Publications by authors named "Altair A Valloto"
Article Synopsis
- The study evaluated how genotype-environment interactions (GEI) affect traits in Holstein cattle, specifically age at first calving (AFC), age at first service (AFS), and calving interval (CI), using data from 179,492 animals in Paraná, Brazil.
- Researchers applied a reaction norm model to assess environmental gradients and heritability of these traits, finding moderate heritability for AFC (0.23) in easier environments, but low heritability for others.
- Significant GEI effects were noted for AFC and AFS, indicating that cattle that perform well in one environment may not do so in another, highlighting the complexity of breeding strategies.
This study investigated the age at first calving in Holstein heifers and its impact on various production parameters. A sample of 737 Holstein heifers born between 2015 and 2018 and finishing their first lactations between 2018 and 2020 was included. Cluster analysis revealed three groups based on age at first calving: high precocity, medium precocity and low precocity.
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- The study aimed to analyze genetic factors related to the fat-to-protein ratio (F:P) in Holstein cows during early lactation, considering its relationship with milk yield, somatic cell score, and calving intervals.
- It used extensive data from over 77,000 cows collected between 2012 and 2022 and employed advanced statistical models to estimate heritability and correlations between traits.
- Findings indicated low heritability for F:P and other traits, with certain genetic correlations suggesting potential conflicts that could hinder overall genetic improvement in milk production and quality.
Our objective was to evaluate the genetic merit of Holstein cattle population in southern Brazil in response to variations in the regional temperature by analyzing the genotype by environment interaction using reaction norms. Fat yield (FY) and protein yield (PY) data of 67 360 primiparous cows were obtained from the database of the Paraná Holstein Breeders Association, Brazil (APCBRH). The regional average annual temperature was used as the environmental variable.
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- The study aimed to assess how Holstein cattle’s genetic traits, particularly somatic cell scores (SCS), respond to changes in environmental temperature by analyzing genotype by environment interaction (GEI).
- Data was collected from over 67,000 primiparous cows in Brazil, considering temperature variations between 17°C and 19.5°C, using advanced statistical models to evaluate genetic responses of different bulls.
- Results indicated that while some genetic variations occurred with temperature changes, the overall GEI for SCS was deemed insignificant, suggesting temperature does not need to be factored into genetic evaluations for this breed in southern Brazil.
Objective: This study assessed the possible existence of genotype by environment interactions for milk, fat and protein yields in Holstein cattle raised in one of the most important milk production basins in Brazil.
Methods: Changes in the genetic parameters and breeding values were evaluated for 57,967 animals from three distinct regions of southern Brazil, divided according to differences in climate. The genotype by environment interaction was determined by genetic correlations between regions, estimated by the restricted maximum likelihood, considering the animal model.
The reduction of milk production caused by subclinical mastitis in dairy cows was evaluated through the regression of test-day milk yield on log-transformed somatic cell counts (LnSCC). Official test-day records (n = 1,688,054) of Holstein cows (n = 87,695) were obtained from 719 herds from January 2010 to December 2015. Editing was performed to ensure both reliability and consistency for the statistical analysis, and the final data set comprised 232,937 test-day records from 31,692 Holstein cows in 243 herds.
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