Short communication: Casein hydrolysate and whey proteins as excipients for cyanocobalamin to increase intestinal absorption in the lactating dairy cow

Bioavailability of vitamin B12 is low in humans and animals. Improving vitamin B12 absorption is important for optimal performance in dairy cows and for increasing vitamin B12 concentrations in milk for human consumption. However, when supplemented in the diet, 80% of synthetic vitamin B12, cyanocobalamin (CN-CBL), is degraded in the rumen of dairy cows and only 25% of the amount escaping destruction in the rumen disappears from the small intestine between the duodenal and ileal cannulas. In pigs, vitamin B12 from milk is more efficiently absorbed than synthetic CN-CBL. The objective of this study was to determine the efficacy of casein hydrolysate and whey proteins as excipients for CN-CBL to increase portal-drained viscera (PDV) flux of the vitamin in lactating dairy cows. Four multiparous lactating Holstein cows (237±17 DIM) equipped with a rumen cannula and catheters in the portal vein and a mesenteric artery were used in a randomized Youden square design. They were fed every 2h to maintain steady digesta flow. On experimental days, they received a postruminal bolus of (1) CN-CBL alone (0.1g), (2) CN-CBL (0.1g) + casein hydrolysate (10g), or (3) CN-CBL (0.1g) + whey proteins (10g). Starting 30 min after the bolus, blood samples were taken simultaneously from the 2 catheters every 15 min during the first 2h and then every 2h until 24h postbolus. Milk yield, DMI, and vitamin B12 portal-arterial difference and PDV flux were analyzed using the MIXED procedure of SAS. Milk yield and DMI were not affected by treatments. The portal-arterial difference of vitamin B12 during the 24-h period following the bolus of vitamin was greater when the vitamin was given in solution with casein hydrolysate (2.9±4.6 pg/mL) than alone (-17.5±5.2 pg/mL) or with whey protein (-13.4±4.2 pg/mL). The treatment effects were similar for the PDV flux. The present results suggest that CN-CBL given with casein hydrolysate increases vitamin B12 absorption as compared with CN-CBL given alone.