RESUMEN
Rumen-protected conjugated linoleic acid [CLA] may increase the protein to fat ratio in milk, and potentially improve the energy balance of early lactation cows. The objective of this study was to evaluate the production performance and blood metabolite changes in Holstein cows supplemented with four different doses of CLA postpartum in early lactation. Eight multiparous Holstein cows with at least 25 kg/day milk production were randomly chosen and were included in an experimental design with four three week periods [7 days of adaptation and 14 days of treatment and sampling]. The experiment was carried out with four levels of protected CLA supplement including 0, 50, 100, and 150 g per day per cow. Blood metabolites such as cholesterol and LDL-C content decreased significantly [p<0.05], but other metabolites such as HDL-C, VLDL-C, triglyceride and BHBA did not change [p>0.05]. Milk production increased significantly [p<0.05], and 100 g/day of CLA supplemented treatment resulted in the highest production compared with the other groups. Milk fat percentage of the treated cows was reduced significantly and followed a dose-dependent response. No significant results were observed with regard to the protein content, solids-non-fat and milk density of the milk [p>0.05]. The increased milk production, and decreased blood LDL-C and cholesterol levels indicate an improvement in the physiological state of the cows. Given the enrichment of produced milk using this supplement, it is highly recommended to provide these supplements in dairy cow diets