Effects of non-genetic factors on milk yield and chemical composition of milk from Holstein-Friesian cows

25 Background: In order to accurately determine the performance of cows in terms of milk yield 26 and milk components, it is necessary to determine the extent and direction of environmental 27 factors. Although many studies have explored environmental factors affecting milk yield, there 28 is not enough information about the effects and direction of environmental factors on the 29 composition of milk. Objective: To determine the effects of non-genetic factors, such as 30 calving season, lactation number, lactation stage, animal age, and herd size on milk yield, the 31 chemical composition of raw milk, and Somatic Cell Count (SCC) in Holstein-Friesian cows. 32 Methods: Data were obtained from 15,354 raw milk samples of 5,118 Holstein-Friesian cows 33 at 276 dairy farms in Türkiye. The data analysis was performed using the General Linear Model 34 (GLM) feature of the SPSS statistics program. Results: Mean fat (F), protein (P), dry matter 35 (DM), lactose (L), urea (U), and Log 10 SCC values of cow milk were 3.74 ± 0.01, 3.19 ± 0.01, 36 11.36 ± 0.03, 4.32 ± 0.01%, 21.57 ± 0.28 mg/dL, and 5.244 ± 0.01 cells/mL, respectively. Peak 37 milk yield (PMY), lactation milk yield (LMY), 305-day milk yield (305-d MY), and SCC 38 values were found to be 33.7 ± 0.13, 8,538.33 ± 89.64 kg, 6,479.42 ± 168.96 kg, and 224,164.34 39 ± 4,402.79 cells/mL, respectively. Conclusion: It is recommended to take measures to improve 40 the protein, dry matter, and urea component of milk in dairy farms in Türkiye and investigate 41 in detail the relationship between raw milk urea component, subclinical mastitis, and 42 reproductive features.