Carcass fatness in lambs grazing various forages at different rates of liveweight gain

Abstract

In three experiments, Dorset, Suffolk cross, or Coopworth lambs weighing c. 30 kg in January were offered a range of forages including high-endophyte Nui ryegrass-dominant pasture, white clover-dominant pasture, Moata or Concord ryegrasses, lucerne, rape, or chicory. Herbage allowances were adjusted to achieve target liveweight gains of 300, 200, or 120 g/day and lambs slaughtered at c. 43 kg liveweight from March to May. In Experiment 1, medium and low rates of liveweight gain were compared on both ryegrassdominant and clover-dominant swards. In Experiment 3, the comparison was extended to include a high rate of liveweight gain (300 g/day) on cloverdominant swards. Allowances of Nui ryegrass required to achieve liveweight gains of 200 g/day were over 2 times greater than that of clover and up to 5 times greater than for chicory and lucerne. There was no effect of liveweight gain on carcass GR measurements of lambs grazing ryegrass-dominant pastures when compared at the same carcass weights but lambs growing rapidly on clover-dominant pastures were up to 3 mm fatter (P < 0.01) at the GR site than slower-growing lambs. There was no effect of forage type on leanness of lambs grown at 200 g/day nor was there any effect of forage type and liveweight gain on meat quality. Restricting the diet to maintain lamb liveweight of 43 kg for 30-53 days gave inconsistent removal of fat and can not be recommended as a strategy to produce leaner lambs.A93002

The effects of grazing forage legumes on the performance of finishing lambs

“…There were also no significant between-forage differences in depth of LD muscle or subcutaneous fat at finish. This is in agreement with previous reports that forage type has little effect on carcass composition (Nicol & Mclean 1970;Scales 1993), although Purchas & Keogh (1984) reported leaner carcasses of lambs grazed on Lotus pedunculatus than when grazed on white clover. Carcass weights and killing out percentages for all forages were lower than those obtained by Karnezos et al (1994).…”

The effect of forage type on lamb carcass traits, meat quality and sensory traits

“…This may indicate a higher gut fill in the brassica fed lambs, consistent with the reduced ME of this forage. There is evidence that lambs fed on brassicas will be fatter than those finished on grass (Scales, 1993), a finding supported by the work of Hopkins et al (1995a). In that latter study, again without replication of the treatments, brassica fed lambs had a higher DP than lambs finished on pasture.…”

Effects of food quality on growth and carcass composition in lambs of two breeds and their cross

“…Butler-Hogg and [ohnsson (1986), however, suggested that a higher growth rate could lead to leaner carcasses. The apparent contradiction may arise because the composition of the food changes the effect that growth rate has on carcass composition (Scales, 1993). Lewis et al (2004) showed that lower food protein content decreased growth rate and increased fatness.…”