Changes of phosphorus absorption from several feed ingredients in rainbow trout during growing stages and effect of extrusion on soybean meal.

Japanese research determined the availability of phosphorus in several feed ingredients in digestibility studies conducted with rainbow trout. Phosphorus absorption was measured for fish weighing 2, 5, 10, 20, 50, and 100 grams. Absorption of phosphorus from the various plant protein ingredients was very low in the two-gram fish and increased in early growth stages to plateau when the fish reached ten grams. Phosphorus absorption from the different ingredients were: Pollock meal, 31-46%; sardine meal, 49-59%; meat and bone meal, 36-46%; poultry feather meal, 36-84%; soybean meal, 3.4-37%; extruded soybean meal, 25-58%; soy protein concentration, 3.7-34%; and corn gluten meal. 0-17%. These results showed that extrusion cooking of soybean meal to a temperature of 150 degrees Centigrade improved the availability of phosphorus in soybean meal.

Satoh, S. and co-workers. Changes of phosphorus absorption from several feed ingredients in rainbow trout during growing stages and effect of extrusion on soybean meal. Fisheries Sci. 68(20):325-331, 2003