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.

摘要

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 rapeseed, on the metabolism and milk yield of dairy cows during the first third of lactation. A total of 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 the first, second and third month of lactation. Evaluation of milk yield was carried out based on the results of monthly milk yield control, while the effect on reproduction was evaluated based on data supplied by a farm livestock specialist. At the end of the first month, a higher degree of energy metabolism disturbance was determined in group E in comparison with group C (beta-hydroxybutyrate, 1.05 vs. 0.51 mmol/litre, P<=0.05; nonesterified fatty acids, 0.68 vs. 0.27 mmol/litre, P<=0.01), as well as a higher occurrence of liver damage (bilirubin, 6.50 vs. 4.59 micro mol/litre, P<=0.01; aspartate aminotransferase, 1.66 vs. 1.39 micro kat/litre, P<=0.05; lactate dehydrogenase, 45.2 vs. 34.3 micro kat/litre, P<=0.05). During the entire experiment, the total concentration of cholesterol, HDL-cholesterol and vitamin E rose, and thus in the third month, the values in the experimental group were almost double that of the control group (cholesterol, 7.28 vs. 3.69 mmol/litre, P<=0.0001; HDL-cholesterol, 5.43 vs. 3.26 mmol/litre, P<=0.0001; vitamin E, 19.9 vs. 10.3 micro mol/litre, P<=0.0001). The proportion of HDL-cholesterol was lower in group E (third month, 76.1 vs. 88.8%, P<=0.001). A higher total antioxidant status in the serum of group E during the second (0.96 vs. 0.90 mmol/litre, P<=0.05) and third month of lactation (1.02 vs. 0.94 mmol/litre, P<=0.05) was observed, while other parameters of the antioxidation system (glutathione peroxidase and superoxide dismutase) 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 the 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 results to risk of fatty liver, but without negative impact on the health of dairy cows during the peak period of lactation..