Abstract

In experiment 1 six groups, each of 10 superfine Merino wethers were individually penned indoors and hand-fed chopped lucerne hay with either control pellets, cottonseed meal pellets (CSM) or cottonseed meal plus hydroxymethyl-methionine pellets (CSMEP). Following their shearing, the 6 groups in experiment 2 were hand-fed 1 of 3 chopped lucerne hay:oat rations [75: 25,50: 50,25: 75% (w/w)]. Each sheep was also fed either control pellets (25 g/day) or CSMEP pellets (75 g/day) in a cross-over design experiment. In both experiments, the rations were fed at maintenance level and were offered 3 times a week. Half of the sheep had no rumen ciliate protozoa. In experiments 1 and 2, wool production was measured during a 4 and 6 month period respectively. In experiment 1, defaunation resulted in a 6% increase in clean wool production on the unsupplemented chopped lucerne hay ration. Inclusion of CSM and CSMEP pellets resulted in clean wool growth responses of 16% and 19% respectively. Unacceptable increases in fibre diameter were associated with the increased wool production. In experiment 2, the clean wool response to defaunation was highest (12%) on the 75% chopped lucerne hay ration, when the control pellet was fed. Inclusion of the CSMEP pellet resulted in clean wool growth responses of 0.73, 0.98 and 0.99 g/day in sheep fed on the 75,50 and 25% chopped lucerne hay rations respectively. The wool production responses due to the CSMEP pellet were associated with increases in fibre diameter (0.3 ¦m), length (4 mm/year) and length/diameter ratio (0.4 ¦m/day.¦m) of the wool grown. It was concluded that CSMEP pellets are best fed with a mixed ration containing more grain than chopped lucerne hay. The wool growth response to feeding hydroxymethyl-methionine was considered uneconomic.