ESTRUS INDUCTION IN EWES IN SPRING
Sheep breeding is an important livestock industry in many countries. To further develop sheep breeding, meat productivity should be improved. Estrus induction is used to increase the number of lambing. The research goal is to develop estrus induction schemes in West Siberian mutton sheep in the spring. The research objectives were as following: to study the hormonal status of ewes in the spring; to develop an optimal estrus induction scheme; to detect early pregnancy by ultrasound investigation; and to evaluate some reproductive qualities in ewes. The studies were conducted in 2016 on the farm of the OAO “Mayak” (Rodinskiy District of the Altai Region); the sheep of the West Siberian mutton breed were investigated. Two groups of 30 sheep were formed to test estrus induction schemes. The study results showed that the sex hormone concentration in sheep blood serum before gonadotropic treatment was as following (on the average in the groups): progesterone - 2.9 ± 0.38 nmol L and 3.2 ± 0.2 nmol L; estradiol - 2.3 ± 0.18 nmol L and 2.4 ± 0.30 nmol L. After vitamin and hormone treatment according to Scheme I, the progesterone concentration increased 4.2 times. The estradiol concentration was 2.3 ± 0.48 nmol L, and then decreased to 1.6 ± 0.38 nmol L. When Scheme II was followed, the progesterone concentration increased 2.8 and 7.4 times relative to the initial level. The effectiveness of the estrus induction schemes was determined by the pregnancy detection using the ultrasound scanner Partner PS-310V. When Scheme I was used, pregnancy was detected in 25 ewes of which 36% had two lambs. Under Scheme II, pregnancy was detected in 26 ewes, and 46% had twins.