VTechWorks Repository :: Browsing by Author "McGilliard, Michael L."

Browsing by Author "McGilliard, Michael L."

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Alterations in Lipid Metabolism in Mouse Tissues and Hepatic Cell Lines in Response to the Trans10,Cis12-18:2 Isomer of Conjugated Linoleic Acid
Viswanadha, Srikant (Virginia Tech, 2003-07-15)
Conjugated linoleic acid (CLA) reduces adipose mass in several species. Studies were conducted to determine: 1) the effect of dietary trans10,cis12-CLA on growth, tissue fatty acid profile, mRNA expression for stearoyl-CoA desaturase (SCD) in adipose and liver, and mRNA expression for fatty acid synthase (FAS) in adipose of mice, 2) the effect of a dietary combination of trans-vaccenic acid (TVA) and trans10,cis12-CLA on delta9- desaturation, and 3) the effect of cis9,trans11-CLA, trans10,cis12-CLA, and carnitine palmitoyltransferase-1 (CPT-1) inhibitors on expression of mRNA for CPT-1 and fatty acid profile in mouse hepatocytes (AML-12) and human hepatoma cells (HepG2). In the first study, male or female mice were fed diets containing 0, 0.15%, or 0.30% trans10,cis12-CLA for 6 wk. Epididymal adipose weights (males) and inguinal adipose weights (females) decreased by 81% and 52%, respectively, in response to 0.30% trans10,cis12-CLA. Dry carcass weights decreased from 4.75 g for the control to 3.62 g for mice fed 0.30% trans10,cis12-CLA and the decrease was due to a reduction in ether extract. Liver weights increased linearly from 0.55 g (control) to 0.65 g (0.30% trans10,cis12-CLA). Dietary trans10,cis12-CLA (0.30%) reduced FAS and SCD mRNA in adipose by 60 and 30 % respectively, compared with the control, suggesting reduced lipogenesis and desaturation might be primary factors responsible for reducing body fat. In the second study, adult male or female mice were fed diets containing 0.40% TVA in combination with 0, 0.15, or 0.30% trans10,cis12-CLA for 10 d. Both TVA and trans10,cis12-CLA were incorporated into plasma, liver, adipose, muscle, and bone lipids proportional to their concentrations in the diets. Desaturation ratios were not affected in adipose, liver, and bone. However, ratios of 16:0 to 16:1 and 18:0 to 18:1 increased from 0.81 to 0.86 and 0.15 to 0.19 respectively, in response to dietary trans10,cis12-CLA (0.30%), suggesting inhibition of delta9 desaturation in muscle. In the third study, AML-12 or HepG2 cells were incubated with control media or media containing 15 uM etomoxir (ETM), 30 uM ETM, 15 uM hemipalmitoylcarnitinium (HPC), 30 uM HPC, 100 uM cis9,trans11-CLA, or 100 uM trans10,cis12-CLA for 24 h. Half the cells were harvested for analysis of fatty acids, mRNA for CPT-1, and cholesterol after 24 h. The remaining cells were incubated for an additional 24 h in control medium. Incorporation (% of total fatty acids) of trans10,cis12-CLA was greater than cis9,trans11-CLA in AML-12 (34 vs 23.6) and HepG2 (28 vs 18) cells. Cells incubated with trans10,cis12-CLA had higher ratios of 16:0 to 16:1, 18:0 to 18:1, and 18:2n6 to 20:4n-6, suggesting inhibition of delta9, delta5 , and delta6 desaturation. Cis9,trans11-CLA also reduced ratio of 18:2n-6 to 20:4n-6 in both cell lines. Trans10,cis12-CLA increased mRNA for CPT-1 in both cell lines compared with the control, suggesting enhanced oxidation of fatty acids. In addition, trans10,cis12-CLA caused a 4-fold and 5-fold increase in free cholesterol content of AML-12 and HepG2 cells, respectively. Overall, results demonstrated that trans10,cis12-CLA modulated lipid metabolism in tissues in vivo and altered fatty acid metabolism, cholesterol synthesis, and CPT-1 mRNA in hepatic cell lines in vitro.
A Case Study Assessment of the Feasibility of Blended Training for Agricultural Lenders
Morris, Alicia M. (Virginia Tech, 2004-03-26)
In a globally competitive economic environment, the paradigms of traditional training will be challenged as organizations and academic institutions find cost-efficient systems to educate their clientele groups. Farm Credit of the Virginias (FCV), a one billion dollar agricultural lending institution, commissioned the study team to enhance a traditional training program in marketing and credit to be an Internet-based online educational experience. More specifically, they wanted to know if trainees, staff and interns could accelerate their learning experience in a cost-efficient manner. The study was field tested on agricultural finance and marketing classes at Virginia Tech, as well as a group of trainees, interns and existing staff at FCV. Results indicate a breakeven number of 31 trainees for the FCV online program to be cost effective versus traditional face-to-face methods. Adult trainees reduced the amount of time to become productive employees from one year to six months. Participants spent less than ten percent of their time on the job in online training. Technology, flexibility of time and location, and accelerated learning through mentorship and on-job applications were definite benefits that led to an improved educational experience. It is recommended that a concept of blended education utilizing a combination of online and traditional face-to-face components delivers the superior training experience from an economic productivity and comprehension standpoint, both in adult and academic education.
