ECONOMICS OF MILK YIELD LOSSES IN ONE DAIRY FARM IN MACEDONIA ASSOCIATED WITH CLINICAL MASTITIS

Abstract

Mastitis remains one of the major disease in dairy herds, causing profound economic losses to the entire milk production chain due to changes in the milk quality and milk yield. A one year cross-sectional longitudinal survey was carried out to evaluate milk yield losses associated with occurrence of clinical mastitis cases in one dairy herd. Cows that had clinical mastitis and clinically healthy cows during lactation were included in the study. The traits analyzed were the average of the monthly test day milk yields, cow parities and days in lactation while first case of clinical mastitis was occurred. For these purpose there were recorded data for monthly test day milk yield of the cows at the 2nd, the 3rd and the 4th monthly test day (TD). TDs were chosen according to the average number of days in lactation to diagnose the first case of clinical mastitis. According these criteria, the 2nd and the 3rd TD were made before the diagnosis of the first lactation case of clinical mastitis, while the 4th TD was made after the diagnosis. Monthly test day milk yields were treated as repeated measurement within an animal in General Linear Model (GLM). Statistical model included fixed effect of cow parity and covariance of days in lactation when the first case of clinical mastitis was occurred. Estimated lactation incidence risk (LIR) for CM in observed population of dairy cows was 21.49%. Regardless parities, the first case of clinical mastitis in dairy herd occurred on the average 108.09±83.182 days in lactation. The LIR tended to significantly increased (p<0.001) with increasing the cow parity, as risk factor for occurrence of clinical mastitis. Before contracting the disease, cows with clinical mastitis yielded more milk than did healthy cows. Mastitis clearly affected the milk yield and the difference between the milk yield of the healthy cows and the cows after clinical mastitis was statistically significant. There was a significant decrease in the milk yield before and after the diagnosis of clinical mastitis case (p<0.001). The estimated daily milk yield losses per cow suffered from case of clinical mastitis, between the 3rd TD and the 4th TD, range from 0.9 kg to 26.0 kg, or average 9.6 kg/day. According this, the monthly milk yield losses per mastitic cow, between the 3rd TD and the 4th TD, were 288 kg. If we take in consideration the price of one kg milk of 0.32 euro, than the total daily economic losses per mastitic cow will be around 3 euro’s and monthly losses per cow will be around 92 euro. Regardless of the time of occurrence during the lactation, mastitis had a long-lasting effect on milk yield; cows with clinical mastitis did not reach their premastitis milk yields during the remainder of the lactation after onset of the disease. The daily milk yield must be taken in consideration for more rapid economic analysis of milk losses associated with occurrence of clinical mastitis in dairy herds.