Carbohydrate requirements of finfish and crustaceans

Nutrition supplies the raw materials for the maintenance of life. Some materials are used, for the formation of body tissues (anabolism) and some for the production of energy (catabolism). Foods may be classified as energy and growing foods carbohydrates (CHO), fats and proteins and non energy foods (Minerals, vitamins, water and oxygen). Nutrition of fish has received attention for many years. The nutritional value of a diet is measured by the presence of necessary elements and catalysts an abundant supply of the anxillary foods and a proper balance between the energy and growing foods, A proper balance between the energy and growth foods assures an adequate supply of both energy and raw materials for optimum anabolic activity which in addition to growth includes tissue repair, reproduction and the formation of essential body products

Effects of amylase inhibitor albumin from wheat on the alpha-amylase activity in carp and tilapia

The amylolytic activities of alpha-amylase extracted from Mirror carp (Cyprinus carpio) and Nile tilapia (Oreochromis niloticus) were significantly reduced by purified amylase inhibitor albumin of wheat when tested under in vitro conditions. The action of this inhibitor was rapid and maximum levels of inhibition were attained within 20 minutes. For both carp and tilapia, the enzyme residual activities after inhibition were found to be related inversely to inhibitor concentration and positively to the initial enzyme activity levels. The curvilinear relationships between these parameters were explained by deriving equations of the type: A2 = a+b A1 - c I + d I2 where a, b, c and d are constants, Ai = Initial amylase activity (mU/min), A2 = Residual amylase activity (MU/min), I= Inhibitor concentration as ug protein. Inhibitions were greatest for amylases from gut tissue and ýowest for amylases from gut fluids. 1ug of purified inhibitor was found to contain a potency, to reduce 298 Units of carp gut tissue alpha-amylase and 532 Units of tilapia intestinal tissue alpha-amylase, by 50%. When amylase inhibitor extracted from wheat was incorporated in the feed of carp in its active form for three weeks, it caused a significant reduction in the specific growth rate to only 0.16%/day, while in carp fed autoclaved inhibitort such reduction in growth was not seen and the SGR was maintained at over 1.00%/day. However, despite the presence of active inhibitor in the intestine, the fish were able to maintain alpha-amylase activities in the gut contents at a level similar to that in fish fed denatured inhibitor. This was achieved by hyperactivation of enzyme secretions in the tissues of hepatopancreas and intestine. Hepatopancreas from fish fed active inhibitor exhibited more than two-fold increase in amylase, activity compared to those fed denatured inhibitor. By the third week of the experiment this difference in enzyme activity levels was not apparent but there were also no indications of adaptation or improvement in growth rate. Degenerations in hepatopancreas were also not apparent. Feeding carp with diet containing wheat with its inherent content of inhibitor also caused pancreas hyperactivity and some reduction in growth rate for a short period in comparison to those fish fed autoclaved wheat. In carp, the alpha-amylase activity did not vary depending on the raw or gelatinized nature of starch, both forms elicited equal increases in enzyme activity. However, autoclaving wheat, though effective in inactivating the inhibitor, was found to lower the biological value and digestibility of wheat proteins. Contrary to the result of the carp trials in Nile tilapia, the growth was not significantly reduced by feeding on diet containing active inhibitor and a SGR of 1.57%/day was recorded in comparison to 1.81i/day in tilapia fed denatured inhibitor. Samples of stomach and intestinal contents collected 4 hours after feeding did not reveal the presence of active inhibitor. Apparently the acidic protease, pepsin, in the stomach of tilapia caused the total destruction of the inhibitor in the diet before the contents were passed into the intestinal region. The presence of active amylase inhibitor in tilapia feed did not affect the digestibilities of starch and protein in the diet. Both the groups were able to digest carbohydrates and protein to levels of over 90%. The implications of these results are discussed in relation to feed formulation and fish nutrition

Nutritional studies in the African catfish Clarias gariepinus (Burchell, 1822).

