Bovine Somatotropin (BST) is a naturally occurring hormone in dairy cows which affects milk production levels (Chalupa and Galligan, 1988). The effects of BST have been known since the 1930's but limited supply of this hormone made any large scale commercial use impossible. Recently a low cost source of BST became available through recombinant DNA technology. This low cost availability of the hormone has led to research experiments which show that recombinant BST can significantly increase a cow's ability to produce milk (Peel and Bauman, 1987; Burton et al, 1987; Soderholm et al, 1988; De Boer et al, 1988). A number of studies have examined the firm level impacts of BST on the Canadian dairy industry. This present work will build upon these earlier studies by examining the impacts of BST at the both the firm and aggregate levels for all of the dairy producing regions in Canada. To facilitate this analysis at an aggregate level a linear programming model of the Canadian dairy industry was used. This model describes the dairy sector for each province, including the production, processing, trade and marketing subsectors, and is incorporated into the Canadian Regional Agricultural Model (CRAM), (Webber et al, 1986). Several scenarios were examined representing different government policy responses with the introduction of BST to the Canadian dairy industry. These scenarios are compared to a 1986 "base case" situation of the dairy industry. The first scenario examined represents a "no policy change" situation. Provincial quota levels, producer prices, levies and subsidies all remain unchanged and BST adoption rates are assumed for each province. In order to maintain existing milk production levels with BST a 5% reduction in the national cow herd results. This lower number of animals producing the same amount of milk as in the base case results in a 5% increase in dairy producer income at the national level. In the second scenario the impact of BST on quota values is examined. As in the first scenario all dairy policy instruments remain at 1986 base levels. The decrease in marginal costs for a producer fully adopting BST is then estimated. Using a marginal cost estimate of $32 per hi, the fall in marginal cost was nearly 6% or $2.00 per hi on average for Canada. This results in an 18% increase in what these producers can pay for quota. Using lower marginal cost estimates would result in a greatre increase in this variable and smaller quota increases. In scenario 3 some of the benefits of BST adoption are passed on to consumers. This is done by allowing production levels to expand such that the difference between farm-gate price and supply price remains the same as prior to the introduction of BST. Quota values remain at their base case level. This resulted in a 2% increase in the national supply of raw milk. In the fluid milk market the supply of standard milk increased by 2% and lowfat milk production increased by approximately 3 percent. In the industrial market cheese production increased by 6%, butter production increased by 2% and skim milk powder production fell by approximately 4 percent. In the final scenario the benefits of BST adoption are passed on to the taxpayers. This is accomplished by reducing the dairy subsidy by an amount which just offsets the cost savings in each province as a result of BST adoption. This leads to a decrease in the dairy subsidy of $80 million at the national level or approximately 30% of the 1986 subsidy payment. At the firm level, given the assumptions of this study, the main impacts of BST are a fall in marginal costs of $2 per hi and an increase in quota values of 18%. While these estimates of firm level changes resulting from BST adoption are not trivial they are much less than would be expected with earlier results of milk yield increases of over 25 to 3 5% accompanied by dry matter feed increases of only 10 to 15 percent (Bauman et al, 1985; Soderholm et al, 1988) . Given the assumed Canadian adoption rates of approximately 50% the aggregate level impacts of BST are more moderate. The national herd size falls by 5% and dairy producer incomes are increased by 5% to produce at the base case 198 6 production levels. / Land and Food Systems, Faculty of / Graduate

Previous research in bovine embryology has found that embryos cultured individually have limited ability to develop compared to their counterparts cultured in a group of other embryos. This investigation aimed to find if any of three different interventions over two experiments would increase development of individually cultured embryos to that of group cultured embryos. In the first experiment both the addition of serum/serum replacer and a co-culture with bovine granulosa cells were applied to individually cultured embryos in a 3x2 design. None of the interventions was found to be significantly different from the others, and all resulted in significantly lower development than embryos cultured as a group (avg. 4.7 +/- 1.93% individual vs. 21.7 +/- 3.76% group). However, a significant difference was found in the hatching rate between blastocysts cultured in media including cells (71.4 +/- 17.07%) and those cultured without cells (18.1 +/- 11.63%). In the second experiment, embryos were either cultured in standard droplets or microwells made at the bottom of culture droplets either in groups or individually for a 2x2 design. This experiment experienced poor development in all treatments including the group control, and none of the treatments were found to be significantly different from each other. However, the hatching rate of blastocysts cultured in multiple microwells was significantly higher than those cultured individually in droplets. To summarize, none of the treatments increased the development rate, but embryos cultured with granulosa cell co-cultures and in group microwells showed improvements in hatching rates. / Master of Science

