Phosphorus Availability of 25 Feed Ingredients determined by Bioassay on Toe Ash Content

Abstract

Availability of phosphorus in 25 feed ingredients was determined by biological assay on toe ash content reported previously1) in 10 experiments with 1, 830 chicks.Phosphorus in feed ingredients of animal origin, i.e., fish meals and meat and bone meals, was highly available, while availability of phosphorus in plant oil cakes was very low, being almost zero.Availability of P in yellow corn and milo was as low as almost zero. Generally speaking, P in wheat, wheat bran and barley was available with availability of higher than 60. Significant strain difference in P availability was observed between two strains of wheat, i.e., Glenlea and Pitic 62, which were bred in Canada for feed use. Availability of P in Pitic 62 wheat was over 100, while that in Glenlea wheat was 37. Availability of P in rice and rice brans, raw, roasted or defatted, was 15 in average.Phosphorus availability of 1:1 mixture of fish meal and soybean meal was 49, which was close to an average of P availabilities of fish meal and soybean meal determined separately, i.e., 119 and 7, respectively. The finding suggests that content of available P in formula feed could be estimated as a sum of available P in each of the ingredients.It was pointed out that errors in estimation of P availability of ingredients, such as plant oil cakes and yellow corn, which have very low content of available P, was much larger than that of ingredients with level of available P, such as fish meal. This is partly due to mathematical reason and partly due to variation of toe ash content of chicks fed a diet containing low level of additional available P.