Influence of mastitis on milk yield in Holstein cows

The objectives of the current study were to investigate the incidence of mastitis in a private dairy herd and the effect of the disease on the lactation milk yield (LMY), and on the daily average of the weekly milk yield (DMY). Only cows with no disease and cows with mastitis were included in the analyses. Mixed model procedures were used to analyse the DMY. Incidence of mastitis in the herd was 26.22%. The incidences of first, second and third parity groups were 19.94%, 33.74% and 40.74%, respectively. Daily milk losses because of mastitis varied between 0.76 kg/d and 4.56 kg/d. The total milk loss was 600.87 kg for cows that became mastitic in the first six weeks of lactation and was 503.86 kg for cows that became mastitic after the sixth week of lactation. The milk losses of cows that contracted mastitis after the sixth week of lactation, began three weeks before the diagnosis. The mastitic cows failed to reach their healthy levels of milk yield during the rest of the lactation. The results indicate that weekly lactation records are useful in early detection of mastitis.