No description available.

No description available.

Two clinical studies were conducted to evaluate the effects of recombinant bovine somatotropin in daily, weekly or bi-weekly injected preparations on milk yield, feed efficiency and reproduction. In the first study, a linear dose-response effect of recombinant bST on milk yield with doses of up to 150 mg · 7d-1 was observed. Feed intake was not affected and feed efficiency was increased by bST during lactation. Body condition at the end of lactation was lower in cows supplemented with bST. Feed intake during the dry period following bST supplementation was not affected by bST given during lactation. When differences in body condition were taken into account, efficiency of conversion of dietary energy to milk energy was not affected by bST supplementation. In another study of bST supplementation during lactation, a daily dose of 10.3 mg · d-1 and a sustained release formulation of 350 mg · 14d-1 did not increase milk production or feed efficiency. In the absence of a milk production response, reproductive performance was not affected by bST supplementation. Progesterone production in the second oestrous cycle post partum was higher in cows receiving bST but oestrous activity was not affected. Body condition at calving did not affect milk production, response to rbST or reproductive performance. Cows calving with a body condition less than 3.25 consumed more feed per unit of body weight and resumed ovarian cyclic activity later than cows calving with a body condition greater or equal to 3.25. An epinephrine challenge during the dry period was performed to evaluate whether the effects of bST supplementation during lactation on adipose tissue metabolism persisted during the dry period. Lipid mobilisation by cows having received bST during lactation, as described by the release of non-esterified fatty acids following the epinephrine challenge, did not differ from control cows. Two studies designed to evaluate the effect of bST on oestradiol-induce

Long-term administration of recombinant bovine somatotropin (rbST) significantly increased milk and 3.5% fat-corrected milk production without altering milk composition. These effects occurred regardless of breed, parity or drug delivery system (daily or sustained-release) utilized. Somatotropin did not affect apparent digestibility of rations, dry matter intake, crude protein intake, energy intake or energy balance. Body energy reserves, measured as body condition scores, decreased during rbST treatment resulting, together with the increase in milk yield, in an improvement of the efficiency of conversion of feed to milk for cows treated with rbST. Body condition was completely regained during the dry period. No effects of rbST on mastitis or metabolic diseases were observed. During lactation, injection of rbST produced elevated circulating concentrations of non-esterified fatty acids, glucose, insulin, bST and IGF-I but lipid composition of liver and ketogenic functions were not altered. These lipolytic and diabetogenic activities might contribute to the galactopoietic response elicited by rbST. Somatotropin did not modify the nutritional status of cows during pregnancy or the nutritional status and growth rate of their calves from birth to weaning. / With regard to reproduction, somatotropin augmented ovarian progesterone production during the first two estrous cycles post-injection and during gestation. These effects may have been mediated through increased ovarian IGF-I synthesis. Somatotropin enhanced the GnRH-induced LH response at 14 d postpartum. In spite of these positive observations, somatotropin treatment tended to produce longer calving to conception intervals. Nevertheless, the higher persistency of milk production by cows treated with rbST may compensate for this difference economically.

Thesis (M.S.)--Ohio University, June, 1995. / Title from PDF t.p.

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

No description available.

Efficacy of a sustained-release formulation of bST was evaluated for two consecutive lactations. Response in milk and milk component yield was positive and very consistent for multiparous cows between lactations. Average responses in milk production for the first lactation and for the 320-, 640-, and 960-mg$ cdot$28d$ sp{-1}$ doses of bST were 4.3, 5.2 and 5.9 kg$ cdot$d$ sp{-1}$, respectively. Response was 4.9 kg$ cdot$d$ sp{-1}$ for the average of the second lactation with 640 mg bST$ cdot$28d$ sp{-1}$. Primiparous cows responded with the same numerical magnitude as multiparous cows but with higher variability. BST caused a response in milk yield irrespective of the stage of lactation when injections commenced, but the magnitude of response was greater at latter stages of lactation. No adverse effect of treatment on final body condition score and achievement of proper condition for a subsequent lactation was found. No effect of treatment was observed on health parameters in either lactation. Trends towards longer days open and more breedings per conception were apparent for both lactations. Total milk protein, caseins and whey proteins were not changed at any stage of lactation and for the average of the full lactation. BST did not significantly change proportions of $ alpha sb{s}$-, $ beta$- and K-caseins. Milk fat percentage and milk fatty acid profiles were not different between control and any dose level of bST for a complete lactation. Maximum response in milk yield for the different doses of bST was from d8 to 12 of the 28d cycle and was almost eliminated by d22 to 24. A 3.1 and 3.6 kg$ cdot$d$ sp{-1}$ milk augmentation with bST was estimated in cows infused for 6d with glucose and saline, respectively during peak lactation. There was no apparent milk yield response when cows were infused with insulin + glucose but cows exhibited positive energy balance, weight gain and only 5% less milk. Insulin + glucose infusion increased milk protein 11% and 14% compa

Dairy cows fed diets supplemented with 2.5% calcium-salt fatty acids (CSFA) (DM basis) during early lactation produced more 4% FCM than cows fed the control diet. Feeding this diet also increased whole lactation performance. Supplementing diets with 1.25% CSFA or animal fat did not increase production performance of cows. Dietary fats were used directly for greater milk production and, based on unchanged body condition scores, did not alleviate body fat mobilization. Changes in the milk fat content and composition due to fat supplemented diets were negligible. A slight decrease in milk protein and SNF percentage was observed with CSFA but not with animal fat feeding. Palatability of the diets was good and DM intake was not impaired. Feeding animal fat at 1.25% and CSFA up to 2.5% of the DM does not impair forage digestibility and nitrogen balance. Dietary fat increased plasma triglyceride (TG) and cholesterol concentration. Injection of 10.3 mg d$ sp{-1}$ or 350 mg 14d$ sp{-1}$ of recombinant bovine somatotropin (rbST) did not change 4% FCM production or milk composition at any stage of lactation.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed June 26, 2009). PDF text: v, 114 p. : ill. ; 1.05 Mb. UMI publication number: AAT 3352316. Includes bibliographical references. Also available in microfilm and microfiche formats.