Effects Of Methionine Chelated Zn/Cu/Mn On Immune Status And Hoof Health In Dairy Cows

The aim of this study was to evaluate effects of methionine chelated Zn/Cu/Mn on immune status and hoof health in lactating Holstein cows. The gait score of each cow was determined using a 5-point gait score system. Forty-eight Holstein cows in early lactation were randomly assigned into 1 of 2 treatments: 1) Control(CON): basal diet supplemented with 50 mg Zn, 12 mg Cu, 20 mg Mn/kg DM as sulfate salts; 2) Chelated trace mineral(CTM): basal diet supplemented with 50 mg Zn, 12 mg Cu, 20 mg Mn/kg DM as metal methionine hydroxyl analog. Cows in each treatment were composed as cows with hoof diseases(LH, n = 12) or healthy cows(HE, n = 12). The trial lasted for 180 days. Milk yield and milk composition was tested biweekly. Foot and mouth disease(FMD) vaccine was injected at day 90, and then blood samples were collected at day 90, 120, 150, 180 to detect FMD antibody titers. The samples of serum, milk, hoof and hair were taken at day 0, 90, and 180 to test the serum antioxidant variables, serum bone metabolic biomarkers, immune indices, microscopic appearance of hoof tissues, hoof hardness and mineral levels, respectively.The results showed that no differences were detected in milk yield and milk composition between healthy cows and cows with hoof diseases(P > 0.05). Cows receiving CTM had lower milk fat concentrations(P < 0.05) than that in CON, but no difference was observed on milk yield and other milk components(P > 0.05) between them. Compared with healthy cows, decreased superoxide dismutase activities and increased malondialdehyde levels were shown in cows with hoof diseases(P < 0.05). Serum malondialdehyde levels and oxidized glutathione(GSSG) levels were significantly lower(P < 0.05) and the change of malondialdehyde levels was greater(P < 0.01), while serum superoxide dismutase activities, glutathione peroxidase activities, reduced glutathione(GSH) levels, GSH/GSSG ratios and metallothionein levels were significantly higher(P < 0.05) and changes of superoxide dismutase activities, GSH levels and GSH/GSSG ratios were greater(P < 0.01) due to CTM supplementation. There was no significant difference between healthy cows and cows with hoof diseases for joint damage biomarkers levels(P > 0.05). Cows receiving CTM had a significantly lower procollagen-II N-terminal peptide levels and C-terminal telopeptide of type II collagen levels(P < 0.05) than that in CON, and the change of procollagen-II N-terminal peptide levels was greater(P < 0.01). No differences were detected in immune indices between healthy cows and cows with hoof diseases(P > 0.05). Immunoglobulin A levels was very significantly higher(P < 0.01) and FMD antibody titer-O type was significantly higher(P < 0.05) due to CTM supplementation. Compared with healthy cows, decreased serum Zn/Mn, hoof P, hair Cu/Mg levels were shown in cows with hoof diseases(P < 0.05) and the difference of serum Zn/Mn and hoof P levels were very significant(P < 0.01). The Zn levels of hoof and hair were very significantly higher(P < 0.01) and serum Zn/Cu/Mn and hair Cu/Mn levels were significantly higher due to CTM supplementation(P < 0.05). Compared with healthy cows, decreased hoof hardness levels were shown in cows with hoof diseases(P < 0.05). CTM tended to increase the hood hardness on day 90 after supplementation(P < 0.1), while significant improvement of hoof hardness was observed on day 180 due to CTM supplementation(P < 0.05). Compared with healthy cows, increased fragmentation of collagen fibers and decreased hoof horniness density were shown in cows with hoof diseases. Cows receiving CTM had higher hoof horniness density than that in CON.In summary, poor hoof histological structures in cows with hoof diseases resulted in lower hoof hardness, which may be related to imbalance of mineral metabolism and oxidative stress. Increased levels of Zn, Cu and Mn in three different tissues(hoof, serum and hair) were observed in cows supplemented with chelated trace minerals due to its higher absorption and utilization. Chelated trace minerals can enhance the anti-oxidative ability, which will promote the enhancement of immunity and normal development of hoof.