LAUSR

Abstract The aim of the study was to determine effects of dietary clinoptilolite (CPL) supplementation on β-hydroxybutirate (BHB) serum levels and milk fat to protein ratio (FPR) during early lactation in Holstein-Friesian cows. Seventy cows of the Holstein-Friesian breed, aged from 3 to 5 years, kept in a farm nearby Đurđevac, Croatia, were used in the study. The cows were randomly assigned into two groups, either test, in-feed CPL treated; CPL (n = 35) or control, non-treated group; CON (n = 35). The CPL group received 50 g of natural modified CPL preparation in the ratio for dairy cows, twice a day, from third month of pregnancy. Blood and milk samples were collected from the cows after parturition on days 7, 12, 19, 26 and 33 of lactation. The average value of BHB was higher in the CON than in the CPL group (1.03 ± 0.78 vs. 0.82 ± 0.42 mmol/L), as well as average value of FPR (1.32 ± 0.20 vs. 1.24 ± 0.14), but without significant differences. The highest BHB serum levels were obtained on days 12 and 19 of lactation in the CON group and in the CPL group on day 12. The cows in CPL group had lower BHB levels and FPR ratio, mostly, in the optimal range or below, while cows from CON group had FPR higher than optimal on days 19, 26 and 33 after parturition. In the CON and CPL groups 17.5% and 7.9% cows, respectively suffered from subclinical ketosis. On days 7, 12 and 19 non-esterified fatty acids were significantly higher in the CON group than in the CPL group. The cows from the CON group were in severe and longer negative energy balance than the cows from the CPL group. In conclusion, the CPL had positive effects on BHB serum levels and FPR during early lactation in Holstein-Friesian cows.