SHORT REVIEW OF THE NUTRITONAL VALUE OF DIFFERENT METHIONINE SOURCES IN FISH

Alexandros Samartzis* and Cláudia Figueiredo-Silva
 
Evonik (SEA) Pte. Ltd.
3 International Business Park #07-18
Nordic European Centre Singapore 609927
alexandros.samartzis@evonik.com

The 100% bioavailability of free amino acids (AA) has been demonstrated in several terrestrial and aquatic species and, as a result, the use of supplemental AA in animal feed has become common practice across different sectors of the animal feed industry, including aquaculture. The supplementation of low fishmeal or plant protein based diets with one or more limiting essential AA (EAA) to match animal requirements, was proven to be a cost-effective decision to reduce feed costs while maintaining or even increasing animal performance. Among the different EAA currently used in the fish feed, methionine (Met) is commonly the first-limiting EAA. Therefore, the interest of both industry and academia in assessing the nutritional value of the different Met sources available commercially, grew considerably in the last years. Different Met products are commercially available, including DL-Met, L-Met, 2-Hydroxy-4-(methylthio)butanoic acid (HMTBa) and HMTBa calcium salt (HMTBa-Ca). DL-Met and L-Met were shown to be both effectively utilized by terrestrial animals (Baker, 2006) and aquatic species, namely rainbow trout (Kim et al. 1992 & Powell et al., 2017) and Atlantic salmon (Figueiredo-Silva et al. 2014). Although not statistically significant, the slightly lower bioavailability of L-Met (82-83%) relative to DL-Met found in salmonids requires further investigation, but agrees with earlier data obtained in salmon (Sveier et al. 2001), rainbow trout (Kim et al. 1992) and in hybrid striped bass (Keembiyehetty and Gatlin III, 1995), showing that D- and/or DL-Met are at least as effective as L-Met. Further studies on the nutritional value of HMTBa products compared with DL-Met conducted in fish concluded that HMTBa and HMTBa-Ca are less available than DL-Met (reviewed by Lemme 2010; Lemme et al. 2012, Figueiredo-Silva et al. 2014; Powell et al. 2017). Applying regression analysis and comparing the slopes of the regression lines between sources based upon weight gain, nutritional value of HMTBa-Ca relative to DL-Met varied between 22% in Nile tilapia and channel catfish, and 62% in red drum (Figure 1). A critical review of the studies reporting on the nutritional value of different Met sources will be provided.

References

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