ABSTRACT


Daniel Claro M.1
 
During 3 consecutive seasons, 1971-1973, the infertility rate was determined for 365 adult ewes and 422 2 - tooth in the scrub Country and 582 adult ewes and 212 2-tooth in Tussock Country in Magallanes (Chile). Twinning rate was also studied using 733 and 715 adult ewe lambings from Scrub and tussock Country respectively. Also, 278 2-tooth lambings were controlled in Tussock Country. Corriedale sheep were use and data presented is base on ewes surviving till parturition. Scrub and Tussock Countries were used as treatments and years as replications for statistical analysis.
lnfertility Rate. An infertility rate of 15.89% in Scrub Country and 21.99% inTussock Country was found for adult ewes, difference being significant (P ≤ 0,01).Infertility rate in 2-tooth is significantly (P ≤ 0,01) higher than in adult ewes being of 28.09% and 28.77% for Sctub and Tussock Country respectively.
Twinning Rate. A twinning rate of 3.68% and 1.82% was found for ewes inSctub and Tussock Country while for 2-tooth it was 1.44% in Tussock Country. Nosignificant differences were found among twinning rates.
Key words:
1Ing. Agr., M. Agr., Sci., Programa Producción Ovina, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.