Genetic parameters for stayability to consecutive calvings in Zebu cattle

Abstract

Longer-lived cows tend to be more profitable and the stayability trait is a selection criterion correlated to longevity. An alternative to the traditional approach to evaluate stayability is its definition based on consecutive calvings, whose main advantage is the more accurate evaluation of young bulls. However, no study using this alternative approach has been conducted for Zebu breeds. Therefore, the objective of this study was to compare linear random regression models to fit stayability to consecutive calvings of Guzerá, Nelore and Tabapuã cows and to estimate genetic parameters for this trait in the respective breeds. Data up to the eighth calving were used. The models included the fixed effects of age at first calving and year-season of birth of the cow and the random effects of contemporary group, additive genetic, permanent environmental and residual. Random regressions were modeled by orthogonal Legendre polynomials of order 1 to 4 (2 to 5 coefficients) for contemporary group, additive genetic and permanent environmental effects. Using Deviance Information Criterion as the selection criterion, the model with 4 regression coefficients for each effect was the most adequate for the Nelore and Tabapuã breeds and the model with 5 coefficients is recommended for the Guzerá breed. For Guzerá, heritabilities ranged from 0.05 to 0.08, showing a quadratic trend with a peak between the fourth and sixth calving. For the Nelore and Tabapuã breeds, the estimates ranged from 0.03 to 0.07 and from 0.03 to 0.08, respectively, and increased with increasing calving number. The additive genetic correlations exhibited a similar trend among breeds and were higher for stayability between closer calvings. Even between more distant calvings (second v. eighth), stayability showed a moderate to high genetic correlation, which was 0.77, 0.57 and 0.79 for the Guzerá, Nelore and Tabapuã breeds, respectively. For Guzerá, when the models with 4 or 5 regression coefficients were compared, the rank correlations between predicted breeding values for the intercept were always higher than 0.99, indicating the possibility of practical application of the least parameterized model. In conclusion, the model with 4 random regression coefficients is recommended for the genetic evaluation of stayability to consecutive calvings in Zebu cattle.

Genomic evaluation for novel stayability traits in Nellore cattle

“…STAY53 and STAY63 presented heritability estimates equal to 0.15. These estimates are greater than those reported by Silva et al (), who presented heritability estimates of STAY63 in Nellore cattle ranging from 0.03 to 0.07. In contrast, the results of the present study corroborate with Teixeira et al () and Bonamy et al () who reported heritability for STAY63 of 0.14 and 0.16, respectively.…”

“…These estimates are greater than those reported by Silva et al (2017), Thus, one can conclude that, although STAY63 allows the female to be successful with up to two reproductive failures, it is not directly associated with cows that present reproductive failures concentrated at the beginning of its reproductive life. This may be associated with traditional Brazilian beef cattle production systems, where cows that do not re-breed and heifers that do not become pregnant during the breeding season, are culled.…”

“…The most common stayability measurement (STAY63) is usually defined as a binary trait assuming as success the cow that had three (or more) calving up to 76 months of age (Schmidt et al, ; Silva et al, ). This definition limits the number of cows with measurements, as young animals will not have records until they reach 76 months of age.…”

Genetic correlations among weight and cumulative productivity of crossbred beef cows1

“…Simulation showed random regression may be somewhat better than other approaches for predicting the percentage of sires' daughters that survive to a specific age (Jamrozik et al, 2008). Random regression of stayability to consecutive calvings has shown that stayability to the second calving is a good indicator of stayability to later calvings (Jamrozik et al, 2013;Silva et al, 2018), enabling earlier evaluation of sire EBV based on daughters' records than is possible with a single observation of stayability to an older age.…”

Modelagem de propriedades reológicas de argilas esmectitas do estado da Paraíba para uso em fluidos de perfuração de poços de petróleo

“…Com as superfícies obtidas, pode-se prever os valores das propriedades para qualquer mistura do intervalo considerado com base nas proporções dos seus componentes [9,10]. Esta metodologia tem encontrado aplicações importantes em várias áreas tecnológicas, tendo sido aplicada em tecnologia de argilas com grande sucesso [11][12][13][14][15]. Em todos os casos essa metodologia levou a uma maior eficiência e confiança nos resultados obtidos e simultaneamente possibilitou a otimização dos sistemas com um mínimo de experimentos.…”