I. Marinov1, D. Dimov2, T. Penev2*
1Department of Animal Husbandry – Ruminants and Dairy Farming, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Applied Ecology and Animal Hygiene, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 2 April 2021; accepted for publication 30 September 2021)
Abstract. The aim of the study was to determine the dependence between Test Day (TD) milk productivity traits and somatic cells count (SCC) in milk and also the influence of the factors: farm, parity and TD recording season of Holstein cows. The survey included a total of 484 lactating cows from 8 cattle farms in Bulgaria. A total of 3473 TD records including data on TD milk yield, fat %, protein % and SCC in milk were used. A statistically significant effect of the farm, recording season, and SCC on TD milk yield, fat % and protein % was reported. The highest TD milk yield was reported in spring (22.42 kg), followed by winter (21.95 kg). In winter and autumn were reported higher mean values for TD fat (3.77 and 3.84%) and TD protein (3.38 and 3.40%) content in milk. At the highest SCC – above 999 000 cells/ml, the highest average daily milk yield – 24.1 kg and the lowest fat (3.48%) was reported. With the highest and positive statistically significant value was the phenotypic correlation between TD milk yield and SCC (0.21). The correlation with TD fat % was statistically significant, with negative value (- 0.07).