|Mayeux Jr, Herman|
Submitted to: Sheep and Goat Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2006
Publication Date: 2/1/2006
Citation: Brown, M.A., Mayeux, H.S. 2006. Grazing performance of hair sheep. Sheep and Goat Research Journal. 20:60-65.
Interpretive Summary: Ample forage resources are available in the Southern Great Plains to support profitable small ruminant grazing systems. However, wool sheep are poorly adapted to the heat, humidity, and internal parasites common in this region. Tropically-adapted sheep such as the St. Croix, Katahdin, and Gulf Coast breeds are more adapted but there is a need to evaluate postweaning performance on forage of purebred and crossbred lambs from these breeds. Research at the Grazinglands Research evaluated the performance of tropically-adapted breeds and their crosses with wool breeds under grazing and drylot management. Tropically adapted breeds generally had lower postweaning performance than wool breeds in both grazing and drylot management. Tropically adapted x wool breed lambs were generally intermediate between the parental purebreds. Exceptions occurred in summer grazing with Katahdin and Suffolk purebreds and crosses where purebred Katahdins and Suffolks were comparable in gain on bermudagrass and there was an indication of an advantage for the crossbred over purebred lambs for drylot ADG and possibly stocker ADG. These exceptions may relate to expression of heat tolerance in the Katahdin and Katahdin crossbred lambs. Hair sheep and crosses not only may provide advantages in summer grazing, but may also be best suited for forage gains where costs of gain are lower, even though gains on pasture were less than gains in the drylot in all breeds and crosses.
Technical Abstract: Lambs from three diallel mating plans (Dorset-St. Croix, n=140; Rambouillet-Gulf Coast, n=80; Katahdin-Suffolk, n=78) and a terminal-cross mating plan (Suffolk-sired from Dorset, St. Croix, and reciprocal-cross ewes, n=100) were used to evaluate postweaning grazing performance of traditional meat breeds and tropically-adapted breeds of sheep. Tropically adapted breeds generally had lower postweaning performance than wool breeds in both grazing and drylot management with the exception that purebred Katahdin. and Suffolks were comparable in gain on bermudagrass. Tropically adapted x wool breed lambs were generally intermediate between the parental purebreds except in the Katahdin x Suffolk diallel where there was an indication of heterosis for drylot ADG and possibly stocker ADG. In more general terms, sheep seemed to perform poorly on forages compared to performance on mixed diets in drylot. These results do indicate a consistent advantage in direct breed effects for wool breeds over tropically-adapted breeds in drylot management systems. The results also suggest that there is little expression of genetic effects in sheep managed on forages, although direct effects for heat adaptation in tropically-adapted breeds may compensate for the superior direct breed effects for growth in the wool breeds under summer grazing. Keywords: Postweaning, tropically-adapted, wheat pasture, grazing