Characteristics of progeny test herds and their effects on the genetic evaluation of young sires
Vierhout, Crystal N. (Virginia Tech, 1998-02-06)
Our purpose was to examine characteristics of progeny test herds and their effects on the genetic evaluation of young sires. Data for a study of response to pedigree selection by stud were evaluated from 6238 Holstein sires in four USDA animal model evaluations from January 1995 to February 1997. When data were restricted to the nine major semen producing organizations, a common intercept and slope for prediction of daughter yield deviation from pedigree merit were appropriate for milk but R2 was low at 0.14. We detected no important differences in response to pedigree selection among progeny testing methods used by major semen producing organizations. Data for a study of specific progeny test herds were 4154 Holstein progeny test herds from two AI studs and 6361 remaining herds from two states. We grouped herds into four categories, 21st Century Genetics and Genex progeny test herds, other Minnesota herds and other New York herds. Herds were described by DHI profile and average cow evaluation data. Cows with extreme yield deviations (± 3 herd standard deviations) were identified, as were daughters of progeny test bulls with extreme daughter performance relative to pedigree merit of the bull. 21st Century Genetics and Genex appear to have chosen the larger, genetically superior and better managed herds from within their regions in which to conduct their progeny testing. We were not able to predict if a bull was going to exceed or fail to meet pedigree prediction by characteristics of the progeny test herds in which he was sampled.
Development of an expert system for the evaluation of reproductive performance and management of Virginia dairy farms
Domecq, Joseph John (Virginia Tech, 1990-08-05)
An expert system for dairy herd reproductive management for microcomputer was developed using an expert system shell and Turbo Pascal. A dairy extension reproductive specialist provided information for the system and empirical support was provided by research. The expert system initially examines days open, days to first insemination, percent of possible estruses observed, and number of breedings per conception to determine whether a problem exists. Interpretations ranging from “excellent” to “severe” were established for each parameter. “Excellent” and “adequate” interpretations correspond to a 12 to 13 mo calving interval. The system then selects for evaluation one of three areas that influences days open; days to first insemination, efficiency of detection of estrus, or conception percentage. Once an area has been selected for further evaluation, the expert system utilizes information from the user and from DHIA reproductive management reports developed by the Dairy Records Processing Center in Raleigh, NC. The reproductive reports are captured in a computer file and read by the expert system to identify problems of conception categorized by production, parity, service, days in milk, breed, and service sire. In addition, questions are asked by the expert system to isolate problems in data accuracy, semen handling, AI technique, detection of estrus, signs of estrus, and other management areas. Recommendations and suggestions are given. The expert system was designed to be used by extension personnel who may not have extensive knowledge of computers or reproductive management. The compiled program runs on an IBM compatible personal computer with 640K memory. Ten Virginia DHIA herds with conception problems were evaluated by the expert system and the extension specialist. Of 100 potential problem areas, the expert system and extension specialist identified 47, agreeing on 85% of them. Most discrepancies resulted from the expert applying a more restrictive standard when values were close to a preselected threshold.
Development of mouse morulae after encapsulation in alginate microgels or poly-l-lysine microcapsule
Krentz, Kathleen J. (Virginia Tech, 1991-07-16)
Three experiments were conducted to evaluate in vitro and in vivo development of zona pellucid a-intact (ZPI) and zona pellucida-free (ZPF) mouse embryos after encapsulation in either 2% sodium alginate or 0.1% poly-L-Iysine (PLL). In Experiment 1, rate of development of ZPI embryos (n = 150) from morulae to hatched blastocysts was measured after encapsulation in alginate or PLL and as unencapsulated controls. Following encapsulation, developmental stages were recorded every 24 h for 120 h. Percentage of encapsulated embryos completely hatched from the zona pellucid a were not different from each other but were lower than unencapsulated controls at 48, 72, 96 and 120 h. Development of ZPI and ZPF mouse embryos after encapsulation in either alginate or PLL was examined in Experiment 2. Developmental stages and diameters were recorded every 24 h for 72 h. At 72 h, embryos were stained and fixed on slides to examine nuclei. Percentage of ZPI embryos developing to expanded blastocysts, their diameters and nuclear counts were not different from each other or from ZPF embryos. Percentage of ZPI embryos initiating hatching or completely hatched from the zona pellucida, their diameters and nuclear cell numbers were also similar. In the final experiment, ZPI mouse morulae were unencapsulated or encapsulated in either alginate or PLL and transferred into recipients to examine in vivo development. Recipients were allowed to develop fetuses to term. Recipients receiving encapsulated embryos failed to deliver pups. However, five of six recipients of unencapsulated embryos (n = 71) delivered a total of 16 live pups. Additional transfers were performed to examine viable fetuses and resorption sites on day 10 of gestation. Pregnancy rates, diagnosed by the presence of via bIe fetuses or resorption sites, were similar for all treatments: unencapsulated (71.4%), a1ginate (87.5%) and PLL (87.5%). However, the total number of viable fetuses present was higher for unencapsulated embryos (42.1 %) when compared to embryos in alginate microgels (17%) and embryos in PLL microcapsules (14.60/0). Additionally, recipients of alginate and PLL encapsulated embryos had more resorption sites (4 0/0 and 13.4%) when compared to recipients of unencapsulated embryos (0%). These investigations demonstrated that development of encapsulated ZPI mouse morulae is impaired at the hatched blastocyst stage; however, encapsulated ZPI and ZPF mouse morulae develop similarly in size and nuclear counts. In vivo development of ZPI morulae was also impaired due to an asynchronous condition between the uterine environment and the developing embryos.
