Composition of enzyme mixtures influences the faecal digestion of a weaner pig feed

Estimates of energy release from corn:soy and wheat-based diets of approximately 0.2 MJ/kg were identified in response to the use of xylanase (Feng et al. 2013) using a two-phase semi-automated simulated digestion system (SDS) in vitro that simulated the gastric and intestinal phases of digestion in the grower pig. The present study sought to extend these findings through examination of mannanase and protease inclusions in enzyme mixtures containing xylanase and other exogenous enzymes in weaner pigs.

Thirty mixed sex, PIC-type pigs [initial body weight (BW) of 12.8 ± 0.59 kg (mean ± SE)] were obtained from a commercial herd and assigned by sex and BW to one of five treatments consisting of either phytase alone (PHY; EC3.1.3.26, 0.1 U/g) or in combination with xylanase (EC3.2.18, 8 U/g), cellulase (EC3.2.1.24, 0.24 U/g) and amylase (EC3.2.1.4, 0.05 U/g). Protease ((EC3.2.23.6) and mannanase (EC3.2.1.78) inclusions were adjusted to provide calculated activities of 0, 0.6, 1.5, 1.8 and 2.4 U/g, for treatments PHY, XCA, XCP, XCM and XMP, respectively. Enzymes were obtained from commercial sources [AsiaPac (Dongguan) Biotechnology]. A pelleted corn:soybean meal-based diet was formulated to provide 13.8 MJ digestible energy (DE)/kg and 9 g/kg available lysine. It contained distillers dried grains with soluble (DDGS), rice bran and rice bran meal at 5%, 3.95% and 3.5% of the diet, respectively. This provided a calculated non-starch polysaccharide (NSP) content of 124 g/kg. Pigs were housed individually in a climate controlled room. Feed and water were available ad libitum. Feed use was monitored daily over a 28-day period commencing at d 18 after introduction to the facility. Body weight was recorded weekly. Faecal output was determined by total collection on d 25 to 27 for estimation of the coefficients of total tract apparent digestibility (CTTAD) for dry matter (DM), crude protein (CP) and fibre. Chemical analyses were undertaken using standard laboratory procedures (PONY Laboratories, Shenzhen). Acid detergent fibre (ADF) and neutral detergent fibre (NDF) were estimated after the methods of van Soest and Wine (1968). Data were analysed using a GLM procedure (Minitab^®, Version 14.0; USA) blocked for treatment and sex. Initial BW was used as a covariate in the analysis of BW and feed intake.

Feed:gain tended to decline (P = 0.15) with increased mannanase and protease inclusion (Table 1). The CTTAD of CP increased (P < 0.025) with increased protease and mannanase inclusion. All combinations containing the XCA mixture increased the CTTAD (P < 0.05) of the ADF fraction above that of the single enzyme (PHY).

Table 1.  Performance measures and coefficients of total tract apparent digestibility (CTTAD) in young pigs receiving mannanase (M) and protease (P) in enzyme mixtures

The results support those previously obtained in vitro with multiple enzyme inclusions producing greater component digestibility. Effects on BW gain were marginal but not unexpected. Small group sizes (n < 10) and the relatively low NSP content of the diet challenge the identification of statistically significant production responses. Further commercial studies will determine whether trends to reduced intake and weight gain with higher inclusions of mixed enzymes can be offset by gains in feed use efficiency.