Genetic parameters of milk production and reproduction traits of Girolando cattle in Brazil

Abstract

The objective of this study was to estimate the heritability and genetic, phenotypic, and environmental correlations between 305-day milk yield (305MY), age at first calving (AFC), calving interval (CI) and dry period length (DPL), as well as to compare the productive and reproductive performances of several groups of Girolando cows during their first, second and third parturitions in Brazil. Genetic parameters were estimated using uni-and bi-trait analyses via restricted maximum likelihood (REML). Heritability estimates were similar between uni-and bi-trait analyses and varied from 0.20 to 0.28, 0.00 to 0.08 and 0.07 to 0.14 for 305MY, CI and DPL, respectively, whereas AFC was 0.20. Genetic correlations between 305MY and AFC (-0.49) or DPL (-0.40 to -0.79) show a favourable association. However, an unfavourable genetic association was verified between 305MY and CI (0.59) in the first calving. Environmental and phenotypic correlations between 305MY and CI or DPL showed a favourable association (-0.25 to -0.42 and -0.14 to -0.44). Concerning the cow breed group, a decrease in 305MY was observed as the fraction of the Gyr breed increased, whereas animals from the 1/2 Holstein þ1/2 Gyr crossbreeding group yielded better performances for AFC and CI. These results reveal large genetic, phenotypic and environmental variations that could be used in selection programmes.

Heritability estimates and genetic correlations of various production and reproductive traits of different grades of dairy cattle reared under subtropical condition

“…Dabdoub () reported a negative and significant correlation of milk production with age at first calving, which is in agreement with the results of the present research study. Similarly, Canaza‐Cayo et al () also reported negative genetic correlation between 305MY and AFC (−0.49) implies that part of the additive genes that positively influence milk yield acts on reducing age at the first calving. Therefore, the selection process to increase milk yield would result in a greater precocity of heifers.…”

“…Climatic stresses such as high humidity, high ambient temperature and inadequate or uneven rainfall negatively affect the productivity of dairy cows in tropical conditions. (Canaza-Cayo, Lopes, Cobuci, Martins, & Silva, 2018;Toghiani, 2012).…”

Estimates of genetic and crossbreeding parameters for 305-day milk yield of Girolando cows

“…Higher heritability for 305MY in Girolando cows were reported by Canaza-Cayo et al (2018) (0.27) andFac o et al (2008) (0.21). The differences in heritability estimates found in these studies can be attributed to several factors, such as production level, population size, analysis model, variable assessed (fitted, or total milk production), and environmental effects (Canaza-Cayo et al 2018). Regardless of the variations between heritability estimates by the mathematical models for 305MY, all estimates showed moderate heritability, that is, these mathematical models can be used to estimate genetic parameters of milk production at 305 days.…”

“…According to Fac o et al (2008), the genetic recombination observed in some types of mating produces detrimental effects to milk production. Canaza-Cayo et al (2018) found better productive performance for the 3/4 H and 7/8 H groups and attributed this result to the improved environment of these herds, which favoured the performance of animals with higher proportion of Holstein genes. However, animals with heterosis coefficients of 0.438 and 0.469 (5/8 H group) from different crosses showed a positive heterosis effect ( Table 1).…”

“…Thus, heterosis does not guarantee that crosses can bring favourable epistatic interactions. In this case, a subsequent selection programme is important because the large genetic compositions of the Girolando breed can guarantee moderate genetic gains for milk production and contribute to the improvement of the productive efficiency of the herd when properly used in breeding programmes (Canaza-Cayo et al 2018).…”