomic data. Results: Using comparative genomics, we then linked this microbial network to that of the host animal using a set of interface metabolites likely to be transferred to the host. When the host sheep were fed a grain-based diet, the induced microbial metabolic network showed several critical differences from those seen on the evolved forage-based diet. Grain-based (e.g., concentrate) diets tend to be dominated by a smaller set of reactions that employ metabolites that are nearer in network space to the host's metabolism. In addition, these reactions are more central in the network and employ substrates with shorter carbon backbones. Despite this apparent lower complexity, the concentrate-associated metabolic networks are actually more dissimilar from each other than are those of forage-fed animals. Because both groups of animals were initially fed on a forage diet, we propose that the diet switch drove the appearance of a number of different microbial networks, including a degenerate network characterized by an inefficient use of dietary nutrients. We used network simulations to show that such disparate networks are not an unexpected result of a diet shift. Conclusion: We argue that network approaches, particularly those that link the microbial network with that of the host, illuminate aspects of the structure of the microbiome not seen from a strictly taxonomic perspective. In particular, different diets induce predictable and significant differences in the enzymes used by the microbiome. Nonetheless, there are clearly a number of microbiomes of differing structure that show similar functional properties. Changes such as a diet shift uncover more of this type of diversity.
Dietary phosphorus effects on characteristics of mechanically separated dairy manure
Knowlton, Katharine F.; Love, Nancy G.; Parsons, C. A. (American Society of Agricultural and Biological Engineers, 2005)
One approach to reduce nutrient losses from livestock farms is to apply biological waste treatment systems such as biological nitrogen (N) removal or enhanced biological phosphorus (P) removal (EBPR) to reduce the nutrient content of land-applied waste. The EBPR process takes advantage of the ability of P-accumulating organisms (PAOs) to sequester excess P as polyphosphate granules in their cytoplasms, yielding a P-depleted liquid effluent and a P-enriched biomass. Biological N removal systems result in the conversion of organic or ammonia-N to innocuous N-2 gas. Understanding the variation in parameters such as chemical oxygen demand (COD), total and volatile suspended solids (TSS and VSS), and ammonia-N (NH3-N) is necessary to design these systems. Our objectives were to evaluate the effects of diet and manure separation on parameters important to reactor design. Waste was collected from nine cows fed a high P diet (0.47% P), a low P diet (0.32 % P), or low P with exogenous phytase plus cellulase (0.32 % P), in a replicated Latin square design (three 3 X 3 squares). Total collection of milk, urine, and feces was conducted on days 19 to 21 of each period, a mixed slurry (urine, feces, and water) was created, and slurry was separated mechanically to generate liquid effluent. Slurry contained more COD, solids, N, and P than liquid effluent, but the COD:P ratio was similar in the two wastes. The ratio of COD:N was higher in slurry than in separator effluent, but the ratio in both wastes was sufficient to support biological N removal. The P content of slurry, liquid effluent, and manure solids from cows fed low P was lower than from cows fed high P, and the COD content of effluent was higher with the low P diet. The COD:P ratio of all wastes was sufficient to support EBPR and biological N removal, but variation was observed with diet. Waste from cows fed low P had a higher COD:P ratio than that of cows fed high P, and waste from cows fed the enzyme-supplemented diet had a lower COD:N ration than that of cows fed the control diet. Dairy manure slurry and effluent will support EBPR and biological N removal. Dietary effects on parameters important to the design of advanced waste treatment systems were observed, but were not of a magnitude that would affect reactor design.
Effect of composting and soil type on dissipation of veterinary antibiotics in land-applied manures
Chen, Chaoqi; Ray, Partha P.; Knowlton, Katharine F.; Pruden, Amy; Xia, Kang (2018)
The objective of this study was to determine the fate of commonly used veterinary antibiotics in their naturally excreted form when manure-based amendments are applied to soil. Beef cattle were administered sulfamethazine, tylosin, and chlortetracycline and dairy cows were treated with pirlimycin. The resulting manure was composted for 42 d under static or turned conditions and applied at agronomic N rates to sandy, silt, and silty clay loam soils and compared with amendment with corresponding raw manures in sacrificial microcosms over a 120-day period. Antibiotic dissipation in the raw manure-amended soils followed bi-phasic first order kinetics. The first phase half-lives for sulfamethazine, tylosin, chlortetracycline, and pirlimycin ranged from 6.0 to 18, 2.7 to 3.7, 23 to 25, and 5.5–8.2 d, respectively. During the second phase, dissipation of sulfamethazine was negligible, while the half-lives for tylosin, chlortetracycline, and pirlimycin ranged from 41 to 44, 75 to 144, and 87–142 d, respectively. By contrast, antibiotic dissipation in the compost-amended soils followed single-phase first order kinetics with negligible dissipation of sulfamethazine and half-lives of tylosin and chlortetracycline ranging from 15 to 16 and 49–104 d, respectively. Pirlimycin was below the detection limit in the compost-amended soils. After incubating 120 d, antibiotics in compost-amended soils (up to 3.1 μg kg−1) were significantly lower than in manure-amended soils (up to 19 μg kg−1, p < .0001), with no major effect of soil type on the dissipation. Risk assessment suggested that composting can reduce antibiotic resistance selection potential in manure-amended soils.
