Six lactating Holstein cows fitted with rumen cannulae and T-type cannulae in the proximal duodenum were used to measure digesta and nitrogen compounds flow to the small intestine during early and midlactation. Fish meal and soybean meal provided 54 and 56% of the protein in the diets composed of corn grain, corn silage and orchardgrass hay, and which contained 15.4 and 15.5% crude protein and 20.9 and 20.5 acid detergent fiber. Spot samples of digesta were collected from the rumen, duodenum and rectum over a period of 72 hours. Co-EDTA and ytterbium were used as liquid and particulate digesta markers to estimate flow and digestibility of nutrients. Cytosine was used as microbial marker. True organic matter digestibility in the stomachs was 48.4, 49.8, 44.9, and 53.2% for fish meal and soybean meal diets and early and midlactation respectively. Protein degradability in the stomachs were 47.2, 65.8, 56.7, and 56.2% for fish meal and soybean meal diets and early and midlactation respectively. Amino acids intake was greater for soybean meal diet but total amino acids reaching the the duodenum were similar for both diets. Valine, methionine, lysine and histidine were less degraded for fish meal but were extensively degraded in soybean meal diet. Least degraded for both diets were glycine, valine, serine, proline and histidine. The advantage of greater quantity of protein escaping ruminal degradation with fish meal supplementation was counterbalanced by less microbial synthesis in the rumen partly explaining the similar response obtained with diets especially in early lactation. / Ph. D.

The effect of selenium (Se) supplementation, by ad libitum salt-mineral mixture (SMM) and/or Se injection, on bovine immune response was evaluated in three experiments. Sixty weaned beef calves, with marginal blood Se (67 μg Se/1), were allotted to one of six Se treatment groups in a 70-day experiment. Antibody responses to lysozyme were lower in calves fed 20 ppm Se salt-mineral mixture (SMM) ad libitum as compared to calves fed 20 ppm Se SMM and injected with 0.1 mg Se + 1.0IU vitamin E/kg body weight, IM, or with calves ad libitum fed 80, 120, 160, or 200 ppm Se SMM. Blood Se on day 70 was higher in calves fed 80, 120, 160, or 200 ppm Se SMM than calves fed 20 ppm Se and injected with 0.1 mg Se + 1.0 IU vitamin E/kg of body weight, IM. An ad libitum 120 ppm Se SMM was compared to Se injection in 80 mid-gestation beef cows that were Se-deficient (50 μg Se/l blood). Supplementation with 120 ppm Se SMM increased blood Se in cows and calves to > 100 μg/l, increased IgG concentrations in colostrum, and increased IgG concentrations in serum of post-suckle calves. Calves from Se-adequate dams had higher Se concentrations in blood and higher average daily gains at 60 days than Se-deficient calves injected with Se at birth. An ad libitum 120 ppm Se SMM was compared to Se injection in 60 Se-deficient (41 μg Se/l blood) weaned beef calves in a 56-day experiment. Calves fed 120 ppm Se SMM and unsupplemented control calves had higher antibody responses to lysozyme than calves injected with 0.1 mg Se + 1.0 IU vitamin E/kg body weight. Blood Se concentrations increased in calves fed 120 ppm Se SMM, did not change in calves injected with 0.1 mg Se/kg body weight, and decreased in control calves. Se treatment did not affect IgA response in tears of calves. / Ph. D.

A series of experiments were conducted to measure the mode of action by which fishmeal exerts its effect on milk composition of dairy cows. Production Study One measured the effect of increased fishmeal intake on milk production and milk composition in dairy cattle. Milk fat percentage and yield were decreased by increased fishmeal intake. This decrease was not associated with changes in ruminal fermentation patterns. Plasma long-chain n-3 polyunsaturated fatty acids were increased with increased fishmeal intake. Mammary slices from lactating bovine mammary gland were incubated with eicosapentaenoic acid. Changes in ¹⁴C-acetate metabolism were measured. Acetate oxidation and incorporation into milk lipid were not changed by eicosapentaenoic acid. However, tissue from mammary gland of cows milked 6 to 8 h prior to slaughter had 2 fold higher activity than tissue milked 1 h before slaughter. Disappearance of dry matter, crude protein, and lipid in fish meal from undegradable bags in the rumen was measured. Dry matter and crude protein degradation of fish meal were similar to published values. Lipid escaped rapidly with greater than 70% removed by 8 h. A subsequent fish oil infusion study revealed that intraruminal fish oil treatment did not significantly alter ruminal fermentation, or change fatty acid profiles in duodenal digesta, plasma, or milk. Duodenal infusion increased plasma concentrations of n-3 fatty acids but did not affect milk lipid fatty acid composition. A second production study compared the effects of fish meal versus fish oil on milk production and composition, and changes in fatty acids in plasma and milk. Fish meal significantly increased plasma n-3 fatty acids compared to the fish oil treatment. Residual fatty acids contained in fish meal seemed to be protected from rumen degradation and probably remained intact for digestion and absorption since plasma n-3 fatty acid concentrations increased. No changes in milk yield or composition were due to the experimental treatments. Fat in fish meal and fish oil source differed significantly in their ability to alter milk composition and plasma fatty acid profiles. / Ph. D.

