Effects of crossbreeding and certain environmental factors on multiple births, wool production and growth in sheep

Abstract

SUMMARYMultiple birth percentage and wool production were studied on 338 ewes (907 lambing and 873 shearing records) representing two purebreds, Oxford (O) and Suffolk (S), and four crossbreds, O × S, S × O, Cheviot (C) × O and C × S mated to purebred and crossbred rams during 9 years. Oxford ewes had 24–32% (P<0·01) fewer multiple births than ewes of the other groups, while little difference between S and the crossbreds was observed. The heterosis of the OS and SO groups was 14·6 ± 4·1%. Multiple births tended to increase 0·8% for each kg increase in body weight of the dam (r = 0·13). The repeatability estimate for multiple births was 0·24. Fleece weight was significantly affected by age and by breed group, with OS and SO crosses producing 17% more wool than their parental breeds. The repeatability of fleece weight was estimated at 0·52 ± 0·15. Fleece weight was significantly correlated with multiple birth percentage (0·09) and body weight (0·32).Suffolk ewes averaged 9·5 kg heavier than O ewes throughout their reproductive life. The two reciprocal crosses were heavier than both parental breeds. Suffolk ewes reached their maximum body weight at 4 years of age while Oxfords continued to gain weight up to 6 years.