Effect of high levels of zinc supplementation in feed on blood serum leptin concentration in late gestation cows, calves serum immunoglobulin G and total protein and their health

Increase in blood Zn bioavailability improves production and immune system. Due to the relation among zinc, leptin and immune system, this trial conducted to investigate the effect of zinc supplementation more than NRC recommendation on serum concentration of zinc and leptin in late gestation cows and its consequent colostral IgG and also its passive transfer to newborn calves, calves serum total protein and health scores.

This trial was conducted from 25 days before expected parturition day to 30 days after calving. Thirty-six multiparous Holstein cows by mean of 3.1 and 2.9 lactation for control and high zinc level treatment respectively, fed diets containing 75 and 150 mg/kg of dry mater Zn. Feeding was once a day at 09:00. Diets were isocalorie and isonitrogenous and the only difference was the proportion of Zn. Blood samples were taken from cows tail vein to determine Zn and leptin concentrations on -25 and -5 days relative to estimated parturition time. Immediately postcalving, calves were weighed and removed from the dam to prevent nursing and cows were moved to a maternity barn, milked, and a colostrum sample was collected. Calves fed colostrum of their own dam and a sample of colostrum used to determine concentration of IgG. Calves jugular vein used for blood sampling to test seral IgG and total protein twenty-four hour after birth. Individual animal health score (nasal, eye and ear, fecal, cough and rectal temperature) were assigned (using a calf health-scoring system developed by the School of Veterinary Medicine, University of Wisconsin-Madison) to calves for 30 days.

Using 150 mg/kg of Zn in the diet increased seral Zn and leptin 5 days before calving compared with control (P<0.05). Colostral IgG and also calves seral IgG and total protein increased by consuming high level of Zn. Positive correlation was observed between colostral and calves seral IgG. Calves health scores had no significant difference between treatments.

Probably supplementation of high level of Zn in late gestation diets, by increasing in dams seral Zn and leptin, improves calves immune system.

Using 150 mg/kg of Zn in the diet increased seral Zn and leptin 5 days before calving compared with control (P<0.05). Colostral IgG and also calves seral IgG and total protein increased by consuming high level of Zn. Positive correlation was observed between colostral and calves seral IgG. Calves health scores had no significant difference between treatments.

Probably supplementation of high level of Zn in late gestation diets, by increasing in dams seral Zn and leptin, improves calves immune system