Impact of Season on some Reproductive Hormone Profiles in Nigerian Bunaji and Sokoto Gudali Cows

This study was designed to determine the effect of season on luteinizing hormone (LH) properties (concentration, frequency and amplitude), progesterone (P ) and cortisol concentration during 4 the hot dry season (HDS), cold rainy season (CRS) and cold harmattan season (CHS). Twelve cows were used in this study. Temperature humidity index (THI) and rectal temperature were determined. Blood samples were collected twice a week to assay P and cortisol concentration. 4 Blood samples were also collected every 15 minutes for 2 hours on the 3 windows of the oestrous cycle on window 1(day 5), window 2 (day 10) and window 3 (day 15) to determine LH properties. THI values were 93.9 (HDS), 92.9 (CRS) and 45.2 (CHS). Ambient rectal temperature was insignificantly higher in HDS (38.09) and CRS (38.12) than CHS (37.33). There were no significant differences (P > 0.05) in LH pulse frequencies or amplitudes among the 3 seasons and their windows. LH concentration was significantly higher (P < 0.05) in CRS (2.50ng/ml) than CHS (1.52ng/ml) and HDS (1.45ng/ml). P was 2.131ng/ml (HDS) and 1.849ng/ml (CRS) and 4 were significantly different (P < 0.05) from CHS (1.432ng/ml). Cortisol analysis indicated no significant differences (P > 0.05) between CHS (2.624ng/ml) and HDS (2.080ng/ml) while there were differences (P < 0.05) between CRS (1.422ng/ml) and CHS. The current study concludes that the three LH properties are collectively useful in determining the effect of season on the fertility of these cows. Based on these LH properties, the best season to breed these cows is the cold rainy season (CRS).