Leaf protein concentrate as a protein source in diets for carp and rainbow trout.

Abstract

The nutritional quality of a leaf protein concentrate (LPC) prepared from rye grass was investigated by feeding experiments with carp and rainbow trout. The feeding experiments were carried out with diets in which the protein component consisted of either LPC or casein alone or with various combinations of these materials. Digestibility of the LPC was high (86%) and the digestibility of the protein in diets containing both LPC and casein was generally greater than 90%. Values for protein efficiency ratio (PER) and net protein utilization (NPU) of LPC, determined in experiments of 15 days' duration(carp) and 17 days' duration (rainbow trout), were also relatively high and were clearly improved by combination with casein. In particular, higher PER and NPU values were obtained with carp given a diet containing a mixture of LPC (43% of total protein) and casein (57% of total protein) than when either protein was fed singly. Relatively good growth rates of carp given diets containing LPC were maintained in experiments lasting 40 days. The experiments with rainbow trout demonstrated that at least 40% of the dietary casein may be replaced with LPC without reduction in PER, NPU or growth rates.