Tabapuã breed in Northeastern Brazil: genetic progress and population structure

Dirlane Novais Caires,Paulo Luiz Souza Carneiro,Milton Rezende Teixeira Neto,Raimundo Martins Filho,Laaina De Andrade Souza,Carlos Henrique Mendes Malhado

doi:10.1590/s1516-35982012000800008

Dirlane Novais Caires, Paulo Luiz Souza Carneiro + Show 4 more

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https://doi.org/10.1590/s1516-35982012000800008

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Abstract

The objective of this study was to evaluate the history of the Tabapua breed in Northeastern Brazil by determining its population structure and genetic progress. Pedigree information from animals born in the period between 1965 and 2006 and weight-adjusted data at 205 (W205), 365 (W365) and 550 (W550) days of age for bovines born between 1975 and 2006 were used. The (co)variance components and genetic value were estimated using the application MTDFREML. Also, the software ENDOG was used for pedigree analysis and parameter estimation based on the probabilities of gene origin, inbreeding and average generation interval. The heritability coefficients for direct genetic effects were 0.21±0.03, 0.26±0.04 and 0.36±0.05 for W205, W365 and W550, respectively. During the first 20 years studied, the observed effective size was small. The generation intervals by gametic pathway were: 7.7±3.4 (sire-son), 7.8±3.7 (sire-daughter), 6.9±3.3 (dam-son), 6.8 ± 3.1 (dam-daughter), and mean interval of 7.3±3.4 years. The studied population showed moderate heritability coefficients, whereas the genetic gains based on the studied traits may be higher than those estimated by genetic tendencies. Reduced generation interval, increased effective size and continuous mating control of relatives are important strategies for the genetic progress of the Tabapua breed in the region.

Highlights

Knowledge of the different factors that potentially interfere in the selection process and genetic progress, such as effective size, generation interval and genetics are of great importance for the feasibility of breeding programs (Malhado et al, 2008a)
Means and coefficients of variation (CV) for weights adjusted at 205 (W205), 365 (W365) and 550 (W550) days of life were 173.84±29.61 kg and 17.03%; 232.88±42.64 kg and 18.31%; 302.27±59.56 kg and 19.70%, respectively. These means are above those observed by Ferraz Filho et al (2002), in a study involving the Tabapuã breed, whose values were 170.30, 222.40 and 286.45 kg for weight-adjusted data at 205 (W205), W365 and W550, respectively
The direct heritability coefficients were 0.21±0.03, 0.26±0.04 and 0.36±0.05 for W205, W365 and W550, respectively (Table 1). These estimates are considered of moderate magnitude and reveal that the selection could be efficient and provide genetic progress over the years, mainly when it comes to weight at 550 days of life

Summary

Introduction

Breeding programs are deemed fundamental to improve the productive traits of cattle; it is necessary to monitor the results achieved by selection in order to pursue alternatives to improve genetic gains.Such monitoring can be done through evaluation of genetic changes over time, aiming to verify the genetic progress achieved and helping in adjustments, whenever necessary (Euclides Filho et al, 2000).The study of genetic tendency is a measure for assessing changes caused by a selection process, regarding specific traits, over the years (Holanda et al, 2004); in addition, this study indicates the hits and misses of the adopted selection methods and helps determine the continuity - or not - of selection strategies.Likewise, knowledge of the different factors that potentially interfere in the selection process and genetic progress, such as effective size, generation interval and genetics are of great importance for the feasibility of breeding programs (Malhado et al, 2008a). Breeding programs are deemed fundamental to improve the productive traits of cattle; it is necessary to monitor the results achieved by selection in order to pursue alternatives to improve genetic gains. Such monitoring can be done through evaluation of genetic changes over time, aiming to verify the genetic progress achieved and helping in adjustments, whenever necessary (Euclides Filho et al, 2000). The use of information contained in pedigrees is of great importance for studies of population structures, as this is a low-cost technique as compared with other techniques, as for instance, the use of molecular markers (Carneiro et al, 2009)

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