Short communication: Factors affecting vitamin B12 concentration in milk of commercial dairy herds: An exploratory study

Only bacteria can synthesize vitamin B-12, and this requires adequate Co supply. The natural source of vitamin B-12 in human diets comes from animal products, especially those from ruminants. This study aimed to describe variability regarding vitamin B-12 concentration in milk among and within commercial dairy herds in early lactation. A secondary objective was to explore potential causes for this variability such as genetic variation and diet characteristics. In total, 399 dairy cows (135 primiparous and 264 multiparous; 386 Holstein and 13 Jersey cows) in 15 commercial herds were involved. Milk samples were taken at 27.4 +/- 4.1 and 55.4 +/- 4.1 d in milk. Neither parity (primiparous vs. multiparous) nor sampling time affected milk concentrations of vitamin B-12. Nevertheless, vitamin B-12 concentration in milk was highly variable among and within dairy herds. The lowest vitamin B-12 concentration in milk of cows was observed in the Jersey herd. Among herds, vitamin B-12 concentration in milk ranged from 2,309 to 3,878 pg/mL; one glass (250 mL) of milk from those herds would provide between 23 and 40% of the vitamin B-12 recommended daily allowance. Among individual cows, however, this provision varied between 16 and 57% of the recommendation. In spite of the limited size of the studied population, the heritability value was 0.23, suggesting that genetic selection could modify milk vitamin B-12 concentration. We observed a positive relationship between milk vitamin B-12 concentration and dietary acid detergent fiber content and a negative relationship between milk concentration of vitamin B-12 and dietary crude protein content.