The effect of introducing purified β-glucans to a wheat-based diet on total tract digestibility and gaseous manure emissions from pigs as compared with consumption of a β -glucan-rich, barley-based diet

Consumption of barley-based diets has been demonstrated to reduce manure odour and ammonia emissions generated from pig production, but is associated with depressed nutrient digestibility when compared with wheat-based formulations. It was hypothesised that supplementation of a wheat-based diet with purified mixed-linkage β (1,3) (1,4)-D-glucan (β -glucans) to levels comparable with a barley-based diet may beneficially ameliorate manure odour and ammonia emissions, without depressing nutrient digestibility. A complete randomized design experiment was conducted to investigate the effect of dietary β -glucans source and an enzyme composite containing β -glucanase and β -xylanase on energy and nutrient digestibility, distal gastrointestinal tract fermentation, manure odour and ammonia emissions from finishing boars. Twenty-eight boars (74.2 kg SD 3.6) were assigned to one of four dietary treatments (n = 7); (1) a barley-based diet (B), (2) a barley-based diet + enzyme composite (BE), (3) a wheat-based diet + purified β –glucans (WG) and (4) a wheat-based diet + purified β -glucans + enzyme composite (WGE). The wheat-based diets containing purified β -glucans were formulated to contain concentrations of total β -glucans comparable with the barley-based diets.

Consumption of the WG diet increased the coefficient of total tract apparent digestibility (CTTAD) of gross energy (P = 0.001) and N (P = 0.001) compared with the B diet. Pigs offered the WG diet had increased manure ammonia emissions (P = 0.042) compared with the B diet. There was no significant difference between consumption of the WG diet and the B diet on subsequent manure odour emissions.

In summary, the current study demonstrates that β-glucans may be added to a wheat-based diet without depressing nutrient digestibility as compared with a barley-based diet. Furthermore, manure odour from pigs offered a wheat-based diet containing β –glucans may be improved to levels comparable with a barley-based diet. However β-glucan supplementation was ineffectual at attenuating manure ammonia emissions comparable with consumption of a barley-based diet.