REPRODUCTIVE MANAGEMENT OF HAIR SHEEP WITH PROGESTERONE AND GONADOTROPINS IN THE TROPICS

A study was conducted at a farm near Colima, Mexico, to evaluate the r eproductive performance of 60 hair sheep and 30 F1 crossbreds (Ramboui llet or Dorset X Rambouillet) with progesterone and gonadotropin treat ments. Sheep gazing was supplemented with a protein bank of Leucaena l eucocephala. Ewes were supplied with a concentrate of 3 Mcal ME/kg and 18% CP 1 month before and 1 month after lambing. Oestrus synchronizat ion or induction was performed with progesterone and gonadotropins. Fe males were bred 48-69 h after sponge retrieval. Of the treated sheep 9 7% showed oestrus. Average fertility was 66%. Seasonally low lambing r ate was from March to July in the absence of hormone treatments. Hormo ne treated sheep (hair sheep and crossbreds) showed increased (P < 0.0 1) fertility in 8 out of 12 months. Higher difference in fertility was due to treatment in January to May. Fertility was highest from June t o December. Overall prolificacy of treated ewes was 1.93 +/- 0.32 vers us 1.79 +/- 0.21 for controls. Hormone treated ewes had a greater perc entage 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 since controls had more single lambs, overall b irth weight was in favour of controls (2.20 versus 1.85). It is conclu ded that crosses of Rambouillet or Rambouillet X Dorset males with Pel ibuey and Barbados Blackbelly hair ewes increased lamb crop, birth wei ght, and number of parturitions per ewe per year under tropical condit ions in Mexico. (C) 1998 Elsevier Science B.V.