Insulin-like growth factor I in follicular development and function in postpartum beef cows.
The objective of this study was to determine whether nutrition affects follicular growth and(or) steroid and insulin-like growth factor I (IGF-I) concentrations in follicular fluid. Beginning 6 d after calving, Hereford-cross cows (n = 28) were fed either 14 (ad libitum) or 7 (restricted) kg.animal1.d-1 of chopped alfalfa-brome hay. Half the cows in each treatment were ovariectomized on d 20 (OVX-20) and the remaining half on d 35 (OVX-35) postpartum. Cow weight and condition score were recorded weekly, and blood was collected thrice weekly for determination of insulin, IGF-I, glucose, and free fatty acid (FFA) concentrations. At ovariectomy, follicular fluid from each follicle greater than or equal to 4 mm in diameter was aspirated for determination of IGF-I, progesterone (P4), and estradiol-17 beta (E2) concentrations. Restricted cows lost more weight after calving than did ad libitum cows (P less than .0001), although all cows lost similar amounts of body condition (time postpartum, P = .008). Concentrations of FFA were elevated (P less than .0001) in restricted cows from wk 2 through 5 after calving but did not change with time in ad libitum cows. Plasma concentrations of glucose were lower in restricted than in ad libitum cows (59.6 +/- .4 vs 61.8 +/- .4 mg/dl; P = .05), but insulin and IGF-I were similar (P greater than .10) between dietary treatments.(ABSTRACT TRUNCATED AT 250 WORDS)
Rutter
L M
LM
Alberta Agriculture, Edmonton, Canada.
Manns
J G
JG
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002417:Cattle; D004435:Eating / Q000502:physiology*; D004967:Estrogens / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D015571:Follicular Fluid / Q000737:chemistry; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology*; D009752:Nutritional Status; D006080:Ovarian Follicle / Q000502:physiology*; D010052:Ovariectomy / Q000662:veterinary; D049590:Postpartum Period / Q000502:physiology*; D011374:Progesterone / Q000032:analysis; D015431:Weight Loss
D001786:Blood Glucose; D004967:Estrogens; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011374:Progesterone; D007334:Insulin-Like Growth Factor I