Nutritional Value and Technological Suitability of Milk from Cows of Three Polish Breeds Included in the Genetic Resources Conservation Programme
The study included milk obtained from cows of three native cattle breeds, i.e. White-backed (BG), Polish Red (RP) and Polish Black-and-White (ZB) kept under conventional conditions. The reference group consisted of milk from Polish Holstein-Friesian cows (PHF) maintained in the intensive system and milk from Simmental cows (SM) kept under conventional conditions. The following parameters were determined in 976 samples of milk: content of fat, protein, casein, lactose and solids; acidity (pH value); heat stability; rennet coagulation time; content of α-lactalbumin, β-lactoglobulin, serum albumin, lactoferrin and lysozyme. Additionally, a certain proportion of samples was investigated for fatty acid profile and content of macro- and microelements. Cows of native breeds produced milk of higher nutritional value (higher content of whey proteins and polyunsaturated fatty acids, including CLA) and more suitable for processing as compared to PHF cows. Milk from cows of the Polish Red breed was the most valuable in terms of these parameters, which can be associated with a distinctive phylogenetic origin of this breed. The favourable parameters in regard to the nutritional value and technological suitability of milk obtained from analysed population of cows of 3 breeds included in the programme of genetic resources conservation are therefore an important reason of validity for subsequent implementation of this programme.
Slaughter Value of Young Polish Black-and-White, White-Backed, Polish Holstein-Friesian and Limousin Bulls Under Semi-Intensive Fattening
The objective of the present study was to compare the slaughter value of young bulls of two breeds included in the genetic resources conservation programme, namely Polish Black-White and White-backed with young Polish Holstein-Friesian (dairy type) and Limousin (beef type) bulls. This is the first study to evaluate the meat performance traits of White-backed cattle in several-centuries history of the breed in Poland. It was determined that populations of White-backed and Polish Black-and-White cattle represent the dual-purpose type desirable in the genetic resources conservation programme. The indices obtained for the analysed traits of slaughter value from young Polish Black-and-White and White-backed bulls were intermediate between Polish Holstein-Friesian (dairy type) and Limousin (beef type), but closer to those of the Polish Holstein-Friesian breed. The analysed muscles of young bulls had a very similar content of basic chemical components. The relatively high amount of proteins (22.85-23.23%) in musculus longissimus lumborum and in musculus semintendinosus (22.43-23.06%) should be emphasized.
A total of 2,484 lactations in 760 Polish Holstein-Friesian cows were analysed. Calculations were made of length of life, length of productive life, total number of days in milk, number of calvings, ratio of days in milk to length of productive life, lifetime milk yield (kg), daily yield at the peak of lactation (kg) and lactation persistency as the percentage difference between daily milk production in the 2nd and 10th month in milk. The cows were divided into three groups according to lactation persistency (decrease in production): group I – up to 30%, group II – 30.1–50% and group III – over 50%. Lactation persistency significantly influenced (P≤0.01) length of life and efficiency of milk production in the analysed cow population. Cows with yield over 30 kg at the peak of lactation followed by a moderate decrease (40%) lived longest (over 6 years) and produced the most milk (nearly 28,000 kg). Yield of primiparous cows at the peak of lactation and its course were found to have a significant effect on length of life and lifetime milk production. The long period of high peak yield (over 30 kg of milk) in the primiparous cows in group I (with the best lactation persistency) in the long term proved to be detrimental, as these cows had the shortest productive life (2.3 lactations on average) and lifetime milk yield about 4,000 kg lower than in the cows in groups II and II (with the poorer lactation persistency).
An evaluation was conducted of the suitability for fattening in a semi-intensive system (mainly with fodders from permanent grassland) and the slaughter value of 15 young bulls of the Polish Red (PR) breed and 10 each of the White-Backed (WB) and Polish Black-and-White (BW) breeds. The reference group consisted of young bulls of the Black-and-White variety of the Polish Holstein- Friesian (HF) breed and the Simmental (SIM) breed, fattened on the same farms. Control fattening was carried out until the age of 18 months. Mean daily weight gain in the bulls of the native breeds during the control fattening period (which lasted 314-358 days) was 0.9 kg, similarly to HF, but significantly lower (P≤0.05) than in the Simmentals (986 g). During the entire fattening period, i.e. from birth to the age of 18 months, daily weight gain was 832 g in PR and 889-919 g in WB and BW. Dressing percentage was lowest in PR bulls (51.69%), and higher in WB (53.1%) and BW (53.49%), with values similar to the reference group, i.e. young bulls of the Simmental (52.97%) and HF (53.29%) breeds. The difference between PR and BW (1.8%) and HF (1.6%) was statistically significant (P≤0.05). In the EUROP classification system, the carcasses of the young bulls of the native breeds were most often placed in classes R- and O+ (conformation) and 2+ and 3- (fat cover), as in the case of young HF bulls. Carcasses of young Simmental bulls were assigned to much higher classes. The young bulls of the three Polish native breeds evaluated are good material for fattening in a semi-intensive system (mainly with fodder from permanent grasslands), while the young PR bulls were the least suitable