Effect of dietary levels of lipid and carbohydrate on growth performance, body composition, nitrogen excretion and plasma glucose levels in rainbow trout reared at 8 or 18°C

Abstract

― Trout reared at 8 or 18C were fed twice a day almost to satiation with 1 of 3 experimental diets. The diets were formulated to contain the same levels of protein (43%, dry matter (DM) basis) and digestible energy (around 15 kJ/g DM), but different carbohydratenipid ratios (30:7 to 23:14). Time-course studies of nitrogen excretion and glycaemia were also carried out. After 12 weeks of feeding, growth, protein retention and body composition were not influenced by the dietary treatment in trout reared at 8C. At 18C, the protein retention was not affected by dietary treatment, but the weight gain tended to be higher in trout fed the diet with the lowest carbohydratellipid ratio. This result was due to higher body lipid deposition in these trout. Nitrogen excretion was not influenced by dietary treatment, but was higher at 18C than at 8C because of a higher feed intake. Glycaemia increased with dietary level of digestible carbohydrate and the highest plasma glucose level was attained later at 8C in comparison to 18C. trout / carbohydrate/lipid ratio / growth performance / glycaemia / temperature Rsum ― Effets du rapport glucides/lipides de l'aliment sur les performances de croissance, la composition corporelle, l'excrtion azote et le glucose plasmatique chez la truite Arc-en-ciel leve 8 ou 18C. Des truites Arc-en-ciel leves 8 ou 18C ont t nourries 2 fois par jour presque satit avec l'un des 3 rgimes exprimentaux. Les rgimes ont t formuls pour contenir les mmes taux de protines (43%, sur la base de la matire sche (MS)) et d'nergie digestible (environ 15 kJlg MS), mais diffrents rapports glucidesllipides (30/7 23/14). Les volutions dans le temps de l'excrtion azote et de la glycmie ont aussi t tudies. Aprs 12 sem d alimentation, la crois- sance, la rtention protique et la composition corporelle n'ont pas t influences par le rgime ali- mentaire chez les truites leves 8C. 18C, la rtention protique n'a pas t affecte par le rgime alimentaire, mais le gain de poids tendait tre plus lev chez les truites recevant le rgime riche en lipides (16% MS). Ce rsultat a t d un dpt plus lev en lipides chez ces truites. L'ex- crtion azote n a pas t influence par le rgime alimentaire, mais a t plus leve 18C qu 8C cause d'une consommation d'aliment plus importante. Le taux de glucose plasmatique a augment avec la quantit de glucides digestibles du rgime et le pic de glycmie est apparu plus tard 8'C qu' 18 C. truite / rapport glucidesAipides /performance de croissance / glycmie / temprature