GROUND RAPESEED FROM LOW ERUCIC ACID (LEAR) CULTIVARS SPAN AND ZEPHYR WITH OR WITHOUT ORGANIC ACID TREATMENT AS A DIETARY INGREDIENT FOR GROWING–FINISHING PIGS

Sixty-four crossbred weanling pigs, equalized between gilts and barrows, were fed ad libitum from 17 to 89 kg liveweight on eight dietary treatments. Diets contained 0 or 10% ground full-fat rapeseed of either Brassica campestris cv. Span or Brassica napus cv. Zephyr, both low erucic acid types. The rapeseed was treated with 0, 5 or 10% of a mixture of ⅔ acetic–⅓ propionic acid prior to grinding. One treatment was fed a diet without rapeseed or organic acids and a second fed 1% organic acids without rapeseed, a level equivalent to 10% acid added to rapeseed. The two rapeseed cultivars were similar in composition except that Span contained 1.0% C 22:1 (erucic acid) in the oil compared with 5.2% C 22:1 in Zephyr. Daily feed intake, daily gain and efficiency of feed conversion were not significantly influenced by treatment. Digestible energy (DE) per kg gain was depressed by rapeseed with or without organic acid treatment. DE and metabolizable energy coefficients were reduced by the inclusion of dietary rapeseed with or without organic acids, but the acids alone did not depress digestibility. Digestible nitrogen (DN) and N retention were not influenced significantly by diet. There was an overall trend for improved carcass quality in all treatments receiving rapeseed, or rapeseed with organic acids. There was a general increase in 18:2, 18:3 and 20:1 and decrease in 16:0, 18:0 and 16:1 (Zephyr rapeseed only) fatty acids in the carcass backfat of pigs receiving rapeseed or rapeseed plus organic acids. There was less than 0.05% C 22:1 in any of the backfats. There were no significant treatment × sex interactions. Gilts had superior carcass leanness and superior DE and DN coefficients with improved N retention compared with barrows.