Choline plays a crucial role in lipid metabolism for fish, and its deficiency in aquafeed has been linked to compromised health and growth performance. A 56-d experiment was conducted to examine the effects of dietary choline on lipid composition, histology and plasma biochemistry of yellowtail kingfish (Seriola lalandi; YTK; 156 g initial body weight). The dietary choline content ranged from 0·59 to 6·22 g/kg diet. 2-Amino-2-methyl-1-propanol (AMP) (3 g/kg) was added to diets, except for a control diet, to limit de novo choline synthesis. The results showed that the liver lipid content of YTK was similar among diets containing AMP and dominated by NEFA. In contrast, fish fed the control diet had significantly elevated liver TAG. Generally, the SFA, MUFA and PUFA content of liver lipid in fish fed diets containing AMP was not influenced by choline content. The SFA and MUFA content of liver lipid in fish fed the control diet was similar to other diets except for a decrease in PUFA. The linear relationship between lipid digestibility and plasma cholesterol was significant, otherwise most parameters were unaffected. When AMP is present, higher dietary choline reduced the severity of some hepatic lesions. The present study demonstrated that choline deficiency affects some plasma and liver histology parameters in juvenile YTK which might be useful fish health indicators. Importantly, the present study elucidated potential reasons for lower growth in choline-deficient YTK and increased the knowledge on choline metabolism in the fish.

The bioaccessibility of total lipids and fatty acids (FA) in raw and grilled gilthead seabream (Sparus aurata) was determined using an in vitro digestion model. The particular impact of grilling on the FA profile of seabream was also studied. In addition, the influence of lipid class on the bioaccessibility of each FA was analysed. Grilling did not change the relative FA profile, and only the absolute values were altered. However, the relative FA profile varied across lipid classes, being more dissimilar between TAG and phospholipids. Long-chain SFA and PUFA seemed to be less bioaccessible. Moreover, grilling reduced bioaccessibility of protein, fat and many FA, with the highest reductions found in PUFA such as the DHA. Strong evidence supporting a predominantly regioselective action of lipase during in vitro digestion was found, and the impact of this phenomenon on FA bioaccessibility was assessed.

The purpose of this study was to determine biochemical changes occurring in blue mussels (Mytilus edulis) fed effluent from an Atlantic cod (Gadus morhua) aquaculture facility over a period of ten weeks, compared to those in mussels fed a commercial shellfish diet and those supplied only filtered seawater. The total lipid and fatty acid content (mg g-1 wet weight) significantly decreased for mussels fed effluent during the experiment. The only change in the lipid class composition (% total lipid) at the end of the experiment was a significant increase in the proportion of acetone mobile polar lipids. There were several significant changes in the fatty acid composition (% total fatty acid) including an increase in the proportion of 18:1ω9, 18:2ω6, 20:4ω6, 21:5ω3 and the dienoic non-methylene-interrupted fatty acids 20:2a and 22:2b and significant decreases in the proportions of 16:0, 18:4ω3 and 20:5ω3. The increase in non-methylene interrupted dienes suggests that the amount of essential fatty acids in the effluent may be insufficient for optimal mussel growth. The presence of the terrestrial plant marker 18:2ω6 in both the fish feed and the effluent and its increased proportion in mussels fed effluent suggest that this fatty acid may have potential as a marker for aquaculture wastes.

The effect of slaughter weight and breed on the composition of intramuscular fat (IMF) of seven Spanish cattle breeds was studied. Lipid classes and fatty acids were evaluated in young bulls of seven local Spanish cattle breeds, Asturiana, Avileña, Morucha, Parda Alpina, Pirenaica, Retinta and Rubia Gallega, slaughtered at a live weight of 320 kg (veal type) and 550 kg (yearling bull type). Higher slaughter weight and early maturating breeds produced higher IMF content in the longissimus muscle (P < 0.001), which was linked to a reduction in phospholipids, monoglycerides, diglycerides, cholesterol and free-fatty acids content, but an increase in triacylglycerols. Besides, heavier animals displayed a higher percentage of saturated and monounsaturated fatty acids (MUFA), but a lower polyunsaturated fatty acids (PUFA) percentage (P < 0.001). The increase in triglycerides (TG), saturated fatty acids (SFA) and MUFA illustrates the increasing importance of lipid storage as fattening proceeds and the acquisition of ruminal functionality. The feeding system based on cereals had a strong influence on the fatty acid profile, giving the studied beef a relatively high PUFA/SFA and n-6/n-3 ratios.