Changes in the real-time registration of milk β-hydroxybutyrate according to stage and lactation number, milk yield, and status of reproduction in dairy cows.

This study investigated changes in the real-time measured levels of milk β-hydroxybutyrate according milk yield, lactation number and status of reproduction in dairy cows. A total of 378 cows were selected. According to their reproductive status the cows were classified as belonging to the following groups: Fresh (1 - 44 days after calving. n=43). Open (45 - 65 days after calving. n=78), Inseminated (1 - 35 days after insemination. n=133). Pregnant (35 - 60 days after insemination and pregnant (relatively pregnant) (n=124). The cows were milked with DeLaval milking robot (DeLaval Inc., Tumba, Sweden) in combination with a Herd Navigator (Lattec I/S. Hillerød. Denmark) analyser. We observed that milk β-hydroxybutyrate (BHB) had a tendency of increasing with an increase of lactation number. The average BHB in multiparous cows was 11.111% higher in com- parison with primiparous cows (p⟨0.001). We found higher BHB concentration in the multipa- rous cows in all reproduction status groups (p⟨0.001). A strong positive statistically significant (p⟨0.001) relationship has been found between BHB and the average milk yield within all groups of primiparous cows although we found a statistically unreliable coefficient of correlation (from -0.202 to 0.057) between highest milk yield and BHB in primiparous and multiparous cows. Copyright© by the Polish Academy of Sciences.