Regulation of luteinizing hormone secretion in prepubertal heifers fed an energy-deficient diet.
The effects of feeding a diet restricted in energy on the endocrine mechanisms regulating LH secretion in prepubertal heifers were examined. On Day 0, thirty heifers were assigned to be either ovariectomized (OVX; n = 10), ovariectomized and administered an estradiol implant (OVXE; n = 10), or to remain ovary-intact (INT, n = 10). Five heifers each were then assigned to be fed either a control (C) or a two-phase, low-to-high energy (L), dietary treatment. The C diet was formulated to support weight gains of 1.1 kg/day throughout the experiment (Day 0-197). Heifers receiving the L treatment were provided a diet restricted in energy (33% of C diet) from Day 0-127 followed by a diet similar to that fed to heifers receiving the C treatment from Day 128-197. Secretion of LH increased rapidly following ovariectomy in C-OVX and L-OVX heifers. During the period of energy restriction, LH pulse frequency was reduced, and mean LH concentration, pulse amplitude, and pituitary response to LHRH were greater in L-OVX than in C-OVX heifers. In L-OVXE and L-INT heifers, secretion of LH was low and unchanged during the period of dietary energy restriction. In contemporaneous treatment groups fed the C diet (C-OVXE and C-INT), frequency of LH pulses increased gradually during this period and C-INT heifers attained puberty on Day 121 +/- 18. Upon switching heifers in the L-OVX, L-OVXE, and L-INT treatments to the C diet, all characteristics of LH secretion changed markedly within 14 days to levels similar to those detected in the C treatments.(ABSTRACT TRUNCATED AT 250 WORDS)
Kurz
S G
SG
Department of Animal Science, Ohio State University, Columbus 43210.
Dyer
R M
RM
Hu
Y
Y
Wright
M D
MD
Day
M L
ML
D000818:Animals; D002417:Cattle / Q000502:physiology*; D004040:Dietary Carbohydrates; D004958:Estradiol / Q000502:physiology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000378:metabolism*; D009747:Nutritional Physiological Phenomena; D010052:Ovariectomy; D010507:Periodicity; D010902:Pituitary Gland / Q000378:metabolism; D011374:Progesterone / Q000097:blood; D012741:Sexual Maturation; D015430:Weight Gain
D004040:Dietary Carbohydrates; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone