Genetic variability in residual feed intake in rainbow trout clones and testing of indirect selection criteria (Open Access publication)

Abstract

-Little is known about the genetic basis of residual feed intake (RFI) variation in fish, since this trait is highly sensitive to environmental influences, and feed intake of individuals is difficult to measure accurately. The purpose of this work was (i) to assess the genetic variability of RFI estimated by an X-ray technique and (ii) to develop predictive criteria for RFI. Two predictive criteria were tested: loss of body weight during feed deprivation and compensatory growth during re-feeding. Ten heterozygous rainbow trout clones were used. Individual intake and body weight were measured three times at threeweek intervals. Then, individual body weight was recorded after two cycles of a three-week feed deprivation followed by a three-week re-feeding. The ratio of the genetic variance to the phenotypic variance was found high to moderate for growth, feed intake, and RFI (VG/ VP = 0.63 ± 0.11, 0.29 ± 0.11, 0.29 ± 0.09, respectively). The index that integrates performances achieved during deprivation and re-feeding periods explained 59% of RFI variations. These results provide a basis for further studies on the origin of RFI differences and show that indirect criteria are good candidates for future selective breeding programs. rainbow trout / clone / residual feed intake / indirect criteria / selection

Genetic assessment of residual feed intake as a feed efficiency trait in the Pacific white shrimp Litopenaeus vannamei

“…Having an estimated heritability for RFI during the grow-out period is critical for future genetic selection on this trait in the breeding population of L. vannamei . This is the first study that evaluates genetic parameters of RFI in shrimp, and the estimated heritabilities of RFI during the two successive growth periods (0.641 ± 0.237 and 0.707 ± 0.252, respectively) were higher than most of the previously published estimates in other species, ranging from 0.18 to 0.64 in cattle [ 12 , 35 – 37 ], from 0.18 to 0.47 in pigs [ 15 , 38 , 39 ], from 0.21 to 0.83 in poultry [ 40 – 42 ], and 0.29 in fish [ 9 ]. These heritabilities are most likely overestimated, in part because the common environmental effects could not be partitioned out.…”

“…For example, it is not possible to determine whether an improvement in FER results from a decrease in feed intake, an increase in weight gain, or both. RFI was first used in beef cattle by Koch et al [ 6 ] and later introduced in poultry [ 7 ] and fish [ 8 , 9 ]. RFI is defined as the proportion of feed intake that is not accounted for by expected requirements for body weight maintenance and production.…”

“…Most heritability estimates published for terrestrial agricultural animals show that RFI is moderately to highly heritable [ 14 – 18 ] and direct selection aimed at improving this trait for multiple generations has proven effective [ 19 , 20 ]. Regarding aquatic species, almost all studies on RFI have been carried out in fish and have revealed pronounced genetic variability [ 8 , 9 , 21 ]. To date, few studies have analyzed RFI in shrimp.…”

“…As a prerequisite for evaluating feed efficiency, accurate measurement of individual feed intake during a given period is required but producing such individual data on a large scale in shrimp is a major challenge, since shrimp are usually farmed in large groups. Individual feed intake of fish reared in groups is measured by X-ray technology but the repeatability between measurements is low (from 0.09 to 0.32) and thus repeated measurements are necessary to buffer day-to-day variations [ 9 , 22 ]. Moreover, Quinton et al [ 23 ] showed that the heritability of feed efficiency estimated by this method is low (6 ± 10%).…”

“…A feeding test is often conducted over weeks to months for different species. Because of the potential mortality of shrimp, a testing period of several weeks is reasonable [ 8 , 9 , 21 , 26 ]. Furthermore, given the importance of the grow-out period during L. vannamei production, a test during this period is preferable.…”