published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

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

No description available.

Chicken strains divergently selected for either abdominal fat deposition, avian leukosis (ALV) resistance or Marek's disease (MD) resistance were analyzed for restriction fragment length polymorphism (RFLP) in the growth hormone gene (GH). A total of four polymorphisms were identified, one at a SacI restriction site (PS1) and three at MspI restriction sites (PM1-PM3). Restriction mapping indicated that all polymorphisms were in exons and/or introns and not in flanking regions of the gene. Selection for abdominal fat composition significantly affected the frequency of polymorphisms at PM2, but not at the other restriction sites (p $<$ 0.0004). The PM2$ sp{+}$ allele (presence of a restriction site) was fixed in the fat line and occurred at a frequency of 63% in the lean line. Selection for ALV-resistance resulted in significant differences in the frequency of polymorphisms at PS1 and PM3. Selection for MD resistance also affected the frequency of polymorphisms at PS1 and PM3.

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.

Bibliography: leaves 239-259. / 259 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Concentrations of minimal medium components and fermentation parameters were optimized for high level constituitive expression of recombinant methionyl porcine growth hormone in E. coli. Improved yields were obtained when the magnesium concentration was reduced, and the ammonium chloride concentration increased. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1995

Bibliography: leaves 239-259. / 259 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Concentrations of minimal medium components and fermentation parameters were optimized for high level constituitive expression of recombinant methionyl porcine growth hormone in E. coli. Improved yields were obtained when the magnesium concentration was reduced, and the ammonium chloride concentration increased. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1995

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