Genetic study of quantitative traits supports the use of Guzerá as dual-purpose cattle

Abstract

Objective:The aim of this study was to estimate genetic parameters for 305-day cumulative milk yield and components, growth, and reproductive traits in Guzerá cattle. Methods:The evaluated traits were 305-day first-lactation cumulative yields (kg) of milk (MY305), fat (FY305), protein (PY305), lactose (LY305), and total solids (SY305); age at first calving (AFC) in days; adjusted scrotal perimeter (cm) at the ages of 365 (SP365) and 450 (SP450) days; and adjusted body weight (kg) at the ages of 210 (W210), 365 (W365) and 450 (W450) days. The (co)variance components were estimated using the restricted maximum likelihood method for single-trait, bi-trait and tri-trait analyses. Contemporary groups and additive genetic effects were included in the general mixed model. Maternal genetic and permanent environmental effects were also included for W210. Results:The direct heritability estimates ranged from 0.16 (W210) to 0.32 (MY305).The maternal heritability estimate for W210 was 0.03. Genetic correlation estimates among milk production traits and growth traits ranged from 0.92 to 0.99 and from 0.92 to 0.99, respectively. For milk production and growth traits, the genetic correlations ranged from 0.33 to 0.56. The genetic correlations among AFC and all other traits were negative (-0.43 to -0.27). Scrotal perimeter traits and body weights showed genetic correlations ranging from 0.41 to 0.46, and scrotal perimeter and milk production traits showed genetic correlations ranging from 0.11 to 0.30. The phenotypic correlations were similar in direction (same sign) and lower than the corresponding genetic correlations. A c c e p t e d A r t i c l e 4 Conclusion: These results suggest the viability and potential of joint selection for dairy and beef traits in Guzerá cattle, taking into account reproductive traits.

Genomic prediction in Brazilian Guzerá cattle: application of a single-step approach to productive and reproductive traits

“…The existence of "double proven" sires, i.e., sires genetically evaluated for dairy and beef traits (Bruneli et al, 2020), allows the farmers to choose concomitantly for meat and milk production improvement. Moreover, there is no genetic antagonism among reproductive, dairy and growth traits in Guzerá cattle as showed in previous studies (Brito et al, 2020;Carrara et al, 2022) and also on this paper. Thus, it is possible to select for one purpose without loss in the others.…”

“…Recently, comparative genomic studies using the ssGBLUP method have been conducted including variance components from ssGREML (Cesarani et al, 2019;Sungkhapreecha et al, 2021;Jang et al, 2022). The variance components used in prediction of pedigree-based breeding values (EBV) were obtained from single-trait model by REML in a previous study and more details can be found in Carrara et al (2022).…”

The contribution of a MOET nucleus scheme for the improvement of Guzerá (Bos indicus) cattle for milk traits in Brazil

“…However, it is below the theoretical genetic gain (1%-2%) expected, considering some assumptions (Rendel and Robertson, 1950), which could have resulted in a gain between 20 and 40 kg milk/year for the Guzerá cattle. This result reveals the potential for genetic progress in the Guzerá cattle, mainly considering the heritability described for MY305 (0.32 ± 0.04) for this breed (Teepker and Smith, 1990;Carrara et al, 2022). Otherwise, the time to reach the asymptotic rates of genetic gain will be slow (Dentine and McDaniel, 1987).…”

“…Two aspects should be taken into account. First, the genetic correlation between milk and fat yield (0.96 ± 0.02) in Guzerá ( Carrara et al, 2022 ), although high, is not perfect and the genes’ action on these traits may be different. Thus, no proportional genetic progress in fat yield, due to direct selection for milk production, is expected ( Meinert et al, 1988 , Quinton and MacMillan, 1996 , van Binsbergen et al, 2012) .…”

“…Considering the negative annual phenotypic (−160 g) and genetic (−10 g) progress for the population without data for the MOET animals, and considering the notable annual phenotypic (+960 g) and genetic (+160 g) progress in the MOET nucleus, the progress in the whole Guzerá population can be also attributed to the contribution of the indirect selection for protein production in this scheme. This was because the genetic correlation between milk and protein production (0.97) is high ( Carrara et al, 2022 ). Therefore, the results found for fat and protein production should have occurred as a correlated response to selection since the selection in the Guzerá MOET nucleus had focused on milk production.…”