Cottonseed hulls (CSH), chopped orchardgrass (OG) or alfalfa (ALF) hays were added to corn silage-based rations to determine effects on dry matter intake (DMI), nitrogen balance (NB), rumen volatile fatty acids (VFA), and rumen fluid (RFD) and solids (RSD) dilution rates. DMI was highest for added fiber rations and higher for CSH than hay rations. Digestibility of DM was depressed for added fiber rations with lowest for CSH. Most favorable NB was for CSH rations. Rumen VFA were not altered by fiber additions. Highest RFD was for 0% rations and lowest for 9% rations, however CSH had greatest positive influence on RFD. RSD trend was similar to that for RFD. In Experiment II, 4 corn silage-based rations containing 9% OG, ALF, or CSH plus a Control (9% OG) were compared for effect on DMI, rumen VFA, chewing time (CT), RSD, and RFD. Ration density decreased with OG and ALF whereas CSH had no effect compared to Control. DMI was higher for CSH compared to OG and ALF. Total CT (min/d) and Roughage Value Index (CT/kg DMI) were reduced for ALF compared to OG. Total VFA were lower for added fiber rations compared to Control. Acetate:propionate (APR) and non-glucogenic (NGR) ratio were not affected by fiber additions. RFD was reduced for ALF compared to OG whereas CSH was higher than OG and ALF. Reduced RFD was associated with reduced total CT for ALF. RSD was not affected by fiber additions. Chopped OG was supplemented at 0, 9, or 18% of ration DM in a finely chopped corn silage-based ration. Analysis of covariance was performed using 18 lactating Holsteins. Ration density decreased with each increment of OG. DMI was highest for 18% OG ration. Cows on 0% showed decreased DMI whereas cows on 9 and 18% rations increased DMI from covariate period. Rumen acetate, APR and NGR increased while propionate and total VFA decreased with increasing OG. RFD and RSD increased with increasing OG supplementation. Response to 9 and 18% supplementation of OG, ALF, or CSH to corn silage-based rations appears to follow similar pattern as when all-forage rations were compared to all-concentrate rations for lactating dairy cows. A more quantitative evaluation of physical form is needed for dairy rations and feedstuffs leading to an acceptable routine evaluation procedure. / Ph. D.

The farmer that fed silage made a profit of $606.20 for the twenty-six years or had received an average profit of $23.31 each year per steer. The farmer that fed hay and straw made a profit of $298.76 for the twenty-six years or an average profit of $11.49 each year per steer. The farmer that fed stover and corn meal made a profit of $140.56 for the twenty-six years or an average profit each year of $5.40 per steer. From a survey of seventy farms and 4,380 head of cattle, we find that the average carload shipment is about three care per cattlemen in Southwest Virginia allowing twenty head to the car, this would mean sixty per year. At this rate the farmer that fed silage would have made $36,372.00. The farmer that fed hay and straw would have made $17,925.00 and the farmer that fed stover and corn meal would have made $8,433.60. The cost of silage for the twenty-six years was $412.04, for hay and straw $521.54, and for stover and corn meal $439.70. / M.S.

