Abstract
Residual feed intake (RFI) is the most used measure of feed efficiency. However, considering the importance of concentrates in the ration, a new index, the residual concentrate intake (RCI), was here defined. RCI aims to measure the individual efficiency in converting the concentrate into animal products. Brown Swiss young bulls (N = 736) were genotyped at 41,183 loci. Animals were housed in pens equipped with an automatic feeding system able to recognise the animal and record the concentrate intake. The diet consisted of concentrate and hay (ad libitum). The new RCI index was calculated as the residuals of the linear regression of concentrate intake on metabolic live weight and average daily gain. Animals were ranked according to their corrected RCI and divided into low (LRCI) and high phenotypes (HRCI). A low heritability (0.06 ± 0.03) was estimated using only genomics for this new index. Results from multivariate (M-GWAS) and Bayesian (B-GWAS) approaches were combined to identify SNP associated with RCI. The M-GWAS selected 698 SNPs potentially associated, whereas no significant markers were obtained in B-GWAS. Markers in the last approach were ranked according to their posterior inclusion probability and the first 698 were retained. Only SNPs in common between sorted B-GWAS and M-GWAS (N = 11) were considered associated with RCI. A total of 48 candidate genes were retrieved near these SNPs. Most of them were previously reported to be associated with feed efficiency and RFI. The combined use of multivariate and Bayesian techniques allow to identify SNPs associated with the investigated trait. Highlights RCI could be promising to select animals 48 candidate genes were found associated with RCI Multivariate technique allowed to identify significant SNPs
Highlights
Feed costs contribute to up to 60% of production costs in the dairy cattle industry (Connor 2015)
residual feed intake (RFI) has been investigated in beef, dairy, and dual-purpose cattle (Cantalapiedra-Hijar et al 2018; Kenny et al 2018; Romanzin et al 2021)
The residual concentrate intake (RCI) phenotypes were calculated as the residuals of a linear regression model of concentrate intake on metabolic live weight and average daily gain (ADG) (Arthur et al 2005)
Summary
Feed costs contribute to up to 60% of production costs in the dairy cattle industry (Connor 2015). 1991; Manafiazar et al 2013; Berry and Crowley 2013). Among different indexes suggested to evaluate feed efficiency in cattle, the most popular is probably the residual feed intake (RFI) It is obtained by subtracting the actual from the expected individual intake required by the animal for its maintenance and production. Being RFI by definition independent from production and body weight, animals with low RFI can consume less feed without reducing the production level. RFI has been investigated in beef, dairy, and dual-purpose cattle (Cantalapiedra-Hijar et al 2018; Kenny et al 2018; Romanzin et al 2021)
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