The Thai Journal of Veterinary Medicine


Investigation on response of LH to gonadotropin releasing hormone (LRH) treatment in 3 young swamp buffalo bulls was carried out every second month for 4 occasions. The animals were 16, 17 and 19 months old at the beginning of the trial. Response of plasma LH to LRH treatment was described in term of "total response" calculated from the area under the curve during 150 mn. It was shown that magnitude of LH response of the animals at the age group of 16-18 no. was higher than those in the older age groups (19-21 mo and 22-25 mo). Mean plasma LH decreased to preinjection levels within 5.5 h after LRH treatment. Furthermore, mean total LH response (ug/ml x 150 mn) was highest in the younger age group 1.03 ± 0.33 when compared with those in the 2 older age groups (0.87 ± 0.12 and 0.51 ± 0.19 respectively). The total LH responses of the younger and older groups were different from those of the mean (0.82 ± 0.28) which was similar to those in the 19-21 mo group. This finding indicated the more sensitive of hypophysis to LRH treatment in the younger animals than those reach puberty and after.

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