Hormones and the treatment of sterility of dairy cattle--the assay of pituitary gonadotropic and thyrotropic hormones of dairy cattle

To all livestock breeders there Is probably no greater burden than the problem arising from sterility or failure to breed. This problem is very serious in all tropical countries and especially in East Pakistan, Asia. In countries where dairy cattle are greatly improved by scientific breeding, nutrition and management, a heifer on the average calves for the first time at about 24 months. In East Pakistan a heifer generally gives birth to the first calf at about 42 months. Besides, the average interval between two successive calvings is also much longer than in other countries. In a survey made in 1947-48(44) it was found that out of 1000 cows selected at random from different places over the province 13.8 percent were totally sterile, 40 percent calved at intervals of 16 to 20 months, 30 per cent at 20 to 24 months, 11 per cent at 13 to 16 months and 5.1 percent at 24 to 36 months. Of all the cows which were not termed sterile only 20.3 per cent settled at first breeding, 20.4 percent at second, 26.4 percent at third, 11 per cent at fourth, 6 per cent at fifth, 7 per cent at sixth and 9 per cent at more than six services(all natural breeding).

Sterility literally means complete incapability of reproduction but the problem that is faced by dairy cattle owners is both sterility and difficult breeding. So sterility may be relative or absolute. The causes of sterility or difficult breeding may be of different origin, e.g., genetic, developmental and physiological. This investigation deals mostly with the physiological aspect of the sterility problems in dairy herds.