Effect of Dietary Fish Oil on Mammary Gland Development and Milk Production of Holstein Cow
Barfourooshi, Hoda Javaheri; Towhidi, Armin; Sadeghipanah, Hassan; Zhandi, Mehdi; Zeinoaldini, Saeed; Dirandeh, Essa; Akers, Robert Michael (2018-10)
The aim of this study was to evaluate the effect of feeding oil supplement on mammary gland development and milk production responses in Holstein cows. Ten multi pa rolls Holstein cows (42.2 +/- 9.2 d before calving, 3.25 +/- 0.25 body condition score, and 620 +/- 35 kg body weight) were randomly assigned to treatments. Treatments were a diet with oil added as palm oil (PO; n=5), or fish oil (FO; n=5) given to cows until 63 d in milk. Milk yield was recorded daily, milk composition (fat, protein, lactose, total solid and somatic cell count) was measured weekly and fatty acid profiles of milk fat were determined at first and last week of the experiment. Samples of mammary tissue were obtained at 7 and 63 d in milk by biopsy gun. Tissue slides were analyzed by Image .1 software. Results showed that fish oil supplemented diet compared to the palm oil supplemented diet increased milk production after 6 weeks of lactation (P<0.05), content of polyunsaturated fatty acids milk fat (P<0.05) and docosahexaenoic acid (P<0.01). Moreover, n-6:n-3 ratio was decreased by fish oil supplement (P<0.05). Histological studies showed that FO increased the relative percentage of tissue area occupied by epithelial cells as well as a number of total alveoli in each microscopic field (P<0.05). Data suggested that feeding fish oil during the dry period and early lactation could improve development and function of the mammary gland in the dairy cow.
Effect of drought stress on in vitro neutral detergent fiber digestibility of corn for silage
Ferreira, G.; Martin, L. L.; Teets, C. L.; Corl, Benjamin A.; Hines, S. L.; Shewmaker, G. E.; De Haro-Marti, M. E.; Chahine, M. (2021-03)
The objective of this study was to determine the effect of drought stress on neutral detergent fiber (NDF) and lignin (LIG) concentrations and on in vitro dry matter digestibility (IVDMD) and in vitro neutral detergent fiber digestibility (IVNDFD) of leaf blades and stem internodes of corn for silage. Eight plots were blocked (i.e., 4 blocks) and randomly subjected to a watered (W) or non watered (NW) treatment. Within each block, plots were split into 7 sub-plots, to which 1 of 7 corn hybrids were randomly assigned. Before planting, all plots were irrigated with 150 mm of water to ensure a consistent emergence of corn seedlings. After this pre-planting irrigation, NW plots were not irrigated ever again. After planting, W plots were irrigated with 225 and 360 mm of water pre-tasseling and post-tasseling, respectively. Stem internodes and leaf blades from the second phytomer below (LOWER) and the second phytomer above (UPPER) the ear insertion were collected to determine tissue composition and digestibility. Drought stress increased the concentration of NDF in both leaf blades (628 vs. 613 mg NDF/g DM) and stem internodes (625 vs. 572 mg NDF/g DM). Drought stress decreased IVDMD in stem internodes (0.575 vs. 0.525 IVDMD) but had no effect on IVDMD of leaf blades (0.561 IVDMD). Similarly, drought stress decreased IVNDFD in stem internodes (0.422 vs. 0.391 IVNDFD) but had no effect on IVNDFD of leaf blades (0.536 IVNDFD). Drought stress increased the concentration of lignin in the cell wall of leaf blades (161 vs. 141 mg/g CW) but had no effect on stem internodes (266 mg/g CW). Under the conditions of this study, water supply had a minimal effect on lignin concentration in the cell wall and did not increase the in vitro digestibility of fiber in corn for silage. The latter observation is contrary to the general industry belief that water stress increases fiber digestibility in forages.
