Effects of protein level, methionine supplementation and carbohydrate type of the diet on liver lipid and plasma free threonine contents in the lactating rat

Abstract

Summary -Eight groups of 13-15 female rats were fed purified diets after littering. Four groups received a low protein (8% casein) diet (groups 8) and the others, a normal protein (20% casein) diet (groups 20). Carbohydrates were supplied either as starch (groups S) or as starch plus 40% fructose (groups F). Half the animals received a 0.4% methionine supplementation (groups M). Four or five dams per group were sacrificed on days 2, 7 and 14 after littering.The diet intake was increased by methionine supplementation, substitution of starch for fructose and increased protein content, mainly during the second week of lactation. This influenced weight variation of the dams and litter growth.On all days, the plasma levels of cholesterol esters, triglycerides and phospholipids were positively correlated with the dietary protein level.On days 7 and 14, the liver neutral lipid content was increased in rats fed the low protein diets supplemented with methionine (groups 8SM and 8FM) and the normal protein diets containing 40% fructosq (groups 20F and 20FM).The plasma free threonine content was positively correlated with the protein level in the diet. On day 14, rats fed a low protein diet had a threonine deficiency, except those in groups 8S and 8F. The plasma free threonine content of these rats was not reduced, possibly due to an impaired utilization of this amino acid.The liver lipidosis observed during lactation, in contrast to that observed during growth with a low protein diet, was not due to a threonine deficiency.

Leucine and methionine deficiency impairs immunity to gastrointestinal parasites during lactation

“…The present data showed that HP-Met feeding penalised dam weight gain but not litter weight gain relative to HP feeding. The importance of methionine supply in lactating rats has long been recognised ( 51 ) , and improved dam weight gain during lactation has been observed upon methionine supplementation in both low- and high-casein diets ( 52 ) . Substantial body-weight loss of approximately 44 % has also been observed in non-lactating adult rats fed methionine-restricted foods ( 36 ) .…”