Brassicaand Sugarbeet Forages for Lambs-Growth Performance of Lambs and Composition of Forage and Dock-Fat Fatty Acids

Abstract

Brassica species are well suited for late fall production, and provide a high-quality forage for growing lambs (Ovis aries). This study was conducted to compare growth and fatty acid composition of adipose tissue of lambs that grazed either of two Brassica forages with lambs that grazed sugarbeet (Beta vulgaris L.) forage. The Brassicas were planted in early August as a second crop following flat pea (Lathyrus latifolius L.) silage harvest. Seventy-two ewe lambs were randomly allotted to nine replicates of eight lambs. Three replicates of lambs were randomly assigned one of three forage diets. They grazed either tyfon (B. campestris L. × B. rapa L.), ‘Green Globe’ turnips (B. rapa L.), or sugarbeet tops and roots from 4 November to IS December. Thirty-six of the lambs continued on the treatments until 6 January when they were slaughtered. Subcutaneous (dock) adipose tissue was obtained at slaughter for fatty acid analysis. Total gains, final weights (6 January), carcass weights, and dressing percents were less (P < 0.05) for lambs that grazed beet tops and roots than lambs grazing either tyfon or turnips. Quality and yield grades of carcasses were not different. Adipose tissue of lambs that grazed beet forage had more (P < 0.05) 12:0 and 14:0 and less (P < 0.05) 19:0 and 18:3 fatty acids than adipose tissue from lambs that grazed turnips or tyfon. Lambs that grazed Brassica forages showed improved performance late in the season compared with lambs that grazed beet forage. Fatty acid composition of depot fat was influenced by type of forage grazed by the lambs.