Plasma α-tocopherol content and its relationship with milk somatic cells count in Italian commercial herds

In the last few years vitamin E supplementation in dairy cattle and its activity on udder health has been often controversially debated. This work was aimed to investigate relationship between plasma vitamin E concentration and milk somatic cell count in healthy cows in commercial herds. 49 multiparous cows from two commercial dairy herds in Milan area were monitored from the day of dry off until 90 DIM. BCS was assessed and blood samples were collected at dry off, day 0, 30, 60 and 90 postpartum. Plasma was analyzed for α-tocopherol, Zn and Se content. Quantification of NEFA and BOHB was performed in serum samples. Milk production and composition was obtained from routinely test-day of Italian milk producers association. Somatic Cell Score (SCS) was calculated and included in the dataset. Analysis of data was performed using MIXED repeated and CORR procedures of SAS. Vitamin E plasma concentration significantly decreased at day of calving and progressively increased in the first 90 days of lactation. A significant (P<0.01) negative (-20%) correlation was observed between NEFA serum content and α- tocopherol plasma concentration. Serum selenium content was positively correlated (+31%, P<0.05) to zinc concentration. Grouping cows on the basis of their plasma α-tocopherol content higher or lower than 3 mg/mL at dry off, SCS at 30 and 60 DIM tended to be higher in lactating animals with lower content of α- tocopherol (1.12 vs. 1.72, P=0.18 at 30d; 0.92 vs. 1.72, P=0.07 at 60d). No significant differences were observed on analyzed parameters when cows were grouped based on their plasma α- tocopherol content higher or lower than 2 mg/mL at day of calving. Overall low SCS values in investigated animals (mean values at days 30, 60 and 90; 1.42, 1.32, 1.58) could explain the lack of correlation between plasmatic vitamin E and somatic cell score. However, plasma α-tocopherol content at dry off could be usefully correlated with somatic cell count in fresh cows.