Delvan Silva

Federal University of Viçosa | UFV · Department of Animal Science

Traits related to calving have a significant impact on animal welfare and farm profitability in dairy production systems. Identifying genomic regions associated with calving traits could contribute to refining dairy cattle breeding programs and management practices in the dairy industry. Therefore, the primary objectives of this study were to estim...

Background The selection of individuals based on their predicted breeding values and mating of related individuals can increase the proportion of identical-by-descent alleles. In this context, the objectives of this study were to estimate inbreeding coefficients based on alternative metrics and data sources such as pedigree (FPED), hybrid genomic r...

Background The genotype-by-environment interaction (GxE) in beef cattle can be investigated using reaction norm models to assess environmental sensitivity and, combined with genome-wide association studies (GWAS), to map genomic regions related to animal adaptation. Including genetic markers from whole-genome sequencing in reaction norm (RN) models...

Background Non-additive genetic effects are often ignored in livestock genetic evaluations. However, fitting them in the models could improve the accuracy of genomic breeding values. Furthermore, non-additive genetic effects contribute to heterosis, which could be optimized through mating designs. Traits related to fitness and adaptation, such as h...

Feed efficiency plays a major role in the overall profitability and sustainability of the beef cattle industry, as it is directly related to the reduction of the animal demand for input and methane emissions. Traditionally, the average daily feed intake and weight gain are used to calculate feed efficiency traits. However, feed efficiency traits ca...

Beef cattle affected by feet and legs malformations (FLM) cannot perform their productive and reproductive functions satisfactorily, resulting in significant economic losses. Accelerated weight gain in young animals due to increased fat deposition can lead to ligaments, tendon and joint strain and promote gene expression patterns that lead to chang...

Heat stress negatively affects livestock, with undesirable effects on animals' production and reproduction. Temperature and humidity index (THI) is a climatic variable used worldwide to study the effect of heat stress on farm animals. Temperature and humidity data can be obtained in Brazil through the National Institute of Meteorology (INMET), but...

This study is aimed at estimating genetic parameters, effective population size, inbreeding, and inbreeding depression for birth weight, weaning weight, and average pre-weaning daily weight gain (ADG) in Piau pigs. We used information from 3841 Piau pigs, and four linear models were fitted in single-trait analyses, including or excluding maternal g...

Characterized by the incomplete development of the germinal epithelium of the seminiferous tubules, Testicular hypoplasia (TH) leads to decreased sperm concentration, increased morphological changes in sperm and azoospermia. Economic losses resulting from the disposal of affected bulls reduce the efficiency of meat production systems. A genome-wide...

There is a great worldwide demand for cheese made with buffalo milk, due to its flavour and nutritional properties. In this context, there is a need for increasing the efficiency of buffalo milk production (including lactation persistence), which can be achieved through genomic selection. The most used methods for the genetic evaluation of longitud...

We aimed to estimate genetic parameters for growth, reproductive, and carcass traits in Tabapuã cattle. Phenotypic data were collected between 1990 and 2019 in 1,218 farms, and the pedigree file had 340,868 animals. The traits evaluated were body weight at 120 (W120), 210 (W210), 365 (W365), and 550 (W550) days of age; age at first calving (AFC), s...

The assessment of the presence of genotype by environment interaction (GxE) in beef cattle is very important in tropical countries with diverse climatic conditions and production systems. The present study aimed to assess the presence of GxE by using different reaction norm models for eleven traits related to growth, reproduction, and visual score...

The objective of this study was to evaluate the effect of inbreeding, through pedigree and genomic-based inbreeding coefficients, on the selection (postweaning) weight (WSel), scrotal circumference (SC), and days to calving (DC) and to evaluate the effect of recent and ancient inbreeding in these traits in Nellore cattle. A total of 1,446 animals g...

The objective of this study was to evaluate the gain in accuracy of genomic predictions by adding selected sequence variants to a high-density SNP panel and using weighted or regular single-step GBLUP (ssGBLUP) for age at first calving evaluations in Nellore cattle. Phenotypic records from 224,110 heifers from the Alliance Nellore database and 42,7...

Reaction norm models (RNM) can be used to assess environmental sensitivity of animals for traits affected by genotype by environment interaction. Three RNM were tested for weaning weight (WW) in Nellore cattle. Phenotypic data from 772,855 animals were obtained from the Aliança Nelore dataset. The best model, according to the AIC criteria, was a sp...

A genome-wide association analysis was performed to identify genomic windows and the underlying positional candidate genes associated with feet and legs malformation (FL) in Nellore cattle. Single Nucleotide Polymorphism (SNP) effects were estimated from 295,031 pedigree records from animals with phenotypes, 12,537 genotypes for FL and 461,057 SNPs...

This study aimed to estimate genetic parameters, effective population size, inbreeding, and inbreeding depression for birth weight, weaning weight, and average pre-weaning daily weight gain (ADG) in Piau breed pigs. We used information from 3841 Piau pigs, and four linear models were fitted in single trait analyzes including or excluding maternal g...

Increasing productivity through continued animal genetic improvement is a crucial part of implementing sustainable livestock intensification programs. In Zebu cattle, the lack of sexual precocity is one of the main obstacles to improving beef production efficiency. Puberty-related traits are complex, but large-scale data sets from different “omics”...

Informações fenotípicas de 551,930 animais provenientes da base de dados Aliança Nelore foram utilizados para estimar a variância genética aditiva direta e materna, e de ambiente permanente materno para ganho de peso do nascimento à desmama (GND). Inicialmente, ajustou-se um modelo animal para estimar o gradiente ambiental (definido como as estimat...

