Serum concentrations of IGF-I in postpartum beef cows.
Four experiments assessed changes in serum IGF-I under various physiologic conditions in postpartum cows. In Exp. 1, anestrous suckled cows (n = 25) were infused for 6 d with either saline or glucose at two different infusion rates. In Exp. 2, anestrous cows (n = 29) received either a saline (weaned and suckled controls) or 3 g/d phlorizin (weaned phlorizin) infusion for 3 d. Calves from the weaned groups were removed from 15 h before and throughout infusions. In Exp. 3, cycling suckled cows (n = 20) received prostaglandin F2 alpha (PGF2 alpha) when the 5-d saline or phlorizin infusion began. In Exp. 4, suckled cows (n = 20) had ad libitum access to feed or received 50% of control feed consumption from 30 to 40 d postpartum. Increasing glucose availability (Exp. 1) increased (P less than .05) serum IGF-I by 30 to 35%. IGF-I remained stable after weaning (Exp. 2) in phlorizin-infused cows (128.8 +/- 12.7 ng/ml), but increased (P less than .05) by 3 d after calf removal in weaned control cows (152.2 +/- 7.5 ng/ml). IGF-I also remained stable in phlorizin-infused cows following PGF2 alpha injection (Exp. 3), but increased in control cows by 2 d after PGF2 alpha (156.8 +/- 18.3 on d 2 vs. 133.7 +/- 9.8 ng/ml pre-injection; P less than .05) and remained elevated (P less than .05) during the periovulatory period. In cows receiving restricted feed intake (Exp. 4), IGF-I decreased by approximately 50% within 4 d of feed restriction (71.3 +/- 9.4 vs 137.4 +/- 16.6 ng/ml; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
Rutter
L M
LM
University of Saskatchewan, Saskatoon, Canada.
Snopek
R
R
Manns
J G
JG
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle / Q000097:blood*; D004435:Eating; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D007262:Infusions, Intravenous / Q000662:veterinary; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D010695:Phlorhizin / Q000008:administration & dosage / Q000494:pharmacology; D049590:Postpartum Period / Q000097:blood*; D011247:Pregnancy; D013002:Somatomedins / Q000032:analysis*; D014886:Weaning
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D010695:Phlorhizin; D005947:Glucose