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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 content of several common fibrous ingredients fed to nursery pigs, and then evaluate the effect of dietary fermentable fiber level on growth performance and fecal microbial composition of nursery pigs.
Methods: In trial 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, apple pomace, or soybean hulls. In trial 2, 180 nursery pigs were housed in 30 pens (6 pigs / pen) and randomly allotted to be fed five diets with different fermentable fiber to total dietary fiber ratios, which were 0.52, 0.55, 0.58, 0.61, and 0.64, respectively.
Results: Fermentable fiber content in sugar beet pulp, apple pomace, and soybean hulls was greater than that in other ingredients. Water binding capacity of fibrous ingredients was positively correlated to the digestibility of total dietary fiber, acid detergent fiber, and non-starch polysaccharides in test ingredients. Pigs fed the sugar beet pulp, apple pomace, and soybean hulls diets had greater fecal acetic acid and total short-chain fatty acids concentrations compared with pigs fed other diets. Fecal acetic acid and total short-chain fatty acids concentrations were positively correlated with fermentable fiber content in experimental diets. Average daily weight gain and average daily feed intake of pigs quadratically increased as the ratios of fermentable fiber to total dietary fiber increased. Pigs in fermentable fiber-64% group showed higher ACE index and fecal acetic acid concentration compared with pigs fed the dietary fermentable fiber/ total dietary fiber ratio of 0.52 to 0.61.
Conclusion: Compared with the classification system of soluble dietary fiber and insoluble dietary fiber, fermentable fiber could better describe the mechanism by which dietary fiber has beneficial effects on pig gut health.
Zhang, G., Zhao, J., Song, X., Yang, M., Wang, H., & Wu, Y. (2023). Feeding dietary fermentable fiber improved fecal microbial composition and increased acetic acid production in a nursery pig model. Journal of Animal Science, 101, skad260. https://doi.org/10.1093/jas/skad260