The effect of dietary particle size and enzyme supplementation on N and P excretion were investigated in a 3 × 2 × 2 factorial arrangement, with three particle sizes (400, 700, or 850 μm), two levels of a carbohydrase cocktail [0 or 444 added units (U) β-glucanase plus 1385 added U xylanase kg-1 diet], and two levels of phytase (0 or 374 added U phytase kg-1 diet), for a total of 12 dietary treatments. Diets (70% barley, 25% peas) were formulated to contain 3.25 Mcal digestible energy (DE) kg-1, 1.6 g digestible lysine Mcal-1 DE, and 1.2 g kg-1 available P. Sixty pigs (25.3 ± 1.4 kg) had restricted access (3 × maintenance DE) to feed, and five individual pig observations for each of the 12 mash diets were obtained. Reducing particle size from 700 to 400 µm reduced total P excretion 12% and increased P digestibility and retention 15% (P < 0.05), while phytase reduced total P excretion 28% and increased P digestibility and retention 42% (P < 0.01). Reducing particle size from 850 and 700 to 400 µ m decreased total N excretion 4 and 7%, respectively (P < 0.05). Carbohydrase did not affect P digestibility or excretion (P > 0.10), but increased digestibility of N and energy (P < 0.05). Carbohydrase interacted with particle size for energy digestibility (P < 0.01) and with phytase for N and energy digestibility (P < 0.05). Particle size affected N excretion and energy digestibility more than enzyme supplementation, while phytase affected P excretion more than particle size, suggesting that particle size reduction and phytase supplementation are effective to reduce nutrient excretion of grower pigs. Key words: Particle size, carbohydrase, phytase, pig, nitrogen, phosphorus
Genetics of residual feed intake in growing pigs: Relationships with production traits, and nitrogen and phosphorus excretion traits1
