|Van keuren, Robert|
Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/14/1995
Publication Date: N/A
Citation: Interpretive Summary: Today's consumers are demanding leaner meat products because of perceptions that fat consumption leads to health problems. The type of feeding system, especially the finishing system used for ruminant animals, has been shown to affect the time required for finishing ruminants as well as the efficiency of feed utilization by the animal. This study evaluated grain versus pasture-growing/finishing versus finishing on concentrate after grazing on pasture on growth and tissue accretion in lambs. When slaughtered at the same market body condition, lambs grazed or backgrounded on forages have lower daily gains, slower accretion of body tissues but more carcass lean and less fat than lambs placed in drylot and fed a high concentrate diet immediately following weaning. Lambs grazed on alfalfa finish sooner than those grazed on ryegrass. One of the biggest benefits to forage-based finishing systems for ruminants may be the improved efficiency of production resulting in reduced waste for end product processing.
Technical Abstract: Weaned Targhee X Hampshire lambs (average BW = 27.6 kg) were used to determine the effects of concentrate feeding, forage grazing or finishing on concentrate after grazing upon growth and carcass tissue accretion. Lambs were assigned randomly and balanced by weight and sex to five replicated treatments (12 lambs/treatment): all-concentrate in drylot (DL); ;rotational grazing alfalfa (ALF); rotational grazing ryegrass (RG); RG for 62 d, then DL (RGDL); RG for 62 d, then ALF (RGALF). Lambs were slaughtered when fat thickness over the ribeye was estimated at 3.8 to 5.6 mm. Lamb growth and carcass measurements included ADG, accretion of bone, lean, and fat in the carcass, and final BW. Lambs on DL had the highest (P = .001) ADG, whereas lambs on RG treatments tended to have the lowest ADG and heaviest final BW. Compared with DL, ALF lambs had lower (P < .05) ADG, but comparable final BW. Lambs that grazed RG had more (P = .001) carcass lean weight than lambs fed in DL, but carcass lean weight of lambs grazed on AL did not differ (P > .05) from that of lambs on DL or RG treatments. Carcass fat was less (P = .001) for ALF than for DL, RGDL, or RGALF treatments. Daily accretion of bone, lean, and fat was highest (P = .001) for DL. Daily accretion of lean and fat for RG was less (P = .001) than for ALF but did not differ (P > .05) from that of RGALF. Lean:fat ratio in weight gain for DL was less (P < .01) than ALF and RG, which were similar to RGDL and RGALF. When slaughtered at the same level of fat over the ribeye, DL-fed lambs had higher ADG and fewer days on test than grazed lambs. However, lambs finished or backgrounded on forage had high lean:fat tissue gain and a higher percentage of lean in their carcasses than DL-fed lambs.