Partial replacement of soybean meal with Methylobacterium extorquens single-cell protein in feeds for rainbow trout (Oncorhynchus mykiss Walbaum)

Abstract

A feeding trial was conducted with juvenile rainbow trout (15-16 g initial weight) to assess the effects of including single-cell protein (SCP) produced from Methylobacterium extorquens in trout feeds. Three isonitrogenous and isoenergetic diets were produced: a control diet and two experimental diets containing 5% or 10% bacterial protein meal replacing soybean meal. Triplicate tanks, each containing 35 fish, were fed each diet to apparent satiation in a constant-temperature (15°C), flow-through tank system for 12 weeks. No statistically significant differences in final fish weight or other fish growth parameters were observed. Similarly, feed efficiency parameters showed no significant differences among groups. Nutrient retention indices (protein, fat, energy) were relatively high and similar among fish in each dietary treatment group, as were whole body proximate compositions. Fish survival was high, with a small but statistically significant increase for the 10% SCP diet. Overall, results demonstrate that SCP from M. extorquens is a safe and effective alternative protein for rainbow trout diets at the low inclusion levels tested. Slightly lower weight gain in fish fed the 10% SCP diet was largely due to lower feed intake, suggesting that adding palatability-enhancing ingredients to feeds may allow higher levels of M. extorquens SCP to be used without compromising fish growth. K E Y W O R D S alternative proteins, rainbow trout, single-cell protein, sustainable feeds wileyonlinelibrary.com/journal/are Aquaculture Research. 2018;49:2218-2224.

Partial replacement of fishmeal with Clostridium autoethanogenum single‐cell protein in the diet for juvenile black sea bream ( Acanthopagrus schlegelii )

“…A study indicated that growth inhibition of rainbow trout fed SCP produced from M. extorquens was directly proportional to the reduction in feed intake (Hardy et al, 2018 Values are presented as mean ± SD (n = 6); values with different superscripts in the same row differ significantly (p < .05). A study indicated that growth inhibition of rainbow trout fed SCP produced from M. extorquens was directly proportional to the reduction in feed intake (Hardy et al, 2018 Values are presented as mean ± SD (n = 6); values with different superscripts in the same row differ significantly (p < .05).…”

“…Majority of the studies on the use of SCP in aquafeeds suggested that palatability might be an important reason for the unsuitability of these SCP ingredients to replace fishmeal completely. A study indicated that growth inhibition of rainbow trout fed SCP produced from M. extorquens was directly proportional to the reduction in feed intake (Hardy et al, 2018 Values are presented as mean ± SD (n = 6); values with different superscripts in the same row differ significantly (p < .05). 2 Initial body weight (IBW, g).…”

“…Nevertheless, in general, a burgeoning SCP industry has attracted considerable attention for practical fish feed application on account of their advantages in terms of productivity and high protein content. In rainbow trout (Oncorhynchus mykiss), SCP from Methylobacterium extorquens was reported as a safe and meaningful alternative protein for diets at an inclusion level of 10% (Ronald W. Hardy, Patro, Pujol-Baxley, Marx, & Feinberg, 2018). Atlantic halibut (Hippoglossus hippoglossus) could adapt to a diet containing 9% of bacterial protein meal produced from natural gas without negative effects on growth performance and feed efficiency ratio (Aas et al, 2007).…”

Fishmeal alternative from renewable CO2for rainbow trout feed

“…The inclusion of alternative protein products in aquaculture diets is often limited by lower levels of digestible protein or issues with palatability. The use of SCP products is no exception, and in fact, a reduction to feed intake was believed to be a larger issue over the nutritional value of the diets (Hardy et al., 2018). In the current study, rainbow trout showed a similar acceptance of the feeds, with no leftover feed being observed in the tanks, while the apparent digestibility of SCP was generally high.…”

“…Similarly, the presence of ANF in other protein sources, such as cottonseed meal and rapeseed meal, was also shown to reduce the productivity of S. salar (Foroutani et al., 2018) and rainbow trout Oncorhynchus mykiss (Deng et al., 2014). Due to the sensitivity of salmonids to ANF, research is increasingly exploring the feasibility of using non‐plant‐based proteins as FM alternatives, which has included single cell proteins (SCP) from yeast (Rumsey, Hughes, Smith, Kinsella, & Shetty, 1991) or bacteria (Aas et al., 2006; Hardy, Patro, Pujol‐Baxley, Marx, & Feinberg, 2018; Perera, Carter, & Houlihan, 1995; Tlusty et al., 2017). In fact, SCP can be a more sustainable and readily available resource, particularly when cultured from nutrient‐rich effluent farm water.…”