Brady Campbell, Program Coordinator, OSU Sheep Team
The most common method for finishing lambs in the United States is the use of a high concentrate diet. Although high concentrate diets allow for lambs to be finished at a younger age, one down fall of this feeding strategy is that lambs may to accumulate an excessive amount of carcass fat. An alternative method to finish lambs would be the use of pasture. Forage fed lambs develop less carcass fat, but require a longer period of time to finish and are harvested at an older age when compared to concentrate fed lambs. In order to determine which feeding strategy will yield the greatest amount of marketable product, a comparison of light and heavy weight lambs on two different diets has been summarized.
In order to make this comparison, lambs were harvested at two different weights (light: 115 lbs. and heavy: 170 lbs.) and fed two different diets (lambs fed a concentrate formulated diet (Table 1): concentrate fed lambs; lambs grazing ryegrass: forage fed lambs). As for the results, lambs fed to a finishing weight of 170 lbs. and fed a high concentrate diet developed an excessive amount of carcass fat. Lambs grazing on ryegrass had leaner carcasses, but from a production standpoint, these lambs required more time to reach a heavier slaughter weight (170 lbs.) when compared to concentrate fed lambs. From a consumer standpoint, the wholesale cuts from heavy weight forage fed lambs were less palatable as indicated by a consumer taste panel.
When lambs were fed to similar weights, all wholesale cuts (leg, loin, rack, and shoulder) from concentrate fed lambs were heavier than those of forage fed lambs. Lambs fed to a heavier live weight also had a heavier carcass weight when compared to the light lambs, regardless of diet. Heavy weight lambs showed an increase in loin weight, with concentrate fed lambs having a heavier loin when compared to forage fed lambs. However, this weight difference can be attributed to the increase in carcass fat of the concentrate fed lambs and therefore adding to the weight of the loin muscle. Heavy weight forage fed lambs exhibited more lean mass in all wholesale cuts when compared to heavy weight concentrated fed lambs due to an increase of fat in the concentrate fed lambs.
Therefore, increasing slaughter weights of forage fed lambs can increase lean muscle mass. Increasing slaughter weights of concentrate fed lambs will increase lean mass to a lesser extent as concentrate fed lambs accumulate more fat. Forage fed lambs may require more time to achieve a desired finishing weight, however, forage fed lambs will result in leaner and higher yielding carcass when compared to concentrate fed lambs. Additional research is needed in order to determine the palatability of lamb fed alternative finishing diets.
Borton, R. J., S. C. Loerch, K. E. McClure, and D. M. Wulf. 2005. Characteristics of lambs fed concentrates or grazed on ryegrass to traditional or heavy slaughter weights. II. Wholesale cuts and tissue accretion. J. Anim. Sci. 83: 1345-1352.