Abstract
In response to concerns over availability and cost of fishmeal for aquaculture feeds, a study was conducted to evaluate the suitability of a protein extract from coastal Bermuda grass for channel catfish (Ictalurus punctatus). The coastal Bermuda grass was treated by soaking in liquid anhydrous ammonia under high pressure at 70 C, a process known as Ammonia Fiber Explosion (AFEX), followed by alkaline extraction, isoelectric precipitation and centrifugation. Amino acid analysis of the extracted protein indicated a generally balanced profile that was first limiting in methionine. A laboratory feeding trial was conducted in which four isonitrogenous and isocaloric diets containing incremental levels of the extract were evaluated. The control diet contained 10% menhaden fishmeal and experimental diets were formulated so that the extract replaced 33, 66 and 100% of the fishmeal on an equal-protein basis. Each diet was fed to triplicate groups of channel catfish fingerlings initially weighing approximately 10 g/fish for 9 weeks. Apparent protein and organic matter digestibility of the extract also was determined utilizing chromic oxide as an inert marker. Results of the feeding trial indicated that substitution of the extract at all levels did not significantly (P>0.05) affect weight gain, feed efficiency, protein efficiency ratio, net protein utilization, intraperitoneal fat or hepatosomatic index of channel catfish. Apparent protein and organic matter digestibility coefficients of the extract were 85 and 89%, respectively. These data indicate that the extract can replace fishmeal in channel catfish diets. Further research to evaluate substitution of other ingredients with the protein extract appear warranted.
Buentello, J. Alejandro (1995). Evaluation of coastal Bermuda grass protein extract as a substitute for fishmeal in practical diets for channel catfish (Ictalurus punctatus). Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -B835.