Linear Index Selection to Improve Traits Defined as Ratios

Gunsett, F. C.

doi:10.2527/jas1984.5951185x

Cited by 176 publications

(151 citation statements)

References 5 publications

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“…Característica (1) h Gunsett (1984) avaliou a seleção de características definidas como proporção, em que uma quantidade desigual de pressão de seleção é colocada no componente ou na característica de maior variação genética, o que resulta em respostas imprevisíveis para a seleção ao longo dos anos. Este autor, ao comparar a eficiência da seleção direta para uma razão de dois componentes e do índice linear para os mesmos dois componente derivados, concluiu que a abordagem em índice foi associada à maior resposta à seleção.…”

Section: Resultsunclassified

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

Claro

Mercadante

Silva

2012

Pesq. agropec. bras.

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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.

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Section: Resultsunclassified

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

Claro

Mercadante

Silva

2012

Pesq. agropec. bras.

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“…Because milking speed is available on Irish milk recorded cows using do-it-yourself milk recording (Berry et al, 2006), phenotypic information on which to undertake routine genetic evaluations for milking speed is feasible. The advantage of using such a residual trait rather than a flow rate trait is that the latter is a ratio trait and expected responses to selection can be difficult to ascertain (Gunsett, 1984) because of the poor statistical properties of ratio traits. Milking speed has an economic value (Boettcher et al, 1998;Prints et al, 2002), and therefore breeding for milking speed within a balanced breeding programme is feasible and advisable to reduce the cost of production.…”

Section: Discussionmentioning

confidence: 99%

Genetics of milking characteristics in dairy cows

Berry

Coyne

Coughlan³

et al. 2013

Animal

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Genetic selection for milking speed is feasible. The existence of a correlation structure between milking speed and milk yield, however, necessitates a selection strategy to increase milking speed with no repercussion on genetic merit for milk yield. Residual milking duration (RMD) and residual milking duration including somatic cell score (RMDS), defined as the residuals from a regression model of milking duration on milk yield or milk yield plus somatic cell score (SCS) have been advocated. The objective of this study was to undertake a first ever genetic analysis of these novel traits. Data on electronically recorded milking duration and other milking characteristics from 235 005 test-day records on 74 608 cows in 1075 Irish dairy herds were available. Variance components for the milking characteristic traits were estimated using animal linear mixed models and covariances with other performance traits, including udder-related type traits, were estimated using sire models. The heritability of milking duration, RMD and RMDS was 0.20, 0.22 and 0.18, respectively. There were little differences in the heritability of RMD or RMDS when defined using genetic regression. The genetic standard deviation of RMDS defined on the phenotypic or genetic level was 36.8 s and 37.6 s, respectively, clearly indicating considerable exploitable genetic variation in milking duration independent of both milk yield and SCS. The genetic correlation between phenotypically derived RMDS and milk yield was favourable (20.43), but RMDS was unfavourably genetically correlated with SCS (20.30); the genetic correlations with both traits when RMDS was defined at a genetic level were zero. RMDS defined at the phenotypic level was negatively (i.e. unfavourable) genetically correlated (20.35; s.e. 5 0.15) with mastitis; however, when defined using genetic regression, shorter RMDS was not associated with greater expected incidence of mastitis. RMDS, defined at the genetic level, is a useful heritable trait with ample genetic variation for inclusion in a national breeding strategy without influencing genetic gain in either milk yield or udder health.

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“…However, it is known that ratio traits such as FCR may be problematic for selection. In a study comparing the selection responses of direct selection on a ratio trait consisting of two components to a linear index trait derived from the same components, Gunsett (1984) concluded that the use of a linear index increases selection responses compared to direct selection. Archer et al (1999) and Arthur et al (2001a) pointed out that selection to improve FCR does not always lead to improvement of feed efficiency in future generations since selection against FCR can also produce larger animals, which need more energy for maintenance even if they have superior WTG.…”

Section: Heritabilitymentioning

confidence: 99%

Genetic parameters for fatty acid composition and feed efficiency traits in Japanese Black cattle

Inoue

Kobayashi²,

Shoji³

et al. 2011

Animal

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We estimated the genetic parameters related to feed intake (FI), feed efficiency traits (including feed conversion ratio (FCR) and residual feed intake (RFI) of digestible crude protein (DCP) and total digestible nutrients (TDN)), beef marbling score (BMS), melting point of fat (MP) and fatty acid composition. Fat and meat (Musculus trapezius) samples were taken from the carcasses of 863 Japanese Black steers derived from 65 sires, for determination of the MP and fatty acid composition of the total lipid in intramuscular adipose tissue. Genetic parameters were estimated using uni-and bivariate animal models. In addition, pedigree information for 4841 animals was used. Heritability estimates for BMS, MP, individual fatty acids, monounsaturated fatty acids (MUFA), the ratio of saturated fatty acids to MUFA (MUS) and the ratio of elongation (ELONG) were generally high. The FI values of TDN and DCP were also high, but FCRs and RFIs of those were low (0.09 to 0.22). Genetic correlation of BMS with MP was 20.34 (favorable) and with C18:1, MUFA, MUS and ELONG values were 0.40, 0.28, 0.29 and 0.37, respectively (favorable). Genetic correlations of MP with C18:1, MUFA, MUS and ELONG were negative (also favorable) and high (20.85, 20.98, 21.00 (20.996) and 20.66, respectively). The correlation estimates for feed efficiency traits of DCP were quite similar to those of TDN. Genetic correlations of BMS with FCRs and RFIs of TDN and DCP were all positive (unfavorable; 0.21 to 0.51), and in particular, the correlations with RFIs of those were high. The correlations of C18:1, MUFA, MUS and ELONG with RFIs of TDN and DCP were positive (unfavorable) but low (0.06 to 0.17), whereas the corresponding correlations with FCRs of those were all negative (favorable; 20.38 to 20.10). These results suggest that the quantity and quality of beef fat can be simultaneously improved and that the quality of beef fat (fatty acid composition) can be improved directly or indirectly with MP. Furthermore, selecting MP or fatty acid traits does not significantly affect feed efficiency.Keywords: genetic parameter, beef cattle, fatty acid composition, feed efficiency ImplicationsFat quantity and fat quality traits have high heritability estimates and show favorable genetic relationships with each other. Some genetic relationships between fat quality traits and feed efficiency traits are unfavorable, but all of these are weak relationships. These results indicate that it may be convenient to improve fat quality traits genetically and to simultaneously improve the quantity and quality of beef fat. Furthermore, selecting fat quality traits does not significantly affect feed efficiency. We can expect to improve the quality of beef fat without reducing feed utilization efficiency.

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Linear Index Selection to Improve Traits Defined as Ratios

Cited by 176 publications

References 5 publications

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

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

Genetics of milking characteristics in dairy cows

Genetic parameters for fatty acid composition and feed efficiency traits in Japanese Black cattle

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