Dry matter intake prediction of Holstein heifers
Hubbert, Charles J. (Virginia Tech, 1991-07-17)
Data sets from six locations containing 631 dairy heifers and 5409 observations of individual dry matter intake (DMI) were used to develop an equation to predict DMI. Data were contributed by Pennsylvania State University, University of New Hampshire, Purina Mills, Kansas State University, University of Minnesota, and Virginia Tech. Objectives varied by location and trials within locations but all contained DMI (kg/d), BW (kg), age (wk), DM, and CP, and ADF percentages of ration DM. Daily gains (g) were calculated from consecutive BW. Season was expressed as sine wave of Julian day plus 60 d times Ï divided into 180. Average daily temperature, humidity, and wind data were collected from Minnesota and Virginia and analyzed with BW to determine their effect on DMI. Sire PTA milk, protein, and fat of heifers were recorded from all sources to determine the relationship of genetics with DMI. Diet measurements (DM, CP, and ADF percent of ration DM) were analyzed with BW to determine their impact on DMI. Two equations were developed using backwards elimination techniques. The first equation was: DMI = -12.63 + .0587(BW) - .0000264(BW2) - .000 12(BWxDM) - .000477(BWxADF) + .292(DM) - .00103(DM2) - .413(CP) + .01349(CP2) + .181(ADF) - .0025(DMxCP) - .00269(DMxADF) + .00509(CPxADF) with an R2 of .90. Because body weight and diet variables were highly correlated, a smaller model could be created with one diet variable. A smaller model would also be more practical to use if accuracy was not lost. Body weight and ADF were used for second model: DMI = -1.71 + .0429(BW) - .0000246(BW2) - .00023(BWxADF) + .032(ADF) - .00068(ADF2) with an R 2 of .87. Previous DMI prediction equations from Virginia Tech were validated using all data from other locations and had R2 of .90 and .84 with this data set. Body weight raised to the .53 power most accurately described the relationship of DMI and BW. Temperature and DMI had a quadratic relationship. Higher DMI were observed at extreme temperatures between -10 to 27° C. Humidity and temperature x humidity accounted for more variation of OMI than season and other environmental measures, but were not included in the small model due to availability of these measurements and they did not change OMI by .1 kg/SO. Sire PTA milk by groups showed differences among heifer groups although no trends were found. Dry matter percent and CP percent had linear and quadratic relationships with OMI. Maximum OMI plateaued between 75 and 950/0 OM and occurred at extreme percentages for CP between 9 and 27%. Acid detergent fiber percent had a negative linear relationship with OMI between 7 and 45%.
The effect of crop yield and feed price variability on profitability of dairy farming in Virginia: a target MOTAD approach
Johnson, Christian J. (Virginia Tech, 1991-02-05)
Dairy farming in Virginia could be more profitable if price and yield risks affecting the cost and availability of feed inputs such as corngrain, corn silage, alfalfa and ryelage are reduced. Price and yield risk facing dairy farmers in Virginia can be reduced through a marketing strategy like hedging and government commodity program participation. The overall objective of this study is to evaluate how the variability of price and yields of particular feed crops affect the variability of expected returns in dairy farming. Specific objectives include: 1) to evaluate the relationship between feed production risk and the level and variability of net returns for a representative dairy farm in Virginia; 2) to evaluate the relationship between price risks of purchased feed inputs and the variability of net returns; 3) to draw implications from the results that can be used to help dairy farmers better manage feed production risk. To accomplish these objectives, the target MOTAD risk analysis technique is used. The empirical model is developed in four steps. First, the model activities such as milking and feeding of cows, heifer and calf activities, crop production, harvesting, labor, and buying and selling activities were created. Second, variable yields based on probability elicitation from dairy farmers were generated. Third, variable prices based on commodity options were generated; and fourth a target income constraint was derived. Results from the analysis indicated that the target income constraint was exceeded in every state of nature for the representative farm resulting in an efficiency frontier of a single point. Increasing the assumed debt-asset ratio and annual debt service requirement, resulted in a risk-return tradeoff with lower levels of risk (measured as mean deviation below target or MDBT) being obtained at the expense of lower levels of expected returns. At a higher debt asset-ratio, when the mean deviation below target (MDBT) was varied over a range of values, the quantity of crops harvested also varied. The average harvested acres of alfalfa and corn silage increased as the MDBT increased while the harvested acres of corn grain and ryelage decreased. Alfalfa harvest is increased because less forage in terms of ryelage is harvested and the average quantity of corn grain decreases as the MDBT increases because more com silage is grown in place of the costlier but less risky ryelage. The results show that hedging and participation in the government feed grain program could lead to effective risk reduction and increases in expected returns for the dairy farmer. Government program participation increased expected returns at all debt-asset ratios. Both government programs and hedging reduced risks at higher debt-asset ratios. Government program participation led to larger gains in expected returns as the availability of land increased.
