Effects of dietary crude protein level and N-carbamylglutamate supplementation on nutrient digestibility and digestive enzyme activity of jejunum in growing pigs

Abstract

Three experiments were conducted to investigate the effects of dietary crude protein (CP) level and N-carbamylglutamate (NCG) supplementation on apparent total tract digestibility (ATTD) and ileal digestibility of nutrients and digestive enzyme activity of jejunum in growing pigs. In experiment 1, 10 Duroc × Landrace × Yorkshire barrows (initial BW: 48.7 kg) were allotted to a three-period switchback design with five experimental diets and two replicate pigs per diet in each period. Diets were categorized as high CP (HP, 18% CP), moderate low CP (MLP, 15% CP), very low CP (VLP, 12% CP), and MLP and VLP with 0.1% NCG supplementation. Feces and urine were collected from day 6 to day 11 after a 5-d adaptation period. The DE, ME, and ATTD of GE, OM, CP, NDF, ADF, and P decreased (P < 0.01) with a reduction of dietary CP, but no effect of dietary treatments on pig daily N retention was detected. The NCG supplementation increased (P < 0.01) DE and ATTD of ADF of the VLP diet. In experiment 2, 10 jejunal-cannulated Duroc × Landrace × Yorkshire barrows (initial BW: 44.5 kg) were fed five diets for three periods as experiment 1. Jejunal fluid was collected on days 6 and 8 after a 5-d adaptation period. The digestive enzymes activity was not affected by dietary CP level, except for α-amylase, for which there was a decrease (P < 0.01) in pigs fed VLP diets compared to HP and MLP diets. In experiment 3, 12 ileal-cannulated Duroc × Landrace × Yorkshire barrows (initial BW: 46.7 kg) were allotted to a three-period switchback design with six diets and two replicate pigs per diet in each period. The six experimental diets consisted of five experimental diets as experiment 1 and one N-free diet. Ileal digesta was collected from day 6 to day 8 after a 5-d adaptation period. Results indicated that apparent ileal digestibility (AID) of CP and P and ileal digestibility of Arg, His, Ile, Leu, Phe, and all dispensable AA, except Pro, decreased (P < 0.01) in pigs fed VLP diet compared to HP and MLP diets, but AID of GE, OM, EE, NDF, and ADF were not affected. The supplementation of NCG in the VLP diet increased (P < 0.01) the AID of CP and ileal digestibility of Arg, His, Leu, Phe, Val, Ser, and Tyr. In conclusion, reducing dietary CP level decreased nutrient digestibility, but improved the efficiency of dietary N utilization and reduced N emission. Moderate reduction of dietary CP level had a minimal effect on nutrient digestibility and digestive enzyme activity. Additionally, NCG supplementation plays a beneficial effect on nutrient digestion only if the dietary CP level is extremely lowered.

Compromised Hindgut Microbial Digestion, Rather Than Chemical Digestion in the Foregut, Leads to Decreased Nutrient Digestibility in Pigs Fed Low-Protein Diets

“…By supplementing crystalline amino acids, LP diets can precisely satisfy the amino acid requirements of livestock and poultry while saving feed costs and reducing nitrogen pollution via excretion, which is considered the key to efficient animal husbandry [ 17 ]. However, recent studies have demonstrated that even when the limiting amino acid nutrient requirements are satisfied, the growth performance of pigs fed LP diets is impaired, which may be related to the compromise in nutrient digestibility [ 3 , 4 , 18 ]. In the present experiment, cross-feeding, microbial flora analysis, and in vitro fermentation assays were applied to investigate the focal point of the effects of dietary CP content on nutrient digestibility in pigs.…”

Effects of Inclusion of N-Carbamylglutamate in the Non-Protein Diet on Growth and Slaughter Performance, Meat Quality, Nitrogen Metabolism and Antioxidant of Holstein Bulls

“…Previous studies showed that dietary NCG had a beneficial effect on the feed efficiency of broilers and pigs [ 22 , 23 ]. NCG supplementation has a beneficial effect on nutrient digestion only if the dietary CP level is extremely lowered [ 24 ]. In addition, NCG improved the relative weight of the small intestine and intestinal morphology of pigs, which is beneficial for intestinal digestion 7.…”

Low Crude Protein Diet Affects the Intestinal Microbiome and Metabolome Differently in Barrows and Gilts

“…The gastrointestinal tract was removed after the pigs’ abdominal cavities were opened. A colonic content sample of each pig, which has the most abundant microbiota populations in all intestinal sections and where protein fermentation is thought to mostly occur in the region ( Williams et al, 2001 ; Wang Y. et al, 2020 ), was collected in 5 mL sterile frozen tubes, immediately flash-frozen in liquid nitrogen, and stored at -80°C for further analysis.…”

“…Studies in piglets showed that dietary protein levels altered the intestinal microbiota compositions and microbially-derived metabolites ( Rist et al, 2013 ). In growing-finishing pigs, because of their relatively stable microbiota structure, studies focused on environmental influences of N extraction ( Zhao et al, 2019 ; Kim et al, 2020 ; Wang Y. et al, 2020 ). In fact, increasing studies indicate that the compositions and structure of the intestinal microbiota can change dynamically in response to many factors, including feed ( Isaacson and Kim, 2012 ; Ananthakrishnan, 2015 ).…”