Lactation performance and serum biochemistry of dairy cows fed supplemental chromium in the transition period
This study was conducted to evaluate the effect of supplemental chromium on performance and blood serum biochemistry of dairy cows. Thus, 20 multiparous Holstein cows (parity 3) were equally divided into two groups, group one (control), which received no chromium supplementation and group two (treatment) which received 5 g/day chromium methionine from week 5 prior to parturition until 12 weeks thereafter. Milk production and milk composition were evaluated on 4, 8 and 12 weeks after parturition. Serum biochemistry concentrations (serum glucose, cholesterol, triglyceride, total protein, and cortisol and insulin concentration) and blood hematology (red blood cell, hematocrit, hemoglobin concentration and percentage neutrophils, lymphocytes, monocytes, basophiles, eosinophils and ratio of neutrophils to lymphocytes) were measured on 2 and 5 weeks prior to parturition and 1 and 4 weeks thereafter. Results indicate that milk production was significantly affected by chromium-methionine supplementation during the entire period (P<0.01) but no significant effect on milk composition was found. Supplemental chromium had no significant effect on serum glucose, cholesterol, triglycerides and insulin concentration and blood hematology parameters (P<0.05). However, chromium supplementation tended to increase significantly, serum total protein concentration and decrease cortisol concentration (P<0.05). The results of this experiment showed that chromium methionine supplementation in multiparous dairy cows diet may improve their milk yield in transition period.
Key words: Dairy cow, transition period, chromium-methionine, milk yield, serum biochemistry.