Effect of early grain feeding of steers on postabsorptive capacity to utilize acetate and glucose
Wettathperuma Arachchige, Deepthi Nayananjalie (Virginia Tech, 2012-12-12)
The aims of the first study were to determine the effects of early weaning followed by a period of high-grain feeding on signaling protein phosphorylation in muscle and on acetate clearance in growing steers. Twelve Angus X Simmental steers were used in the study. Six steers were weaned early (EW) and fed a high-gain diet for 148 d and the remainder were weaned at the normal age (NW). Longissimus muscle tissue biopsies were collected to determine total and phosphorylated forms of AMP kinase and downstream proteins of the mTOR signaling pathway. Of the 12, 8 steers were used to assess acetate clearance at different age points. During early grain feeding, phosphorylated:total ratios of rpS6 and S6K1 were greater in EW steers and they had lower acetate clearance rates and greater synthesis rates. The objectives of second study were to assess the effects of early grain feeding on acetate and glucose turnover rates, palmitate synthesis, and on acetate and glucose preference by subcutaneous, intramuscular and visceral adipose tissues in finishing steers. Sixteen Angus x Simmental steers were infused continuously with [2H3] acetate (n = 8) or [U-13C6] glucose (n = 8), over a 12 h period immediately prior to harvest. Plasma acetate and glucose enrichment, and palmitate enrichment in different adipose tissue locations were determined. There were no treatment effects on acetate or glucose turnover rates or palmitate fractional synthesis rates (FSR). Acetate turnover and palmitate FSR from acetate were greater than the corresponding rates from glucose. There were no differences in preference for acetate or glucose among the fat depots. In conclusion, phosphorylation ratios of signaling proteins were not affected treatment. Acetate clearance increased when steers were heavier and older. Thus older calves are able to clear more acetate per unit of time and body mass than younger calves reflective of an enhanced ability to utilize the substrate. There were no differences in preference for acetate and glucose among the major fat depots. Thus diets leading to high glucose supply will not preferentially direct energy storage to intramuscular stores.
Effect of energy and undegraded intake protein on growth and feed efficiency of growing Holstein heifers
Bethard, Greg L. (Virginia Tech, 1994-09-30)
Two trials using 32 heifers each evaluated response to undegraded intake protein (UIP) (30 or SO% CP), energy (supporting .S9 or .91 kg ADG), and source of UIP (blood meal or combination protein supplement). Trial one was a 2x2 factorial, with two levels of energy and UIP. High UIP was achieved with blood meal supplementation. From 6-13 mo of age (phase I), high energy increased ADG and DMI, and high UIP decreased DMI. DM efficiencies (kg DMIlkg BW gain) improved with high energy and high UIP, and roN efficiencies (kg IDN/kg BW gain) improved with high UIP. From 13 mo until calving (phase n), heifers were housed together and fed a common diet. Low energy, high UIP treatment had the highest ADG (1.01 kg/day) for phase I, but the lowest for phase n (.33 kg/day), and low energy, low UIP treatment had the lowest ADG (.62 kg/day) for phase I, but the highest for phase n (.S3 kg/day). Overall ADG from 6 mo until calving averaged .S9 kg/day, and was not affected by energy or UIP. In trial 2, two levels of energy and two sources ofUIP were compared, resulting in four treatments: low energy, high UIP with combination protein supplement; low energy, high UIP with blood meal; low energy, low VIP with soybean meal; and high energy, low UIP with soybean meal. Combination protein supplement contained blood meal, com gluten meal, and fish meal. Trial was 300 days long, and began at 6.5 mo. of age. Dry matter intake and ADO were increased with high energy, but not affected by VIP. Overall DM efficiency was not affected by VIP or energy level. Results of both trials indicate VIP may improve feed efficiency of growing Holstein heifers.
