Dietary fiber in a low-protein diet during gestation affects nitrogen excretion in primiparous gilts, with possible influences from the gut microbiota

Abstract

We investigated the effects of dietary fiber (DF) supplementation in normal or low crude protein (CP) diets on reproductive performance and nitrogen (N) utilization in primiparous gilts. In total, 77 Landrace × Yorkshire (LY) pregnant gilts were randomly allocated to four dietary treatments in a 2 × 2 factorial design. The groups comprised 1) equal intake of normal CP (12.82% and 0.61% total lysine), 2) low CP (10.53% and 0.61% total lysine), and 3) with or 4) without DF supplementation (cellulose, inulin, and pectin in a 34:10:1 ratio). A low-protein diet during gestation significantly reduced daily weight gain from days 91–110 of pregnancy (-162.5 g/d, P = 0.004). From N balance trials conducted at days 35–38, 65–68, and 95–98 of pregnancy, DF addition increased fecal N excretion at days 65–68 (+24.1%) and 95–98 (+13.8%) of pregnancy (P < 0.05), but reduced urinary N excretion (P < 0.05), resulting in greater N retention at each gestational stage. DF increased fecal microbial protein levels and excretion during gestation. A low CP diet also reduced urinary N excretion at different gestational stages. An in vitro fermentation trial on culture media with non-protein N urea and ammonium bicarbonate (NH4HCO3) as the only N sources revealed that microbiota derived from feces of gestating gilts fed the high DF diet exhibited a greater capacity to convert non-protein N to microbial protein. Microbial fecal diversity, as measured by 16S rRNA sequencing, revealed significant changes from DF, but not CP diets. Gilts fed a low CP diet had a higher number of stillbirths (+ 0.83 per litter, P = 0.046) and a lower piglet birth weight (1.52 kg vs. 1.37 kg, P = 0.006), regardless of DF levels. Collectively, DF supplementation to gestation diets shifted N excretion from urine to feces in the form of microbial protein, suggesting that the microbiota had a putative role in controlling N utilization from DF. Additionally, a low-protein diet during gestation negatively affected the litter performance of gilts.

Effects of Dietary Fiber, Crude Protein Level, and Gestation Stage on the Nitrogen Utilization of Multiparous Gestating Sows

“…In other studies, the combined supplementation of inulin and cellulose to increase both dietary SF and ISF contents had positive effects on ovarian follicular development in gilts [ 6 , 7 ] and litter size [ 8 ] in gestating sows. The current findings revealed that DF addition to both normal and low CP diets did not negatively affect the ADG of gestating sows, which is consistent with previous research using pectin, inulin, and cellulose as DF [ 4 ]. However, the ADG during days 91 to 110 of gestation was not affected by DF supplementation in sows fed the low CP diet but was increased by DF in gestating sows fed the low CP, indicative of the effect of DF and CP levels on the nutrient utilization of late gestating sows.…”

“…Gestating sows were moved to stainless-steel metabolism crates to measure their nitrogen balance, as previously described [ 4 , 12 ]. There were two nitrogen balance trials conducted on days 30 to 38 and 90 to 98 of pregnancy.…”

“…Dietary fiber (DF) is mainly included in the diets for gestating sows to improve the gut fullness, reduce the incidence of constipation and promote gastrointestinal health with the colonization of beneficial commensal microbiota and their physiologically active by-products such as short-chain fatty acids (SCFAs) following fermentation [ 3 ]. The level of DF is another regulator of nitrogen balance, which increases the fecal nitrogen excretion while reducing the nitrogen excretion in urine [ 4 , 5 ], but the effect of dietary fiber inclusion at different levels of dietary crude protein on the nitrogen utilization and reproductive performance remains uncertain. Inulin is a water-soluble fiber (SF) belonging to a group of non-digestible carbohydrates called fructans, and it is easily fermented by microbiota in the gut.…”

Low Protein Diet Improves Meat Quality and Modulates the Composition of Gut Microbiota in Finishing Pigs

“…Dietary high CP level would increase the excretion of excessive nitrogen, reduce the efficiency of nitrogen utilization, and damage gut health by more protein fermentation in the hindgut ( 1 ). Many studies have shown that the reduction of dietary CP levels could effectively reduce the fecal and/or urinary nitrogen excretion in growing pigs ( 23 ), finishing pigs ( 13 ), primiparous gilts ( 24 ), as well as growing goats ( 25 ), and decrease blood urea nitrogen concentration in weaned piglets ( 26 ) and mice ( 27 ). Moreover, lowering dietary CP levels significantly reduced nitrogen consumption without negative consequences on growth performance in growing bulls ( 28 ).…”

Effects of Corn and Broken Rice Extrusion on the Feed Intake, Nutrient Digestibility, and Gut Microbiota of Weaned Piglets

“…Fecal microbiota were collected from each pen at day 28 and used in in vitro fermentation trials, conducted as previously described, but with minor modifications [ 14 ]. Briefly, feces were rectally collected, placed in plastic bags, anaerobically preserved in a foam box filled with ice, and transferred to the laboratory within 2 h. Feces (~70 g) were weighed and mixed with 0.9% sterile saline at 1:5 (g/mL).…”