Resumo

ALFONSO HINOJOSA-CUELLAR, José  e  OLIVA-HERNANDEZ, Jorge. Lambing Distribution by Season in Hair Sheep and Crosses under a Humid Tropical Environment. Rev. Cient. (Maracaibo) [online]. 2009, vol.19, n.3, pp.288-295. ISSN 0798-2259.

Data of 4203 lambing records from 1997 to 2005 of three breed groups of hair sheep were used to determine the lambing distribution under a continuous breeding system throughout the year. The breed groups were Blackbelly (BB), F1 Pelibuey x Blackbelly (F1 P x BB) and a group of females hybrids denominated “Cruce” (Cruce) as a result of groups crossings above indicated with Dorper and Katahdin rams. Reproductive management included the continuous presence of the male. Ewes were exposed to continuous breeding with adult rams. The climatic lambing season were: dry (February to April), rainfall one (May to July), rainfall two (August to October) and rainfall and winds (November to January). The parity orders within each breed group were primiparous and multiparous. Data were analysed with the Chi- square test. The lambing distribution was different (P<0.01) among climatic lambing seasons. The lambing frequency was greater during the rainfall and wind season than the others climatic seasons. Climatic season influenced (P<0.01) the lambing frequency in the breed groups studied.The three breed groups studied showed higher lambing frequency in rainfall and wind season than the other seasons. The F1 P x BB and Cruce primiparous ewes had lower lambing frequency (P<0.01) in rainfall than the other seasons. The BB, F1 P x BB and Cruce multiparous ewes had higher lambing frequency (P<0.01) in rainfall and wind season than the other seasons. The lambing performance of hair sheep under a continuous breeding system had seasonal variation, the primiparous and multiparous ewes showed a peak lambing in rainfall and wind seasons. The climatic seasons affected the lambing frequency in the breed groups studied.

Palavras-chave : Lambing season; dorper; katahdin; hair sheep; tropic; seasonally.