Meta-análise de parâmetros genéticos relacionados ao consumo alimentar residual e a suas características componentes em bovinos

Abstract

Resumo -O objetivo deste trabalho foi estimar, por meio de meta-análise, a herdabilidade (h 2 ) e as correlações genética (r g ) e fenotípica (r f ) do consumo alimentar residual (CAR), e das suas características componentes, em bovinos de 19 raças ou grupamentos genéticos. Foram utilizados 22 trabalhos científicos publicados entre 1963 e 2011, de oito países, o que totalizou 52.637 bovinos com idades que variaram de 28 dias até a idade de abate. As estimativas de CAR, consumo de matéria seca (CMS), ganho médio diário (GMD) e peso metabólico (PV 0,75 ) foram ponderadas pelo inverso da variância amostral. A variação da h 2 de cada característica entre os estudos foi analisada por quadrados mínimos ponderados. Os efeitos de sexo, país e raça foram significativos para h 2 de CAR e explicaram 67% da variação entre os estudos. Para CMS, os efeitos de país e raça foram significativos e explicaram 96% da variação. As estimativas combinadas de h 2 foram: 0,255±0,008, 0,278±0,012, 0,321±0,015 e 0,397±0,032 para CAR, CMS, GMD e PV 0,75 , respectivamente. As estimativas combinadas de correlação genética e fenotípica foram baixas entre CAR e GMD e entre CAR e PV 0,75 (de -0,021±0,034 a 0,025±0,035), e de média magnitude entre CAR e CMS (0,636±0,035 a 0,698±0,041) e entre CMS, GMD e PV 0,75 (0,441±0,062 a 0,688±0,032). O CAR apresenta estimativa de herdabilidade menor que a de suas características componentes.Termos para indexação: consumo de matéria seca, correlação genética, eficiência alimentar, estimativas combinadas, herdabilidade, peso metabólico. Meta-analysis of genetic parameter estimates of residual feed intake and of its component traits in cattleAbstract -The objective of this work was to estimate, by meta-analysis, the heritability (h 2 ) and the genetic (r g ) and phenotypic (r f ) correlations of residual feed intake (RFI), and of its component traits in beef cattle from 19 breeds or genetic groups. Twenty-two scientific papers published from 1963 to 2011, from eight countries, totaling 52,637 cattle of ages from 28 days up to slaughter, were evaluated. The estimates of RFI, dry matter intake (DMI), average daily gain (ADG) and metabolic weight (BW 0.75 ) were weighted by the inverse of sample variance. The variation between studies of h 2 for each trait was analyzed by weighted least squares. The effects of sex, country and breed were significant for h 2 of RFI, explaining 67% of variation between studies. For DMI, country and breed effects were significant and explained 96% of variation. Pooled estimates of h 2 were: 0.255±0.008, 0.278±0.012, 0.321±0.015, and 0.397±0.032 for RFI, DMI, ADG and BW 0.75 , respectively. Pooled estimates of genetic and phenotypic correlations were low between RFI and ADG and between RFI and BW 0.75 (from -0.021±0.034 to 0.025±0.035), and moderate between RFI and DMI (0.636±0.035 and 0.698±0.041) and between DMI, ADG and BW 0.75 (0.441±0.062 to 0.688±0.032). The trait RFI has lower heritability estimates than its components.

Evidence of negative relationship between female fertility and feed efficiency in Nellore cattle1,2

“…However, the heritability for days to calving obtained in the present study was higher than that reported for B. taurus (Mu et al, 2016) and B. indicus (Forni and Albuquerque, 2005), whereas the heritability for RFI was lower than either B. taurus (Mu et al, 2016) or B. indicus (Santana et al, 2014). Although the heritabilities estimated using part of the present feed efficient database are high for the traits involved in the calculation of RFI, 0.41 to 0.53 for DMI, ADG, and metabolic midtest weight (Grion et al, 2014;Ceacero et al, 2016), the estimates obtained for RFI are lower than those reported in the literature (Del Claro et al, 2012).…”

Polymorphisms in the GHRL gene and their associations with traits of economic interest in beef cattle

“…Feed efficiency traits, such as residual feed intake and dry matter intake, in Nellore cattle show heritability estimates of 0.30 and 0.41, respectively (Del Claro et al, 2012). In turn, the heritability estimates for meat quality traits, such as back-fat thickness and loin eye area, are 0.24 and 0.33, respectively (Meirelles et al, 2010).…”

Residual Feed Intake as a Measure to Select Genetically Productive Beef Cattle: A Review

“…There was no correlated response in weight per year and in weight gain, and the effectiveness of low RFI selection in reducing feed costs was proven without affecting production. The RFI is important because it reduces the direct economic impacts of reduced feed intake, as well as the effects of environmental impact on reducing methane emissions from enteric fermentation of ruminants [5]. Farmers usually select cattle only for their size, and the biggest disadvantage would be the increased energy requirement for the cattle to perform its basic activities such as walking or grazing [6].…”

“…The studies evaluated were related in chronological order (Table 2), with estimation of the heritability (h 2 ) of the RFI characteristic, definition of RFI, number of animals, sex, country, breed and age in which animals were tested, the data were adapted from Del Claro et al [5].…”

“…RFI, residue of regression of dry matter intake on phenotypic values of metabolic body weight and average daily gain; M = male, F = Female. Adapted from Del Claro et al[5].…”