The influence of season on tonic luteinizing hormone (LH) and progesterone levels in cattle in a subtropical environment

Author: B.P. Louw, A.W. Lishman, A. van Niekerk and S.F. Lesch
Year: 1983
Issue: 4
Volume: 13
Page: 253 - 256

Plasma LH and progesterone levels were measured daily from the sixth to the fifteenth day of the oestrous cycle in Friesland cows during December (summer) of one year, and April/May (autumn), June/July (winter) and September (spring) of the following year. Five to seven cows were sampled per season, and they were subjected to a plane of nutrition designed to maintain body mass throughout the experimental period. Mean tonic LH levels during autumn (2,26 ± 0,07 ng/ml) were significantly (P 0,01) higher than those obtained during summer (1,95 ± 0,06 ng/ml) and spring (1,94 ± 0,07 ng/ml), but not significantly higher than those obtained during winter (2,15 ± 0,07 ng/ml). The mean area under the LH curve for cows sampled during autumn was significantly (P 0,05) greater than that for cows sampled during summer and spring. The season did not influence progesterone concentrations. The possible reasons for the seasonal differences in tonic LH secretion are discussed.


Keywords: Cattle, LH, Progesterone, season
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