The influence of pasture species and exogenous oestrogen treatment on the live-weight gain and carcass composition of lambs

Abstract

The live-weight gain, carcass weight, and carcass composition of wether lambs grazing two different pasture species have been studied.The 56 lambs (by Dorset Down rams out of Border Leicester X Corriedale ewes) of approximately 8 weeks of age were randomised to four treatment groups. Two of the groups were grazed on pure perennial ryegrass and two on pure lucerne for 7 weeks before slaughter. Seven of the lambs in each of the treatment groups received 336 )Lg diethylstilboestrol by subcutaneous injection weekly. Carcass composition was determined by chemical analyses.The lambs grazed on lucerne grew at 0.37 kg/day, 76% faster than those on perennial ryegrass (0.21 kg/day). The hot carcasses of the lucerne-grazed group were 7.0 kg heavier than those of the perennial ryegrass group and differed in composition (+ 3.7% fat, -3.1% water, + 0.8% protein, no difference in ash). This difference in carcass composition is explained by the increase in carcass weight.Oestrogen treatment enhanced live-weight gain (+ 0.04 kg/day); did not affect hot carcass weight; reduced the fat content of the carcass by 2%; and increased the water content by a similar figure. These results are discussed in relation to previous work on pure pasture species and implantation of diethylstilboestrol, and brief reference is made to the relative rates of growth of the carcass components.

Effect of herbage species and feeding level on internal parasites and production performance of grazing lambs

“…In both years lambs grazing lucerne and chicory grew faster than lambs grazing grasses when offered the same allowance of green DM which is consistent with the findings of Nicol & McLean (1970) and Komolong et al (1992). The latter workers concluded that an improved supply of non-ammonia N relative to the digestible energy intake best explained the difference in growth rate between chicory and Wana cocksfoot.…”

Effect of cattle grazing strategies and pasture species on internal parasites of sheep

“…Lucerne has been shown to give higher lamb growth rates than grass-based pastures (Nicol & McLean 1970;Scales et al 1995). However, in the present experiment its use did not improve ewe or lamb liveweights, nor did it assist in reducing lamb worm burdens.…”

The production and utilization of lucerne in New Zealand

“…The livcwcight gain (gd^') of lambs fed on lucerne compared to lambs fed on white clover, ryegrass and ryegrass/white clover pastures Jagusch and McConnell 1971Raltray el al. 1976McLean ^/flA, 1965Nicol and McLean 1970McLean etal, 1962McLean ei at.. 1965Jagusch etat., 1979Jagusch etat.. 1979Joyce ei ai, 1972Highicffl/.. 1972Highiera/.. 1972 occurs by not harvesting the autumn growth until the lucerne is dormant in early winter (Douglas, 1971). In regions where some winter growth occurs, autumn and winter spelling or winter spelling alone gave greater additional spring production than the growth which was foregone by being un-uti!ised (Janson, 1974(Janson, , 1975d.…”

“…Overseas, phyto-oestrogens in lucerne improved the growth of wether lambs but not ewe lambs where meals were made from lucerne containing low and high coumestrol levels (Oldfield et ai, \ 966), but in the grazed situation Nicol and McLean (1970) considered it unlikely that phyto-oestrogens would contribute to high liveweight gains. High coumestrol levels are likely where leaf fungal diseases are active but where diseased lucerne was compared to non-oestrogenic lucerne kept free of fungal diseases by fungicide sprays.…”