Growth performance and preference studies to evaluate solvent-extracted Brassica napus or Brassica juncea canola meal fed to weaned pigs1

Inclusion of conventional dark-seeded (Brassica napus) and novel yellow-seeded (Brassica juncea) canola meal (CM) can potentially replace soybean (Glycine max) meal (SBM) in pig diets. Our objective was to examine the preference of weaned pigs fed diets containing SBM or B. napus or B. juncea CM and to compare it against previously reported growth performance data (Exp. 1 and 2). In Exp. 1 and 2, growth performance was evaluated using 220 and 240 weaned pigs, respectively, by replacing dietary SBM with up to 20% B. napus (Exp. 1) or 24% B. juncea CM (Exp. 2). Feeding up to 20% B. napus CM to pigs did not affect growth performance, but increasing inclusion of B. juncea CM linearly reduced (P < 0.001) ADFI, ADG, and G:F most likely due to the higher content of glucosinolates, particularly gluconapin in B. juncea CM as confirmed by principle component analysis. In Exp. 3 and 4, SBM and B. napus and B. juncea CM fed at 20% dietary inclusion were evaluated in 2 preference studies using 216 and 144 pigs of 35 d of age, respectively. Pens equipped with 2 feeders housed 8 or 4 pigs per pen, in Exp. 3 and 4, respectively. Diets formulated to equal NE and standardized ileal digestible AA were offered in a paired choice as mash (Exp. 3) or pellets (Exp. 4) for 3 consecutive 7-d periods (3 d nontest and 4 d preference test). The 3 treatments offered were (i) SBM vs. B. napus CM, (ii) SBM vs. B. juncea CM, and (iii) B. napus vs. B. juncea CM. Pigs preferred SBM (P < 0.001) over B. napus and B. juncea CM diets, and pigs preferred B. napus (P < 0.001) over B. juncea CM diet. High content of the glucosinolate gluconapin likely reduced feed preference in B. juncea more than in B. napus CM. In conclusion, the contrast between preference and performance studies feeding CM to pigs indicates that preference studies should be interpreted cautiously until validated by growth performance data.