Environmental and genetic factors influencing milk and growth traits of Awassi sheep in Cyprus. Heterosis and maternal effects

Abstract

Data on 5234 purebred and crossbred ewes and 6457 purebred and crossbred lambs of both sexes, born from 1978 until 1986 at two government farms (Athalassa and Orites) were used to study some environmental and genetic factors that affect ewe productivity, milk production and lamb growth. Breed and heterosis effects (individual and maternal) were also estimated. Most of the environmental factors examined were significant sources of variation for the reproductive and production traits of the ewes and the growth traits of the lambs. Chios ewes were significantly more prolific than Awassi and crossbred ewes. Chios also produced heavier litters at birth and at weaning than Awassi ewes. On the other hand, Awassi ewes had a higher milk production compared with all other breed groups. Awassi lambs were heavier at birth, at weaning and at 105 days of age and had a faster growth rate than Chios lambs. Crossbred lambs were mostly heavier and faster growing, both before and after weaning than either purebred group. All estimates of individual heterosis for ewe reproductive and production traits were negative except for total lamb weight at weaning. On the other hand, estimates for maternal heterosis were positive, although those for milk production were close to zero. All lamb traits exhibited positive heterosis effects of crossbreeding. In addition, individual heterosis was more important than maternal heterosis.