Growth performance of nursery pigs fed pelleted wheat-based diets containing graded levels of supplemental xylanase

The nutritive value of wheat for monogastric animals varies due to, among other factors, the fibrous cell wall structure of the grain. For example, correlation of digestible energy (DE) content in 15 Canadian wheat samples with their chemical characteristics revealed that the non-starch polysaccharides’ content, specifically the concentration of arabinose and xylose, explained more than 70% of the variation in DE content (Zijlstra et al. 1999). Degradation of dietary fibrous components using xylanase stimulated feed intake, nutrient digestibility and digesta short chain fatty acids in weaned pigs fed wheat diets (Walsh et al. 2014). However, few studies have examined the effects of higher (>2000) doses of xylanases. It is hypothesised that growth performance of pigs fed wheat-based diets after weaning will be improved in a dose-dependent manner by supplemental xylanase. Therefore, the objective was to provide growth performance data for nursery pigs fed graded levels of supplemental xylanase in wheat-based diets.

A basal diet was formulated to meet or exceed the NRC (1998) nutrient requirements for nursery pigs for a two-phase feeding program: 10 to 20 kg body weight (BW) (Phase I, d 0–21) and 20 to 50 kg BW (Phase II, d 22–42). Wheat, soybean meal, barley, wheat millrun and canola meal were respectively included at 35, 27, 10, 7 and 6% in Phase I diets and 48, 27, 10, 10, and 0.6% in Phase II diets. Diets were fortified with amino acids, vitamins, and minerals to meet nutrient requirements according to NRC (1998). The DE content was 14.1 MJ/kg and 13.9 MJ/kg and true ileal digestible Lys was 13.5 and 12.5 g/kg in Phase I and II, respectively. For each phase, two other test diets were prepared by adding 2000 U or 4000 U of xylanase (XU)/kg of feed. Diets were prepared in pellet form at 70°C. A total of 192 piglets (9.2 ± 0.16 kg BW; mean ± SEM) were weaned and based on their BW assigned in a completely randomised block design to pens containing two barrows and two gilts to give 12 replicate pens per diet. Pigs had free access to feed and water. Feed intake and BW were measured weekly to determine average daily feed intake (ADFI), average daily gain (ADG) and gain to feed (G : F). Data were analysed using linear and quadratic contrasts (SAS^®; USA).

Assayed dietary xylanase activities in the control, 2000 and 4000 XU diets in Phase I were <100, 1506 and 3754, respectively; corresponding values for Phase II diets were <100, 1633 and 3782, respectively. Supplemental xylanase tended to improve ADG in a linear fashion (P = 0.060) (Table 1). As a result, pigs receiving diets with 4000 XU/kg were 1.5 kg heavier (P = 0.024) relative to the control-fed pigs at the end of the experiment. The ADFI was not affected (P > 0.10) by feeding treatments. However, supplemental xylanase linearly improved G : F (P = 0.040) such that pigs fed 4000 XU/kg exhibited 2.7% greater G : F relative to the control. In conclusion, pigs fed wheat-based diets with xylanase during the initial 42 days after weaning were heavier at the end of the study, and utilised feed more efficiently compared with pigs fed a control diet without addition of xylanase.

Table 1.  Effects of graded levels of xylanase on growth performance of nursery pigs fed wheat-based diets after 42 days