Increasing the value of raw bulk milk quality based on mammary glands as production units vs. the udder in dairy cows with mastitis

The current study measured the influence of milk of subclinically infected glands by different bacteria species on the cows milk and suggests different parameters for milk payment. The effects of bacterial infection or inflammation on gland milk yield were related to the bacteria species that caused the infection. The volume of milk of the inflamed gland from the cows milk yield was significantly lower (P<0.001) for the glands previously infected by Escherichia coli (PIEc) and those infected with Streptococcus dysgalactiae. Coagulation properties, rennet clotting time (RCT) and curd firmness (CF) also depended on the bacteria causing the infection. RCT values of all the inflamed glands were significantly longer (P<0.001) and CF values were significantly lower than that of the healthy ones. Moreover, in the whole milk, CF was also significantly lower and not proportional to the volume of the milk from the inflamed gland of the cows milk. Calculating the predicted 40% dry matter curd weight (PCW) on the cow level, including the healthy and inflamed glands or the healthy glands alone, found that for 9 of 13 PIEc cows, the presence of the affected glands milk in the whole cow milk resulted in a negative PCW value. Likewise, 5 of 20 cows infected by S. dysgalactiae had negative delta values. Unlike the latter bacteria, PCW from milk of glands infected with CNS increased, although in a lower magnitude than in the healthy glands. No correlation was found between logSCC in the whole cow milk (healthy and inflamed glands) and PCW.