Effect of chelated chromium supplementation on lactation performance and blood parameters of Holstein cows under heat stress

The objective of this study was to determine the effects of chelated chromium supplementation on lactation performance and blood components of Holstein cows under heat stress. One hundred and sixty multiparous lactating Holstein cows (120–130 days post-partum), were used in this study. Animals were divided equally (80 cows/treatment) and were randomly allocated to one of two treatment diets. Diet 1, was total mixed rations (TMR) without chromium (Cr) added and served as a control. Diet 2, basal diet, with chromium yeast (chelated chromium) added at manufacturerʹs recommended level (4 g/head per day). The average maximum and minimum air temperatures were 29.0 and 24.80° C respectively. The averaged temperature–humidity index (THI) was 78.6 units. Adding chromium yeast to the diet of dairy cows increased milk yield and feed intake. No significant differences were found between the two treatments in milk fat, protein, lactose, and solids non-fat (SNF) percentage. Adding chromium to the diet of lactating cows did not show any effect on blood serum level of hemagglutination test (HA), albumen, and glucose, while concentration of total blood protein and globulin was decreased. The ratio of albumin/globulin and cholesterol level increased significantly by adding chromium (P < 0.01). chelated chromium to the diet of dairy cows under heat stress improved milk yield and feed intake without affecting milk component.