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Microencapsulation of hydrosoluble additives to artificial diets for cyprinid larvae to avoid leaching
254
Abstracts/Aquaculture
129 (1995) 251-259
Several indicators of metabolic disturbances, i.e. a yellow-brown spotted or yellow-coloured liver, many lipofuscin-like granules in the organs and an intestine crowded with starch granules, which are settled with yeast cells, have been observed in sturgeon, trout and carp after feeding with commercial feeds. In addition, the glycogen level in the blood is increased drastically. Inadequate feeding with a surplus of carbohydrates is thought to be the main reason for these effects. Four feeding experiments with sturgeon hybrids (Acipenser baeri X A. ruthenus) (270 g), trout (Oncorhynchus mykiss) (220 g) and carp (Cyprirzus carpio) (96 g) comparing a carbohydrate-free diet and a commercial feed with a carbohydrate content of 19% showed a significant improvement in the above-mentioned characteristics. The experiments demonstrated that carbohydrate-free feed can distinctly improve product quality and the physiological status of sturgeon hybrids impaired by unphysiologically high carbohydrate assimilation. Because the influence of carbohydrates on carp and trout is lower than on sturgeons, improvement in physiological status and product quality is less significant in these species. As a rather primitive fish group, the sturgeons are obviously not able to manage inadequate carbohydrate assimilation in a sufficient manner. These results have only a preliminary character, and there is a need for further investigations in this field.
Microencapsulation of hydrosoluble additives to artificial diets for cyprinid larvae to avoid leaching M. Petitjeana, I. Csengerib “University of Paris 7, UF Environment, 2 place Jussieu, F-75251 Paris Cedex 05, France bFish Culture Research Institute, P.O. Box 47, H-5541 Szarvas. Hungary
Cyprinid larvae fed on a gelatin-casein diet supplemented with hydrosoluble vitamins and minerals had poor growth and survival, due to leaching of the additives. These must be protected and microencapsulation seems a good process for protection, Microencapsulation of the whole diet is difficult and gives a poor yield. However, as for amino acid supplementation, nylon microencapsulation of hydrosoluble vitamines by interfacial polymerization is possible. In the present study, the procedure by Chang ( 1966) was used with modification. The reactants were hexamethylene diamine and sebacoyl chloride, but our dispersant was hexane, and the surfactant was a mixture of Brij 92 and Brij 96 (FLUKA, Switzerland). Serial experiments gave us the ratio with the best hydrophil/lipophil balance giving the most stable emulsion. A polyvitamin solution could have been capsulated with good results. However, as the partition coefficient of hexamethylene diamine between hexane and water was high and, as hexamethylene diamine quickly diffused into the hexane, the polymerization reaction had produced extracapsular nylon formation. To avoid this, there are 3 possibilities: (a) to add gelatin to the watery solution (obliging one to operate above 4O”C, which is not practical); (b) to replace hexamethylene diamine by higher diamines in the series (which is very expensive); (c) choosing a convenient solvent. We preferred replacing hexane by dodecane as dispersant and consequently there was no more diffusion of hexamethylene diamine. After again determining the best ratio of Brij 92/ Brij 96 in serial experiments, we obtained microcapsules of polyvitamin solution of 10-20 pm diameter with a good yield.
Abstracts/Aquaculture
129 (1995) 251-259
Several indicators of metabolic disturbances, i.e. a yellow-brown spotted or yellow-coloured liver, many lipofuscin-like granules in the organs and an intestine crowded with starch granules, which are settled with yeast cells, have been observed in sturgeon, trout and carp after feeding with commercial feeds. In addition, the glycogen level in the blood is increased drastically. Inadequate feeding with a surplus of carbohydrates is thought to be the main reason for these effects. Four feeding experiments with sturgeon hybrids (Acipenser baeri X A. ruthenus) (270 g), trout (Oncorhynchus mykiss) (220 g) and carp (Cyprirzus carpio) (96 g) comparing a carbohydrate-free diet and a commercial feed with a carbohydrate content of 19% showed a significant improvement in the above-mentioned characteristics. The experiments demonstrated that carbohydrate-free feed can distinctly improve product quality and the physiological status of sturgeon hybrids impaired by unphysiologically high carbohydrate assimilation. Because the influence of carbohydrates on carp and trout is lower than on sturgeons, improvement in physiological status and product quality is less significant in these species. As a rather primitive fish group, the sturgeons are obviously not able to manage inadequate carbohydrate assimilation in a sufficient manner. These results have only a preliminary character, and there is a need for further investigations in this field.
Microencapsulation of hydrosoluble additives to artificial diets for cyprinid larvae to avoid leaching M. Petitjeana, I. Csengerib “University of Paris 7, UF Environment, 2 place Jussieu, F-75251 Paris Cedex 05, France bFish Culture Research Institute, P.O. Box 47, H-5541 Szarvas. Hungary
Cyprinid larvae fed on a gelatin-casein diet supplemented with hydrosoluble vitamins and minerals had poor growth and survival, due to leaching of the additives. These must be protected and microencapsulation seems a good process for protection, Microencapsulation of the whole diet is difficult and gives a poor yield. However, as for amino acid supplementation, nylon microencapsulation of hydrosoluble vitamines by interfacial polymerization is possible. In the present study, the procedure by Chang ( 1966) was used with modification. The reactants were hexamethylene diamine and sebacoyl chloride, but our dispersant was hexane, and the surfactant was a mixture of Brij 92 and Brij 96 (FLUKA, Switzerland). Serial experiments gave us the ratio with the best hydrophil/lipophil balance giving the most stable emulsion. A polyvitamin solution could have been capsulated with good results. However, as the partition coefficient of hexamethylene diamine between hexane and water was high and, as hexamethylene diamine quickly diffused into the hexane, the polymerization reaction had produced extracapsular nylon formation. To avoid this, there are 3 possibilities: (a) to add gelatin to the watery solution (obliging one to operate above 4O”C, which is not practical); (b) to replace hexamethylene diamine by higher diamines in the series (which is very expensive); (c) choosing a convenient solvent. We preferred replacing hexane by dodecane as dispersant and consequently there was no more diffusion of hexamethylene diamine. After again determining the best ratio of Brij 92/ Brij 96 in serial experiments, we obtained microcapsules of polyvitamin solution of 10-20 pm diameter with a good yield.