Effects of Fiber Concentration and Fermentation Rate on Reproductive Performance, Nutrient Digestibility, and Immune Response of Lactating Sows.

High fiber diets are known to have many benefits to sows (e.g., improving reproductive performance such as vitality of piglets, stimulating gut health, and improving well-being), and due to their fermentation properties, they may have different functions in lactating sows. Fast fermentable fiber favors the growth of beneficial microbiota which contributes to improved gut health, and slow fermentable fiber increases the fecal mass and provides a delayed release of some nutrients which benefits the farrowing process of sows. On the other hand, high fiber diets may reduce feed intake and nutrient digestibility. The objective of this study was to investigate the effects of dietary fiber concentration and fermentation rate on lactating sow performance, nutrient digestibility, and immunity. Four diets were formulated with increasing fast fermentable fiber, with diets 1 and 2 formulated at low (15%) total dietary fiber (TDF) and diets 3 and 4 at high (25%) TDF. The proportion of fast fermentable fiber in total diet of 4 treatments were 1.25%, 2.5%, 3.75%, and 5% respectively. The main fiber sources were sugar beet pulp, oat hull, and barley. Digestible energy, crude protein, and lysine levels were comparable among each treatment group. A total of 136 lactating sows (Landrace × Large White) were blocked by parity, body weight (BW), and back fat (BF), and then randomly assigned to each block (8 blocks). Feed allowance was set to increase from 3 kg/d (primiparous) or 3.5 kg/d (multiparous) at farrowing to a maximum of 7 kg/d or 8 kg/d at 7d or 8d post farrowing. Results showed that sows in high fiber groups had an increased litter weight gain and BF loss (P < 0.05), and sows in fast fiber groups showed a decreased BW and protein loss (P < 0.05). Low fiber fed sows showed a significantly increased digestibility of protein, gross energy (GE), and dry matter compared with high fiber ones (P < 0.05). Sows fed with slow fermentable fiber in the low fiber groups showed greater digestibility of GE, protein, and dry matter compared with the ones fed with fast fermentable fiber; however, the opposite was true in high fiber groups. Fiber concentration and fermentation rate did not show significant effects on serum IL-8, IL-10, TNF-a, or endotoxin of sows (P > 0.05). In conclusion, high fiber diet increased BF loss and negatively influenced nutrient digestibility while having positive effects on litter growth. The negative effects of fiber were partially compensated by increasing the soluble fraction. Based on the current study, when feeding lactating sows a diet with high fiber, a relative increase of fast fermentable fiber is the most favorable feeding strategy. [ABSTRACT FROM AUTHOR]