The Effect of Inbreeding on Lifetime Performance of Dairy Cattle
Smith, Lori A. (Virginia Tech, 1997-01-27)
Data for this study were age-adjusted linear scores on all cows scored between 1980 and 1993. Lifetime production information on these cows and their herdmates was used to calculate Relative Net Income adjusted for opportunity cost (RNIOC) for the 2,249,835 cows with an 84 month herdlife opportunity. The effect of inbreeding was analyzed using both a fixed and animal model, with little difference in results. Inbreeding depressed RNIOC by $12.69 in a fluid market and $11.53 in a manufacturing market per 1% increase in inbreeding. Addition of somatic cell information in the profit function had little effect. Heritabilities of profit functions were .16 and .14 for a fluid and manufacturing market, respectively. Animal model estimates of inbreeding depression were +.16 days, -6.7 days and -5.1 days for age at first freshening (AFF), days of productive life (DPL) and days in milk (TDIM), respectively. Inbreeding decreased first lactation mature equivalent milk, fat, and protein by 23.7 kg, .85 kg, and .76 kg, respectively and lifetime milk, fat, and protein production by 176.9 kg, 6.4 kg, 5.6 kg, respectively per 1% increase in inbreeding. Inbreeding had little effect on conformation traits. Effects of inbreeding were cumulative, exacting a larger effect on lifetime profit functions than on individual traits, when expressed as a percent of additive standard deviation. This study gives evidence that though not alarming, inbreeding has a deleterious effect on the lifetime performance of dairy cattle.
Effect of nonstructural carbohydrates and rumen undegradable protein on intake, growth, and body condition of dairy heifers
Tomlinson, Dana J. (Virginia Tech, 1990-05-12)
Effect of varying levels of neutral detergent fiber and total digestible nutrients on dry matter intake of dairy heifers
Tomlinson, Dana J. (Virginia Tech, 1988-05-12)
One hundred and eight Holstein dairy heifers were divided into two weight blocks based on beginning body weight (E = < 182 kg, light, > 270 kg, heavy). Heifers within weight blocks were randomly assigned to one of five treatments. Treatments consisted of three levels of NDF (35%, 45%, 55%) at 100% ofNRC TDN recommendation, and three levels of TDN (85%, 100%, 115 of NRC) at 45% NDF for light heifers. For heavy heifers, treatments consisted of three levels of NDF (40%, 50%, 60%) at 100% NRC TDN, and three treatments with similar levels of TDN at 50% NDF. Heifers were fed total mixed rations of corn silage, alfalfa haylage, ground orchardgrass hay, soybean meal, high moisture corn and a mineral mix formulated for 0.68 kg ADG. Mean gains (kg/d) were 1.07 and .96 for the light and heavy blocks, respectively. DMI as a percent of BWT differed across NDF levels for light heifers (3r'= 2.96, 2.56, 2.57, 2.57, and 2.87 % of BWT for the low, med., high NDF, and low, high TDN treatments, respectively). Heavy heifer DMI% did not differ (.Â¥= 2.45, 2.40, 2.24, 2.15, and 2.42 % ofBWT for low, med., and high NDF, and low, high TDN treatments, respectively). Equations to predict DMI were developed using intake information from this and a previous study. Backward stepwise regression was utilized to generate a simplified model. Model selected was: DMI (kg/d) = -5.9781 + (2.2120E-05 * BWTSQ) - (5.5527 * GAIN) + (2.7837 * GAINSQ) + (0.4668 * NDF) + (5.3930 * NDFSQ) + (0.03285 * DM) + 1 (7.7859E-03 * BWT * GAIN);11 = 514, rz = .67.
Effects of Calfhood Respiratory and Digestive Disease on Calfhood Morbidity and First Lactation Production and Survival Rates
Rossini, Katherine Lynn (Virginia Tech, 2004-06-08)
Calf health data and first lactation records for 2556 cows born in a commercial dairy herd between June 1998 and June 2001 were studied to determine the effects of calfhood disease on survival and performance. Operator-treated respiratory disease occurrences within the first year of life and digestive disease occurrences within the first 45 d of life were analyzed to determine their effects on calfhood morbidity, age at first calving, 305-d first lactation production, and mortality in first lactation. Of the 2556 records used, 2083 calves contracted respiratory or digestive disease at least once, 1254 calves had digestive disease only, 771 had respiratory disease only, and 191 calves had both diseases. Occurrence of calfhood digestive disease increased the chance of calfhood respiratory disease 2-fold. Age at first calving increased 0.53 mo with multiple occurrences of respiratory disease versus none. Calves born in the winter calved at 25.4 mo, whereas calves born in spring calved at 24.5 mo. Respiratory disease had the largest effect on calves born in the spring, resulting in 23.9 mo age at first calving for no occurrence and 25.4 mo for multiple occurrences. No significant effect of disease was detected for 305-d milk yield, fat yield, or SCC, but protein yield decreased by 0.05 kg/d with increased calf respiratory disease. Although calfhood disease had no influence on illness as a cow, disease-free calves had a 5% advantage in probability of remaining in the herd through 305-d, and an 8% advantage at 730-d compared with calves with 2 or more disease occurrences. In conclusion, calfhood occurrences of respiratory and digestive disease had a slight impact on age at first calving, depending on season of birth, and minimal impact on production performance through 305-d of first lactation. The occurrence of respiratory or digestive disease caused a decrease in survival rate from calving through 305-d in first lactation and 730 d after calving.