Effect of planting density on nutritional quality of green-chopped corn for silage
Ferreira, Gonzalo; Alfonso, Mauro; Depino, Sebastian; Alessandri, Esteban (American Dairy Science Association, 2014-09)
The objective of this on-farm study was to determine the effect of corn planting density on the nutritional quality of whole-plant corn for silage. This study was performed in a commercial 1,900-cow dairy farm located in Piedritas (Buenos Aires, Argentina). Two commercial hybrids (A and B) were planted in experimental plots within a cornfield destined for corn silage. Hybrids were sown at a theoretical seeding rate of 60,000, 70,000, 80,000, and 90,000 seeds/ha in 4 replicates per hybrid. Plots were eight 50-m-long rows separated by 52 cm. Corn was planted with a no-till seeder equipped with a pneumatic dosing machine. Ten plants within each plot were cut by hand at 15 cm above ground. Whole plants were chopped, weighed, mixed thoroughly, and frozen until analysis. Nutritional composition was determined by near-infrared reflectance spectroscopy. Harvesting occurred at one-quarter milk-line [31.4% dry matter (DM)] and one-half milk-line (34.5% DM) stages of maturity for hybrids B and A, respectively. No interactions between hybrid and planting density were observed for any of the variables of interest. Planting density did not affect either plant DM weight or DM, crude protein, neutral detergent fiber, acid detergent fiber, or starch concentrations of whole-plant corn. Dry matter yield was significantly increased at higher planting densities. The similar per-plant biomass and nutritional quality among different densities can be explained by the abundant precipitation observed during this growing season (719 mm since the beginning of fallow until harvest). In conclusion, greater yields of silage can be obtained by increasing corn planting density without affecting its nutritional composition, although the effect of planting density with limiting resources (e.g., precipitation) still needs to be elucidated.
Effects of dietary cis 9, trans 11-18 : 2, trans 10, cis 12-18 : 2 or vaccenic acid (trans 11-18 : 1) during lactation on body composition, tissue fatty acid profiles, and litter growth in mice
Loor, J. J.; Lin, X. B.; Herbein, J. H. (Cambridge University Press, 2003-12)
Cis 9, trans 11 (c9, t11)-18:2 and trans 10, cis 12 (t10, c12)-18:2 are the major conjugated linoleic acid (CLA) isomers in dietary supplements which reduce milk fat content in nursing women. The present study evaluated the effects of each CLA isomer or vaccenic acid on body composition and tissue fatty acids during lactation in mice. Dams were fed 30 g rapeseed oil (control)/kg diet or 20 g control plus 10 g 18: 0, trans 11-18: 1 (t11-18 : 1), c 9, t1 1-18: 2, or t10, c12-18: 2. Dietary t10, c12-18: 2 reduced food intake by 18 % and carcass fat weight of the dams by 49 % compared with the other treatments. Milk fat percentage ranked by treatment was 18: 0 > t1 1-18: 1 = c 9, t11-18:2 > t10, c12-18:2. The sum of saturated 12:0 to 16:0 in milk fat was lower when c9, t11-18:2 was fed compared with the control, 18:0, or t11-18: 1 treatments. Dietary t10, c12-18:2 caused further reductions in milk fat 12:0 to 16:0. The proportion of CLA isomers was 3-fold greater in milk fat than in the carcasses of the dams. The pups nursing from the dams fed t10, c12-18:2 had the lowest body weights and carcass fat, protein, and ash contents. Nursing from the dams fed c9, t1 l-18:2 also resulted in lower carcass fat compared with the 18:0 or t1 l-18 : 1 treatments. The ratios of cis 9-16: 1:16:0 or cis 9-18: 1:18:0, proxies for Delta(9)-desaturase activity, were markedly lower in the carcasses of the dams and pups fed t10, c12-18: 2. The ratio of 20: 4n-6:18: 2n-6, a proxy for Delta(6)- and Delta(5)-desaturase and elongase activity, in the liver of the dams and pups fed t10, c12-18: 2 also was lower. Dietary t1 l-18 : 1 enhanced the content of c9, t1 l-18 : 2 in milk fat and carcasses. As in previous studies, the reduction in food intake by t10, c12-18: 2 could not entirely account for the marked decrease in carcass fat content and milk fat concentration. T10, c12-18: 2 probably had a negative effect on Delta(9)-desaturase and mammary de novo fatty acid synthesis. Although these effects need to be confirmed in lactating women, the results suggest that the consumption of supplements containing t10, c12-18: 2 should be avoided during the nursing period.
