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Vztah mezi průběhem dojení a dojivostí a zdravotním stavem mléčné žlázy
SEZIMOVÁ, Kateřina
The thesis deals with the relationships between the course of milking and the order of milking during the day, milk yield, stage of lactation, breed affiliation of cows and changes in the course of milking and other monitored indicators in cows with masti-tis. The literature review discusses current trends concerning the milking process, milk flow, monitoring of milking parameters, management software and factors that affect the whole milking process. The overview, which focuses mainly on mastitis and the risk factors associated with it, also covers various udder diseases. Data from each milking was collected for two farms and then the effect of the different grading cri-teria on the observed milking parameters were assessed. These were milking order, number of days in lactation on milking day, milk yield, average milk flow (in the first 15 s, 15 to 30 s, in the second 30 s and in the 2nd min of milking), proportion of milk yield in the first 2 min of the total milk yield, maximum and average milk conductivi-ty and temperature, average and maximum milk flow, total milking time and milking time at milk flow below 1 l/min. Subsequently, the data for DIM, milk yield, average milk flow (in the first 15 s, 15 to 30 s, in the second 30 s and in the 2nd min of mil-king) and the proportion of milk yield in the first 2 min were calculated. The diffe-rence between the maximum and average conductivity values and the difference between the milk flow values in the second 30 s of milking and in the second 15 s from the start of milking were also calculated. From the results it was found that Holstein cows, compared to dairy cows of the Czech Spotted Cattle breed, have a higher average milk yield, higher average milk flow and shorter total milking time. Also, milk yield in the morning milking is not always higher than in the afternoon milking. The average milk flow was highest from day 61 to day 120 of lactation. In the case of excessive flow, total milk yield, milk yield in the first 2 min of milking and its share of total milk yield were higher. In bimodal milk flow were found higher milk flow in the first and second 15 s of milking and also higher maximum milk flow and lower flow in the second 30 s of milking. A puzzling finding was the milk con-ductivity, as it decreased on the day of mastitis, when the conductivity should be highest. According to some authors, milk conductivity should always increase with the temperature of the milk sample, but this claim was not confirmed from the results.
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