COMPARATIVE-ASSESSMENT OF BIOLOGICAL EFFICIENCY OF CROSSBRED LAMBS FROM 2 COMPOSITE LINES AND DORPER SHEEP

Reproduction, growth and biological efficiency of two Composite dam lines, developed from Finnsheep and indigenous breeds, were investigated and compared to Dorpers. Composite and Dorper ewes were mated to Dorper rams. Ewes were exposed to three 30-d joining periods in 2 years. Litter size was 1.35, 1.48 and 1.08 lambs born to Composites 1, 2 and Dorpers, respectively. Lambs born per lambing opportunity (fecundity) were 0.88, 0.93 and 0.75 for the three groups, respectively. Birth weights (BW) of lambs of Dorper ewes were higher than those of Composite ewes (P less than or equal to 0.05), but not weaning weight (WW) (at approx. 63 d) or 100 d weight (100 W). Cumulative DDM intake (DDMI) was 49% greater in Dorper ewes than in Composites. Total carcass weight (CW) and carcass energy content produced (E) per ewe was higher in Dorper, while CW/100 kg DDMI and E/kg DDMI were higher in Composites. In terms of these efficiency parameters, Composites were 84 and 79% more efficient than Dorpers in the 2-yr period. Ewes producing twins were 43% more efficient than those producing singles. Optimum efficiency was calculated at approx. one twin slaughtered every 8 months. Results demonstrated that owing to the outstanding performance and small size of these Composites, efficiency can be improved considerably by using them in crossbreeding systems.