Dietary fiber source and stage of gestation impact water balance, fecal physicochemical properties, serum electrolytes, and markers of gut motility in sows

The study aimed to evaluate the impact of carbohydrase supplementation, soluble fiber from sugar beet pulp (SBP; 20%), and insoluble fiber from corn dried distillers grains (DDGS; 20%) on water balance, serum electrolytes, gut motility, and fecal physicochemical properties in gestating sows. Thirty-six sows, with an initial body weight of 186 ± 4.6 kg, balanced by parity, were assigned randomly to a 2×2 factorial arrangement of treatments from day 28 to 109 of gestation. The factors were fiber type (insoluble (IF; 355 g/d) or soluble (SF; 98 g/d)) and enzyme supplementation (Rovabio Advance P10). The feeding level was 2.1 kg per day. Two 8-day metabolism periods occurred during mid- (days 50-59) and late-gestation (days 99-108). Fecal samples for physicochemical property analysis and serum samples were taken on day 1 of each period. Water balance was measured from days 4-7, with a water allowance set at 80 mL/kg of body weight per day. Data were analyzed using a linear mixed model, with parity as a random effect and fiber, enzyme, period, and their interactions as fixed effects. Daily water allowance was used as a covariate when necessary. Urine output increased by 22.3% in sows fed IF compared to SF, and by 30.5% from mid- to late-gestation (Fiber, Period P<0.05). Fecal moisture was 21.8% higher in sows fed SF and increased by 12.3% from mid- to late-gestation (Fiber, Period P<0.05). The SF treatment increased fecal water holding capacity (P<0.001) and fecal water binding capacity by 76.6% (P=0.044). Regardless of diet, fecal water binding capacity increased in late gestation (Period P=0.035). Urine output increased by 30.5% in late gestation (Period P=0.028) and fecal moisture output increased by 12.3% (Period P=0.015). Serum sodium and chloride concentrations were increased in late gestation (P<0.05). Plasma cholecystokinin tended to be 28% greater in sows fed SF (P=0.070), and motilin levels decreased among all groups from mid- to late-gestation (Fiber×Enzyme×Period P=0.006). Circulating 5-Hydroxytryptamine decreased in late gestating sows fed carbohydrases (Period×Enzyme P=0.002), as well as sows fed SF (Fiber P=0.004). These findings suggest a redistribution of water in the gastrointestinal tract of late gestational sows fed SF, altering fecal hydration and gut motility.