Effects of lactation month and season on test-day milk yield and milk components in Holstein cows

This study aims to determine the correlations between the test-day milk yield (TDMY) and the fat and protein content as well as the fat and protein yields in Holstein dairy cows and to investigate the effects of lactation period and sampling season on these parameters. The study material consists of 1.380 records of a total of 151 head of Holstein dairy cows raised on a private farm in Samsun province. In the study, the mean TDMY, fat content, protein content, fat yield and protein yield were recorded as 20.6 +/- 5.10 kg, 3.97 +/- 0.734%, 3.23 +/- 0.276%, 0.81 +/- 0.210 kg and 0.66 +/- 0.160 kg, respectively. The effects of lactation period and sampling season on the TDMY, fat content, protein content, fat yield and protein yield were found statistically significant (P<0.01). Statistically significant negative correlations were determined between the TDMY and the fat and protein content, but positive and statistically significant (P