LAUSR

The study was conducted to understand the effect of seasonal change on blood biochemical parameters and verify potential blood biochemical parameters which were selected as candidates for thermal stress response evaluation of Chinese Holstein cows in the previous study using independent individuals. A total of 652 healthy lactating Holstein cows from Sanyuan dairy farm were selected as experimental animals. Their milk production data and blood samples used for detection of blood biochemical parameters, were collected in spring (April), summer (August), fall (November) and winter (January), respectively, as well as the continuous temperature and humidity of cowsheds. The changes in 13 blood biochemical parameters (ACTH, BUN, COR, CRP, GH, GLU, HSP70, LD, LPO, NE, PRL, SOD, T3) among seasons were evaluated by MIXED models in SAS9.2 software. Our results showed that 1) The temperature and humidity index (THI) before sampling for continuous 8 days displayed experimental animals had no stress in spring and fall, but in summer and winter experienced heat and cold stress, respectively; 2) All of above 13 blood biochemical parameters had highly significant difference among seasons (P < 0.01). The concentrations of 8 parameters were significantly higher in summer (P < 0.05), but other 5 parameters were significantly lower (P < 0.05). In winter, 6 parameters were significantly higher (P < 0.05), and other 5 parameters were significant lower (P < 0.05); 3) The changes of 8 parameters (such as GH, PRL) between summer and fall, as well as 6 parameters (such as ACTH, SOD) between winter and fall were consistent as the previous study. These results revealed that heat and cold stress had serious effects on physiological condition of Chinese Holstein cows, and multiple parameters had been confirming to be used as candidates for the evaluation of temperature stress in Holstein cows.