The effect of feeding increasing inclusion of extruded Brassica juncea canola expeller on growth performance and nutrient digestibility in weaned pigs

Abstract

Expellers contain more dietary energy than meals to support growth performance of young pigs. The feeding value of extruded Brassica (B.) juncea canola expeller was evaluated feeding 240 weaned pigs (initial body weight 7.6kg), starting 1 week after weaning at 19 days of age. The extruded B. juncea expeller contained (as is) 344g crude protein, 15.7g chemically available lysine (Lys), 169g ether extract, 127g acid detergent fibre, 195g neutral detergent fibre/kg and 11μmol/g total glucosinolates. Pigs were fed five pelleted wheat-based diets for two growth phases: Phase 1, days 0–14; and Phase 2, days 15–35. Diets including 0, 60, 120, 180 and 240g extruded B. juncea expeller/kg were formulated to provide 10.0 and 9.7MJ net energy (NE)/kg and 1.17 and 1.06 standardised ileal digestible (SID) Lys/MJ NE for Phase 1 and 2 diets, respectively. The extruded B. juncea expeller substituted soybean meal. Diets were balanced for NE by decreasing canola oil inclusion from 55 to 29 and 26 to 0g/kg for Phase 1 and 2, respectively; and for amino acids by increasing crystalline amino acids. Increasing dietary inclusion of extruded B. juncea expeller linearly reduced (P<0.001) apparent total tract digestibility of dry matter, gross energy and crude protein and decreased diet digestible energy values in both phases. For days 0–35, increasing inclusion of extruded B. juncea expeller did not affect feed efficiency, but quadratically increased average daily feed intake (ADFI; P<0.001) and average daily gain (ADG, P<0.01), which corresponded with a quadratic increase (P<0.01) in intake of NE and SID Lys. On day 35, pigs fed 60, 120, 180 and 240g extruded B. juncea expeller/kg were 1.1, 1.5, 1.5 and 1.1kg heavier (P<0.05), respectively, than control pigs. Feed energy values may explain the achieved performance. For diet formulation, we used 22.46MJ NE/kg for canola oil (NRC, 1998) instead of the more recent 31.63MJ NE/kg (NRC, 2012). Using the revised NE value, calculated diet NE values (as fed) decreased from 10.55 to 10.30 in Phase 1 and from 9.92 to 9.71MJ NE/kg in Phase 2 diets for pigs fed 0 to 240g extruded B. juncea expeller/kg. In conclusion, reduced diet NE value coincided with increased NE and SID Lys intake that consequently increased ADG. The linear increase of ADFI and ADG may have been curved at 240g extruded B. juncea expeller/kg by increased dietary glucosinolates intake that prevented further increases in ADFI.