Effect of Breed and Feeding System on Content of Selected Whey Proteins in Cow's Milk in Spring-Summer and Autumn-Winter Seasons

The objective of the present study was to evaluate the effect of breed and feeding system on the content of selected whey proteins in cow's milk collected in the spring-summer and autumn-winter periods. A total of 2,278 milk samples from Black- and Red-and-White variety of Polish Holstein-Friesian cows and Simmental and Jersey cows were examined. In each sample the content of selected whey proteins, i.e. alpha-LA, beta-LG, lactoferrin, BSA and lysozyme, was analysed by RP-HPLC method. Evaluation of the simultaneous effect of breed and production season on whey protein content showed significant interactions (P≤0.05 and P≤0.01) for all analysed whey proteins. The milk of Simmental cows kept in the conventional system was characterized by a higher content of whey proteins (with the exception of BSA), in comparison to the cows managed under TMR system. Furthermore, for most of the evaluated components, except the content of BSA and lysozyme and the alpha-LA/beta-LG ratio, the simultaneous effect of feeding system and production season was also found.