Proceedings of the New Zealand Society of Animal Production.
1992, 52: 211-216
Proceedings of the New Zealand Society of Animal Production.
1992, 52: 211-216
Inverdale genotype (++ vs I+) had no significant influence on any liveweight or fleece weight examined so both genotypes were combined. Relative to a Romney industry control line, the three lines derived from screening for high prolificacy with subsequent selection on ovulation rate (Romneys, Perendales and Coopworths) had significantly heavier ewe hogget (12 month) liveweights after adjustment for non-genetic factors with weights of 32.9 (100), 38.7 (118), 39.1 (119) and 41.4 (126) kilograms (percentage relative to Romney controls). Hogget fleece weights (kg) were 2.38 (100), 2.69 (113), 2.29 (96) and 2.89 (121) respectively.
The Inverdale gene had a large effect on reproductive traits, increasing ovulation rate by 0.98 and increasing litter size by 0.31. However, this was negated by a lower survival rate in the progeny resulting in little change in net reproductive rate. Relative to Romney industry controls the high prolificacy Romney (++), Perendale and Coopworth flocks all had higher ovulation rates which translated into heavier weight of lamb weaned per ewe mated with weights of 16.8 (100), 20.9 (124), 21.9 (130), and 26.0 (155) kilograms respectively. The benefits were still substantial even after consideration of wool clipped and correction for ewe liveweight. The flocks represent a valuable genetic resource for improvement of the sheep industry.
Keywords: NZSAPAB; Sheep; breed; Coopworth; Perendale; Romney; prolificacy; liveweight; fleece weight; reproduction.
