Studies on digestibility and digestive enzyme activities in Labeo rohita (Hamilton) juveniles: effect of microbial α-amylase supplementation in non-gelatinized or gelatinized corn-based diet at two protein levels

Abstract

A 60-days feeding trial was conducted to delineate the effect of both gelatinized and non-gelatinized corn with or without supplementation with exogenous a-amylase at two dietary protein levels (35% and 28%) on dry matter digestibility, digestive enzymes and tissue glycogen content of Labeo rohita juveniles. Three hundred and sixty juveniles (average weight 10±0.15 g] were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets containing either 35% or 28% crude protein were prepared by including gelatinized (G) or non-gelatinized (NG) corn as carbohydrate source with different level of microbial a-amylase (0, 50, 100 and 150 mg kg -1 ). The dry matter digestibility of G corn fed groups was significantly higher (P < 0.05) than that of the NG corn fed groups. Hepatosomatic index (HSI), liver glycogen and intestinal amylase activity of G starch fed groups were significantly higher (P < 0.05) than those of the NG corn fed groups. However, the reverse trend was found for gastrosomatic index (GSI), muscle glycogen and intestinal protease activity. Addition of 50 mg a-amylase kg -1 feed improved the dry matter digestibility of NG starch fed groups, which was similar to that of the G corn fed groups or NG corn supplemented with 100/150 mg a-amylase kg -1 feed. HSI, liver glycogen and intestinal amylase activity were significantly increased (P < 0.05) at minimum level of a-amylase in the feed (50 mg kg -1 ) and did not increase due to further inclusion of amylase in the diet. Supplementation with a-amylase at 50 mg kg -1 increased the intestinal amylase activity beyond which no significant changes were observed. Protease activity of liver and intestine was highest (P < 0.05) in higher crude protein (CP) fed groups, but protease activity of the intestine was significantly higher in the a-amylase supplemented groups. Hence, it was concluded that feed with 28% CP containing either G corn without a-amylase or NG corn with 50 mg a-amylase kg -1 may be used as the alternative carbohydrate source for L. rohita juveniles.

Modulation of key metabolic enzyme of Labeo rohita (Hamilton) juvenile: effect of dietary starch type, protein level and exogenous α-amylase in the diet

“…There was no significant difference on the blood glucose level in the G corn group at different aamylase levels (0, 50, 100 and 150 mg kg -1 feed) because G starch is easily broken down to glucose for which there was no role of a-amylase for further breakdown of starch, which is in agreement with Kumar et al (2006b). Fish have been initially thought to be diabetic because of their poor ability to control the blood glucose level either due to insufficient insulin secretion or differences in the activities of hepatic glycolytic and gluconeogenic enzymes, as found in Table 4 Effect of starch type, a-amylase level, CP level and their interaction on hexokinase, glucose-6-phosphatase, fructose-6-phosphatase and Glucose-6-phosphate dehydrogenase activity in liver of L. rohita fingerlings at the end of the experiment 1982a, b) and channel catfish (Wilson and Poe 1987).…”

“…Cowey et al (1977bCowey et al ( , 1981 also reported that high protein diet has been shown to produce an increased FBPase activity in trout. Kumar et al (2006b) reported that a-amylase supplementation increased the utilization of starch by increasing gut amylase activity in L. rohita juveniles. Thus, in the present study, decreased gluconeogenesis may be due to the availability of more digestible NS Non-significant carbohydrate because of gelatinization and/or supplementation of a-amylase, whereas an increased gluconeogenic enzyme activity is to fulfill the metabolic need for glucose not met by the diet.…”

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“…Similar observation were also made by many researchers for different species, Ng et al (1998) (1999) in Clarias gariepinus; Ng and Chen (2002) in Clarias macrocephalus × C. gariepinus., Kumar et al (2006) in Labeo rohita, Lin et al (2007) in Oreochromis niloticus × Oreochromis aureus; Zhou et al (2013) in Ctenopharyngodon idella. Increased endogenous enzyme activities lead to increased apparent nutrient digestibilities in Labeo rohita due to dietary exogenous enzyme, which is consistent with the findings of Ogunkoya et al (2006), who also found that exogenous enzyme supplementation to the soybean meal based diet improves the apparent digestibility coefficient of dry matter, protein, lipid and carbohydrate in Oncorhynchus mykiss.…”

Modulation of key enzymes of glycolysis, gluconeogenesis, amino acid catabolism, and TCA cycle of the tropical freshwater fish Labeo rohita fed gelatinized and non-gelatinized starch diet

“…Wilson (1994) reported that an adequate level of carbohydrates in fish diet reduces catabolism of protein and lipid for energy purposes and provides metabolic intermediates for the synthesis of other biologically important compounds. The carbohydrate digestibility in fish, however, depends on the dietary carbohydrate level, molecular complexity (Bergot 1993;Catacutan and Coloso 1998;Hutchins et al 1998;Small and Soares 1999), and the technological treatments applied (raw/cocked or gelatinization/extruded; Bergot and Bréque 1983;Kumar et al 2006). According to Kumar et al (2008a), another factor that affects carbohydrate digestibility is its gelatinizationed ratio.…”