Reproduction, growth and survival of Merino ewes and lambs in south-western Queensland and their response to trace element supplementation

Abstract

The effects of cobalt (Co), selenium (Se), copper (Cu) and Co + Se + Cu plus manganese, iodine and zinc (All) supplements on the liveweight change, fleece weights, reproduction and survival of Merino ewes and their lambs were studied on 3 commercial properties (W, B and G) in south-western Queensland during 1978 and 1979. There was no significant effect of supplementation on ewe and lamb liveweights or ewe fleece weights in 1978 (723 mm rain). In 1979 (303 mm rain), ewes given Co and All supplements were significantly (P<0.05) heavier than all other ewes at weaning, but lamb weaning weights were not improved by any supplements. Zinc and manganese may have only been effective for a short period following dosing. Weaner lambs given supplements of Co, Se and Co+Se had significantly (P<0.05) higher greasy fleece weights (3.67 kg) than unsupplemented lambs (3.38 kg). In 1978, there was no significant effect of supplementation on reproductive rate. On property W, only 68% of maiden ewes successfully mated and this flock had a significantly (P<0.05) higher rate of reproductive wastage (27%) than did flocks on properties B (12.5%) and G (16.5%). The mean liveweights of maiden ewes for properties W, B and G in this year were 39.1, 35.1 and 37.1 kg, respectively. In 1979, ewes given the All supplement had significantly (P<0.05) lower overall rates of reproductive wastage (12.2%) than did ewes without supplement (30.2%). Supplementary treatments did not improve ewe or lamb survival. In 1978, ewe mortality between joining and weaning was significantly (P<0.05) higher on property W (24.2%) than on property G (7.0%). In 1979, there were no significant effects of either age or property on ewe mortality between joining and weaning. Neither trace element supplementation to ewes nor the sex of the lamb had a significant effect on lamb survival between marking and weaning.