The effect of Gonadotrophins on estrus induction and fertility in prepubertal gilts

The aim of our study was to investigate the efficacy of exogenous gonadotrophin to induce puberty and pregnancy in prepubertal gilts which had reach the weight of fully grown pigs. The animals used in the study included 195 crossbreed German Landrace gilts aged between 150-180 days old, weighing between 75-90 kg and 24 crossbreed German Landrace adult male pigs. The prepubertal gilts of Group I (n = 65) and Group II (n = 65) were first administered with single IM dose of 1500 IU PMSG. At the same time, animals from the Group III (n = 65), which formed the control group, received 2 ml of a placebo. Seventy two hours after the PMSG administration, animals from the group I received IM 500 IU hCG while 8 μg of GnRH was given to the Group II. Animals from the control group were administered at the same time with a placebo. Twenty four hours after hCG, GnRH placebo administrations, the gilts were exposed to the male pigs during 72 hours. Pregnancy diagnosis was performed by ultrasonic techniques between 35-45 days after mating. Estrus symptoms were recorded in 56 animals (86.2 %) from the Group I, 4.2 ± 0.4 days after the last administration the estrus was detected in 55 animals (84.6 %) from the Group II, 4.3 ± 0.5 days after the end of the treatment. In the control group, 61 animals exhibited estrus behaviour spontaneously 48 ± 10,4 days after the last placebo administration. Pregnancy was diagnosed in 53 animals of the Group I (81.5 %), 51 of the Group II (78.5 %) and 57 of the control group (87.7 %). The size of the first litter was a 7.8 ± 1.3 in Group I, 7.6 ± 1.4 in Group II and 10.2 ± 1.1 in the control group. It has been concluded that, a fertile estrus can be induced using exogenous gonadotrophins (PMSG and hCG) or a treatment associating PMSG with GnRH in prepubertal gilts and that these treatments improve lifetime reproductive performance.