Synchronization of oestrus in sheep: Use of different doses of progestagen outside the normal breeding season (Short communicati

Author: J.P.C. Greyling, W.F. Kotzé, G.J. Taylor, W.J. Hagendijk and F. Cloete
Year: 1994
Issue: 1
Volume: 24
Page: 33 - 37

One hundred and thirty Merino ewes were used to test the efficiency of different doses of medroxyprogesterone acetate (MAP) progestagen to synchronize oestrus outside the breeding season. Three treatments, consisting of intravaginal progestagen doses (60 mg, 40 mg, and halved 60 mg MAP sponges) were applied for 14 days. Each ewe (35 per treatment) received an intramuscular injection of 300 1U PMSG at sponge withdrawal. The fourth group (n = 25) served as a control. No significant difference was found in the oestrous response and the duration of the induced oestrous period between the different treatments following sponge withdrawal. The mean length of the induced oestrous period for all treatments did not differ significantly from the natural oestrous period (29.4 ± 7.6 vs. 25.9 ± 6.8 h, respectively). The mean serum LH and progesterone concentra¬tions for the observation period did not differ significantly between the 60 mg, 40 mg and halved-sponge treatments (6.95 ± 8.74 and 0.28 ± 0.33; 9.17 ± 13.38 and 0.33 ± 0.47; 6.83 ± 6.09 and 0.20 ± 0.16 ng/ml, respectively). For the respective treatments, the mean position of the LH peak was 45.6, 46.8 and 42.0 h following sponge withdrawal, and 4.8, 3.6 and 0 h (oestrus) following the onset of oestrus, compared to 6.0 h for the control. MAP absorption over the 14-day period was 20.4% for the 60 mg treatment, 41.5% for the 40 mg treatment and 41.2%

Keywords: anoestrus, dose, progestagen, sheep, synchronization
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