Survival, growth and wool production of South Australian strong-wool Merino and first-cross Merino lambs from birth to 16 months of age

Abstract

South Australian strong-wool Merino, Poll Dorset and Border Leicester rams were joined to 766 South Australian strong-wool Merino ewes at Minnipa Research Centre, South Australia. The survival, body growth and carcasses of the wether progeny were assessed at 3-4 1/2 months of age. The survival, body growth and wool growth of the ewe progeny were measured from birth to 16 months of age. There were no significant differences between breeds in lamb survival at birth or from 3 to 16 months of age. Merino lambs had the lowest lamb survival between birth and three months of age, the difference being significant (Pt0.05) with Border Leicester x Merino (BL x M) lambs and close to significance (P-0.07) with Poll Dorset x Merino (PD x M) lambs. At three months of age PD x M and BL x M lambs were 19 and 11% heavier respectively than Merino lambs (all differences P < 0.05). Corresponding differences at 16 months of age were 31 and 28% respectively (PD x M and BL x M did not differ significantly from each other; other differences P < 0.05). A greater percentage of BL x M (92 .5) and PD x M (89 .5) lambs grew to a marketable weight (27 kg or greater) than did Merino (63.8) lambs (P < 0.001). Dressing percentage and carcass weights were higher and mean grade scores lower for both PD x M and BL x M breeds compared with the Merino (P < 0.05). PD x M lambs had higher dressing percentages and lower grade scores than BL x M lambs (P < 0.05). Carcass weight, adjusted for differences in fasted liveweight, and carcass grade score, adjusted for differences in carcass weight, were higher in the PD x M breed than either the Merino or BL x M (P< 0.05). BL x M and strong-wool Merino ewe hoggets grew similar amounts of clean wool, and 26-31% more clean wool than the PD x M. There were differences (P< 005) between all breeds for both staple length and fibre diameter, the BL x M having the longest staples and greatest fibre diameter. We concluded that PD x M lambs were superior to the South Australian strong-wool Merinos for meat production, but BL x M and Merinos grew more wool to hogget age. The relative economic merit of the breeds may vary with the prices of the products measured in this study and with the value of the ewes for sale at hogget age.