UV-B light irradiation during automatic milking for vitamin d supplementation in dairy cows

Vitamin D has a significant role in mineral metabolism, bone tissue homeostasis, and immunity. Cattle can synthetize vitamin D in the skin in a linear dose dependent manner of ultraviolet irradiation. The objectives of this study were to investigate the possibility of vitamin D supplementation with narrow-band UV-B irradiation during automatic milking time and to determine the influence of hair and pigmentation of skin and hair on cutaneous vitamin D3 synthesis in dairy cows. Holstein Friesian cows from one farm were enrolled into the study. A narrow-band UV-B light (peak irradiation at 295 nm) was custom-made and mounted into the automatic milking system. Cows were split into three equal random groups using stratified sampling based on milk yield in the previous lactation, days after calving and the percentage of black area on their back. The first group was shaved and exposed to a daily dose during automatic milking, the second group was left unshaved and irradiated during the automatic milking with maximal possible dose and the third group served as control. The cows were blood sampled before and 60 days after the start of irradiation. The concentration of 25-hydroxyvitamin D was measured using an automated immune enzyme fluorescence assay. The increase in the 25-hydroxyvitamin D concentrations before and after the irradiation was statistically significant (p>0.001) between the shaved, unshaved and control groups. The irradiated groups shaved and unshaved produced more milk per day than the control group. Narrow-band UV-B LED light limited to automatic milking time was successful in increasing the concentrations of 25-hydroxyvitamin D in Holstein Friesian cows. Hair was reducing cutaneous vitamin D production. UV-B irradiation of cows during automatic miking is a novel way of vitamin D supplementation that does not expose farm equipment and personnel to UV-B irradiation and does not interfere with the daily routine on farm.