Abstract:
Animal Production in Australia THE AVAILABILITY OF METHIONINE IN PROTEIN CONCENTRATES FOR GROWING PIGS JANE LEIBHOLZ* The requirements of pigs weighing l0-20 kg live weight for methionine and cystine has been summarized as 5.6 g/kg of diet (National Research Council 1979), at least half of which must be in the form of methionine. Many diets for young pigs are marginal in their total content of methionine, and there is no information on availability of methionine for young pigs from different protein concentrates. A basal diet of wheat and lupins was prepared which contained 1.5 g methionine/kg. This basal diet was supplemented to contain 1.7, 1.9, 2.1 and 2.3 g methionine/kg with synthetic methionine or one of the five protein concentrates shown in Table 1. The diets were fed - libitum to 125 pigs between 28 and 56 days of age. ad Availability of methionine was calculated by the slope ratio technique relative to synthetic methionine (Batterham et al. 1979). TABLE 1 The availability of methionine from slope ratio analyses as assessed with pigs between 28 and 56 days of age The availability of methionine in the five protein concentrates, as measured by three production criteria is presented in Table 1. Based on liveweight gain the availability of methionine was lower in cottonseed meal (0.75) than that of synthetic methionine but not in the other four protein concentrates. None of the availability values for'N balance and feed conversion ratio differed significantly from that of synthetic methionine. The average weight gains of the pigs fed the basal diet was 61 g/day while that of the pigs given the diets containing 2.3 g methionine/kg was 292 g/day with feed conversion ratios of 2.56 and 1.34 respectively. These results lead to the ine content of feed ingredients methionine can be used, and that the true availability figures. diets deficient in their content conclusion that in the for pigs 28-56 days of there is only a small The growth of pigs was of methionine. calculation of the methionage the values for total advantage from including markedly reduced by giving BATTERHAM, E.S., MURISON, R-D., and LEWIS, C.E. (1979). Br. J. Nutr. 41: 383. NATIONAL RESEARCH COUNCIL (1979). 'Nutrient Requirements of Swine'. (Ktional Academy of Sciences: Washington, DC.) * Department of Animal Husbandry, University of Sydney, Camden, N.S.W. 2570. 664