Özet:

The possibilities of synchronizing lambing and increasing reproduction by using exogenous hormones in Karakaş ewes raised under rural farm conditions and growth characteristics of their lambs were investigated. 112 Karakaş ewes at 2-5 ages were randomly assigned into treatment (n = 45) and control (n = 67) groups during breeding season. The ewes in treatment group were placed with 60 mg Medroxyprogesterone acetate (MPA) containing intravaginal passaries for 14 days and received 600 IU PMSG injections at passary withdrawal. Ewes in the control group were not treated and allowed to mate at their natural estrus. Ram introduction for both groups was performed in pasture in village common flock in free mating system. Litter size and twinning rates for treatment and control groups were 1.06 and 1.04; and 6.45 and 4.08 %, respectively, for the first two cycles related to passary withdrawal (P > 0.05). When the expected lambing time was considered, the proportions of the lambed ewes in the first 7 and 10 days were 70.97% and 70.97% for treatment, and 20.41% and 26.53% for control group. The differences in lambing rates in both periods between groups were significant (P < 0.05). Birth weight, 1st, 2nd, 3rd and 4th month live weights, weaning weight and daily live weight gain in treatment group lambs were 3.63 ± 0.13, 9.30 ± 0.41, 16.54 ± 0.50, 23.62 ± 0.77, 31.97 ± 0.66, 31.57 ± 0.92 and 0.221 ± 0.008 kg; and, in control group lambs were 3.26 ± 0.12, 10.11 ± 0.44, 17.80 ± 0.53, 26.30 ± 0.82, 34.59 ± 0.75, 34.42 ± 0.96 and 0.244 ± 0.008 kg, respectively. Except birth weight, treatment group lambs' live weights in all periods were lower than control ones (P < 0.05 and P < 0.01). The results of this study indicate that in order to run studies to control reproduction by using exogenous hormones in rural conditions successfully some precautions and technical support are required.

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