The effect of the mating season on the performance productive of corriedale ewes and lambs

Abstract

During 1994 and 1995 the effect of the mating season (early and a mid-Autum) on the nutritional status, reproductive performance and wool production of 528 Corriedale ewes as well as the growth rate of their lambs was studied at the Experimental Station Dr. Mario A. Cassioni. Animals coming from a flock mated in April-May and weaned on 4 January of 1994 were stratified at the beginning of the experiment by age and body condition and assigned at random to treatments. Graing was continuous and mostly on natural pastures. The number of marked lambs per ewe joined was higher in the later services (77.7 vs 62.1%; P=0.0006). This figure was a consequence of the improvement in the fertility registered in the first year (81.6 vs 62.3%), and in the survival rate of lambs born later in the second year of the experiment  (96.7 vs 85.1%). Wool production was similar in both seasons (4.3 vs 4.2 Kg, early and mid-Autumn, respectively; P>0.10), while daily gain of lambs in the first 85-90 days was higher for the early matings (0.134 vs 0.116 Kg/day; P=0.0001), although of insignificant biological meaning. Results suggest that displacement of services from beginning to middle Autumn, maximized productivity indexes mainly obtained through a reduction of lambs mortality for those lambs born in Spring that profit from the improvement registered at lamming.