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 × 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 × 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 × 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 ≤ 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 ≤ 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 ≤ 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 ≤ 0.05) feed day−1 than pigs on the 100% maize diet. DM intake decreased by 57.8 (SEb = 21.3) g day−1 (P ≤ 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 (SEb = 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 P2 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.