Call number: LD2668 .T4 1984 H537 / Master of Science

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

Call number: LD2668 .T4 1986 K58 / Master of Science / Animal Sciences and Industry

No description available.

These studies were conducted to examine the influence of several variables on the growth hormone binding protein (GHBP) in serum of pigs. Continuous long term porcine somatotropin (pST) injections (daily for 6-7 wk) increased GHBP activity (p < .05). However, periodic short term pST injections (daily, every second d or every fourth d for 2 wk) did not cause significant change in GHBP levels (p > .40). No difference was observed between fed animals and animals fasted for 5 days (p > .3). Between 0 and 6 mo of age boar and gilt serum GHBP activity were not significantly different from each other, but increased significantly with age in both sexes(p < .0001). There was no significant correlation between serum GHBP and body weight in this study (p > .30). In pregnant sows, GHBP concentrations were highest at the beginning (day 72) of the third trimester (p< .05). These values were compared with information in the literature on serum growth hormone (GH) concentrations and GH receptor activity under similar conditions. Growth hormone receptor activity reported by other researchers and GHBP activity appear to vary concurrently except during fasting which may indicate alternate regulation of either the GHBP or the GH receptor. / Graduation date: 1992

The role of plasmin and plasminogen activators (PA) in bovine lactation and porcine ovulation has been examined. There is no difference in the activation pattern of plasminogen to plasmin throughout the whole range of somatic cell counts (SCC) and from third to ninth month in lactation. The ratio of (plasminogen + plasmin)/plasmin, which serves as an index of the activation process, was 7.27 during early (first and second month) and 4.23 during late lactation (tenth month) and both values are different (p $<$ 0.01) from all the other ratios throughout the whole range of SCC and from third to ninth month in lactation suggesting limited and increased activation of plasminogen to plasmin during early and late lactation, respectively. Macrophages produce but they do not secrete urokinase-PA, suggesting a minor role in influencing milk plasmin. Somatotropin administration resulted in a suppression of milk plasmin in vivo. Insulin-like growth factor-1 (IGF-1), the most likely mediator of the effects of somatotropin on the bovine mammary gland, inhibited the induction of tissue-PA (t-PA) production which is observed when mammary epithelial cells are cultured in the absence of IGF-1. Plasmin and t-PA increased while PA inhibitor-1 decreased in porcine granulosa, theca interna cells and follicular fluid just prior to the time of expected ovulation suggesting a role for plasmin in follicle rupture.

No description available.

Experiments were conducted with sows and littermate-gilts to investigate the effect of dietary zinc (Zn) restriction during either part or most of the pregnancy and lactation on dams and their offspring. / Reduced dietary Zn (13 ppm) during the last 4 wk of pregnancy and first 2 wk of lactation presented no serious consequences to the dam or offspring. Reduction of dietary Zn throughout pregnancy and lactation (10 ppm) caused overt signs of Zn deficiency in one-half of the gilts, however, their offspring exhibited no obvious abnormalities. Zinc restriction did not affect feed consumption but depressed plasma and urinary Zn and plasma alkaline phosphatase activity (APA). The use of the balance technique and radiotracers revealed that gilts deficient in Zn initiated protective mechanisms such as, increased Zn absorption reduced endogenous Zn excretion, prolongation of the biological half life of Zn; all these responses affected higher efficiency of Zn utilization. / Despite the protective mechanisms, gilts depleted in Zn exhibited prolonged stressful parturition and a high incidence of intrapartum and neonatal mortality than control gilts. Piglets from gilts depleted in Zn showed depressed birth weight, reduced concentrations of plasma Zn, Cu and ammonia and low APA and hematocrit, increased plasma concentrations of glucose and lactate, reduced content of Zn in liver, heart, lung, skin, bone and carcass and higher concentrations of Cu and Mn in various tissues compared to controls. Zinc depletion did not change the Zn content of colostrum but did change it in milk. Content of Cu, Fe, and Mn was effected in colostrum and milk. Weight of piglets was lower at one wk but not at two wk of age. Two-week old piglets exhibited lower Zn and higher Cu concentrations in plasma; reduced Zn and increased Cu and Mn concentrations in liver and bone and changes in Cu and Mn in other tissues. At the end of lactation, gilts depleted in Zn exhibited low level of Zn and APA in plasma; reduced Zn content in liver, spleen, heart, small intestine; increased Cu content in liver and small intestine; increased Zn and Mn content in brain. / Although gilts depleted in Zn exhibited a highly efficient handling of Zn via homeostatic mechanisms, the reduced amount of corporal exchangeable Zn in these gilts caused biochemical changes affecting the performance of the dam and the offspring. (Abstract shortened with permission of author.)

Graduation date: 1992

No description available.