An enzymatic hydrolysate of bovine casein were studied for molecular size and antigenic properties. As determined by Sephadex G-25 gel filtration, polypeptide fractions having molecular weights greater than 1,000 were not detected in the soluble fraction of the casein hydrolysate. Antigenicity of the fraction was not detected by heterologous passive cutaneous anaphylaxis in guinea pig-rabbit antiserum system mediated by immunoglobulin G types of antibody (guinea pig passive cutaneous anaphylaxis) and its inhibition test. Furthermore, it was not detected by rat long latency homologous mediated by immunoglobulin E antibody and its inhibition test. To prepare anticasein immunoglobulin E serum for rat long latency homologous passive cutaneous anaphylaxis, immunization of rats was by single subcutaneous injection of casein with aluminum hydroxide. Antiserum with highest passive cutaneous anaphylaxis titer (1:64) against bovine casein was obtained by a dose of 2,000 micrograms of the protein at day 12.

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Lactoferrin was determined by the immunological method of Laurell in bovine colostrum and milk from 1 to 547 days after parturition (60 samples). Iron which was closely contacted with the bacterio static effect of lactoferrin, and nitrogen distribution were also measured. Lactoferrin contents in bovine colostrum, transitional milk, matured milk, and milk in later lactaable differences among samples from individual cows. The lactoferrin to whey protein ratios in colostrum, transitional milk, matured milk and milk in later lactation were 3.3, 6.9, 7.2 and 5.2%, respectively. in colostrum, then decreased with elapsing of lactation days and was very low in milk in later lactation. Significant correlation was observed between the concentrations of lactoferrin and whey protein nitrogen (r=0.666). No correlation, however, was observed between the lactoferrin and iron concentrations. Iron is likely to be contained at approximately constant level in matured milk.

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