Effects of diet on phosphorus digestion in dairy cattle
Yang, Tzu-Hsuan (Virginia Tech, 2006-08-08)
Two studies were conducted to evaluate the effects of diet on phosphorus (P) digestion in dairy cattle. The objective of the first study was to evaluate the effects of forage and non-fiber carbohydrate (NFC) content on total P (TP) and inositol phosphates-P (IPs-P) digestion. Samples of feed, duodenal digesta and feces from a previously conducted study were analyzed for TP and IPs-P. In this study, eight lactating Holstein cows were fed diets containing either 60 or 35% forage and either 30 or 40% NFC in a 2 × 2 factorial with replicated 4 × 4 Latin square design. Dietary TP content (% DM) was 0.35, 0.36, 0.36, 0.36 and dietary IPs-P content (%DM) was 0.08, 0.13, 0.06, 0.11 for diets with forage: NFC ratio 35:30, 35:40, 60:30, and 60:40, respectively. Increasing dietary forage content decreased IPs-P and TP intake, fecal TP excretion, and total tract IPs-P digestibility (72.4 vs. 61.4%). Fecal IPs-P excretion tended to decrease as increasing forage content. Duodenal IPs-P and TP flow and apparent TP digestibility were unaffected by forage content. Increasing dietary NFC content increased IPs-P and TP intake, duodenal IPs-P flow, fecal IPs-P excretion, total tract IPs-P digestibility (61.4 vs. 72.4%), and apparent TP digestibility (32.8 vs. 41.6%). Dietary forage and NFC content affected IPs-P and TP digestion. The second study was to evaluate the effects of increasing dietary beet pulp (BP) content to replace high moisture corn (HMC) on ruminal and post-ruminal digestion of TP and IPs-P. Eight lactating Holstein cows were fed diets containing 0, 6.1, 12.1 or 24.3% BP in a replicated 4 × 4 Latin square design. Samples of rumen contents, duodenal digesta, and feces from this previously conducted study were analyzed for TP and IPs-P content. Linear and quadratic effects of BP content were analyzed using Proc Mixed of SAS. Dietary TP and IPs-P content were reduced linearly with increasing BP (0.59, 0.58, 0.57, 0.56% TP and 0.15, 0.14, 0.13, 0.11% IPs-P). Intake, ruminal content, and rumen pool size of TP decreased with increasing BP content. Digestion of TP and duodenal flow and fecal excretion of IPs-P and TP were not affected. With increasing dietary BP content, IPs-P intake was reduced, ruminal IPs-P pool size was reduced, and rumen turnover time (h) of IPs-P was increased. Apparent ruminal IPs-P digestibility (36.5, 31.8, 24.6, 13.6 %) and apparent total tract IPs-P digestibility (85.3, 82.7, 82.1, 79.1%) decreased linearly with increasing BP. Fecal excretion of IPs-P averaged 5.2 g/d. Replacing HMC with BP reduced digestion of IPs-P. The majority of IPs-P disappearance occurred post-ruminally. In conclusion, dietary BP, forage, and NFC content affected IPs-P digestion in dairy cows.
Effects of Milk Replacer Composition on Measures of Mammary Development in Holstein Heifer Calves
Daniels, Kristy M. (Virginia Tech, 2008-04-15)
This study was to evaluate effects of milk replacer (MR) composition on: mass and composition of mammary parenchyma (PAR) and fat pad (MFP), growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis gene expression, and putative mammary epithelial stem cells. The hypothesis was that diet during the pre-weaning period alters the development, persistence, or activity of populations of putative mammary epithelial stem cells, possibly through involvement of GH/IGF-I axis molecules. Twenty-four newborn heifers were fed one of four MR diets: CON (20% CP, 21% fat MR fed at 441 g DM/d), HPLF (28% CP, 20% fat MR fed at 951 g DM/d), HPHF (27% CP, 28% fat MR fed at 951 g DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1431 g DM/d). Animals were harvested on d 65 of life and mammary tissue was subjected to biochemical, molecular, and histological examination. By design, the effects of diet were evaluated at a common chronological age, but not necessarily at the same physiological age (body weight). Results from heifers reared on CON were compared to the average results from heifers reared on the other 3 diets. The second comparison evaluated the effect of increased fat in MR when protein content and intake were the same. The final comparison evaluated the effect of increased intake of a high-fat, high-protein MR. Neither diet composition nor nutrient intake in pre-weaned heifers affected PAR weight, PAR composition, GH/IGF-I axis gene expression, or putative mammary epithelial stem cell abundance when assessed at a common chronological age. Changes in MFP size and composition were observed, but no diet effect on GH/IGF-I axis gene expression in MFP was observed. This suggests nutrition is not critical for regulating the expression of local GH/IGF-I axis components or stem cell populations in the developing heifer mammary gland.
