Effects Dietary pH and Electrolyte Concentration on Utilization of Crystalline Amino Acids by Fingerling Carp

Abstract

Feeding experiment was conducted for 6 weeks to clarify effects of supplemental electrolyte and/or dietary pH on utilization of an amino acid diet using fingerling carp. Growth and feed effciency improved without noticeable effect on feed consumption as the dietary pH was raised from 4.6 to 5.2 or 5.8 together with rise in Na level from 0.13% to 1.23% or 1.73%, due to substitutions of Asp and Glu with Na•Asp and Na•Glu, respectively. Also change in the dietary pH alone showed the similar effects on the growth and feed effciency when pH of the diet was lwered from 4.9 to 4.5 by addition of acetic acid, where Asn and Gln were used instead of Asp and Glu to raise the original dietary pH to about 6. When the dietary pH were kept at 5.7-5.9 levels with use of Asn and Gln instead of Asp and Glu, supplement of K (1.41%) as acetate form up to equimolar level of Cl from supplemented Arg•HCl and Lys•HCl resulted in better growth and feed efficiency than that of Na (0.70%). However, excess supplements of K (2.30%) and Na (1.23%) depressed growth and feed effciency almost to half in the former and only slightly in the latter with significantly elevated feed consumption in both cases. Rise in the dietary pH level alone or combination with increment in Na level resulted in the decline of moisture with increased fat content as well as fall in Na, K and ash contents in the whole body of fish sampled at the end of the experiment. However, almost completely opposite results were obtained when Na or K level was raised with little change in the dietary pH.