HEPATIC AND RENAL BETAINE-HOMOCYSTEINE METHYLTRANSFERASE ACTIVITY IN PIGS AS AFFECTED BY DIETARY INTAKES OF SULFUR AMINO-ACIDS, CHOLINE, AND BETAINE

In Exp. 1, young pigs were fed a basal diet containing .17% methionine (Met) (.14% digestible Met), and .48% cystine (.38% digestible cystin e) for 14 d (34 to 48 d of age). Treatment additions were .25% DL-Met, .34% betaine, .30% choline, or .25% DL-Met and .34% betaine. Methionin e, but not betaine or choline supplementation, increased (P <.05) weig ht gain and feed efficiency. Hepatic betaine-homocysteine methyltransf erase (BHMT) activity was increased (P <.05) by betaine and choline su pplementation but was not affected by Met deficiency. Renal BHMT activ ity was increased (P <.05) by Met deficiency and was further increased (P <.05) by betaine supplementation. In Exp. 2, 10-kg pigs were fed t he basal diet from Exp. 1 supplemented with enough DL-Met to bring the total basal Met to .24% (.20% digestible Met), Treatment additions co nsisted of .20% DL-Met or .34% betaine, and diets were fed for 16 d (3 4 to 50 d of age). Feed efficiency increased (P <.05) in response to M et, but not to betaine, supplementation. Hepatic BHMT activity increas ed (P <.05) in response to betaine and Met, but no changes in renal BH MT activity occurred. Although statistically significant changes in he patic and renal BHMT activity occurred in both experiments, the magnit ude of the responses was probably not physiologically important. There fore, in contrast to previous findings with rats and chicks, it does n ot seem that hepatic and renal BHMT activity in pigs is influenced sub stantially by Met deficiency, or by surfeit levels of choline or betai ne.