Apparent digestibility of selected ingredients in diets for juvenile grouper, Epinephelus coioides (Hamilton)

Abstract

Apparent digestibility coe⁄cients (ADCs) for dry matter (ADC dm ) and crude protein (ADC cp ) of selected feed ingredients were determined in vivo for grouper using passive faeces collection (Guelph System). A reference diet (RF) and test diets (consisted of 70% RF and 30% test ingredient) with 1% Cr 2 O 3 as an inert indicator were used. An RF contained 45% protein, 10% fat and 15.7 kJ g À1 metabolizable energy. Three isonitrogenous and isocaloric diets, each contained a test ingredient (white ¢sh meal, white cowpea meal and ipil-ipil leaf meal), were used in a growth study based on ADC cp of feed ingredients. An RF without Cr 2 O 3 was a control. The ADC values of experimental diets were also determined. In grouper, the ADC dm of white cowpea meal, defatted soybean meal, wheat £our and shrimp meal (74^76%) were signi¢cantly lower than that of squid meal (99%), but comparable with those of the ¢sh meals (84^89%). No signi¢cant di¡erence was observed between the ADC dm of ipilipil leaf meal, rice bran and wheat £our (56^73%). The ADC cp of white cowpea meal and defatted soybean meal were similar to those of the ¢sh meals, squid meal and shrimp meal (94^99%). The ADC cp of wheat £our was comparable with that of ipil-ipil leaf meal (79^83%). Rice bran had the lowest ADC cp value of 43%. Based on speci¢c growth rate (SGR), the growth of ¢sh fed white cowpea meal-based diets was similar to that of the control ¢sh (3.23 .3% day À1 ). Also, no signi¢cant di¡erence was observed between the ADC dm (68^72%) and ADC cp (88^91%) of white cowpea meal-based diet and the control diet. The results suggest that ADC values can be used as indicators to determine the nutritional value of feed ingredients.White cowpea meal can be incorporated as a protein source in practical diet for grouper at 20.5% of the diet with no adverse e¡ect on growth.

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“…Fish are unable to make use of phytate-nutrient complexes because they lack the enzyme phytase (Riche et al, 2001). Tannins hinder the digestive process by binding to digestive enzymes such as protease resulting in a decrease in proteolytic enzyme activity, leading to reduced protein digestibility (Eusebio et al, 2004). Tannins also decrease the absorption of essential vitamins (Francis et al, 2001).…”

“…The poor performance (growth, protein utilisation and digestibility) of fish fed MM diets may be attributed to the negative effects of anti-nutrients. According to Eusebio et al (2004) the presence of anti-nutrients may hinder the digestibility and utilisation of dietary nutrients. Phytate reduces the bioavailability of nutrients due to formation of complexes such as a phytate-mineral/protein complex.…”

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“…On the other hand, Wilson and Poe (1985) reported that the channel catfish, an omnivorous species with clear preference for APs, can digest in excess of 70% of raw starch gross energy contents. Dietary plant ingredients can affect gastrointestinal transit time of feed as a result of the presence of fibres and sugars, and alter the digestibility of nutrients ingested by the fish (Storebakken et al, 1999;Eusebio et al, 2004;Zhou et al, 2004). According to Eusebio et al (2004), as dietary fibre is part of the carbohydrate component of plant ingredients, most fish cannot utilize it.…”

“…Dietary plant ingredients can affect gastrointestinal transit time of feed as a result of the presence of fibres and sugars, and alter the digestibility of nutrients ingested by the fish (Storebakken et al, 1999;Eusebio et al, 2004;Zhou et al, 2004). According to Eusebio et al (2004), as dietary fibre is part of the carbohydrate component of plant ingredients, most fish cannot utilize it. However, low dietary concentrations of dietary fibre (3-5%) may have a beneficial effect on fish growth.…”

“…Fish use around 80% of dietary dry matter; ADC DM describes especially how efficiently the feeds or feed ingredients are digested, and how much of their nutrient contents can be made available to fish for maintenance and growth. Also, ADC DM generally provides a better estimate of the quantity of indigestible materials in the feeds or feed ingredients, rather than that of the individual nutrient (Eusebio et al, 2004).…”