Two feeding trials were conducted involving diets supplemented with soybean meal, dried brewers, and wet brewers grains. The first trial involved 24 first-calf heifers averaging 82 d postpartum. After a 20 d protein depletion period in which a 9.4% CP diet was fed, cows were randomly assigned to a 2 x 3 factorial where pelleted (P) or unpelleted (UP) soybean meal supplemented corn diets to 12.2% (L), 15.4% (M), and 18.1% (H) crude protein. During depletion, milk production, dry matter intake, and yields of milk protein, fat, and solids decreased in the range of 15 to 25%. However, these all increased to pre-depletion levels after 26 d of repletion. Considering repletion response separately resulted in no significant differences between P and UP for milk production and constituents, feed intake, and plasma urea. However, using depletion to covariably adjust means resulted in P diets favoring greater milk production (P < .01) than UP as well as protein, fat, and solid yields. This response may be caused by a significant increase in feed intake for P diets. Use of a depletion period did increase precision of results but its use in practical feeding trials is controversial. Results in milk, milk protein, fat, and solid yields, and plasma urea were linear with protein level (L vs H). The second trial involved 44 multiparous cows averaging 114 d postpartum. Eight cows remained on a control (CON) diet of 11.7% CP while all others were randomly assigned in a 3 x 3 factorial in which dried (DBG) and wet brewers grains (WBG), and soybean meal (SBM) supplemented the CON to 14.8 (L), 16.3 (M), and 18.0% (H) CP. Diet composition varied in corn silage and ensiled ground-corn but alfalfa silage was constant on a dry matter basis. All diets were superior to CON in milk production and constituent yield. Brewers diets were superior to SBM for milk yield, protein, and solid yields. Part of this response may be related to superior intake for diets containing brewers and lower rumen ammonia and plasma urea. Cows receiving brewers diets have higher intakes than SBM and brewers appear to be utilized more efficiently. For mid-lactating cows an increase in milk at 18.0% CP resulted from brewers diets but not SBM. The H level resulted in a significant increase in milk yield and protein (kg) but also had the highest plasma urea and rumen ammonia level. / M.S.

Ruminant animals consuming low N-diet have been reported to have increased urea reabsorption with the Nguni being categorized as N-recycling ruminant. The enzymes associated with N-cycling are hypothesized to contribute to survival of the Nguni in harsh conditions. Enzymes responsible for such a function needed to be characterized in order to determine their effect in the functioning of the Nguni as opposed to Hereford breed. Crude enzymes from both breeds were separated from most or some contaminants by sephadex G-25, DEAE sephacel, and different affinity column chromatography. CPS and GDH were successfully purified and characterized by LC-MS/MS and further analysed by ProteinPilot™, blasted and matched >95% with those of Bos Taurus. Comparison of characterized enzymes and those which failed to ionise such as ARG, GS and GA was done using kinetics and graphs annotating specific activities. Partial purification and characterization was in part achieved. / Life & Consumer Sciences / M. Sc. (Life Sciences)

Ruminant animals consuming low N-diet have been reported to have increased urea reabsorption with the Nguni being categorized as N-recycling ruminant. The enzymes associated with N-cycling are hypothesized to contribute to survival of the Nguni in harsh conditions. Enzymes responsible for such a function needed to be characterized in order to determine their effect in the functioning of the Nguni as opposed to Hereford breed. Crude enzymes from both breeds were separated from most or some contaminants by sephadex G-25, DEAE sephacel, and different affinity column chromatography. CPS and GDH were successfully purified and characterized by LC-MS/MS and further analysed by ProteinPilot™, blasted and matched >95% with those of Bos Taurus. Comparison of characterized enzymes and those which failed to ionise such as ARG, GS and GA was done using kinetics and graphs annotating specific activities. Partial purification and characterization was in part achieved. / Life and Consumer Sciences / M. Sc. (Life Sciences)

Master of Science / Department of Agricultural Economics / Ted C. Schroeder / Glynn T. Tonsor / Cattle feeders face significant profit risk when placing cattle on feed. Risks arise from both financial and biological sources. To date, few standardized measures exist to measure current risks against historic levels, or to obtain forward looking risk estimates. Those that do exist could benefit from updates and inclusion of additional risk elements. This study measures the risk of expected profits when cattle are placed on feed. This study creates a forward-looking estimate of expected feedlot profits using futures and options market data as price forecasts. Joint probability distributions are created for prices and cattle performance variables affecting feedlot profit margins. Monte Carlo simulation techniques are then employed to generate probability distributions of expected feedlot profits. Results show cattle feeding is a risky business and cattle feeders have been placing cattle on feed facing significantly negative expected returns since June, 2010. This assessment of negative expected profits is consistent with other findings. Over the study’s 2002 to 2013 time frame, the relative risk to cattle feeding profits accounted for by feed costs has been increasing, while the relative risk levels from feeder cattle and fed cattle prices remain steady. Additionally, the probability of realized per-head profits greater than $100 has been decreasing since 2009 and the probability of realized per-head profits less than $-100 has been increasingly rapidly.

Call number: LD2668 .T4 1984 W365 / Master of Science