Secretion of Luteinizing Hormone and Follicle-Stimulating Hormone from Overfeeding Dairy Heifers

Abstract

Secretory effects of gonadotropins and various ovarian and uterine measurements were investigated in 22 prepubertal or postpubertal dairy heifers fed a concentrate to forage ration (60:40) in restricted or ad libitum amounts until they gained 125 kg. Average daily gain of heifers on restricted feeding was 613 g compared with 1218 g for heifers fed for ad libitum intake. During three stages of the experiment blood was collected either at 30-min intervals for two 4-h periods (Stage I and III) or at frequent intervals before and after an injection of luteinizing hormone-releasing hormone (Stage II). At the end of Stage III, all heifers were slaughtered, and ovaries and uteri were collected. Of the variables measured in ovaries and uteri, nutrition affected only number of uterine caruncles (76.5 in ad libitum versus 59.7 in restricted-fed heifers). Excess feeding increased frequency of luteinizing hormone pulses during Stage I but not during Stage II. However, amplitude baseline and overall concentrations of luteinizing hormone were unaffected. Release of luteinizing hormone induced by luteinizing hormone-releasing hormone was reduced in heifers with ad libitum intake. Secretion of follicle-stimulating hormone was not affected by overfeeding. © 1984, American Dairy Science Association. All rights reserved.