title: Glycine is a nutritionally essential amino acid for maximal growth of milk-fed young pigs.
abstract: Analysis of amino acids in milk protein reveals a relatively low content of glycine. This study was conducted with young pigs to test the hypothesis that milk-fed neonates require dietary glycine supplementation for maximal growth. Fourteen-day-old piglets were allotted randomly into one of four treatments (15 piglets/treatment), representing supplementation with 0, 0.5, 1 or 2% glycine (dry matter basis) to a liquid milk replacer. Food was provided to piglets every 8 h (3 times/day) for 2 weeks. Milk intake (32.0-32.5 g dry matter/kg body weight per day) did not differ between control and glycine-supplemented piglets. Compared with control piglets, dietary supplementation with 0.5, 1 and 2% glycine increased (P < 0.05) plasma concentrations of glycine and serine, daily weight gain, and body weight without affecting body composition, while reducing plasma concentrations of ammonia, urea, and glutamine, in a dose-dependent manner. Dietary supplementation with 0.5, 1 and 2% glycine enhanced (P < 0.05) small-intestinal villus height, glycine transport (measured using Ussing chambers), mRNA levels for GLYT1, and anti-oxidative capacity (indicated by increased concentrations of reduced glutathione and a decreased ratio of oxidized glutathione to reduced glutathione). These novel results indicate, for the first time, that glycine is a nutritionally essential amino acid for maximal protein accretion in milk-fed piglets. The findings not only enhance understanding of protein nutrition, but also have important implications for designing improved formulas to feed human infants, particularly low birth weight and preterm infants.
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, 100193, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Wang
authors.forename: Zhaolai
authors.initials: Z
authors.lastname: Dai
authors.forename: Zhenlong
authors.initials: Z
authors.lastname: Wu
authors.forename: Gang
authors.initials: G
authors.lastname: Lin
authors.forename: Sichao
authors.initials: S
authors.lastname: Jia
authors.forename: Shengdi
authors.initials: S
authors.lastname: Hu
authors.forename: Sudath
authors.initials: S
authors.lastname: Dahanayaka
authors.forename: Guoyao
authors.initials: G
authors.lastname: Wu
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D026905:Amino Acid Transport Systems / Q000235:genetics; D000641:Ammonia / Q000097:blood; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000831:Animals, Newborn; D001823:Body Composition; D001835:Body Weight; D019587:Dietary Supplements; D005973:Glutamine / Q000097:blood; D005978:Glutathione / Q000097:blood; D005998:Glycine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D050487:Glycine Plasma Membrane Transport Proteins / Q000235:genetics; D007583:Jejunum / Q000187:drug effects / Q000502:physiology*; D008892:Milk; D021381:Protein Transport / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D011897:Random Allocation; D012694:Serine / Q000097:blood; D013552:Swine; D014508:Urea / Q000097:blood; D015430:Weight Gain / Q000187:drug effects
chemical_list: D026905:Amino Acid Transport Systems; D050487:Glycine Plasma Membrane Transport Proteins; D012333:RNA, Messenger; D005973:Glutamine; D012694:Serine; D000641:Ammonia; D014508:Urea; D000251:Adenosine Triphosphatases; D005978:Glutathione; D005998:Glycine