Effects of different soybean proteins on lipid digestion and growth of yellowtail Seriola quinqueradiata

Abstract

Two experiments were conducted to determine whether the undigested high molecular fraction (HMF) of soybean protein reduces growth of yellowtail through impairment of lipid digestion and absorption. Soybean meal (SBM), soy protein isolate (SPI), digested SPI (DSPI), and digested and purified SPI (DPSPI) were used as experimental diets. In experiment 1 (exp. 1), yellowtail were fed 4 diets with aforementioned soybean products for 3 weeks. In experiment 2 (exp. 2), the fish were fed soybean protein or fish meal (FM) diets for 8 weeks. Growth performance of DPSPI-fed fish was better than that of fish fed other soybean proteins, and comparable to that of fish fed with FM. Plasma and tissue lipid levels of DPSPI-fed fish tended to be higher than those of fish fed other soybean proteins. Significantly lower intestinal lipid levels and higher bile acid levels were found in DPSPI-fed fish than in fish fed with SBM, SPI, and DSPI. These findings indicate that one of the factors contributing to growth depression in yellowtail fed with SBMbased diets is the negative effect of undigested HMF of soybean protein on bile acid levels and lipid digestion.

Taurine: a critical nutrient for future fish feeds

“…Because Kortner et al (2013) worked with Atlantic salmon Salmo salar, the enteritis developed by soy-fed fish likely explains the observation. However, hypocholesterolemia was also observed in S. quinqueradiata fed soy proteins (Nguyen et al, 2011) although soy does not cause enteritis in this species. Certain protein hydrolysates have been shown to effectively bind bile salts at their hydrophobic core or anionic acid group (Howard and Udenigwe, 2013).…”

“…Maita et al (2006) reported similar results, where plasma cholesterol of yellowtail fed soybean-based diets was restored to that of fishmeal-fed fish only when supplemented with both taurine and cholesterol. Although there was an increase in total bile acid content in the anterior intestine in response to the removal of the high molecular fraction, it remained unchanged in the posterior intestine, suggesting that the amount of excreted bile acid was not affected (Nguyen et al, 2011). The soy-based diets were not supplemented with taurine, and despite a slight increase in liver taurine content in response to the lower molecular weight of soy protein, the improvement was quite minor and levels remained about half of that in fish fed the fishmeal control diet.…”

“…Empirical evidence shows that taurine supplementation increases bile salt content in several teleost species (Kim et al, 2007;Kim et al, 2014), although it appears to be independent from dietary lipid levels (Kim et al, 2008). Dietary protein source (fishmeal, conventional soybean meal, or processed soybean meals), however, affects the amount of bile in the chyme (Nguyen et al, 2011) as well as the composition of bile, as demonstrated with rainbow trout by Murashita et al (2013) where the ratio of taurocholic acid to taurochenodeoxycholic acid varied from 0.89 to 11.90. The practical significance of the latter result remains to be elucidated, perhaps in light of recent findings of other properties of bile salts such as signaling, osmosensing, or hormonal actions (Hylemon et al, 2009;Keely et al, 2007;Lefebvre et al, 2009).…”

“…This could partially explain why the removal of the high molecular fraction of soy proteins resulted in the partial recovery of intestinal bile acid in yellowtail when compared to fish fed a fishmeal-based control feed, although plasma cholesterol remained low (Nguyen et al, 2011). Unfortunately, dietary cholesterol composition was not reported, thus it is difficult to discriminate its contribution to this results which may simply reflect dietary levels.…”

Is dietary taurine supplementation beneficial for farmed fish and shrimp? a comprehensive review

“…; Nguyen et al . ,b). Taurine synthesis has been reported to be extremely low or even negligible in yellowtail (Takagi et al .…”