Effects of individual or combined xylanase and phytase supplementation on energy, amino acid, and phosphorus digestibility and growth performance of grower pigs fed wheat-based diets containing wheat millrun

¹ Prairie Swine Centre Inc., Saskatoon, SK, Canada, S7H 5N9; Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5A8
² Prairie Swine Centre Inc., Saskatoon, SK, Canada, S7H 5N9
³ Danisco Animal Nutrition, Marlborough, UK, SN8 1AA
⁴ Department of Animal Science, Michigan State University, East Lansing, MI 48824
⁵ Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5

^* To whom correspondence should be addressed. E-mail: ruurd.zijlstra{at}ualberta.ca.

	Abstract

The objective was to determine if dietary enzymes increase the digestibility of nutrients bound by non-starch polysaccharides (NSP), such as arabinoxylans, or phytate in wheat millrun. Effects of millrun inclusion rates (20 or 40%), xylanase (0 or 4,375 units/kg feed), and phytase (0 or 500 phytase units/kg feed) on nutrient digestibility and growth performance were investigated in a 2 x 2 x 2 factorial arrangement with a wheat control diet (0% millrun). Diets were formulated to contain 3.34 Mcal DE/kg and 3.0 g true ileal digestible Lys/Mcal DE, and contained 0.4% chromic oxide. Each of 18 cannulated pigs (36.2 ± 1.9 kg) was fed 3 diets at 3 times maintenance in successive 10-d periods for 6 observations per diet. Feces and ileal digesta were collected for 2 d. Ileal energy digestibility was linearly reduced (P < 0.01) by millrun and increased by xylanase (P < 0.01) and phytase (P < 0.05). Total tract energy digestibility was linearly reduced by millrun (P < 0.01) and increased by xylanase (P < 0.01). For 20% millrun, xylanase plus phytase improved DE content from 3.53 to 3.69 Mcal/kg DM, a similar content as the wheat control diet (3.72 Mcal/kg DM). Millrun linearly reduced (P < 0.01) ileal digestibility of Lys, Thr, Met, Ile, and Val. Xylanase improved (P < 0.05) ileal digestibility of Ile and Val. Phytase improved ileal digestibility of Lys, Thr, Ile, and Val (P < 0.05). Millrun linearly reduced (P < 0.05) total tract P and Ca digestibility and retention. Phytase (P < 0.01) and xylanase (P < 0.05) improved total tract P digestibility, and phytase and xylanase tended to improve (P < 0.10) P retention. Phytase improved Ca digestibility (P < 0.05) and retention (P < 0.01). The 9 diets were also fed to 8 individually-housed pigs (36.2 ± 3.4 kg) per diet for 35 d. Millrun reduced (P < 0.05) ADFI, ADG, and final BW. Xylanase increased (P < 0.05) G:F, phytase reduced (P < 0.05) ADFI, and xylanase tended to reduce (P = 0.07) ADFI. In summary, millrun reduced energy, AA, P, and Ca digestibility and growth performance compared to that of the wheat control diet. Xylanase and phytase improved energy, AA, and P digestibility, indicating that NSP and phytate limit nutrient digestibility in wheat by-products. The improvement by xylanase in energy digestibility coincided with improved G:F, but did not translate into improved ADG.

Key Words: millrun, phytase, pig, wheat, xylanase

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