Effects of feeding transgenic canola on apparent digestibility, growth performance and carcass characteristics of lambs

This study evaluated the effects of including meal from glyphosate-tolerant (Roundup-Ready ® ) canola (RRC) in barley-based diets for lambs on apparent digestibility of the diets, growth performance of the lambs, and carcass quality and composition. Four isonitrogenous diets were prepared that included canola meal [6.5%, dry matter (DM) basis] from four different sources (two commercially available canola blends, COM1 and COM2; a transgenic line, RRC and the parental non-transgenic line from which RRC was derived, PAR). Apparent digestibilities of the four diets were determined using eight mature wethers (67.8 ± 2.3 kg) in a replicated Latin square with four 21-d periods. No aspect of digestibility (DM, fibre, or nitrogen balance) was influenced by canola source. The growth trial involved 60 early-weaned Arcott lambs (30 ewes; 30 wethers; initial age approximately 2 mo; initial weight 21.5 ± 1.0 kg). The lambs were blocked by weight and gender for assignment to treatments, and fed the diets until reaching or exceeding 45 kg body weight. Intake of DM was similar among lambs fed COM1, COM2 and PAR diets, and between PAR and RRC (COM1, COM2 > RRC, P < 0.05). Diet did not affect (P > 0.05) average daily gain or feed efficiency. Carcass yield grade was higher (P < 0.05) for COM1 and COM2 diets than for PAR or RRC, although carcass composition did not differ (P > 0.05) between PAR and RRC. Canola source did not affect (P > 0.05) meat tenderness, as determined by shear force, drip loss or intramuscular fat content. Meat colour o f RRC-fed lambs did not differ from that of all other treatment groups. In this study, including canola meal prepared from glyphosate-tolerant canola did not alter diet digestibility, feed efficiency, growth performance, carcass characteristics or meat quality of lambs. Key words: Growth, lambs, meat quality, ruminant, transgenic canola