Aquaculture America 2021

August 11 - 14, 2021

San Antonio, Texas

GENETIC AND NUTRITIONAL APPROACHES TO ENHANCE THE EFFICIENCY OF SOYBEAN MEAL UTILIZATION IN RAINBOW TROUT

 Kimia Kajbaf* , Kenneth Overturf ,  and Vikas Kumar
 
Aquaculture Research Institute, Department of Animal , Veterinary and Food Sciences, University of Idaho (UofI), Moscow, ID 83844, USA
kkajbaf@uidaho.edu
 

The  USDA  ARS and UofI have developed several rainbow trout (Oncorhynchus mykiss ) lines that show higher growth rates when fed  an all-plant protein  diet than non-selected lines of trout fed  the plant protein diet or  a fishmeal-based diet. So far, no commercial breeding programs has yet started to improve feed utilization efficiency in fish, mainly because of the difficulty in accurately measuring individual feed intake of fish reared in groups. Using these selected lines we proposed to test if feed conversion ratio (FCR) and body weight variations during successive periods of feed deprivation (FD) and re-feeding (RF) are correlated using  a compensatory feeding regime . The goal of this study was to determine if indirect selection for the  above traits could be used to  develop alternative criteria to improve feed intake of the plant-based fed selected strain.

We began with 1600 fish (av. Int. wt. 30 g) from 12 families of the selected line, fed  the  plant protein  diet (50% soy ,  protein: 41% and lipid: 20%). First, fish were tagged individually  and  reared in  a  common environment, t hey  were  then placed  on feeding challenge  regime for 4 months (one month each challenge either FD or RF), and performance were recorded . Thereafter, fish were separated into four groups (1331 fish) based on individual performance during FD and RF challenge study. FCR was recorded for 3 months in all four groups followed by measuring the stability of  response to  the FD and RF periods (2nd feeding challenge) which was the same as the 1st one. Out of 1331 fish, 143 fish exhibited a similar pattern of weight loss and gain, confirming the stability. As expected, the most efficient group was the FD-/RF+ (FCR=0.99) and the least efficient groups with FCR of ~1.4 were FD-/RF- and FD+/RF- (Figure1A) .   Studying the gut microbiome of  all four groups revealed that despite the variations dictated by FD and RF, the bacterial community of FD-/RF+ group (best performers) shows more stability than the FD+/RF- (worst performers) throughout the feeding challenges (Figure 1B and 1C) .

Conclusively, FCR improved more than 15 %  in  best group (FD+/RF-) compared to  the FD-/RF+ group which means  utilizing these fish selected for  improved feed efficiency will reduce  soybean consumption and greatly decrease the feed cost for sustainable  aquafeed industry.