The effects of dietary protein content and manure handling technique on ammonia emissions during short-term storage of dairy cow manure
Sparks, J. A.; Ogejo, Jactone Arogo; Cyriac, J.; Hanigan, Mark D.; Knowlton, Katharine F.; Gay, S. W.; Marr, Linsey C. (American Society of Agricultural and Biological Engineers, 2011)
An improved understanding of the potential for dietary protein manipulation to reduce ammonia emissions from dairy farms during various stages of manure handling is needed for both modeling and policy-making efforts. The objective of this study was to assess the effects of dietary protein manipulation on ammonia emissions from relatively freshly voided dairy cow manure in three types of removal systems: scraped manure removal systems, flushed manure removal systems, and flushed manure removal systems with a solids separator. Emissions were measured using a dynamic flux chamber for 12 h or more. Ammonia fluxes and emission factors per mass of manure were not affected by dietary protein content because fluxes depended mainly on total ammoniacal nitrogen (TAN) concentration, which did not vary with diet. However, emissions on a per-cow basis were 12% lower with the diet containing 15.0% crude protein as compared to the one with 17.8% (a change in crude protein of 16%) due to reduced urine output. The largest absolute impact of dietary protein manipulation would be with separated liquids because their emission factor was approximately four times higher than for the other types of manure. While dietary protein manipulation can reduce ammonia emissions from manure during long-term storage, its effectiveness in the hours immediately after manure is excreted is limited because emissions are more sensitive to other factors, including temperature and extent of mixing of the manure, that vary widely under real operating conditions on a farm.
Estimation of additive, dominance and epistatic variance components using finite locus models implemented with a single-site Gibbs and a descent graph sampler
Du, F. X.; Hoeschele, Ina (Cambridge University Press, 2000-10)
In a previous contribution, we implemented a finite locus model (FLM) for estimating additive and dominance genetic variances via a Bayesian method and a single-site Gibbs sampler. We observed a dependency of dominance variance estimates on locus number in the analysis FLM. Here, we extended the FLM to include two-locus epistasis and implemented the analysis with two genotype samplers (Gibbs and descent graph) and three different priors for genetic effects (uniform and variable across loci, uniform and constant across loci, and normal). Phenotypic data were simulated for two pedigrees with 6300 and 12300 individuals in closed populations, using several different, non-additive genetic models. Replications of these data were analysed with FLMs differing in the number of loci. Simulation results indicate that the dependency of non-additive genetic variance estimates on locus number persisted in all implementation strategies we investigated. However, this dependency was considerably diminished with normal priors for genetic effects as compared with uniform priors (constant or variable across loci). Descent graph sampling of genotypes modestly improved variance components estimation compared with Gibbs sampling. Moreover, a larger pedigree produced considerably better variance components estimation, suggesting this dependency might originate from data insufficiency. As the FLM represents an appealing alternative to the infinitesimal model for genetic parameter estimation and for inclusion of polygenic background variation in QTL mapping analyses. further improvements are warranted and might be achieved via improvement of the sampler or treatment of the number of loci as an unknown.
Evaluating the relationship between fecal egg count, FAMACHA score, and weight in dewormed and non-dewormed Katahdin rams during a parasite challenge
Galyon, Hailey R.; Zajac, Anne M.; Wright, D. Lee; Greiner, Scott P.; Bradford, Heather L. (Oxford University Press, 2020-10-01)
The objective of this study was to evaluate and to estimate the relationship between fecal egg counts (FECs) and FAMACHA score and the body weight of growing Katahdin rams during a parasite challenge. One of the largest factors negatively influencing reproduction and economics in the sheep industry is gastrointestinal nematode (GIN) parasites. Due to anthelmintic resistance of these parasites, animals are selected for parasite resistance using FEC and FAMACHA scores. Data were used from the Virginia Tech Southwest Agricultural Research and Extension Center Ram Test in Glade Spring, VA, from the year 2012 to 2018 in which animals were tested in 14-d intervals for 70 d. Mixed models for repeated weight measurements were made from backward stepwise selection to evaluate the relationships between weight and GIN FEC. A total of 576 animals within 23 contemporary groups derived from test year and pasture group were analyzed. Ram, contemporary group, and consignor were considered random effects, and fixed effects were birth type, test day, age, age squared, starting weight, FEC, and FAMACHA score. Pairwise contrasts were used in the statistical analysis of parameters and their interactions. Weight and age were found to have a quadratic relationship. Increased FEC was associated with weight loss at a rate of 0.00030 kg/FEC (P < 0.0001). Animals dewormed at any point during the trial weighed less than those that were not and increased with test day to a maximum difference of 4.66 kg (P < 0.001). FAMACHA score was found to be significant (P < 0.05), but a direct relationship with weight was not conclusive. Overall, rams with severe enough parasite load to require deworming had lesser weights, which could impact the profitability of sheep production and reinforced the need to select animals that had greater innate parasite resistance.

Browse

Browsing School of Animal Sciences by Department "Dairy Science"

Results Per Page

Sort Options