Effects of Prepartum Energy and Protein Density on Productivity and Influence of Dietary Iron on Copper Status of Holstein and Jersey Cattle
French, Patrick Douglas (Virginia Tech, 1999-08-16)
In experiment 1, 24 multiparous Holsteins and 24 multiparous Jerseys were assigned at random to one of four diets containing either 1.25, 1.38, 1.50, or 1.63 Mcal NEL/kg DM to determine the effects of prepartum energy density on productivity. Cows were assigned to diets 28 d before expected calving and received a similar diet 0 to 60 d postpartum. Prepartum DMI increased linearly as dietary energy density increased. Non-esterified fatty acids did not differ for energy density and were greater for Holsteins. Milk and 4% FCM increased linearly as dietary energy density increased, although postpartum DMI was quadratic for energy density. Fat yield increased linearly with energy density and protein yield did not differ. Increasing prepartum diet energy density increased yield of milk and 4% FCM. In experiment 2, 26 multiparous and 18 primiparous Jerseys were assigned to one of two CP and rumen undegradable protein (RUP) concentrations 30 d before expected calving to determine the effects of CP and RUP on productivity. Cows received a similar diet 0 to 60 d postpartum. Prepartum CP concentrations were 12 and 15% and prepartum RUP (% of CP) concentrations were 30 and 45%. Dry matter intake was not affected by CP or RUP. Milk yield and 4% FCM yield did not differ for CP or RUP. In addition, milk protein concentration and yield were similar for CP and RUP. Positive calculated metabolizable protein balance for 12% CP and 30% RUP concentrations may have precluded responses to increasing prepartum CP and RUP. In experiment 3, 12 Holstein and 12 Jersey multiparous cows were assigned at random to diets containing 0 or 500 mg FeCO3/kg DM to investigate the effects of dietary Fe on milk production and Cu status. Hepatic Cu did not differ for breeds or Fe supplementation. For Jerseys, hepatic Fe was greater for cows receiving supplemental Fe. Hepatic Zn was similar for breed and Fe supplementation. Plasma Cu was greater for Jerseys compared to Holsteins and did not differ for Fe supplementation. Plasma Fe and Zn did not differ for breeds or Fe supplementation. Iron supplementation did not affect yield of milk or 4% FCM. Dietary Fe did not affect Cu status of Holstein and Jersey cows in this experiment.
Effects of reduced dietary protein and supplemented rumen protected amino acids on the nitrogen efficiency of dairy cows
Bell, Ashley Lorraine (Virginia Tech, 2011-09-30)
Dairy cows are extremely inefficient at converting dietary nitrogen (N) to productive N. Approximately 25-30% of dietary N is used for milk protein while the remaining N is lost to the environment. According to National Research Council (NRC, 2001) recommendations, dairy cow rations are formulated in terms of metabolizable protein (MP) which often causes many amino acids (AA) to be fed in excess. A better understanding of protein and AA requirements could help to improve the nitrogen efficiency of dairy cows. The objective of this work was to examine the effects of feeding a low protein diet supplemented with rumen protected (RP) AA on production and N efficiency of dairy cows. Twenty-four Holstein and 24 Holstein x Jersey crossbred cows were used in a Youden square design consisting of 3 periods. Cows were randomly assigned to one of 8 treatments: 1) a standard diet containing 17% crude protein (+Con), 2) a 15% crude protein diet (-Con), 3) â Con plus RP methionine (+M, 16g/d), 4) â Con plus RP lysine (+K, 47g/d), 5) â Con plus RP leucine (+L, 181g/d), 6) â Con plus RP methionine and lysine (+MK), 7) â Con plus RP methionine and leucine (+ML), and 8) â Con plus RP methionine, lysine, and leucine (+MKL). Cows fed the â Con as well as the +MKL diet experienced a reduction in milk production and milk protein yield (P < 0.05). Dry matter intake decreased only for those animals on the +ML diet (P < 0.05). Milk urea N (MUN) decreased for all diets when compared to the +Con treatment (P < 0.05). In accordance with the decrease in MUN, N efficiency was numerically increased in the diets supplemented with RP AA, but this improvement was not significant. Phosphorylation of signaling proteins important for protein synthesis were also examined. Animals fed the +MK treatment increased phosphorylated and total forms of eukaryotic elongation factor 2 (eEF2) when compared to the +Con and â Con (P < 0.05), but this increase in abundance did not affect the ratio of phosphorylated to total abundance. Feeding dairy cows a low protein diet supplemented with RP AA has the ability to alleviate the loss in milk production associated with feeding a low protein diet as well as to increase nitrogen efficiency.
The Enhanced Milk Yield Effect of Early Lactation Increased Milking Frequency and Bovine Somatotropin Is Additive and Not Synergistic
Hanling, Haylee H.; McGilliard, Michael L.; Corl, Benjamin A. (MDPI, 2023-07-05)
Dairy farm profitability depends on milk yield, so the dairy industry manages cows to improve their productivity. Both bovine somatotropin (bST) and early lactation increased milking frequency (IMF) and milk yield (MY) in dairy cows. The objective of this study was to evaluate the effects of mid-lactation bST administration on milk production in established lactation when combined with the milk yield carry-over effect from early lactation IMF. Thirteen multiparous Holstein cows were milked unilaterally for 20 days in early lactation. The left udder halves were milked twice daily (2X) and the right udder halves were milked four times daily (4X). Udder halves milked 4X produced 8.60 ± 1.40 kg more than 2X on the final day of IMF treatment. Cows were then returned to 2X milking for the remainder of lactation and sampled on alternate days from 74–94 days in milk (DIM). Bovine somatotropin was administered to all cows at 80 DIM. The 4X halves continued to make 2.66 ± 0.12 kg/d more milk than 2X through 94 DIM. Fat, protein, and lactose yields were significantly greater in the 4X halves compared to the 2X from 74–94 DIM. Overall milk yield increased by 2.71 kg/d with bST administration. However, there was no significant interaction between MF and bST administration. We can infer from these data that the mechanisms by which bST and IMF in early lactation increase milk yield are complementary due to their non-synergistic nature of enhancing MY.
