Supplementary feeding pattern and rate of liveweight gain in winter-spring affect wool production of young Merino sheep on the south coast of Western Australia

Abstract

The effects of different supplementary feeding practices in summer-autumn and management strategies on green pasture on liveweight change, wool growth rate, annual wool production and wool characteristics of young Merino wethers were examined at 2 farms. The grain feeding treatments were lupins (L) or lupins and oats (LO) fed in amounts that were adjusted to try and maintain liveweight, or lupins and oats (LOG) fed at a higher rate. The objectives of liveweight maintenance or gain were not always achieved, but liveweight patterns differed between LOG compared with L or LO during summer-autumn. The sheep used at farm 1 were aged 4.5 months and liveweight 32 kg at the start of the experiment, while those at farm 2 were 6.5 months and liveweight 39 kg. The stocking rate in summer-autumn was 8 wethers/ha at both farms. During supplementation, sheep on LOG had a higher (P<0.05) liveweight change compared with those on L or LO (farm 1, 15 v. -8 g/sheep. day; farm 2, -35 v. -51 g/sheep. day) and clean wool growth rates (farm 1, 7.1 v. 6.4 g/sheep. day; farm 2, 5.1 v. 4.8 g/sheep.day). The sheep on LOG grew broader (P<0.05) wool than those on L or LO (farm 1, 19.0 v. 18.5 ¦m; farm 2, 21.7 v. 20.8 ¦m), and at farm 1 length was also greater (P<0.05) (114 v. 111 mm), while at farm 2 staple strength was greater (P<0.01) (22.9 v. 16.4 N/ktex). There were no significant differences in annual clean wool production. There were positive (P<0.01) relationships between staple strength and liveweight change to the time of minimum liveweight in summer-autumn. After green pasture on offer reached 500 kg DM/ha in autumn, different liveweight change patterns were achieved in 2 groups (LS, lower stocking rates; HS, higher stocking rates) of sheep at each farm by adjusting stocking rates. Within a farm, the LS and HS groups were comprised of equal numbers of sheep from each replicate of the supplementary feeding treatments. There were differences (P<0.05 to 0.01) in liveweight change between LS and HS (farm 1, 93 v. 72 g/day; farm 2, 127 v. 60 g/day), the differences being more pronounced at farm 2. The differential stocking rates at farm 2 resulted in differences in clean wool growth rates (P<0.01), in clean wool production (4.22 v. 4.53 kg, P<0.05), and fibre diameter (20.8 v. 21.4 ¦m, P<0.01), but there were no significant effects on staple length or strength. There were no significant effects of the supplementary feeding treatments imposed in summer-autumn on the responses to the stocking rate treatments on green pasture.