Feeding dietary fermentable fiber improved fecal microbial composition and increased acetic acid production in a nursery pig model.

The objective of this study was to determine the fermentable fiber (FF) content of several common fibrous ingredients fed to nursery pigs, and then evaluate the effect of dietary FF level on growth performance and fecal microbial composition. In experiment 1, 54 nursery pigs were randomly allotted to be fed nine diets with six replicate pigs per diet. Dietary treatments included a corn-soybean meal basal diet and eight test diets based on a mixture of the corn-soybean meal diet and corn distillers dried grains with solubles, sunflower meal, oat bran, wheat bran, corn bran, sugar beet pulp (SBP), apple pomace (AP) or soybean hulls (SH). In experiment 2, 180 nursery pigs were housed in 30 pens (six pigs per pen) and randomly allotted to be fed five diets with different FF to total dietary fiber (TDF) ratios, which were 0.52, 0.55, 0.58, 0.61, and 0.64, respectively. Results showed that the FF content in SBP, AP, and SH was greater (P < 0.01) than that in other ingredients. Water binding capacity of fibrous ingredients was positively correlated (P < 0.05) to the digestibility of TDF, acid detergent fiber, and non-starch polysaccharides in test ingredients. Pigs fed the SBP, AP and SH diets had greater (P < 0.05) fecal acetic acid and total short-chain fatty acids (SCFAs) concentrations compared with pigs fed other diets. Fecal acetic acid and total SCFAs concentrations were positively correlated (P < 0.05) with FF content in experimental diets. Average daily weight gain and average daily feed intake of pigs quadratically increased (P < 0.01) as the ratios of FF to TDF increased. Pigs in FF64% group showed higher (P < 0.05) ACE index and fecal acetic acid concentration compared with pigs fed the dietary FF/TDF ratio of 0.52 to 0.61. Compared with the classification system of soluble dietary fiber and insoluble dietary fiber, FF could better describe the mechanism by which dietary fiber has beneficial effects on pig gut health. In nursery pigs, dietary fiber has received increasing attention because of its beneficial effects on the development and functional aspects of the gut. The most common physicochemical classification of dietary fiber is to divide it into two categories based on its solubility in water, as an indicator of its potential function and physiological effects in the gastrointestinal tract. Generally, soluble fiber, as the primary source of microbiota-derived short-chain fatty acids, is considered a useful predictor of the degree of microbial fermentation in the gut. Although fiber solubility may provide the first valuable information regarding physiological considerations of fermentability, it is not applicable to all fibrous ingredients, such as soluble carboxymethylcellulose, which is difficult to ferment. Therefore, this study aimed to determine the fermentable fiber (FF) content of several common fibrous ingredients fed to nursery pigs, and then evaluate the effect of dietary FF level on growth performance and fecal microbial composition of nursery pigs.

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