Maternal lipid intake during pregnancy and lactation alters milk composition and production and litter growth in rats

The relationship between dietary fat content and milk composition, production and litter growth was studied in rats fed during pregnancy and lactation purified diets of equal energy density containing 2.5 or 20 g fat/100 g diet. A subsample of rats (HL-EP group) fed the high lipid (HL) diet but pair-fed on an energy basis with the low lipid (LL) diet group was also studied in a separate experiment. Food intake, dam body weight and litter weight were recorded dairy. Rats were milked on d 14 of lactation. Milk lipid, lactose and protein concentration and milk production were measured. Lactating rats fed the HL diet had significantly higher energy intakes (P < 0.01) and milk production (P < 0.05) than rats fed the LL diet. Milk lipid concentration and daily milk volume and lipid production were significantly higher in the HL group. The HL-EP dams had significantly higher milk lipid, protein and lactose concentrations (P < 0.05) and tended to have higher daily lipid and energy outputs (P = 0.08) than LL rats. Birth weights of pups were similar among groups, but from d 6 on, the pups from the HL and HL-EP groups were significantly heavier (P < 0.05) than pups from the LL group. This investigation presents evidence that the milk fat concentration and the daily output of fat, protein and lactose of lactating rats are altered by dietary fat manipulations, which in turn affect growth of the litter.