Dietary Oil Content Research Articles

Effect of Dietary Mineral Sources and Oil Content on Calcium Utilization and Kidney Calcification in Female Fischer Rats Fed Low-Protein Diets

We studied the effects of dietary mineral source and oil intake on kidney calcification in 4-wk-old female Fischer rats after consuming the AIN-76 purified diet (AIN-76). A modified AIN-76 mineral mixture was used, although the original calcium (Ca)/phosphorus (P) molar ratio remained unchanged. Rats were fed the modified diets for a period of 40 d before their kidneys were removed on the last day. Ca balance tests were performed on days 31 to 36 and biochemical analysis of urine was also studied. Kidney Ca, P, and magnesium (Mg) in the standard diet group (20% protein and 5% oil) were not affected by the mineral source. Kidney Ca, P, and Mg in the low-protein (10% protein) diet group, were found to be influenced by the dietary oil content and mineral source. In particular, the different mineral sources differentially increased kidney mineral accumulation. Pathological examination of the kidney showed that the degree of kidney calcification was proportional to the dietary oil content in the 10% dietary protein group, reflecting the calcium content of the kidney. The information gathered on mineral sources in this study will help future researchers studying the influence of dietary Ca/P molar ratios, and histological changes in the kidney.

Influence of dietary oil content and conjugated linoleic acid (CLA) on lipid metabolism enzyme activities and gene expression in tissues of atlantic salmon (Salmo salar L.)

The overall objective is to test the hypothesis that conjugated linoleic acid (CLA) has beneficial effects in Atlantic salmon as a result of affecting lipid and FA metabolism. The specific aims of the present study were to determine the effects of CLA on some key pathways of FA metabolism, including FA oxidation and highly unsaturated FA (HUFA) synthesis. Salmon smolts were fed diets containing two levels of fish oil (low, approximately 17%, and high, approximately 34%) containing three levels of CLA (a 1:1 mixture of cis-9,trans-11 and trans-10,cis-12 at 0, 1, and 2% of diet) for 3 mon. The effects of dietary CLA on HUFA synthesis and beta-oxidation were measured, and the expression of key genes in the FA oxidation and HUFA synthesis pathways, and the potentially important transcription factors peroxisome proliferators activated receptors (PPAR), were determined in selected tissues. Liver HUFA synthesis and desaturase gene expression was increased by dietary CLA and decreased by high dietary oil content. Carnitine palmitoyltransferase-I (CPT-I) activity and gene expression were generally increased by CLA in muscle tissues although they were relatively unaffected by dietary oil content. In general CPT-I activity or gene expression was not correlated with P-oxidation. Dietary CLA tended to increase PPARalpha and beta gene expression in both liver and muscle tissues, and PPARgamma in liver. In summary, gene expression and activity of the FA pathways were altered in response to dietary CLA and/or oil content, with data suggesting that PPAR are also regulated in response to CLA. Correlations were observed between dietary CLA, liver HUFA synthesis and desaturase gene expression, and liver PPARalpha expression, and also between dietary CLA, CPT-I expression and activity, and PPARalpha expression in muscle tissues. In conclusion, this study suggests that dietary CLA has effects on FA metabolism in Atlantic salmon and on PPAR transcription factors. However, further work is required to assess the potential of CLA as a dietary supplement, and the role of PPAR in the regulation of lipid metabolism in fish.

Influence of dietary oil content on the growth and chemical composition of Atlantic salmon (Salmo salar)

Two extruded diets with oil/protein levels of 260/410 and 360/365 g kg−1 were used to feed Atlantic salmon, from an initial weight of 600 g to a final weight of 4 kg after 1 year of feeding. The experiment was performed using 12 net-pens with 500 fish in each. Every 4 months 10 fish were taken from each net-pen, and analysed for growth and proximate composition. After 4 months of feeding, the chemical composition in the fillets was significantly different for the two different feed groups. The mean fillet fat content was 1% higher in fish fed with high oil content in the feed. There were no differences in the biological values. After 8 months of feeding the difference in mean muscular fat content was 3%, but there was still no difference in the carcass weight. However, a significant difference was found in the intestine weight and the condition factor. One year of feeding resulted in a significant, 10% higher carcass weight, a 2% higher fat-content and a 1% lower protein-content in the fillets of fish fed on the high oil content diet. A drop in pH was found during the winter, but this was not correlated to the feed.

Effects of dietary lipid level and vegetable oil on fatty acid metabolism in Atlantic salmon (Salmo salar L.) over the whole production cycle

Changes in fatty acid metabolism in Atlantic salmon (Salmo salar) induced by vegetable oil (VO) replacement of fish oil (FO) and high dietary oil in aquaculture diets can have negative impacts on the nutritional quality of the product for the human consumer, including altered flesh fatty acid composition and lipid content. A dietary trial was designed to investigate the twin problems of FO replacement and high energy diets in salmon throughout the entire production cycle. Salmon were grown from first feeding to around 2 kg on diets in which FO was completely replaced by a 1:1 blend of linseed and rapeseed oils at low (14–17%) and high (25–35%) dietary oil levels. This paper reports specifically on the influence of diet on various aspects of fatty acid metabolism. Fatty acid compositions of liver, intestinal tissue and gill were altered by the diets with increased proportions of C18 polyunsaturated fatty acids and decreased proportions of n-3 highly unsaturated fatty acids (HUFA) in fish fed VO compared to fish fed FO. HUFA synthesis in hepatocytes and enterocytes was significantly higher in fish fed VO, whereas β-oxidation was unaltered by either dietary oil content or type. Over the entire production cycle, HUFA synthesis in hepatocytes showed a decreasing trend with age interrupted by a large peak in activity at seawater transfer. Gill cell prostaglandin (PG) production showed a possible seasonal trend, with peak activities in winter and low activities in summer and at seawater transfer. PG production in seawater was lower in fish fed the high oil diets with the lowest PG production generally observed in fish fed high VO. The changes in fatty acid metabolism induced by high dietary oil and VO replacement contribute to altered flesh lipid content and fatty acid compositions, and so merit continued investigation to minimize any negative impacts that sustainable, environmentally-friendly and cost-effective aquaculture diets could have in the future. Abbreviations: FO - fish oil; HUFA - highly unsaturated fatty acids acids (carbon chain length ≥C 20 with ≥3 double bonds); LO - linseed oil; RO - rapeseed oil; VO - vegetable oil.

The influence of changes in dietary oil content on the fatty acid profile of backfat in pigs

The fatty add profile of pig fat has profound effects upon both the eating and keeping quality of pig meat. Fatty adds within carcass fat may arise from two discrete sources, being de novo synthesis and direct deposition from fatty acids present In the diet. The relative contribution of these two routes, together with the fatty acid profile of dietary fat, will Influence the chemical composition of carcass fat. It is well established that diets containing high levels of unsaturated fatty acids will result in softer and oilier carcass fat and It Is often considered inappropriate to feed such diets during the finishing phase of pig growth. However the speed with which carcass fat reflects a change in dietary fat has not been quantified. The objective of the current trial was to measure the rate of change in fatty acid profile of carcass fat of finishing pigs following major changes in dietary fat.