The utilization of some single cell proteins by fingerling mirror carp ( Cyprinus carpio)

Abstract

An experiment was conducted to determine the utilization by mirror carp of yeast (PY), bacterial (MB), algal (SA), soybean (SY), casein (CS), and herring (HM) meal proteins as the sole protein sources in semi-purified rations. A low casein (CS LOW) diet was included in the trial so that true digestibility, Net Protein Utilization (NPU) and Biological Values (BV) could be determined. All the feeds contained 30% protein other than the fishmeal and bacterial diets which contained 25 and 35%, respectively. Specific growth rates (%/day) found were MB 2.78 > CS 2.4, HM 2.26 > PY 2.08 > SY 1.24, SA 1.18 and CS LOW 1.13. Food conversion was optimal with diet MB (1.14) followed by CS (1.39), HM (1.42), PY (1.55) < SA (2.50) < SY (2.86) and CS LOW (3.04). Protein efficiency ratio was highest with the low casein diet at 3.24 decreasing in the order HM 2.82, CS 2.48 > PY 2.08 > SY 1.35 and SA 1.15. All the test proteins were well digested, assimilation values ranging from 80.3% (HM diet) to 96.6% (PY diet). The NPU's and BV's calculated from body analysis data were respectively for each protein, HM 64 and 79%, MB 49 and 52%, CS 49 and 52%, PY 47 and 49%, SY 42 and 51%, SA 36 and 41%. The above biological values are compared with various chemical scores based on amino acid analysis of the test proteins. All the results are discussed fully and also compared to values previously obtained with identical diets in rainbow trout experiments.