For some ingredients, especially cereals, the analytically determined values
for some vitamins are not fully available to poultry. This is particularly true
in the cases of biotin and nicotinic acid. Biotin bioavailability in wheat is
thought to be as low as 5%. Nicotinic acid bioavailability in cereals is thought
to be only about 30%. Most other vitamins are assumed to be fully available,
although there is doubt over choline, where some evidence suggests only 70%
in soyabean meal may be available. The total and available vitamin contents
for a range of feed ingredients are given in Table 3.
value.