Effects Of Chromium Polynicotinate On The Performance And Metabolic Parameters Of Dairy Cows During Dry And Early Lactation Period

Experiment was conducted to study the effects of chromium polynicotinate (Cr-NA) on the performance and metabolic parameters of Holstein cows during dry and early lactation period and the optimum dose.Twenty-four healthy multiparous Chinese Holstein cows before delivery (prepartum 28±5d) which had the adjacent milk yields (7900±50kg) and body weight (620±40kg) were randomly allotted to four groups. Cows in the 4 groups were fed the basic diet (prepartum diets Cr4.63mg/kgDM, postpartum diets Cr4.79mg/kgDM) or the basic diet plus different levels of chromium polynicotinate (0.03, 0.06 or 0.09mg/kgW~0.75). The experiment was performed from d 28 prepartum to d 56 postpartum. The results showed that:(1) Dietary optimum chromium polynicotinate supplementation helped to improve dairy cows performance, but had no effects on the percentages of milk fat, milk lactose, milk protein and non fat solid material(P＞0.05).Milk yields with 0.03mg/kgW~0.75 and 0.06mg/kgW~0.75 Cr-NA supplementation increased 1.71% and 3.70% compared to the basic diet. However high level of chromium supplementation decreased 2.80% of milk yield (p＞0.05)(2) Dietary Cr-NA supplementation increased the crude protein apparent digestibility and had the potential positive effects on the apparent digestibility of crude protein and crude fat of postpartum cows. The crude protein apparent digestibility with 0.09mg/kgW~0.75Cr-NA addition significantly increased 15.99% (P＜0.05) at d 14 postpartum. Cr-NA supplementation had the trend to increase the fat apparent digestibility at d 14 postpartum (P＞0.05) and the crude protein apparent digestibility at d 56 postpartum (P＞0.05).(3) The chromium concentration in milk accorded with the national standard of food with no more than 0.09mg/kgW~0.75 of Cr-NA supplementation.(4) Chromium supplementation could adjust blood glucose concentration to meet the energy requirements of cows in different physiological period. Blood glucose concentration decreased at d 7 postpartum (P＜0.05), but increased at d 28 postpartum (P＜0.05) with dietary Cr-NA supplementation at the level of 0.06mg/kgW~0.75 and 0.09mg/kgW~0.75. Dietary Cr-NA supplementation had no effects on blood glucose content at d 7 prepartum and d 56 postpartum (P＜0.05). (5) Cr-NA supplementation could change protein turnover and improve the utilization of nitrogen. With 0.06mg/kgW~0.75Cr-NA supplementation in diet decreased BUN of cows in d 7 prepartum (P＜0.05) and d 7 postpartum (P＜0.05), d 28 postpartum (P＞0.05) and d 56 postpartum (P＞0.05).(6) Dietary Cr-NA supplementation decreased serum NEFA concentration at d 7 prepartum, but had no effects on that of postpartum cows.(7) Cr-NA supplementation could increase immune globulin concentrations and enhanced the immunity of dairy cows. Cr-NA could increase serum IgG content at d 7 , prepartum, especially with 0.06mg/kgW~0.75 and 0.09mg/kgW~0.75 Cr-NA supplementation (P＞0.05). With 0.03mg/kgW~0.75 and 0.06mg/kgW~0.75 Cr-NA supplementation increased IgG concentration at d 7 postpartum.(8) Cr-NA increased blood insulin content and sensitivity, especially with 0.06mg/kgW~0.75 Cr-NA supplementation (P＜0.05). Cr-NA supplementation with 0.03mg/kgW~0.75and 0.06mg/kgW~0.75 decreased blood insulin content at d 7 postpartum (P<0.05), but increased blood insulin content at d 28 postpartum and d 56 postpartum (P＞0.05).(9) With 0.06mg/kgW~0.75 and 0.09mg/kgW~0.75 Cr-NA supplementation decreased cortisol content at d 7 prepartum and d 28 postpartum (P＞0.05) and d 56 postpartum (P＜0.05), helped to alleviate stress damaging.The study showed that Cr-NA supplementation was benefit for Holstein cows during dry and early lactation period. Chromium played important role in regulating energy, protein and lipid metabolism and improved performance and health condition. Cr-NA supplementation at 0.06 mg/kgW~0.75 was the optimal dose for cows during dry and early lactation period.