This study examined effects of dietary protein sources and levels on intestinal health of 21 to 35 d-old weaned piglets fed antibiotics-free diets. A total of 150 weaned piglets(21 d of age) were allotted to 5 dietary treatment groups. Diets were formulated, based on corn-soybean meal, with different protein sources(fish meal and soy protein concentrate) to provide different dietary CP levels. Piglets within 5 dietary treatments were fed diets as follows, respectively: 1) control diet of 17% CP(control); 2) 19% CP diets formulated with more soy protein concentrate(SPC19); 3) fish meal(FM19); 4) 23.7% CP diets formulated with more soy protein concentrate(SPC23); 5) fish meal(FM23). The results showed that piglets from control group had higher ADG and lower incidence of diarrhea compared with those of other groups(P < 0.05). The incidence of diarrhea of piglets in FM19 group was lower than those from SPC23 group and FM23 group(P < 0.05). With the higher CP levels, villous height and villous height to crypt depth ratio of piglets in the duodenum and jejunum were decreased(P < 0.05), but crypt depth was increased(P < 0.05). Comparing control group and other groups, we found the expression of inflammatory cytokines interleukin-1β(IL-1β) and interferon-γ(IFN-γ) were increased(P < 0.05) in the jejunum and colon of piglets, as did cystic fibrosis transmembrane conductance regulators(CFTR) in the distal colon. The relative transcript abundance of Zonula occludens-1(ZO-1) in the jejunum, and occludin in the jejunum and ileum of piglets fed 23.7% CP diets were reduced compared with those fed control diet(P < 0.05). In conclusion, the 17% CP diet without in-feed antibiotics helped improve growth performance and relief of diarrhea of 21 to 35 d-old weaned piglets. Dietary CP level, rather than its source(either fish meal or soy protein concentrate), has more significant impacts on the growth performance and intestinal health of 21 to 35 d-old weaned piglets when fed antibiotics-free diets.
Yunpeng WuZongyong JiangChuntian ZhengLi WangCui ZhuXuefen YangXiaolu WenXianyong Ma
The liver is the most essential organ for the metabolism of ammonia, in where most of ammonia is removed by urea and glutamine synthesis. Regulated by leucine, glutamate dehydrogenase(GDH) catalyzes the reversible inter-conversion of glutamate to ammonia. To determine the mechanism of leucine regulating GDH, pigs weighing 20 ± 1 kg were infused for 80 min with ammonium chloride or alanine in the presence or absence of leucine. Primary pig hepatocytes were incubated with or without leucine. In the in vivo experiments with either ammonium or alanine as the nitrogen source, addition of leucine significantly inhibited ureagenesis and promoted the production of glutamate and glutamine in the perfused pig liver(P < 0.05). Similarly, leucine stimulated GDH activity and inhibited sirtuin4(SIRT4)gene expression(P < 0.01). Leucine could also activate mammalian target of rapamycin complex 1(m TORC1) signaling(P < 0.05), as evidenced by the increased phosphorylation levels of ribosomal protein S6 kinase 1(S6 K1) and ribosomal protein S6(S6). Interestingly, the leucine-induced m TORC1 pathway activation suitably correlated with increased GDH activity and decreased expression of SIRT4.Similar results were observed in primary cultured hepatocytes. Notably, leucine exerted no significant change in GDH activity in SIRT4-deficient hepatocytes(P > 0.05), while m TORC1 signaling was activated.Leucine exerted no significant changes in both GDH activity and SIRT4 gene expression in rapamycin treated hepatocytes(P > 0.05). In conclusion, L-leucine increases GDH activity and stimulates glutamate synthesis from different nitrogen sources by regulating m TORC1/SIRT4 pathway in the liver of pigs.
This experiment studied the effects of dietary protein sources and levels on the gut health of piglets,p H value,and concentrations of microbial metabolites(ammonia-N,volatile fatty acids [VFA],and polyamines) in the distal colonic and proximal colonic digesta of piglets weaned at 21 d of age.A total of 150 early-weaned piglets were allotted randomly to 5 diets: 1) control diet(CT; 17% CP),2) CT formulated with more soy protein concentrate(SPC19; 19% CP),3) more fish meal(FM19; 19% CP),4) CT formulated with more soy protein concentrate(SPC23; 23% CP),and 5) more fish meal(FM23; 23%CP).Results showed high protein level increased fecal score(P < 0.05),but different protein sources did not(P > 0.05).The p H value and ammonia-N concentration of digesta in the proximal and distal colon of FM23 were significantly higher(P < 0.05) than those of CT.Acetic acid,propionic acid,butyric acid and valeric acid concentrations in the proximal colon of FM23 exceeded those of CT,SPC19,and FM19(P < 0.05);however,isobutyric acid and isovaleric acid were not affected(P > 0.05).Histamine and spermidine concentrations of FM23 were higher than those of other treatments(P < 0.05).Propionic acid and butyric acid concentrations in the distal colon were higher of FM23 than of FM19(P < 0.05); putrescine,histamine and spermidine were higher of FM23 than of LP and FM19(P < 0.05).It was concluded that high dietary CP content increased microbial metabolites(ammonia-N,histamine,putrescine) in colonic digesta and aggravated piglets' diarrhea.
