Naked oats (Avena nuda) as a substitute for maize in diets for weanling and grower-finisher pigs

The naked oat (Avena nuda), cultivar Bandicoot (145.6 g kg(-1) crude protein (CP), 35.6 g kg(-1) crude fibre (CF) and 94.3 g kg(-1) ether extract (EE)), was evaluated in the diets of weanling and grower-finisher pigs (Large White X Landrace), Four diets for weanling pigs were formulated on an iso-nutrient basis [approximately 16.3 MJ kg(-1) dry matter (DM) digestible energy (DE), 207.2 g kg(-1) CP, 15.4 g kg(-1) lysine, 8.0 g kg(-1) methionine plus cystine and 2.8 g kg(-1) tryptophan on a DM basis] so that maize-meal was substituted by increasing levels of naked oats (0%; 33%; 67% and 100%). Similarly four diets for grower-finisher pigs were formulated on an iso-nutrient basis (approximately 15.1 MJ kg(-1) DM DE, 200.5 g kg(-1) CP, 11.3 g kg(-1) lysine, 8.0 g kg(-1) methionine and cystine and 2.8 g kg(-1) tryptophan on a DM basis), where maize was substituted in the same way. Weanling pigs (n = 52) were fed ad libitum from 8.7 to 21 kg live weight. Piglets were kept in pairs (one gilt and one castrated boar combined at random), in cages (1.5 X 1 m) with solid floors, fitted with a self-feeder and equipped with an automatic water nipple. Grower-finisher pigs (n = 52), individually housed in flat deck-type cages (1.6 x 1 m), fitted with a self-feeder and equipped with an automatic water nipple, were fed ad libitum from 25.7 up to 89.2 kg, whereafter pigs were slaughtered and carcass characteristics determined. In a digestion trial, maize-meal and naked oats were supplied as sole sources, Although the DM digestibility of maize was slightly higher (P less than or equal to 0.05) in comparison to naked oats, both sources were nearly equal in DE content (respectively 17.7 and 17.9 MJ kg(-1) DM). Crude protein digestibility was higher (P less than or equal to 0.05) for naked oats (83.7%) in comparison with maize (79.3%). No significant effect of the inclusion of naked oats in the diets of weanling pig was observed on feed conversion ratio (FCR) or growth rate, but piglets receiving 100% oat as grain source consumed 17.5% (P less than or equal to 0.02) less feed day(-1) than piglets receiving diets where 33% and 67% of the maize was replaced. Grower-finisher pigs on the diets with 67% and 100% replacement of maize by naked oats consumed 6.8% less (P less than or equal to 0.05) feed day(-1) than pigs on the 100% maize diet. DM intake decreased by 57.8 (SE(b) = 21.3) g day(-1) (P less than or equal to 0.01) with every increment of maize replacement. No significant effect on the diet on average daily gain (ADG) or feed conversion was observed, although ADG was reduced by 11.8 (SE(b) = 8.3) g day(-1) (NS) with every increment of oat inclusion, No significant differences in dressing percentage (mean of 76.7%), percentage meat in the carcass (67.3%) or P-2 back fat thickness (mean of 17.2 mm) were observed. It appears from the results that naked oats can provide a successful alternative to maize in the diets of pigs, although the amount of naked oats in the diets of weaned piglets should not exceed 492.5 g kg(-1). Naked oats can replace a large portion of the protein sources conventionally associated with maize-based diets.