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To fulfil the requirements for methionine, animal diets are widely supplemented with synthetic methionine sources such as L-methionine (L-Met), DL-methionine (DL-Met), and DL-2-hydroxy-4-(methylthio)-butanoic acid (DL-OH-Met). The objective of this study is to calculate the energy cost of the different conversion steps leading to L-Met and to propose energy equivalence values for DL-Met and DL-OH-Met, relative to that of L-Met. The conversion of DL-OH-Met to L-Met involves a nitrogen-sparing effect, because excess nitrogen can be used for the transformation of DL-OH-Met to L-Met, rather than being excreted as urea or uric acid Consequently, the ME-to-GE ratio of DL-OH-Met is 109% in mammals and 114% in birds, compared to the value of DL-Met. Because of differences in metabolism and the formation of hydrogen peroxide in the conversion to L-Met, the NE-to-ME ratios are 96% for DL-Met and 100% for DL-OH-Met in both mammals and birds. The conversion of DL-OH-Met to L-Met is therefore energetically less costly than the conversion of DL-Met. The stoichiometric approach presented here only considers the biochemical conversion steps, without considering the cost of transport and further transformation steps.

International audience; Methionine (Met) is an essential amino acid (AA) in pigs and the third limiting AA in cereal based diets. Met supplementation improves animal’s performance and protein gain. Besides, Met is considered as an important factor in the control of oxidative status with potential benefits on health and meat quality. This study aimed at investigating the effects of dietary Met provided in excess relative to growth requirements on muscle metabolism in finishing pigs. During the last 14 days before slaughter, crossbred pigs were individually fed diets (13.6% protein, 5.8% fat, 10.8 MJ/kg Net energy, 0.73% Lys) supplemented (Met++) or not (CONT) with OH-Met (n=15 pigs/diet). Dietary Met content was 0.22% and 1.1% in CONT and Met++ diets, respectively. Growth rate, carcass lean meat content and Longissimus muscle (LM) weight at slaughter did not differ between the two groups. In LM, the free AA profile was modified (P

Protein turnover is an energy-consuming process that is essential for ensuring the maintenance of living organisms. Gold standard methods for whole-body protein turnover (WBPT) measurement have inherent drawbacks precluding their generalization for large farm animals and use during long periods. Here, we proposed a non-invasive proxy for the WBPT over a long period of time and in a large number of beef cattle. The proxy is based on the rate at which urine-N and plasma proteins are progressively depleted in terms of15N after a slight decrease in the isotopic N composition of the diet (i.e. diet switch). We aimed to test the ability of this proxy to adequately discriminate the WBPT of 36 growing-fattening young bulls assigned to different dietary treatments known to impact the WBPT rate, with different protein contents (normalv.high) and amino acid profiles (balancedv.unbalanced in methionine). The15N depletion rate found in plasma proteins represented their fractional synthesis rate, whereas the slow depletion rate found in urine was interpreted as a proxy of the WBPT. The proxy tested in urine suggested different WBPT values between the normal- and high-protein diets but not between the balanced and unbalanced methionine diets. In contrast, the proxy tested in plasma indicated that both dietary conditions affected the fractional synthesis rate of plasma proteins. We considered that the rate at which urine is progressively15N-depleted following an isotopic diet switch could be proposed as a non-invasive proxy of the WBPT rate in large farm animals.

“Flash” dietary methionine supply as an innovative way to improve pork quality traits. 6. Swine Conference