Effects of elevated blood insulin-like growth factor-I (IGF-I) concentration upon IGF-I in bovine mammary secretions during the colostrum phase.
The objectives of these studies were to determine if the concentration of insulin-like growth factor-I (IGF-I) in mammary colostrum secretions could be altered through manipulation of IGF-I concentrations in blood and to compare the temporal changes of IGF-I in mammary secretions to those occurring for IgG1. Milking of 15 pregnant Holstein cows was stopped at 8 weeks prepartum and they were randomly assigned to one of three treatments. A control (C) treatment consisted of feeding the animals 100% of NRC requirements for protein and energy. A second group of cows was fed as the control group and injected with 1.8 mumol bovine GH/day. The third group was fed at 70% of NRC requirements for protein and energy to cause a moderate nutrient restriction (NR). Body weight was measured weekly. Blood was collected by tail venepuncture at 4 h intervals for 24 h. Mammary secretions were collected and pooled among contralateral front and rear quarters (diagonal) for measurement of volume, IGF-I and IgG1 concentrations. Samples were collected at -7, -5, -2, 0 and 1 week postpartum. Cows on the NR treatment failed to gain weight during the dry period compared with C cows (P < 0.05). Blood GH and IGF-I concentrations (P > 0.1) were unaffected by NR treatment. Cows treated with GH had higher (P < 0.01) serum GH and IGF-I levels throughout the entire treatment period, and higher serum IgG1 at 5 and 2 weeks prepartum (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
Hadsell
D L
DL
Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
Baumrucker
C R
CR
Kensinger
R S
RS
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D003126:Colostrum / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000494:pharmacology; D007074:Immunoglobulin G / Q000032:analysis / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D011247:Pregnancy
D007074:Immunoglobulin G; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone