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This report will cover studies of the metabolism of a supplemental source of L-methionine (L-met), Alimet® feed supplement. The goal of these studies was to gain an understanding of how this methionine precursor is converted to L-methionine and how it is used by the chick, in order to optimise the conditions for its use. The methionine precursor in Alimet is 2-hydroxy-4- (methylthio) butanoic acid (HMB). HMB differs from methionine by having a hydroxyl group on the alpha carbon rather than an amino group. Like synthetic DL-met, HMB has one asymmetrical carbon atom and therefore occurs as a mixture of 50% L-isomer and 50% D-isomer. Because HMB bears a hydroxyl group instead of an amino group, it is an organic acid. Until it is converted to L-met antimicrobial properties of HMB resemble those of organic acids such as lactic acid. Once inside the tissue of the animal, however, HMB is rapidly converted to L-met. Following conversion to L-met, HMB will have the same availability for methyl group transfer or cysteine synthesis as L-met from any other source. This report will cover the bioavailability of HMB polymers, the conversion of HMB to L-met and the role of HMB in normal L-met intermediary metabolism. It will also include a discussion of HMB absorption and incorporation into protein. [ABSTRACT FROM PUBLISHER]

Abstract: Zearalenone is a potent mycotoxin that has estrogenic properties. In vitro results indicate that zearalenone metabolites down-regulate proteins associated with protein synthesis (protein kinase B, Akt) and cellular proliferation (extracellular signal-regulated kinase, ERK). The objectives of this study were to determine the effect of zearalenone on (1) growth performance and signaling for protein synthesis, and (2) reproductive tract development. At 28 d of age, gilts were randomly assigned to consume a commercial basal diet (C) or C+1.5mg/kg zearalenone (n =10) for 4 wk, at which time gilts were euthanized, urine collected, and tissue collected. No differences were observed in average daily gain, average daily feed intake, or gain:feed (P>0.28). Reproductive tract weight (2.4-fold) and uterine endometrial gland development (50%) were increased in zearalenone fed gilts (P<0.01). In uterus, estrogen receptor (ER)-α expression was unchanged (P>0.28), but gilts consuming zearalenone had 2.0- and 3.5-fold higher abundance of ER-β mRNA and protein, respectively (P<0.01). No differences were observed in Akt, mammalian target of rapamycin, or ERK abundance or phosphorylation in muscle (P>0.36). Zearalenone had no effect on growth performance or skeletal muscle signaling in prepubertal gilts, but zearalenone increased reproductive tract size and glandular development, possibly due, in part, to altering the expression of ER-β. [Copyright &y& Elsevier]