title: Phenylalanine flux and gastric emptying are not affected by replacement of casein with whey protein in the diet of adult cats consuming frequent small meals.
abstract: BACKGROUND
  Decreasing the rate of protein emptying from the stomach may improve efficiency of utilization of dietary amino acids for protein deposition. Some studies in rats and humans have shown casein to be more slowly released from the stomach than whey protein. To test if casein induces a slower rate of gastric emptying in cats than whey protein, L-[1-(13)C]phenylalanine (Phe) was dosed orally into 9 adult cats to estimate gastric emptying and whole-body Phe flux.
  
  
  RESULTS
  Concentrations of indispensable amino acids in plasma were not significantly affected by dietary protein source. First-pass splanchnic extraction of Phe was not different between diets and averaged 50% (SEM = 3.8%). The half-time for gastric emptying averaged 9.9 min with casein and 10.3 min with whey protein, and was not significantly different between diets (SEM = 1.7 min). Phenylalanine fluxes were 45.3 and 46.5 μmol/(min · kg) for casein- and whey-based diets, respectively (SEM = 4.7 μmol/(min · kg)).
  
  
  CONCLUSIONS
  In adult cats fed frequent small meals, the replacement of casein with whey protein in the diet does not affect supply or utilization of amino acids. These two milk proteins appear to be equally capable of meeting the dietary amino acid needs of cats.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. ttycholi@uoguelph.ca.
authors.forename: Tanya J
authors.initials: TJ
authors.lastname: Tycholis
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. jcant@uoguelph.ca.
authors.forename: John P
authors.initials: JP
authors.lastname: Cant
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada. vosborne@uoguelph.ca.
authors.forename: Vern R
authors.initials: VR
authors.lastname: Osborne
authors.affiliation: Procter and Gamble Co., Pet Care, Lewisburg, OH, 45338, USA. shoveller.ak@pg.com.
authors.forename: Anna K
authors.initials: AK
authors.lastname: Shoveller
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000378:metabolism; D000818:Animals; D002364:Caseins / Q000008:administration & dosage* / Q000494:pharmacology; D002415:Cats / Q000378:metabolism / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D005260:Female; D005746:Gastric Emptying / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D010649:Phenylalanine / Q000097:blood / Q000378:metabolism*; D000067816:Whey Proteins / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D002364:Caseins; D000067816:Whey Proteins; D010649:Phenylalanine