No abstract

The goal of this paper was to determine the effect of daily production level of primiparous Holstein cows kept on dairy cattle farms in Eastern Croatia on response to heat stress conditions (THI threshold). With that purpose, individual test-day records with data on ambient temperature and relative humidity in the barns were analysed. Data were collected in regular milk recording from 2006-2012. The THI threshold values for daily milk yield were determined by least square analyses of variance for each given THI value (from 68 to 72) using the PROC MIXED (SAS). Low producing cows experienced significant drop at THI=68, while in high producing primiparous Holsteins first significant drop in daily milk yield was observed when THI=69. Also, the amount of daily production drop depended on cow’s production level (0.155-0.256 kg/day in high producing; 0.319-0.460 kg/day in low producing). It could be concluded that the response of primiparous Holstein cows kept in Eastern Croatia to heat stress conditions depends on daily production level.

With the aim of determination of biochemical indicators variability in the plasma and milk and hematological indicators regarding the daily lactose content classes (indicating the mastitis risk) and somatic cell counts classes (indicating the animal’s health status), blood and milk of 75 Holstein cows were sampled. The cows were reared on a commercial dairy farm. A statistical analysis demonstrated that the lactation stage, parity, and statistically significant monthly measurement P < 0.01) affected both the biochemical and hematological parameters. The differences between the analyzed biochemical and hematological parameters due to the mastitis score classes (according to the daily lactose content, DLC, and the somatic cell count, SCC) were present and statistically significant (P < 0.05) in some traits. Furthermore, different trends regarding the mastitis scoring (DCL of SCC) were determined in some traits. Therefore, when using the test-day records as an animal’s mastitis risk and health status indicator, both scoring ways should be used. Finally, in the case of a mastitis risk or mastitis occurrence, other diagnostic methods (such as various mastitis tests) should be used for the sake of an unambiguous detection.