Bovine herpesvirus-1 (BoHV-1) is a pathogen of cattle, which most commonly affects the upper respiratory tract to cause infectious bovine rhinotracheitis (IBR). It can also spread systemically to cause fatalities in calves and abortion in pregnant cattle. The virally encoded mechanisms of this systemic spread are poorly understood and therefore have been addressed by comparing isolates from the respiratory form of disease with isolates that have previously demonstrated systemic spread. A survey of 400 bovine abortions in Scotland from 2007-2009 demonstrated a BoHV-1 prevalence of 2.5%. It also demonstrated the importance of real-time PCR as a diagnostic technique when analysing samples from natural cases. The study of BoHV-1 distribution in the placenta and foetal tissue provided support for a haematogenous route of viral spread. Whole genome sequencing of 11 BoHV-1 isolates using Illumina Solexa technology was completed and added significantly to the sequencing data of BoHV-1. In terms of identifying genetic variation between isolates causing respiratory infection and those causing systemic infection, no differences were observed by SNP or phylogenetic analysis. However, there were significant differences in the extent of variation between essential and non-essential genes, which may reflect the evolution of BoHV-1. An in vivo challenge of the natural host to compare two isolates representing the respiratory and systemic forms of infection showed differences in clinical presentation, histopathological analysis, viral distribution and viral transcript expression, measured throughout the infection period. In particular, it was noted that a more severe ocular infection, rather than respiratory based infection was caused by infection with the ‘systemic’ isolate. Differences in the tropism of the virus were observed early in the infection with the ‘systemic’ isolate showing more association with the nasal mucosa than the trachea. The tonsils demonstrated different responses to the virus and differences in viral transcript expression. However, this may simply represent different stages of virus infection. Both isolates demonstrated spread to the brain at day 10 post infection. In vitro methods were used to study the differences in transcript expression in more detail. In a bovine turbinate cell infection faster replication of the respiratory isolate was observed by a significantly faster development of cytopathic effect. This was also reflected in the higher gene expression levels of the respiratory isolate in the first 12 hours of infection. More isolates were studied to investigate whether these differences were consistent, or as suggested by the sequencing, random differences between isolates. Six isolates were used to infect bovine lung slices. Differences in transcript expression were minimal between the two isolate groups. Immunofluorescence did not provide the sensitivity to detect virus in all samples where PCR showed replication. This compromised the study of co-localization but did show promise as a model to study the tropism of respiratory viruses. Overall, this work has showed that systemic spread of BoHV-1 does not appear to be controlled by virally encoded mechanisms. The in vivo experimental infection suggested host factors may play a large part. Further work is also needed to consider any differences that may exist between reactivated virus and the original infecting isolate.

Determination of an extender protocol which will enhance the viability of frozenthawed bovine spermatozoa will allow producers to obtain higher conception rates due to the increased survival rate of the spermatozoa. Ejaculates of six Brangus bulls (age=18 months) were evaluated for spermatozoal motility, acrosomal integrity, and morphological characteristics (collectively called spermatozoal viability) in two experiments to test our hypotheses that (1) the treatment combination of a 4 hr cooling duration and a 2 hr equilibration with glycerol will result in optimum spermatozoal characteristics after freezing and thawing and (2) rank of three selected extenders relative to their effects on spermatozoal viability after freezing and thawing will be egg yolk-citrate (EC), egg yolk-tris (IMV), and skim milk (milk). In experiment 1, an ejaculate from each bull was partially extended and cooled to 4 ºC for either 2 or 4 hr and then allowed to equilibrate with the glycerolated extender for 2, 4, or 6 hr. Spermatozoal viability was assessed at 0, 3, 6, and 9 hr after thawing. In experiment 1, 4 hr of cooling resulted in a higher percentage of motile spermatozoa than did 2 hr of cooling. The 2 hr equilibration with glycerol yielded lower percentages of motile spermatozoa, acrosomal integrity, and morphologically normal spermatozoa than 4 and 6 hr equilibration durations with glycerol. In experiment 2, we observed a decrease in spermatozoal viability for all three extenders upon freezing and thawing. Viability of frozen-thawed spermatozoa extended in the milk was reduced for all incubation durations, and the IMV extender had a higher percentage of motile spermatozoa than the EC extender at 6 hr of incubation. A higher percentage of intact acrosomes was observed with the IMV extender; however, the EC extender had a higher percentage of morphologically normal spermatozoa than the IMV extender. Our results indicate that at cooling duration of 4 hr and a 4 hr equilibration with glycerol provide the highest level of spermatozoal viability post-thaw of the treatments evaluated and that the IMV extender enhances the percentage of spermatozoa with an intact acrosome for frozenthawed spermatozoa over the EC and skim milk extenders.

