Linseed (LO) and soyabean (SO) oils were evaluated as fish-oil (FO) substitutes in the diets of marketable-sized gilthead sea bream (Sparus aurata). Practical diets were designed factorially with the lipid added as follows (%): FO 100, LO 60þ FO 40, LO 80þFO 20, SO 60þFO 40, SO 80þ FO 20. The effects of experimental diets on growth, fatty acids patterns in liver and muscle, flesh quality variables and activities of selected enzymes involved in lipid synthesis and catabolism were determined at the end of a 7-month trial. Fatty acid composition of liver and muscle generally reflected the fatty acid composition of the diets. The n-3 PUFA levels were significantly reduced by the inclusion of vegetable oils. This tendency was more pronounced for EPA than for docosahexaenoic acid. The n-3:n-6 fatty acid ratio reached the lowest values in fish fed the SO diets; this was associated with a higher liver lipid deposition. No differences were found in fillet texture and pH. However, under conditions of forced peroxidation, muscles from fish fed the SO diets had lower peroxidation levels. Vegetable oil substitution decreased lipogenesis in liver and this effect was greatest at the highest substitution level. In contrast, muscle b-oxidation enzymes had increased activities with vegetable oil substitution. Thus, the lower hepatic lipogenesis was correlated with an increased lipid utilisation in muscle. It is concluded that growth and lipid metabolism were affected by experimental diets. Sea bream: Vegetable oil: Lipid metabolism: Flesh quality: Essential fatty acidsAs the preferred lipid source in commercial diets for cultured fish, the demand for fish oil (FO) for aquatic feeds is increasing. Despite the most optimistic projections forecast, a global demand for aquaculture of about 1·90 million tonnes for the year 2015, production of FO seems to have reached a maximum at about 1·20 million tonnes per year, this value decreasing markedly during El Niño years (Food and Agriculture Organization, 2002). Since that production has to be shared with other uses, such as feeds for broilers and piglets and for pharmacology, there is a great interest in searching for alternative lipid sources in commercial fish feeds.It has been shown in salmonids that FO can be replaced by certain types of vegetable lipid sources by up to 80-100 % without compromising fish growth, but affecting tissue lipid composition and metabolism (Torstensen et al.

We evaluated the effects of dietary fat type on fat metabolism and deposition in broiler chickens. Birds were fed diets containing either 8 g dietary saturated (beef tallow) or polyunsaturated fat (sunflower oil)/100 g for 32 d. The abdominal fat deposition of chickens fed the sunflower oil-enriched diet was significantly lower than that of chickens fed the tallow-enriched diet (2.63 +/- 0.47 versus 3.03 +/- 0.44 g/100 g live wt.; P = 0.033). The specific activities of heart carnitine palmitoyltransferase I and L-3-hydroxyacyl-CoA dehydrogenase were higher (P < or = 0.03) in chickens fed the sunflower oil-enriched diets, indicating a greater rate of beta-oxidation. Liver fatty acid synthetase activity was lower (P = 0.01) in chickens fed the sunflower oil-enriched diet, suggesting reduced hepatic lipogenesis in this group. Postprandial plasma triglyceride levels were significantly lower (P < 0.05) in birds fed the sunflower oil-enriched diet, indicating a higher rate of dietary lipid clearance from the bloodstream to tissues. In conclusion, the lower fat deposition observed in broilers fed sunflower oil-enriched diets appears to be the net result of an increased rate of lipid catabolism and lower rate of fatty acid synthesis despite higher dietary fat absorption.

This chapter gives a general and brief description of the morphological and functional characteristics of the digestive system of the rabbit that may be important for understanding several digestive processes. The changes in these characteristics from the time of weaning until attainment of maturity are discussed.

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The effect of dietary supplementation with 1% l-glutamine and a combination of 1% l-glutamine and 0.5% l-arginine on intestinal health was examined in weaned rabbits. A basal diet was formulated to meet nutrient recommendations. Another 2 diets were formulated by adding 1% (as-fed basis) Gln or a mixture of 1% (as-fed basis) Gln + 0.5% (as-fed basis) Arg (Gln-Arg) to the basal diet. In Exp. 1, a total of 357 rabbits were blocked by litter and assigned at random to the experimental diet to determine mortality (119 per diet) and growth performance (35 per diet; from weaning at 25 to 56 d of age). Rabbits were fed the experimental diets for a 2-wk period and thereafter received a commercial diet. Rabbits weaned at 25 d (blocked by litter and assigned at random to diets) were slaughtered at 35 d and used to determine apparent ileal digestibility of DM, CP, and AA (Exp. 2, a total of 60 rabbits), intestinal morphology, N-aminopeptidase and myeloperoxidase intestinal activity, the expression of PPARgamma at the ileum and kidney, serum immunoglobulin in healthy and sick rabbits (Exp. 3, a total of 24 rabbits), and ileal and cecal microbial composition by PCR-RFLP (Exp. 4, a total of 45 rabbits). Dietary treatment did not affect ADG, ADFI, or G:F, during the entire fattening period. Supplementation with Gln reduced mortality during the first 2 wk and the whole fattening period from 18.5 to 8.4% (P = 0.023) and from 31.9 to 20.2% (P = 0.039), respectively, whereas no effect was detected for Arg supplementation. Among all the variables studied, the reduction on mortality due to Gln was related to a reduced intestinal colonization (Eimeria lesions) and changes on microbial ecosystem in the ileum and cecum, reducing the frequency of detection of Clostridium spp. (from 86.7 to 33.3%, P = 0.003) at the ileum, and Helicobacter spp. at the ileum (from 86.7 to 46.7%, P = 0.003) and at the cecum (from 86.7 to 46.7, P = 0.028), whereas no effect was detected for Arg supplementation. In conclusion, 1% l-Gln supplementation to postweaned rabbit diets decreased fattening mortality and modified the intestinal microbiota (although no consistent effects were observed on mucosal histology or inflammatory and systemic immune response). Diets containing a combination of 1% Gln and 0.5% Arg were of little additional benefit.