Beef cattle evaluation by feeding efficiency and growth energy indicators based on bioinformatic and genomic technologies (review)

Beef cattle breeding is characterized by significantly higher feed costs per unit of output compared to other livestock industries. For most species of farm animals, breeding to improve the efficiency of feed use has been difficult until recently due to the complexity of the individual assessment of this indicator. The improvement of the trait occurred indirectly, through selection for an increase in the intensity of growth and a decrease in the fat content in carcasses. In 1960-1980, Förster-Technik GmbH (Germany) developed automatic feeding stations for individual fattening to account for data on energy costs for the growth and development of animals, which made it possible to derive the feed conversion rate (FCR), which remains one of the main parameters of feed efficiency (K.R. Koots et al., 1994). FCR as a trait is not important for genetic selection due to moderate heritability (A.A. Sermyagin et al., 2020; D.N. Crews et al., 2005). In this regard, and thanks to data from feedlots, in 1963 a new alternative concept for the FCR indicator, the predicted residual feed intake (RFI), was developed. RFI is an individual characteristic of an animal, which is determined by the results of test fattening (duration from 70 to 84 days), taking into account daily feed intake and live weight gain (R.M. Koch et al., 1963). The advantage of using RFI as a measure of feed efficiency in conjunction with FCR is that selection for a negative RFI will allow for reduced feed intake without compromising growth. In addition, the predicted residual feed intake does not depend on productivity, growth and body size, making it a trait that has a clear breeding value (G. Acetoze et al., 2015; J.A. Archer et al., 2000; G.E. Carstens et al., 2002). It has been established that RFI correlates with FCR (genetic correlation coefficients vary from 0.45 to 0.85), but RFI does not depend on average daily gain (ADG) and metabolic body weight (MWT) (B.W. Kennedy et al., 1993; P.F. Artur et al., 2001). The assertion that individuals of the same body weight require different amounts of feed to achieve the same performance provides the scientific basis for assessing RFI in beef cattle. Due to the fact that RFI is hereditarily determined (heritability coefficients vary from 0.08 to 0.49), a directed search for quantitative trait loci (QTL) is conducted using the GWAS (genome-wide association study) methodology. Since the 2000s, methods have been developed and implemented for assessing the breeding value of farm animals using information on a large number of SNPs (single nucleotide polymorphism), based on the principle of linear modeling. Linear models, depending on the approach to data structuring, are divided into rrBLUP (estimation of the effect of each marker), GBLUP (estimation of breeding value based on genomic relationship), and one of the most common modern one-step estimation method ssGBLUP (genomic breeding value estimation model that takes into account genomic relationship along with pedigree). BayesA and BayesB are applicable non-linear Bayesian models. Scientific studies using genome-wide association analysis have allowed the development of genomic selection programs and the identification of a number of SNPs associated with indicators of feed efficiency. Thus, seven positional candidate genes were found which were previously associated with the efficiency of feed use and growth energy in different types of farm animals, and were recently identified in Angus cattle. The analysis of foreign studies allows us to recommend the use of the described methods both in research work and for production purposes with the prospect of including these parameters in the criteria for genomic evaluation of beef cattle of different breeds bred in Russia.