Vitamin B12 is produced by fermentation and as cyanocobalamin is available commercially for addition to feed. Vitamin B12 is only slightly sensitive to heat, oxygen, moisture and light (Gadient, 1986). Verbeeck (1975) reported vitamin B12 to have good stability in premixes with or without minerals regardless of source of the minerals. Scott (1966) indicated that there is apparently little effect of pelleting on vitamin B12 content of feed.
Results of a large number of animal experiments are about equally divided between those reporting a positive response to dietary cyanocobalamin and those reporting little or no response. Variable responses may be due to several factors, including initial body stores, environmental sources of the vitamin (such as molds, soil and animal excreta), microbial synthesis in the intestinal tract and adequacy or deficiency of other nutrients that influence vitamin B12 requirements. Perhaps the manner in which vitamin B12 is provided may affect the response as well. Wilson et al. (1991) found that intramuscular injection of 2 mg of vitamin B12 to pigs at weaning increased their growth rate and especially the weight gain during the third week. Wilson et al. (1991) did not determine whether dietary vitamin B12 would have produced a similar response. Nesheim et al. (1950) compared the effects of injected with oral administration of vitamin B12. Nesheim et al. (1950) found significant improvements in average daily gains for the vitamin B12-supplemented pigs. Furthermore, the injectable vitamin B12 requirement was around 0.6 µg of vitamin B12 per kg of body weight daily, while the oral requirement was approximately 20 µg per kg of dry matter consumed. Thus, in this experiment, the injectable requirement was approximately half of the oral requirement for vitamin B12.
Vitamin B12 is normally added to diets of all swine. Swine raised in confinement or in management systems in which there is limited access to feces should have a greater dietary requirement for the vitamin. Vitamin B12 supplementation may be warranted under certain conditions where stress, disease or parasites lower feed intake and (or) reduce intestinal absorption. In practice, vitamin B12 fortification of the ration should be adjusted to ensure the margin of safety important to prevent deficiency and allow optimal performance of swine.
