Influence of different levels of dietary pyridoxine on milk composition in the rat.

The effects of five different levels of dietary pyridoxine on milk composition were studied in the rat. Sprague-Dawley strain rats received diets containing 1.2, 2.4, 4.8, 9.6 or 19.2 mg pyridoxine-HCl/kg diet throughout growth, gestation and lactation. Milk samples obtained on days 10, 11, and 12 of lactation were similar in concentrations of total fat, solids-not-fat, carbohydrate, casein and non-casein protein for rats fed the five levels of pyridoxine. The level of vitamin B-6 in milk was significantly higher for rats fed 9.6 or 19.2 mg pyridoxine.HCl/kg diet compared to values for rats fed the three lower levels of vitamin. A higher level of dietary pyridoxine (9.6 mg/kg diet) was required to increase the levels of the vitamin in mammary gland and milk than was needed for maternal liver (4.8 mg/kg) or muscle tissue (2.4 mg/kg). The findings indicated that as the level of pyridoxine was decreased in the diet from an apparently adequate level, the concentration of the vitamin in milk decreased before that in liver or muscle tissue. This suggested that the concentration of the vitamin in milk was an indicator of marginal deficiency of vitamin B-6.