Authors : R.A. Pershing , A.C. Dinges , W.W. Thatcher and L. Badinga
Abstract: Lactating Holstein cows (80 day in milk) were utilized in a completely randomized design to examine the effect of bovine somatotropin (bST) on plasma and uterine contents of IGF-I and IGF-binding proteins (IGFBP). Cows were managed using the Ovsynch/TAI program. On the day of expected ovulation, cows were assigned randomly to receive bST (n = 9) or to serve as untreated controls (n = 8). Within each treatment group, cows were sacrificed on day 3 or 7 postovulation. Blood was sampled daily for plasma bST, progesterone (P4) and IGF-I RIAs. At slaughter, the oviducts and uterine horns ipsilateral to the corpus luteum (CL) were collected, trimmed free of the broad ligament, and flushed with PBS. Plasma P4 profiles and the weights of CL at day 7 postovulation were similar for control and bST-treated cows. Short-term bST treatment had no detectable effects on IGF-I concentration in plasma. Total IGF-I contents in oviductal flushings (OLF) were low and did not differ between stages of the estrous cycle or treatments. In contrast, uterine IGF-I luminal contents increased (P < 0.01) between days 3 and 7 postovulation, and tended to be higher (P < 0.08) in the bST-treated group. All major IGFBPs were present in day-3 ULF, but could not be detected in day-7 ULF. Results indicate that bST effects on reproductive responses in dairy cows may involve peripheral as well as local uterine regulation of IGFs and their binding proteins.
R.A. Pershing , A.C. Dinges , W.W. Thatcher and L. Badinga , 2003. Plasma and Uterine Insulin-Like Growth Factor-I (IGF-I) and IGF-Binding Proteins in Lactating Dairy Cows Treated with Bovine Somatotropin. Journal of Animal and Veterinary Advances, 2: 67-73.