Essential Amino Acid Regulation of Cell Signaling and Casein Synthesis in Mammary Tissue
Arriola Apelo, Sebastian Ignacio (Virginia Tech, 2013-05-24)
Specific AA have been demonstrated to activate signaling pathways that regulate
translation initiation and to stimulate protein synthesis in mammary tissue. The
objectives of this research were to determine the response to Ile, Leu, Met, and Thr in
cellular signaling and "-S1 casein fractional synthesis rates (CFSR). An experiment was
developed as a composite design. The experiment was replicated in tissue corresponding
to 5 cows. Mammary tissue slices (0.12 ± 0.02 g) from lactating dairy cows were
incubated 4 h in treatment media enriched with 2H5 Phe. Following incubation, slices
were homogenized in lysis buffer and caseins were precipitated by acidification to pH
4.6. An aliquot of the pellet was trypsinized and 2H5 Phe enrichment in the 34-
NLLRFFVAPFPE-45 peptide of "-S1 casein was measured by MALDI TOF-MS and
used to determine CFSR (%/h). Western immunoblotting was performed to identify total
and site-specific phosphorylated mammalian target of rapamycin (mTOR, Ser2448),
eukaryotic elongation factor (eEF) 2 (Thr56), ribosomal protein (rp) S6 (Ser235/236),
and eukaryotic initiation factor (eIF) 2" (Ser51). Addition of Ile, Leu, Met, or Thr had
no effect on eIF2" phosphorylation. Isoleucine positively affected mTOR, and rpS6, and
negatively affected eEF2 phosphorylation. Leu had a similar effect on eEF2, but not on
mTOR or rpS6, and these two AA inhibited each other. Thr negatively interacted with
Ile on mTOR and rpS6, and with Leu on eEF2. Increasing concentrations of Ile, Leu,
Met, and Thr caused curvilinear increases in CFSR. The maximum response to Ile, Leu,
iii
Met, and Thr was at 71, 49, 60, and 65% of DMEM concentrations, respectively. All
maximums were above plasma AA concentrations observed in lactating cows fed to meet
NRC requirements. The CFSR estimated at those maximums were similar between AA
(3.6 ± 0.6 %/h). Individual AA effects on CFSR did not correlate with mTOR signaling.
Independent CFSR responses to individual essential AA observed in this study contradict
the single-limiting AA theory assumed in current requirement systems. The saturable
responses of CFSR to these 4 AA also demonstrate the deficiencies of a fixed postabsorptive
AA efficiency approach for determining AA requirements for milk protein
synthesis.
Evaluation of systematic breeding programs in lactating dairy cows
Jobst, Shelly Marie (Virginia Tech, 1998-11-04)
Observing cows in estrus and inseminating them at the optimal time are necessary steps for effective reproductive management of a dairy herd. However, increasing herd sizes can lead to reproductive inefficiency resulting in decreased profits on dairy herds. Synchronization of estrus, through pharmacological control, has been used to improve reproductive efficiency. Systematic breeding programs provide an organized approach for administering artificial insemination (AI) at first service. Moreover, reproductive management is based on a methodical approach for the entire herd rather than for the individual cow. Seven-hundred and thirty four Holstein cows from 16 commercial dairy herds were used to conduct this study evaluating three systematic breeding protocols; 14-d PGF2a, timed AI (TAI), and GnRH-PGF2Î±, in comparison with an untreated control group. Eight herds relied on visual observation as their primary method for detection of estrus, and 8 herds utilized the HeatWatchÂ® (DDx, Inc., Denver, CO) electronic estrus detection system. The average days to first postpartum AI were longer for untreated control cows when compared to the other breeding protocols. First AI conception rates did not differ among control, 14-d PGF2a, or GnRH-PGF2a protocols, but were higher than the TAI protocol. However, first AI pregnancy rates were higher for untreated controls versus hormonally treated cows. Estrus characteristics associated with each protocol were also evaluated and no difference was detected across treatments. An economic analysis determining cost per pregnancy for each protocol when considering drug costs, and pregnancy rates, resulted in the highest cost per pregnancy for TAI followed by GnRH-PGF2a and 14-d PGF2a. These programs should be considered as tools for convenience and efficiency of estrus detection; however, reduced labor costs from less time spent on estrus detection may be offset by the cost of the drug protocols. Cost effectiveness must be calculated on an individual herd basis when deciding whether a systematic breeding program is the appropriate choice.

Browsing by Author "McGilliard, Michael L."

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