The effect of temperament on stress, milk yield and quality in dairy cows

This study aimed to determine the relationships between temperament traits, milk yield and quality, and stress levels in dairy cows. The animal sample consisted of 19 dairy cows from three different breeds (Simmental, Brown Swiss, and Holstein). The animals were subjected to weighing tests, exit velocity tests, and hindlimb activity tests during milking. Lactation milk yield was calculated from milk yield inspections conducted between June and September; dry matter, protein, fat, and lactose contents, as well as somatic cell count, were determined in milk samples. The temperature-humidity index was also determined during morning and evening milkings, and the animals' rectal and abdominal temperatures were recorded. Blood samples were drawn from the animals before the behavioral tests, immediately after the test, and 1 hour after the test to determine cortisol levels. Lactation milk yield in the dairy cows was determined as 2848.2 kg, and the average daily milk yield was 9.77 kg. The milk's dry matter, fat, protein, and lactose levels were found to be 8.56, 2.27, 3.10, and 4.67%, respectively. Somatic cell counts in milk samples taken in July, August, and September were determined to be 102,263 units/ml, 148,895 units/ml, and 116,789 units/ml, respectively. A low negative and statistically significant correlation (r=-0.38, p<0.001) was determined between the weighing test and the time to hatch. According to the findings, it was determined that there was a statistically significant relationship between facial hair vortex score and milk yield (p<0.01). Furthermore, the time factor was found to have a significant effect on cortisol levels assessed by blood samples taken at specific time intervals (p<0.01). A statistically significant relationship was also found between the output velocity time and somatic cell count (p<0.01). However, a significant negative correlation was determined between the temperature and humidity index measured during morning milking and milk yield (p<0.001). A positive but weak correlation (r=0.10, p<0.05) was found between rectal temperature and the temperature humidity index measured in the morning milkings, while the correlation between rectal temperature and the temperature humidity index measured in the evening milkings was low but significant (r=0.19, p<0.001). Additionally, a negative correlation (r = -0.17; p<0.001) was determined between skin temperature and weighing test scores. These results reveal the effects of animal behavior and environmental factors on milk yield and quality, and can be considered to provide significant contributions to herd management practices.