A The effects of somatic cell count on milk yield and milk composition in Holstein cows
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This study was conducted to assess the impact of somatic cell count (SCC) on the test day milk yield (TDMY) and milk composition parameters (fat, solids-not-fat, protein and lactose) of Holstein cows raised in the Kirsehir province of Turkey. A total of 1194 raw milk samples were collected from 195 Holstein cows at different stages of lactation (from 1 to 7), parities (from 1 to 3) and calving seasons (autumn, winter, spring and summer). Also, TDMY and milk composition traits were tested by SCC in four groups (<100x10(3), 100-200(3),10(3), 201-500x 10(3) and >500x10(3) cells/mL). For statistical evaluation, SCC data were converted to log(10) base. The overall means of log(10) SCC, TDMY, fat, solids-not-fat (SNF), protein and lactose were determined as 4.95 0.016, 33.36 a 0.232 kg/day, 3.39 +/- 0.021%, 9.04 +/- 0.013%, 3.32 +/- 0.005% and 4.92 a 0.007%, respectively. Log(10)SCC, TDMY, fat, SNF, protein and lactose were significantly affected by the stage of lactation, parity and calving seasons (P<0.05). An increase in the SCC was accompanied by a decrease in the milk yield as well as its content (P<0.05). Cows' milk with high SCC (>201x10(3) cells/mL) had a lower TDMY than milk with lower SCC (<100x10(3)and 100-200 cells/mL). However, the lowest fat, SNF, protein and lactose were determined in milk with SCC >500x10(3) cells/mL. It was concluded that SCC in milk should not exceed 500x10(3) For Holstein cows, suggesting that monthly control or SCC may be effective For improving milk production and milk quality in Holstein cows.