Vitamin B6

Vitamin B6 is not routinely added in supplemental crystalline form to practical-type diets for swine and poultry, because both corn and soybean meal are plentiful in this B vitamin. Vitamin B6 is about 40% bioavailable in corn and about 60% bioavailable in soybean meal.[17] Moderate heat treatment (80 120°C) of corn seems to enhance B6 bioavailability, whereas greater heat treatment (160°C) decreases availability. Most of the vitamin B6 activity in corn exists as pyridoxal and pyridoxamine, forms that are more heat-labile than pyridoxine. Plant-source feedstuffs may contain B6 as either pyridoxine glucoside or pyridoxallysine, and both of these compounds have minimal B6 bioactivity.[18]

In premixes, vitamin B6 can lose bioactivity, particularly when minerals in the form of carbonates or oxides are present. High temperatures enhance loss of activity. Loss of B6 activity in stored, pelleted complete feeds averages about 20% during 3 mo of storage at room temperature.[14]

When vitamin B6 is added at supplemental levels to animal diets, it is generally added in the form of pyridoxine-HCl. To become active metabolically, pyr-idoxine must be converted to pyridoxal phosphate, and riboflavin is required for this conversion. Thus, riboflavin deficiency can markedly reduce the effectiveness of

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