Rainbow trout silage as immune stimulant and feed ingredient in diets for Mozambique tilapia (Oreochromis mossambicus)

Abstract

Peptides and free amino acids resulting from protein hydrolysis could act as stimulants of fish nonspecific immunity. The study aimed to determine the potential of rainbow trout viscera silage as immune stimulant and feed ingredient for Mozambique tilapia, and to establish whether formic acid used during silage preparation contributed to any effects. Four diets were evaluated: a reference diet (R), one containing 6.5 g kg À1 formic acid (FA) and two silage diets containing 160 g kg À1 (SL, low inclusion) and 285 g kg À1 (SH, high inclusion) silage. Low silage inclusion improved phagocytic activity of leucocytes compared with the reference, while high inclusion showed no improvement. No other non-specific immunity parameters or haematology were affected by any treatments. High silage inclusion significantly decreased growth and led to higher mortality, while formic acid had no effect on growth. It is concluded that rainbow trout viscera silage can stimulate the cellular non-specific immunity of Oreochromis mossambicus, and that protein hydrolysis products (and not formic acid) is responsible for the stimulation. The silage can also serve as source of dietary protein and essential amino acids in tilapia diets. However, both fish growth performance and improvement in cellular immunity are dependent on silage inclusion level.

Comparison of hydrolysed proteins from different raw materials in diets for Mozambique tilapia Oreochromis mossambicus

“…The reason for higher growth in treatment HCL than SH might be because the high silage inclusion was affecting growth rate. An equivalent silage inclusion level has been shown in a previous trial to negatively impact growth in O. mossambicus (Goosen et al 2014a). In a comparative FPH evaluating three hydrolysates from different origins at a single inclusion level in red seabream, it could not be shown that there were significant differences in production performance (Bui et al 2014); however, only two of the ingredients significantly improved performance compared to the control.…”

“…In studies with Nile tilapia (Oreochromis niloticus), total replacement of fishmeal was achieved with fish and shrimp head silage without significant negative impacts of growth (Cavalheiro et al 2007;El-Hakim et al 2007); however, in another study, shrimp head silage replacing more than 15 % of fishmeal leads to significantly decreased growth (Plascencia-Jatomea et al 2002), while shrimp silage included at 6 % of the final diet (corresponding to 20 % fishmeal replacement) had no significant reduction in production performance (Leal et al 2010). In the current trial, total FPH inclusion was restricted, as previous studies using rainbow trout silage in diets for O. mossambicus showed growth depression at dietary protein contribution of 40 g kg -1 (Goosen et al 2014a). Due to the restricted inclusion level of silage and the experimental design where each of the FPH was to contribute equivalent levels of protein to the final diet, the maximum inclusion level of the FPH products was not established in the current trial.…”

“…Diets were formulated to be iso-proteic and isoenergetic (refer to Table 1). The high inclusion level of silage was determined from a previous investigation using rainbow trout silage and Oreochromis mossambicus (Goosen et al 2014a), where 285 g wet silage per kg feed was shown to inhibit animal growth, and this inclusion level was therefore taken to be the maximum for the current trial.…”

“…Tilapias are a globally important group of aquaculture species, and significant amounts of fishmeal are used to produce formulated feeds for them (Bostock et al 2010;FAO 2010). As in other finfish, FPH products have been evaluated as protein source and potential replacers of fishmeal (Cavalheiro et al 2007;El-Hakim et al 2007;Fagbenro et al 1994;Leal et al 2010;Plascencia-Jatomea et al 2002) and soybean meal (Hernández et al 2013), as immune stimulant (Goosen et al 2014a) or to determine the effects of FPH inclusion on intestinal digestive enzyme activity (Santos et al 2013). In fishmeal replacement studies, it was generally found that FPH can replace a portion of the fishmeal in formulated tilapia diets without negatively impacting production performance.…”

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“…Tejeda-Arroya et al (2015) recorded that the inclusion of up to 18% of fish silage in the lamb d iets might imp rove the productive performance and the ruminal fermentation kinetics without any negative effects. Some work have been done recently on fish silage (Tanuja, Mohanty, Kumar, Moharana, & Nayak, 2014;Nørgaard, Petersen, Tørring, Jørgensen, & Laerke, 2015;Ozyurt, Gö kdoğan, Şimşek, Yuvka, Ergüven, & Kuley, 2016;Goosen, Wet, & Görgens, 2016), but limited research has been directed to the potential of using spray-dried fish silage in feed formu lations. The aim o f this study was to compare acid silage with fermented silages, which were produced by using lactic acid bacteria (LAB) naturally existing in fish, for biotransformation of the seafood processing wastes into silages.…”