Gonadotropin-releasing hormone-induced secretion of luteinizing hormone in postpartum beef heifers maintained on two planes of nutrition before and after breeding

• Published in: Journal of animal science Vol. 72; no. 4; p. 998
• Main Authors: Leers-Sucheta, S, Chakraborty, P.K, Rowe, K.E, Turner, H.A, Stormshak, F
• Format: Journal Article
• Language: English
• Published: United States 01.04.1994
• Subjects: Analysis of Variance; Animal Nutritional Physiological Phenomena; Animals; BOVIN DE BOUCHERIE; Cattle - metabolism; DURACION; DUREE; Energy Intake; Female; GANADO DE CARNE; GENISSE; GONADOLIBERINE; Gonadotropin-Releasing Hormone - pharmacology; HORMONA LIBERADORA DE GONADOTROPINA; HORMONAS; HORMONE; Luteinizing Hormone - metabolism; NIVEAU D'ALIMENTATION; NIVEL ALIMENTICIO; NOVILLA; Postpartum Period - metabolism; PUERPERIO; PUERPERIUM; SECRECION; SECRETION; VACA; VACHE
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/1994.724998x

experiment was conducted to examine the effect of pre- and postbreeding nutrition on GnRH-induced LH release in beef heifers on d 3 and 14 of the subsequent postpartum period. Treatment groups consisted of heifers fed high (H; n = 12) and low (L; n = 12) planes of nutrition for 204 d before breeding. Each group was further subdivided to receive either high or low planes of nutrition after breeding in a 2 X 2 factorial arrangement of treatments (H-H, H-L, L-H, and L-L). On d 3 and 14 postpartum, heifers were injected with 100 micrograms of GnRH (i.v.), and blood was collected via jugular venipuncture at 15-min intervals for 2.5 h and at 30-min intervals for an additional 2.5 h for LH analysis. Heifers fed a high level of nutrition throughout gestation (H-H and L-H) had a greater (P 0.05) mean cumulative serum concentration of LH (ng LH.mL-1.min) in response to GnRH on d 3 than did those fed a lower level of nutrition. On d 14, mean cumulative serum concentration of LH in the H-H group was greater (P 0.05) than that of the other three groups. These data indicate that postbreeding nutritional status significantly influenced pituitary responsiveness to GnRH on d 3 and that response to GnRH on d 14 was greatly enhanced by maintaining heifers on a high plane of nutrition both before and after breeding. In addition, the negative effect of low prebreeding nutrition on GnRH-induced LH secretion on d 14 was not overcome by increasing the level of nutrition after breeding