The energetic value of nonstarch polysaccharides in relation to physical activity in group-housed, growing pigs

The dose response effect of dietary nonstarch polysaccharide (NSP) content on physical activity in relation to metabolic rate in pigs was studied. Twelve clusters of 14 pigs (50-kg castrated males) were fed one of four diets, similar in composition, except for the starch and NSP content. The difference in starch and NSP ratio was created by exchanging sugar beet pulp silage (SBPS) for tapioca. On a DM basis, diets contained 0, 5, 10, or 15% SBPS. Pigs were housed in groups and fed at 2.5 times the maintenance energy requirements. Nitrogen and energy balances were measured per cluster during a 7-d experimental period, which was preceded by a 2-wk adaptation period. Dietary composition did not affect ADG. Metabolizability decreased with increasing dietary SBPS content (P < .01). Heat production as well as energy retention were unaffected by the exchange of starch for NSP (P > .1). However, dietary composition affected energy expenditure on physical activity (P < .10). Pigs were more quiet when dietary NSP content increased. Based on heat production data and on apparent digestibility of crude protein, crude fat, and NSP, the estimated net energy value of fermented NSP was 14.8 kJ/g. This relatively high energy value of fermented NSP was mainly related to the lowered energy expenditure for physical activity, 3.9 kJ/g of fermented NSP. The present study demonstrated that the lower energetic utilization of fermented NSP compared with that of starch can be fully compensated in pigs by reducing their physical activity. Thus, energy evaluation systems should account for systematic dietary influences on physical activity.