Section 6
Chapter 5,691

Influence of pre partum and post partum nutrition on luteinizing hormone secretion in suckled post partum beef heifers

Echternkamp, S.E.; Ferrell, C.L.; Rone, J.D.

Theriogenology 18(3): 283-296


ISSN/ISBN: 0093-691X
Accession: 005690213

The influence of nutrition during the last trimester of pregnancy and the early postpartum period on postpartum LH [luteinizing hormone] secretion was evaluated in 2-yr-old Hereford and Simmental heifers maintained on a high or low plane of nutrition (experiment 1) or in Hereford heifers fed a high or low energy (150 vs. 100% NRC [National Research Council]) ration (experiment 2). Amount of LH released with 10 mg estradiol benzoate (i.m.) at 14 and 28 days postpartum in experiment 1 or at 14, 32, 50 and 74 days postpartum in experiment 2 was less (P < 0.01) for heifers fed the low vs. high plane or energy ration and less (P < 0.05) at 14 days postpartum than at subsequent postpartum periods. The interval from estradiol benzoate injection to the LH peak concentration was longer (P < 0.05) in Simmental than Hereford heifers, longer (P < 0.05) in heifers fed the low rather than high energy ration, and longer (P < 0.01) at 14 days postpartum than at subsequent postpartum periods. The amount of LH released was inversely related to the time required for initiation of the release (r = -0.62). Tonic LH secretion was higher (P < 0.05) in heifers fed the high energy ration and was correlated with average daily gain (r = 0.75), but was unaffected (P > 0.05) by days postpartum or breed of cattle. Increased dietary energy intake increases LH secretion and shortens the anovulatory period in suckled postpartum beef heifers.

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