Growth performance, carcass characteristics and pork quality of pigs fed diets containing meal from conventional or glyphosate-tolerant canola

Growth performance, carcass characteristics and pork quality were evaluated for pigs fed barley and wheat-based diets, which included meal from conventional or transgenic glyphosatetolerant (Roundup-Ready) canola. One hundred and forty-four pigs (72 gilts and 72 barrows) weighing 30 3 kg were assigned, three to a pen, on the basis of gender and weight to receive one of four dietary treatments formulated using canola meal from two commercial sources (COM1 and COM2), non-transgenic parental control (PCC) or transgenic (RRC) canola. Pigs were fed a grower diet (75 g kg(-1) canola meal) until 60.5 +/- 4.0 kg and then a finishing diet (150 g kg(-1) canola meal) to 108.6 +/- 7.3 kg at slaughter. Pigs receiving the COM1 and COM2 diets had an overall higher (P < 0.0001) daily feed intake (DFI) compared with pigs fed the PCC and RRC diets. Corresponding average daily gain (ADG) was also increased (P = 0.02) for COM1-fed pigs, although feed conversion efficiencies (FCE) of the pigs were similar (P > 0.05) among diets. Gilts had lower overall DFI (P < 0.0001), ADG (P < 0.0001) and FCE (P = 0.04) compared with barrows. Pigs receiving the PCC and RRC diets had heavier (P = 0.002) liver weights than those pigs fed the COM1 and COM2 diets (2.06 and 2.05 kg vs. 1.95 and 1.96 kg, respectively). Postmortem decline in pH and temperature of the longissimus thoracis (LT) muscle from pigs were not different (P > 0.05) among the dietary treatments. Characteristics of pork quality for the LT muscle, which included objective colour and shear force were also not affected (P > 0.05) by dietary source of canola meal. Gross composition of commercial pork cuts were similar (P > 0.05) among the dietary treatments with the exception of small differences for intermuscular (P = 0.04) and body cavity (P = 0.02) fat in the picnic cut and body cavity (P = 0.02) fat in the loin cut. Differences in DFI, ADG and liver weights of the pigs may be related to higher content of antinutritional glucosinolates (mu moles g(-1)) in the PCC (20.20) and RRC (15.04) varieties compared with COM1 (7.55) and COM2 (7.46) sources of canola meal.