title: An estimate of the methionine requirement and its variability in growing pigs using the indicator amino acid oxidation technique.
abstract: Although AA requirements for the mean of a population of growing pigs have been established using traditional methods, there are no estimates of the variability within the population and whether this variation differs among AA. With the increased use of supplemental Lys in pig diets, there will be an increased need to supplement Met, commonly the second or third limiting AA in corn-soybean diets. The indicator AA oxidation method allows repeated measurements in a short period of time so that the AA requirement can be determined for individual pigs at a similar physiological stage. The objective of this study was to determine the mean Met requirement in individual gilts and to estimate the related variability. Six individually housed female pigs (initial BW = 8.8 kg, SD 1.5) each received diets providing 6 levels of dl-Met. The isonitrogenous and isoenergetic diets contained 0.187, 0.250, 0.290, 0.320, 0.350, and 0.377% Met (analyzed, as-fed basis). Cysteine (0.48%) and Lys (1.44%) concentrations were similar for all diets. Pigs were adapted for 6 d to the basal corn-soybean meal diet (0.187% Met), which was offered at 95 g/kg(0.75) of BW to ensure complete consumption of the test diets. During 4-h oxidation studies, 313.4 kBq, (SD 35.6) of L-[1-(14)C]Phe was mixed with each of 8 half-hourly meals, and expired CO(2) was collected. The breakpoint in Phe oxidation, representing the Met requirement, and its variability, was determined using 2-phase linear regression. Phenylalanine oxidation decreased as the Met content increased from 0.187 to 0.29%. Phenylalanine oxidation was not different (P > 0.2) for diets ranging from 0.320 to 0.377% Met. The dietary Met requirement varied from 0.320 to 0.373% for individual pigs. The mean Met requirement for individual pigs was determined to be 0.340% of diet (SD = 0.024%, CV= 7.1%), with 0.340, 0.364, and 0.388% covering the requirement of 50, 66, and 95% of the population, respectively. The present mean population estimate was similar to the recommended dietary Met concentration of 0.325% for pigs of this BW and feed intake. To maximize profitability, Met levels in starter pig diets should be determined, depending on the cost of crystalline Met and the fraction of the population whose requirement is to be met.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Moehn
authors.forename: A K
authors.initials: AK
authors.lastname: Shoveller
authors.forename: M
authors.initials: M
authors.lastname: Rademacher
authors.forename: R O
authors.initials: RO
authors.lastname: Ball
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002245:Carbon Dioxide / Q000032:analysis; D002250:Carbon Radioisotopes; D018592:Cross-Over Studies; D003545:Cysteine / Q000008:administration & dosage / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D016014:Linear Models; D008239:Lysine / Q000008:administration & dosage / Q000378:metabolism; D008715:Methionine / Q000008:administration & dosage* / Q000378:metabolism*; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010649:Phenylalanine / Q000378:metabolism; D011897:Random Allocation; D013552:Swine / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; D010649:Phenylalanine; D008715:Methionine; D008239:Lysine; D003545:Cysteine