Vitamin B12 is produced by fermentation and is available commercially as cyanocobalamin for addition to feed. Vitamin B12 is only slightly sensitive to heat, oxygen, moisture and light (Gadient, 1986). Frye (1994) reported that storage time through six months had virtually no effect on B12 retention, whereas high heat (45†C, 113†F) at three weeks decreased B12 to 34%. Verbeeck (1975) reported vitamin B12 to have good stability in premixes with or without minerals regardless of mineral source. 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: 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 B12 requirements.
In a survey of 16 commercial egg layer and breeding flocks, Naber and Squires (1993a) reported considerable variation in vitamin B12 content and that some flocks sampled were of marginal vitamin B12 status to support hatchability and maximum egg size. For those flocks at one or two times the dietary requirement, vitamin transfer efficiency from diet to eggs was 43% for vitamin B12.
Vitamin B12 is normally added to diets of all poultry species. Poultry raised in confinement, in management systems where there is limited access to feces for coprophagy, should have a greater dietary requirement for the vitamin. The vitamin B12 fortification of the ration should be adjusted to assure the margin of safety important to prevent deficiency and allow optimum performance in poultry.
