Abstract. Title of the paper: The composition of the Colostrum of some beef cattle breeds according to time of post partum. This research was carried out to investigate the changes of main components of Colostrum with 0–4 days after calving by five beef cattle breds, kept in Hungary. After calving and 24 hours later beef cattle breeds had higher dry matter content in Colostrum compared to that of dairy breeds; but the dairy breeds were superior to the beef cattle breeds from the second day. This relates to the Colostrum of the beef cattle breeds more concentrated than the dairy breeds during the first 24 hours but they reached that values eariier which were characteristic to the normal milk. Examining the protein content of Colostrum there were similar tendencies in change of dry matter content with difference that the protein content of Colostrum of beef cattle breeds was higher than that of the dairy breeds between the 2nd and 4th days, too. On the first and the second days the fat content of Colostrum of the sucklers decreased which was related to the higher dilution in beef cattle breeds. The sugar content of Colostrum of the beef cattle breeds has increased between the calving and the 4th day post partum, and reached the values characteristic to the normal milk – (4.8–5.0%) – on the 5th–6th day. There was not significant difference between the beef and the dairy breeds, neither in sugar nor in the ash content. The ash content of Colostrum reached the values characteristic to the normal milk, 7–8 days after calving.

The whey protein and the non protein nitrogen content of Colostrum of the beef cattle breeds were higher than that ofthe dairy breeds, significantly. Decreasing of these fractions in the beef cattle breeds were more moderate than the dairy breeds as in case of the total protein content, according to time. Our calculations show that whey protein content of the beef cattle breeds reached that values which were characteristic to the normal milk, after the 5th day post partum. Not having found a decided difference in the casein content of Colostrum between the beef and the dairy breeds. The casein content of Colostrum of blonde d' Aquitaine and Limousin higher than that ofthe other kind of beef cattle breeds, which manifests itself in the ratio of whey protein and casein, too. At the same time the ratio of whey protein and casein in both Angus types differ from the other beef cattle breeds in favour of the whey protein.

The calculated immunglobulüj-G values of Colostrum milked immediately after calving were usually much higher at sucklers than at the dairy breeds. This was true especially beUveen the 1st and the 4th days which was connected with the more moderate decrease of IgG fraction in the beef cattle breeds. Similarly the data of the literature the IgG content ofthe fresh milked Colostrum was determined primarily by the breed. According to our examinations this determination becomes more unimportant moving off the time of calving. The energy content of Colostrum at Black Angus and Red Angus rose among the other kind of beef cattle breeds. The average energy content ofthe Colostrum of blonde d' Aquitaine and Limousin was connected with the high protein content of their Colostrum. The energy content of Colostrum of Hungarian Simmental was the lowest.