SummaryThe aim of this study was to characterise the Polish Red cattle breed, the only existing native breed in Poland. The origin and conformation of this breed and its historical development, distribution and performance were described. Moreover, the attention was paid to the attempts to improve the breed milk performance by crossbreeding with Jersey, Danish Red and Angler and beef performance by crossbreeding with Black-and-White, Red-and-White, Simmental and beef bulls.Before the Second World War the Polish Red held the rank of an international breed, and since the middle of the previous century had been found almost throughout Poland. In the 1950s it still constituted 22% of the whole cattle population in Poland. Indeed in 1954 the Polish Red cattle population amounted to over 1.5 million head. Currently, Polish Red cattle are in danger of extinction. Only 300 cows are included in the Program of Genetic Resources Conservation and scarcely several hundred embryos and semen doses are stored in the Semen Bank of the National Research Institute of Animal Production in Balice.In 2001 the number of recorded Polish Red milking cows was 1 201. Their average performance amounted to 3 786 kg of milk with 4.26% of fat and 3.39% of protein. However, milk yield of the cows at the best farms exceeded 5 500 kg.

No abstract

Seasonality in milk performance and reproduction was analysed in low-input mountain farms in the Czech Republic. Two different feeding regimes were distinguished: seasonal pasture and all-year silage feeding in confi nement. Seventeen pastured herds and sixteen confi ned herds of Czech Pied and Holstein breeds (total 12 158 cows) were included in the seven-year study. Seasonal variation of milk, fat and protein yields per lactation according to the month of calving was found in both groups of herds. The highest yields were achieved by autumn-calved, and the lowest yields, by summercalved cows (difference of 542 kg and 474 kg of milk on average in pastured and in confi ned herds, respectively). Higher individual daily yields (up to 2.9 kg on average) were recorded in the period between May and July than in the rest of a year. No effect of month of calving on days-to-fi rstservice and on days-open period was identifi ed.

No abstract

Milk temperature was measured automatically during milking with a view to detecting silent oestrus in dairy cows. A total of 38 silent oestrous periods were studied, based mainly on ovulation and milk progesterone levels together with visual observation.In 78·9% of silent oestrous periods, a significant increase in milk temperature amounting to a mean of 0·6 (s.e. 0·07)°C was found, and this was highly correlated (r = 0·90) with an increased body temperature. In most silent oestrous periods increases in milk and body temperatures and ovulation with milk progesterone levels below 2 μg/l were found, the oestrous cycles being characterized by typical progesterone profiles. In some cows increases in milk and body temperatures and ovulation during a silent oestrous period were associated with non-typical progesterone profiles although most of these occurred shortly after parturition.