Effect of dietary soyabean hulls and metal-amino acid chelated mineral supplementation on growth performance, nutrient digestibility and noxious gas emission in growing pigs

Abstract

A 2 × 2 factorial design Experiment 1 was conducted in order to characterize the effects of soyabean hulls (control or soyabean hulls diet) and metal-ammo acid chelated minerals (MAC) (sulphate or MAC) on growth performance and nutrient digestibility in growing pigs. Forty eight pigs with the initial body weight (BW) 18.0 ± 1.1 kg were assigned on the basis of weight and sex to one of four treatments (2 pigs/pen, 6 replication pens/treatment, 6 barrows and 6 gilts/treatment). Throughout the experimental period, growth performance was not shown to be affected by dietary treatments. The coefficients of the total tract apparent digestibility of dry matter (DM) and nitrogen (N) remained unaffected by soyabean hulls diets or MAC supplementation. In Experiment 2, four barrows were used in a 4 × 4 Latin square design, to determine the effects of soyabean hulls and mineral types on emission of faeces and slurry noxious gas, including ammonia (NH3), hydrogen sulphide (H2S) and mercaptans (R.SH), in growing pigs. Faeces and urine grab samples were collected, and the faeces (300 g) and slurry (faeces + urine = 150 + 150 g) were mixed, stored, and fermented for 5 d in order to evaluate noxious gas emission. Pigs fed diets with soyabean hulls tended to have lower NH 3 emission from faeces (P=0.09) than those fed the control diet, but NH3 emission from the slurry was not affected by soyabean hulls diet (P=0. 12). No significant effects on the faeces or slurry NH3 emission were exerted in MAC supplementation treatment. A significant level of interaction between soyabean hulls and MAC was observed both in the faeces and slurry NH3 emission (P=0.05, P=0.01). Pigs fed diets with soyabean hulls tend to exhibit lower H2S emission from the slurry (P=0.07), but significantly lower levels of H2S emission both from faeces and slurry (P=0.004, P=0.02) was observed when pigs were fed on MAC diets. The emission of R.SH from faeces significantly decreased (P=0.02) in MAC supplementation treatments, but not from slurry, and no soyabean hulls effects or interaction were observed in relation to R.SH emission. We conclude that the interaction between dietary soyabean hulls and MAC may have an effect on noxious gas emission. The emission of NH3 from pig faeces could be substantially reduced by diets enriched with soyabean hulls and emission of H2S both from pig faeces and slurry could be reduced by MAC supplementation.