Oxidation of medium-chain and long-chain fatty acids by polka dot grouper Cromileptes altivelis

Abstract

In this study we tested the hypotheses that higher fat diets will promote greater fat oxidation, and that medium‐chain fatty acids (MCFA) will be more readily oxidized than long‐chain fatty acids (LCFA). The oxidation of dietary MCFA (coconut oil labelled with 14C‐octanoic acid) and LCFA (olive oil labelled singly with 14C‐palmitic acid and 14C‐oleic acid) was measured in a metabolic chamber. MCFA and LCFA were included in the respective diets at 150 and 300 g kg−1. Polka dot grouper fed diets containing MCFA had a significantly higher (P < 0.05) respiration rate [2.4 mmol CO2 BW (kg)−0.79 h−1] and proportion of radioactivity in the respired CO2 (49.5%) than those fed diets containing LCFA [1.2 mmol CO2 BW (kg)−0.79 h−1 and 12.8%, respectively]. The amount of dietary fat did not significantly affect either of these two response attributes. The radioactivity in faeces and regurgitated material was low with diets containing MCFA, but was significantly higher with diets containing LCFA, and increased with increasing LCFA content, suggesting a decrease in digestibility. These results show that MCFA provide this species with a more readily utilizable source of energy than LCFA. Moreover, raising the amount of lipid in the diet above 150 g kg−1 did not increase the oxidation of fatty acids for energy.

Polka-dot grouper, Cromileptes altivelis, can utilize dietary fat efficiently

“…Hence, more MCF was oxidized than LCF simply because less fat was stored. This is consistent with the findings of Smith et al. (2005).…”

“…However, when fish were fed diets with 300 g kg −1 of added fat those fed olive oil apparently oxidized 2.3 g and those fed coconut oil oxidized a similar amount, 2.3 g. This suggests that maximum oxidation of fat is independent of the form in which the fatty acids are supplied. However, Smith et al. (2005) found that fish fed the diet with 300 g kg −1 olive oil had oxidized the added fat at a rate similar to those fed the diet with 150 g kg −1 olive oil.…”

“…Medium‐chain fats (MCF) are more rapidly oxidized than long‐chain fats (LCF) because they are taken up by more tissues and have easier access to mitochondria for subsequent β ‐oxidation (Nanton et al. 2003; Leonhardt & Langhans 2004; Smith et al. 2005).…”

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeriBrandt♀×A. schrenckiiBrandt♂

“…This may be due to the carbon chain lengths of fatty acid in the experimental lipid sources. The ingestion of middle‐chain fatty acids (8–10 carbon, MCFA), in both animals and humans can result in increased ketogenesis, related to their more rapid oxidation compared with long‐chain fatty acid (14–24 carbon, LCFA) as MCFA are taken up by more tissues and have easier access to mitochondria for subsequent β‐oxidation (Nanton, Lall, Ross, & McNiven, ; Smith, Williams, Williams, & Barclay, ). The main difference among linseed oil, soybean oil and fish oil exists in LCFA but not in MCFA, so it is reasonable that serum ketone body level had no significant difference when all experimental lipid sources contained no MCFA.…”

Optimum dietary protein and lipid specifications for grow-out of humpback grouper Cromileptes altivelis (Valenciennes)

“…Feeding nutritionally sub‐optimal feeds can lower the fish's immunocompetence and hence, its ability to deal with environmental stressors (Blazer 1991; Kiron et al 1995; Lall 2000). This may explain the lower survival rate of fish fed the low‐protein, high‐lipid feeds since this species appears unable to metabolize high‐lipid feeds effectively, instead preferring to oxidize protein as an energy source (Williams et al 2004; Smith et al 2005).…”