Reproductive management of hair sheep with progesterone and gonadotropins in the tropics.

摘要

A study was conducted at a farm near Colima, Mexico, to evaluate the reproductive performance of 60 Pelibuey and Barbados Blackbelly ewes and 30 Rambouillet and Dorset X Rambouillet ewes. Sheep grazed pasture supplemented with a protein bank of Leucaena leucocephala. One month before to 1 month after lambing, ewes were supplemented with concentrate (3 Mcal metabolizable energy/kg and 18% crude protein). Oestrus synchronization/induction was performed with progesterone and gonadotropins. Control ewes received no hormone treatment. Females were inseminated 48-69 h after sponge retrieval. 97% of treated sheep showed oestrus and average fertility was 66%. In controls, lambing rate was low from March to July. Hormone-treated sheep had higher (P<0.01) fertility than controls in 8 out of 12 months. The greatest difference between treated and untreated ewes occurred from January to May. Fertility was highest from June to December. Overall prolificacy (number of lambs per ewe exposed) of treated and control ewes was 1.93±0.32 and 1.79±0.21 respectively. Hormone-treated ewes had a greater percentage of twins, triplets and quadruplets than controls. Overall yield of lambs from treated ewes was 29.86 kg per year compared to 19.99 kg for controls. However ascontrols had more single lambs, overall birth weight was higher for controls than treated ewes (2.20 and 1.85). Average birth weight was higher for lambs from crossbred ewes (2.07 kg) than for lambs from Pelibuey ewes (1.99 kg).