A purified diet, the raw material zein and two diets composed of complex foodstuffs (fishmeal, soy, wheat), were tested over a seven and a half (7.5) month period, to obtain the in vivo Apparent Digestibility Coefficients (ADC) for dry matter, crude protein, lipid, carbohydrates, ash, energy and the ADCs of their amino acids, for the African catfish Clarias gariepinus (Burchell 1822). Faeces were collected by sedimentation and digestibility coefficients calculated by use of chromium oxide as external indicator. Apparent digestibility coefficients ranged between 54% and 96%. Crude protein ADCs (81-90%) recorded for diets in this experiment were similar to those previously recorded. Ash digestibility (54-89%) varied significantly between diets probably as the result of the reduced bioavailability of minerals and trace elements in their constituent raw materials. ADCs for individual amino acids ranged between 82% and 99%. Zein, as an experimental feed ingredient for African catfish, showed acceptable ADCs for both gross nutrients and amino acids. When the nutrient level in the test ingredient was very different from that in the reference diet, calculation of ADCs based on relative nutrient contributions appeared necessary. Dextrin (an intermediate product of starch hydrolysis) was the prevalent carbohydrate source in the purified diet. The high carbohydrate digestibility for this diet (72%) suggests high starch digestibility in African catfish and confirms previous hypothesis of good starch utilization in the species due to elevated amylase levels in the anterior part of the intestine. A 26-day experiment was conducted on triplicate groups of sub-adult catfish (102.2g) using two feeding frequencies, twice per day and three times per day with fish fed to appetite on a purified diet. Fish fed twice ate 1.42 % of b. w. d'1, those fed three times consumed 1.27% of b. w. d'1. Fish fed twice also exhibited better growth and food conversion. Despite the use of purified diets, performance indices for the groups fed twice per day were regarded as good compared to previously reported data. Administration of seven diets differing in protein: energy levels over a seventy-six day period, indicated that C. gariepinus (120-233g) performed best when fed diets containing gross energy between 22-24 kJ.g'1, P:E ratio of 21.5-23 mg protein.kJ1, crude protein at 46%, crude lipid at 10-17% and carbohydrate at 26-32%. These data served to confirm the carnivorous nature of C. gariepinus compared to the less carnivorous North American catfish Ictalurus punctatus. However, performance indices for the fastest growing groups where lower than those achieved in experiments by previous researchers, possibly due to the weight range of the experimental animals used, the available tank surface and the employed stocking densities. Carbohydrate levels (26-32%) of the best performing diets during these experiments were much higher than used by previous researchers (16-18%) for the same species and still higher than those employed for other carnivores (15-25%) (salmonids, sea bass, sea bream). Taking into account the high carbohydrate digestibility of all the diets used in these experiments more comprehensive use of carbohydrates in Clarias catfish diet formulations is suggested. The increase of carcass lipid as a result of increased dietary non-protein energy demonstrated for other species has also been demonstrated for African catfish. Blood parameters (haematocrit and total hemoglobin) proved not to be valuable performance indices in relation to general nutritional parameters associated with growth and food utilization. Low carcass incorporation values for arginine and methionine resulted in low requirements (1.97 and 0.26 g.lOOg'1 dietary Crude Protein, respectively) as determined by the carcass deposition technique. The same technique revealed the following values, as g required Amino Acid.lOOg'1 dietary Crude Protein: Histidine 1.39, Isoleucine 1.56, Leucine 4.87, Lysine 4.49, Phenylalanine 4.56, Threonine 2.04, Tryptophan 2.59, Valine 2.08. Diets used in these experiments were characterized by lower levels of arginine, lysine, methionine, cystine, threonine and tryptophan to those proposed by most recent research. It is suggested that the sequence of pre-experimental adaptation and starvation might have exerted an irreparable loss for some of those amino acids and consequently lower values as determined requirements. Furthermore, mediocre oxygen levels prevailing in the employed experimental system in conjunction with sampling manipulations (prolonged emmersion) might have created a shift to ureotelism with a result in low arginine tissue levels. Results of this study could be used to optimize formulations based on the “economically optimal protein level” and the peculiarities of individual culture systems. Such formulations could be based on both conventional and non-conventional foodstuffs of a standard supply and price for the selected country-area, which would standardize production practices, production levels and costs. Use of labelled substrates coupled with further experimentation on the required dietary carbohydrate: lipid ratios and the optimum dietary fatty acid profile will clarify the underlying metabolic pathways and probably lead to better elucidation of the deposition of essential amino acids. More information on the digestibility of various raw materials in conjunction with the determined dietary requirements, will lead to the manufacture of more balanced and cost-effective diets for the African catfish C. gariepinus

Proceedings of the summer institute in recent advances in finfish and shellfish nutrition

Recognising the importance of nutrition in aquaculture the Indian Council of Agricultural Research sanctioned a Summer Institute which was held at the CMFRI, Cochin from 11 to 30th May 1987. Tvventy nine candidates sponsored by the Heads of various research, education and development organizations dealing with aquaculture in the country were the participants. The Institute comprised of lectures, practicals, demonstrations, field visits, group discussions covering the latest developments and recent advances in the field of aquaculture nutrition