No description available.

No description available.

Dissertation (Ph.D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (p.281-340).

Thesis (M.A. in veterinary science)--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 23, 2010). "Department of Veterinary Clinical Sciences." Includes bibliographical references (p. 83-89).

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Master of Science / Department of Diagnostic Medicine and Pathobiology / Melinda J. Wilkerson / Failure of passive transfer (FPT) is one of the main reasons for increased mortality rate in newborn calves and diagnosis is dependent on determination of serum IgG concentrations (diagnosis is based on < 1 g/dL of total IgG). Several qualitative assays are available, but the reference method, single radial immunodiffusion assay (SRID), albeit quantitative measures only one subclass at a time. We set out to develop a competitive multiplex microsphere flow cytometry assay to measure bovine IgG1 and IgG2 concentrations in 30 serum samples acquired from newborn Holstein calves prior to and 24 hours after ingestion of colostrum and to compare the values with SRID. A triplex bead assay was created by mixing three distinct sets of Quantum plex carboxylated fluorescent microspheres that were coated with purified bovine IgG1, IgG2 or albumin using a two step chemical reaction. The triplex protein coated beads were reacted with a cocktail of sheep anti-bovine IgG1 and IgG2. Evaluation of analytical specificity demonstrated cross reactivity between anti-bovine IgG2 and IgG1 coated beads that precluded determination of IgG2 > 0.5 g/dL. Cross reactivity between anti-IgG1 and IgG2 coated beads was minimal and did not affect IgG1 concentrations between 0.15 to 1.2 g/dL. A competitive linear decrease in the fluorescence intensity was observed in the triplex assay when 2-fold dilutions spanning a concentration range of 12 mg/dL – 100 mg/dL of either purified bovine IgG1 or IgG2 were included as a competitive inhibitor of the reaction. Precolostral serum samples from 29 calves were determined to be < 0.4 g/dL by SRID. Standard calibrants for the flow assay were prepared from two fold serial dilutions of purified bovine IgG (stock concentration 10 g/dL) using a precolostral calf serum pool as the diluent. The standard calibrants (IgG1 was 1.0- 0.16 g/dL and IgG2 was 3.4 – 0.22 g/dL) were used as the inhibitors in a triplex assay to develop a standard curve for unknown samples. Dilutions of bovine reference serum containing known amounts of IgG1 (1.2 – 0.15 g/dL) and IgG2 (1.6 – 0.2 g/dL) was used as positive control. The intra Intra-assay and inter-assay precision of the mutiplex assay was good (coefficient of variation < 10%). Since the IgG2 concentrations of post colostral samples were below detection limit, only IgG1 values were compared to the SRID. The agreement between triplex microsphere assay and SRID for IgG1 was poor with a mean bias of 0.743 g/dL towards triplex microsphere assay (95% confidence interval of 0.382 to 1.105 g/dL). Method comparison studies between total IgG determined by SRID and the gamma-globulin fraction determined by serum electrophoresis indicated that the SRID calculated higher values than the protein method (mean bias of -1.4 g/dL, 95% confidence interval was -1.8 to -1.05 g/dL). We hypothesized that the positive bias for the microsphere assay was explained in part by the use of dilution factors, use of standards that had a low analytical range, and erroneously high standards used in the SRID method.