Effect of season and herd on rennet coagulation time and other parameters of milk technological quality in holstein dairy cows

In five herds of purebred Holstein dairy cows,altogether 220 bulk milk samples were collected with the following average parameters: rennet coagulation time (RCT) 265.2 sec.,titratable acidity 6.40 °SH,active acidity 6.72 pH,specific density 1.0281 kg.F,fat content 3.81 g.lOOg1,protein content 3.28 g.lOOg1,lactose content 4.72 g.lOOg-1,and content of solids non-fat content 8.89 g.lOOg1; average values of milk batch volume per herd and diurnal air temperature were 6,072 kg and 8.02 °C,respectively. It was found out that the variable season (spring,summer,autumn or winter) significantly influenced nearly all parameters under study (the only exceptions were values of titratable acidity and milk batch volume). As compared with all other seasons,the significantly shortest RCT was recorded in summer. Further it was also found out that the variable herd influenced all parameters with the exception of average diurnal air temperature. Regardless to differences existing among individual herds,the shortest average RCT was recorded always in summer.