Relationship between changes of quantity and composition of milk with some genetic and environmental factors
1998
Taralik, K. (Godolloi Agrartud. Egyet., Gyongyos (Hungary). Mezogazd. Foiskolai Kar)
Data was analyzed from 252, 152 test-day observations from a database which contained the test-day observations of all cows registered in Hungary between January 1992 and July 1996. This represented cows with different Holstein Friesian gene proportions from 634 herds. The test-day observation registered by the Hungarian Herd Recording Ltd. contained the milk yields, fat and protein percentages and the somatic cell counts. Least square analysis showed significant effects of herd, calendar month of test, stage of lactation, age of cows at calving, construction of cows and somatic cell counts on milk yield and composition. Monthly variation of milk yields was different across years, and the protein percentage followed the inverse of the milk yield variation rather than being influenced by monthly role. In all investigated years the percentages of fat were lower in summer than in winter months. The seasonal patterns of somatic cell counts were inconsistent across years. Somatic cell, fat, and protein content were high during early stages of lactation, reached a minimum at 2-3 months in lactation and rose gradually throughout the rest of the lactation, so following the inverse of change in milk yield. A comparison of younger cows with older ones revealed that somatic cell counts increased from 463,000 to 1,1745,00 cell/ml of milk. The milk yield was the highest in 4 year-old cows
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