When conducting a digestibility trial, pigs are usually fed only twice a day with a restricted feed intake which is not representative of the feeding conditions in a commercial farm. This study aimed to determine the effects of meal size and frequency, and exogenous enzymes (xylanase and phytase) on the digestibility of a high-fiber diet using porcine in vivo and in vitro approaches. Pigs (n = 6) were fitted with a T cannula, and each received all treatments using a 6 × 6 Latin square experimental design. The diets were supplemented (Enz) or not with a combination of xylanase and phytase and distributed into three feeding programs: one received two meals per day that met three times the maintenance energy requirement (2M), one received the same quantity of feed in eight meals (8M), and another received an amount that met five times the maintenance energy requirements in eight meals (8M+). For in vitro experiment, the degradability of fiber with or without xylanase supplementation only was determined. Enzyme supplementation increased apparent ileal digestibility (AID) of dry matter, starch, and degradation of insoluble non-starch polysaccharides (I-NSP) in all in vivo treatments (P < 0.05). The 2M compared with 8M increased the AID of starch and total tract digestibility of organic matter and I-NSP (P < 0.05). Enzyme supplementation decreased the content of insoluble arabinoxylan (P < 0.05) and increased arabinoxylan oligosaccharides (P < 0.05) in the in vivo ileal digesta and in vitro incubation. The results of this study confirm degradation by xylanase of the fiber fraction at the ileal level, which resulted in less fermentation of fiber in the large intestine. However, number and size of meals had little influence on feed digestibility. The consequences of shifting fiber fermentation more towards the upper part of the gastrointestinal tract need further investigation. The in vitro model provided a confirmation of the action of xylanase on the degradation of non-starch polysaccharides.
Keywords: dietary fiber; digestibility; exogenous enzyme; growing pig; meal frequency; meal size.
To reduce cost and also utilize locally produced ingredients, pig diets nowadays can include a large proportion of fiber-rich ingredients. Exogenous enzymes can be added to diets to improve their digestibility and limit negative effects of fiber. Usually, when conducting a digestibility trial, pigs are fed only twice a day with a restricted feed intake which is not representative of feeding conditions in a commercial farm. This study aimed to determine the effect of meal size and frequency, and enzyme supplementation on digestibility of a diet rich in fiber in growing pigs and in vitro. The diets were supplemented (Enz) or not with xylanase and phytase, and according to different size and frequency: one treatment was pig receiving two meals per day with five times the maintenance energy requirement (2M), another received the same quantity of feed in eight meals (8M), and the last received an amount close to ad libitum feeding in eight meals (8M+). An in vitro experiment was also conducted to look at degradability of fiber with and without xylanase. The results showed that xylanase allows degradation of fiber and increases digestibility of dry matter, starch, and energy. The number and size of meals have little influence on digestibility.
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