title: Low-protein diets affect ileal amino acid digestibility and gene expression of digestive enzymes in growing and finishing pigs.
abstract: The objective of this study was to evaluate effects of dietary crude protein (CP) intake on ileal amino acid digestibilities and expression of genes for digestive enzymes in growing and finishing pigs. In Experiment 1, 18 growing pigs (average initial BW = 36.5 kg) were assigned randomly into one of three treatments (n = 6/treatment group) representing normal (18 % CP), low (15 % CP), and very low (12 % CP) protein intake. In Experiment 2, 18 finishing pigs (average initial BW = 62.3 kg) were allotted randomly into one of three treatments (n = 6/treatment group), representing normal (16 % CP), low (13 % CP) and very low (10 % CP) protein intake. In both experiments, diets with low and very low CP were supplemented with crystalline amino acids to achieve equal content of standardized ileal digestible Lys, Met, Thr, and Trp, and were provided to pigs ad libitum. Daily feed intake, BW, and feed/gain ratios were determined. At the end of each experiment, all pigs were slaughtered to collect pancreas, small-intestine samples, and terminal ileal chymes. Samples were used for determining expression of genes for digestive enzymes and ileal amino acid digestibilities. Growing pigs fed the 12 % CP and 15 % CP diets had lower final body weight (P < 0.01) and ADG (P < 0.0001) when compared with pigs fed the 18 % dietary CP diet. Growing pigs fed with the 12 % CP diet showed higher digestibilities for CP (P < 0.05), DM (P < 0.05), Lys (P < 0.0001), Met (P < 0.01), Cys (P < 0.01), Thr (P < 0.01), Trp (P < 0.05), Val (P < 0.05), Phe (P < 0.05), Ala (P < 0.05), Cys (P < 0.01), and Gly (P < 0.05) than those fed the 18 % CP diet. Finishing pigs fed the 16 % CP diet had a higher (P < 0.01) final body weight than those fed the 10 % CP diet. mRNA levels for digestive enzymes (trypsinogen, chymotrypsin B, and dipeptidases-II and III) differed among the three groups of pigs (P < 0.05), and no difference was noted in the genes expression between control group and lower CP group. These results indicated that a reduction of dietary CP by a six-percentage value limited the growth performance of growing-finishing pigs and that a low-protein diet supplemented with deficient amino acids could reduce the excretion of nitrogen into the environment without affecting weight gain.
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China.|University of the Chinese Academy of Sciences, Beijing, 10008, China.
authors.forename: Liuqin
authors.initials: L
authors.lastname: He
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China.|University of the Chinese Academy of Sciences, Beijing, 10008, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.affiliation: Software Department, Nanchang Hangkong University, Nanchang, 330063, Jiangxi, China.
authors.forename: Zhiqi
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China. tjli@isa.ac.cn.
authors.forename: Tiejun
authors.initials: T
authors.lastname: Li
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China. yaokang@isa.ac.cn.
authors.forename: Kang
authors.initials: K
authors.lastname: Yao
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China.|University of the Chinese Academy of Sciences, Beijing, 10008, China.
authors.forename: Zhijie
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Key Laboratory of Agroecological Processes in Subtropical Region, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock and Poultry, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, Hunan, China. yinyulong@isa.ac.cn.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Department of Animal Science, Texas A&M University, College Station, TX, 77843, USA.
authors.forename: Guoyao
authors.initials: G
authors.lastname: Wu
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D001835:Body Weight; D002918:Chymotrypsin / Q000235:genetics / Q000378:metabolism; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000032:analysis / Q000378:metabolism*; D004063:Digestion; D005260:Female; D007082:Ileum / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D013552:Swine / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014362:Trypsinogen / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D014362:Trypsinogen; D002918:Chymotrypsin; C117609:chymotrypsin B
keywords: Amino acid; Crude protein; Digestive enzyme; Low nitrogen; Pig