Influence of increased lipid content in diet in the form of treated rapeseed meal on the metabolism and milk yield of dairy cows in the first third of lactation

The purpose of this study was to evaluate the influence of high lipid concentration in the diet, served as calcium salts of fatty acids from rape, on metabolism and the milk yield of dairy cows during the first third of lactation. 28 dairy cows were divided into experimental (E; n = 14) and control groups (C; n = 14) and monitored within 100 days of lactation since the day of parturition. The diet of both groups had a balanced content of energy and crude protein, while there was a difference in lipid content (C - 3.7% vs. E - 6.99% of dry matter in the diet). Blood and urine samples were taken at the end of 1st, 2nd and 3rd months of lactation. Evaluation of milk yield was carried out based on the results of monthly milk yield control, while the evaluation of reproduction was performed using data supplied by a farm livestock specialist. At the end of the first month, a higher degree of energetic metabolism disturbance was determined in group E in comparison with group C (beta-hydroxybutyrate 1.05 vs 0.51 mmol/l, P ≤ 0.05; nonesterified fatty acids 0.68 vs. 0.27 mmol/l, P ≤ 0.01), as well as a higher occurrence of liver damage (bilirubine 6.50 vs. 4.59 μmol/l, P ≤ 0,01; aspartate amino transferase 1.66 vs. 1.39 μkat/l, P≤ 0.05; lactate-dehydrogenase 45.2 vs. 34.3 μkat/l, P ≤ 0.05). During the entire experiment, the total concentration of cholesterol, HDL-cholesterol and vitamin E rose, and thus in the 3rd month, the values in the experimental group were almost double that of the control group (cholesterol 7.28 vs. 3.69 mmol/l, P ≤ 0.0001; HDL-cholesterol 5.43 vs. 3.26 mmol/l, P ≤ 0.0001; vitamin E 19.9 vs. 10.3 μmol/l, P ≤ 0.0001). The proportion of HDL-cholesterol was lower in group E (3rd month 76.1 vs. 88.8%, P ≤ 0.001). We also determined a higher total anti-oxidant status of serum in group E in the second (0.96 vs. 0.90 mmol/l, P ≤ 0.05) and third months of lactation (1.02 vs. 0.94 mmol/l, P ≤ 0.05), while other parameters of the anti-oxidation system (glutathionperoxidase, superoxiddismutase) did not differ between groups. The total production of milk within the 100 days of lactation in both monitored groups was similar. In group E the concentration of milk protein was lower (3.18 vs. 3.45%, P ≤ 0.01), while the concentration of fat was insignificantly higher (3.55 vs. 3.21%) than in group C. The results of effect on reproduction did not differ significantly either, but the total percentage of gravidity was higher in the experimental group. Our results revealed that feeding of higher doses of lipid (6.99 %) fed in bypass form during the first month after parturition creates the health risk of a fatty liver, but no negative impact on the health of dairy cows was demonstrated during the peak period of lactation.