SUPPLEMENTATION OF A RESTRICTED MATERNAL DIET WITH PROTEIN OR CARBOHYDRATE ALONE PREVENTS A REDUCTION IN FETAL MUSCLE-FIBER NUMBER IN THE GUINEA-PIG

A 60% reduction in maternal feed intake is known to cause a reduction of approximately 20% in biceps brachii fibre number in the guinea-pig fetus. This investigation was designed to isolate the dietary componen t responsible by reducing all dietary components to 60% of the ad lib. level and supplementing the protein, carbohydrate or fat component to the level of the ad lib. intake. Fetal muscles were examined at 50 d gestation to determine numbers of primary and secondary fibres, and at term to determine total fibre number. Fetal and neonatal weights were reduced in all restricted groups (P < 0.05) when compared with ad lib . controls. At term this reduction was significantly less (P < 0.05) i n the protein-supplemented group (20%) than in the 60%-restricted and fat-supplemented groups (43%) and the carbohydrate-supplemented group (34%). Biceps brachii fibre numbers were reduced in the 60%-restricted and fat-supplemented groups by 14-16%, but fibre numbers were similar in control, protein-supplemented and carbohydrate-supplemented groups . Any reduction in fibre number was in the secondary fibre component o f total fibre number. Therefore, biceps brachii fibre numbers were red uced only when maternal diets were deficient in both protein and carbo hydrate.