Influence of food intake but independence of body weight on puberty in female sheep.
The effect of maintaining female sheep at a body weight intermediate between the normal weight for puberty (30-35 kg) and 20 kg (puberty suppressed) on the onset of oestrous cycles was studied. In addition, the influence of ad-libitum food intake or insulin infusion was studied in animals previously maintained at 20 kg. Coopworth ewe lambs (10 weeks old) were allocated to one of 6 treatments: (A) ad-libitum fed (n = 6), (B) ad-libitum fed to 28 kg then maintained at that weight (n = 6), (C) ad-libitum fed to 24 kg then maintained at that weight (n = 6), (D) maintained at 20 kg until Week 29 and then fed ad libitum (n = 6), (E) maintained at 20 kg and infused with 0.1 U insulin/kg/24 h for 2 weeks from 29-31 weeks of age (n = 5), (F) maintained at 20 kg (n = 6). The lambs were penned indoors under natural photo-period, which was decreasing virtually throughout the study, and fed a pelleted concentrate diet which was recorded daily. They were blood sampled twice a week, and plasma was analysed for progesterone. Puberty was defined as the date when plasma concentrations of progesterone first exceeded 1 ng/ml. In addition, ewes in Groups D, E and F were blood sampled every 10 min for 8 h on Days 0 and +12 of the insulin infusion or access to ad-libitum feeding and the plasma was analysed for luteinizing hormone (LH).(ABSTRACT TRUNCATED AT 250 WORDS)
Suttie
J M
JM
MAFTech, Invermay Agricultural Centre, Mosgiel, New Zealand.
Foster
D L
DL
Veenvliet
B A
BA
Manley
T R
TR
Corson
I D
ID
D000375:Aging / Q000502:physiology; D000818:Animals; D001835:Body Weight / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D004971:Estrus / Q000502:physiology; D005260:Female; D007328:Insulin / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D011374:Progesterone / Q000097:blood; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology*; D012756:Sheep / Q000502:physiology*; D013997:Time Factors
D007328:Insulin; D011374:Progesterone; D007986:Luteinizing Hormone