Environmental factors and progeny affecting milk yield and composition during the first lactation

The purpose of this study was to determine whether the milk yield (MY) of primiparous cows is affected by their housing to weaning, the method of providing liquid feed, sire (S) line, and season of birth and calving. Thirty-two heifer-calves were used in the experiment; 19 heifers were kept in individual housing (1H) and 13 in loose housing (LH) from the second day of life. On the seventh day the 1H heifers were divided according to feeding milk replacer (MR) or milk: 10 were relocated from IH to a pen with a computer-controlled feeder (CCF) providing automatic feeding of MR (AF), 9 heifers stayed in IH with bucket drinking (BF). The LH heifers were moved to a nursing cows pen (UF). Heifers were kept in free-stall housing after the first calving. The cows were also divided according to the sire, season of birth and calving. LH primiparous cows produced more milk throughout the first eight months of lactation, more MY, FCM and protein for 305 d lactation (P < 0.05). UF cows had the highest MY throughout the first lactation and reached the significantly highest milk yield and FCM (6894.1 and 6541.9 kg), whereas AF cows, the lowest (5757.5 and 5820.9 kg; P < 0.01) for 305 days of lactation. The contents of fat and total solids (TS) were the highest in group AF. Sire lineages differed in the contents of fat, protein, lactose, non-fat solids (NSF), TS, and MY, lactose and NFS. Cows born and calved in the summer showed lower MY and FCM yields. The most productive cows were born and calved in the winter and spring.