Keywords: milk productivity, lactation, mastitis, somatic cell content, phenotypic factor
The results of the influence of phenotypic factors on the milk productivity of cows and milk quality indicators, in particular, the content of somatic cells, are presented. A reliable effect of the age of the animal, the stage of lactation, the season of the year and the machine milking operator on the physical-chemical parameters of milk and cow disease with mastitis was established.
More than 15,000 milk samples were analyzed and it was revealed that the average somatic cell content in milk was quite high 411 ± 7 thousand per cm3. According to the obtained data, about 20 % of the studied milk samples were obtained from cows with subclinical or clinical mastitis.
According to the results of the analysis of variance, the content of somatic cells for cows of 6 lactation and older (634 ± 53.1 thousand in cm3) was almost two times higher than in heifers (331 ± 9.2 thousand in cm3).
The seasonal changes in average milk yield, fat and protein content in cow’s milk are analyzed. The average daily milk yield varied from 18.3 ± 0.19 kg in January to 21.7 ± 0.17 kg in July, the fat content ranged from 3.72 ± 0.012 % in July to 4.37 ± 0.024 % in December, the protein content – from 3.07 ± 0.011 % in June to 3.35 ± 0.010% in November. The season’s influence was 4.6 %, 10.4 % and 5.8 %, respectively. The lowest average number of somatic cells (306 ± 18.1 thousand in cm3) was observed in milk samples obtained in May, and the highest 539 ± 33.8 thousand in cm3 in January (P<0.05).
The “machine milking operator” factor influence on the average daily milk yield was 4.1 %, on the fat content 5.8%, protein 1.2% and on the content of somatic cells in milk 1.8 %. At the same time, the difference between the maximum and minimum values was: for a daily milk yield of 5.4 kg, for a fat content of 0.53%, for a protein of 0.14%, and for a somatic cell content of 403 thousand in cm3.
The percentage of cows with mastitis also reliably depended on the machine milking operator. The greatest number of cases of cow diseases with mastitis was observed in the sixth group (29.3 ± 3.46 %), which was more than three times higher than in the eighth group (9.0 ± 2.65 %).
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