O objetivo deste trabalho foi avaliar o ganho em acurácia e a capacidade preditiva utilizando informação genômica em comparação com a predição considerando o pedigree (BLUP) para características reprodutivas em bovinos Nelore. As características utilizadas foram idade ao primeiro parto, probabilidade de prenhez aos 18 meses, stayability, reconcepçã...

O objetivo deste estudo foi realizar uma meta-análise multi-característica para identificar polimorfismos (SNP) pleiotrópicos em características de precocidade sexual em bovinos Nelore. As características consideradas foram idade ao primeiro parto (IPP), perímetro escrotal (PE) e probabilidade de prenhez aos 18 meses (PP18). Análises de associação...

O objetivo desse estudo foi comparar modelos de normas de reação (MNR) para produção de leite em até 305 dias (PL305) em bovinos da raça Girolando. Foram utilizados 60.256 dados fenotípicos da primeira lactação. Os gradientes ambientais (GA) foram definidos considerando as soluções dos grupos de contemporâneos utilizando o modelo animal. Em seguida...

1. Uniformity in animal products is an important aspect of the production system. Several studies have reported estimates of genetics on residual variance in different species, indicating that it could be exploited to improve uniformity by selection. Nevertheless, there are no reports about the possibilities of such a selection strategy in meat qua...

Reproductive efficiency is major determinant of the dairy herd profitability. Thus, reproductive traits have been widely used as selection objectives in the current dairy cattle breeding programs. We aimed to evaluate strategies to model days open (DO), calving interval (CI), and daughter pregnancy rate (DPR) in Brazilian Holstein cattle. These rep...

The progenies of international bulls in diverse climatic conditions and management levels may lead to different expressions of their genetic potential resulting in a re-ranking of these bulls. Therefore, evaluate the presence of genotype by environment interaction (G × E) within and across countries is important to guide the decision-making on alte...

The profitability of dairy activity is influenced by the genetic selection of economically important traits. In this context, the correct estimation of genetic parameters and the knowledge regarding candidate genes involved in the expression of genetically associated traits may help develop appropriate breeding strategies for the Guzerá breed. In t...

We investigated the applicability of ssGBLUP methodology under the autoregressive model (H‐AR) for genomic evaluation of longitudinal reproductive traits in Portuguese Holstein cattle. The genotype data of 1,230 bulls and 1,645 cows were considered in our study. The reproductive traits evaluated were interval from calving to first service (ICF), ca...

BACKGROUND In the last few months we have been experiencing a serious epidemic, which has spread throughout the world. The COVID-19 virus has already killed and infected thousands of people. A question that arises is about the risk groups, and if men would be more susceptible to this disease than women. In addition, what secondary factors would hav...

We aimed to clarify if the infection and death rate by COVID-19 differ among gender in the top 50 countries with the highest death rates. Also, we investigated if secondary variables such as HDI, number of hospital beds, average age, temperature, percentage of elderly, smoker and obesity are contributing to the variability observed among countries....

This study focused on the identification of QTL regions, candidate genes, and network related genes based on the first 3 lactations (LAC3) of milk, fat, and protein yields, and somatic cell score (SCS) in Portuguese Holstein cattle. Additionally, the results were compared with those from only first lactation (LAC1) data. The analyses were performed...

We investigated the efficiency of the autoregressive repeatability model (AR) for genetic evaluation of longitudinal reproductive traits in Portuguese Holstein cattle and compared the results with those from the conventional repeatability model (REP). The data set comprised records taken during the first four calving orders, corresponding to a tota...

Autoregressive (AR) and random regression (RR) models were fitted to test‐day records from the first three lactations of Brazilian Holstein cattle with the objective of comparing their efficiency for national genetic evaluations. The data comprised 4,142,740 records of milk yield (MY) and somatic cell score (SCS) from 274,335 cows belonging to 2,32...

Although several studies have investigated the factors affecting imputation accuracy, most of these studies involved a large number of genotyped animals. Thus, results from these studies cannot be directly applied to small populations, since the population structure affects imputation accuracy. In addition, factors affecting imputation accuracy may...

The multiple-lactation autoregressive test-day (AR) model is the adopted model for the national genetic evaluation of dairy cattle in Portugal. Under this model, animals' permanent environment effects are assumed to follow a first-order autoregressive process over the long (auto-correlations between parities) and short (auto-correlations between te...

Test-day milk, fat and protein yields and somatic cell score (SCS) of Brazilian Holstein cattle were used to study the effect of fixed (HTDF) vs random (HTDR) contemporary groups (herd-test-date) with or without unknown parent groups (UPG) using an autoregressive test-day animal model for genetic evaluations. Therefore, four models were used in thi...

The objective of this work was to evaluate the criteria for the formation of contemporary groups (CGs) in the genetic evaluation of body weight at weaning in Nellore cattle. A total of 713,474 records from 3,066 herds located in Midwestern and Northern Brazil were used. Data were obtained from the genealogical registry of zebu breeds of the Brazili...

We estimated genetic correlations between partial and total body weight gain (BWG) and individual feed conversion (FC) aiming to identify possible partial traits as selection criteria in meat quail breeding programs. Data included 379 records from two different genetic lines (188 quails from UFV1 and 191 from UFV2). The following traits were evalua...

A progeny test representing the milk yield was simulated to evaluate the effect of heterogeneity of environmental variance on genetic evaluation of sires in situations of unequal number of progeny per sire between herds, eliminating, at random, daughters per sires in environments of low and high environmental variability. In all situations involvin...

A total of 204,912 records of birth weights up to 550 days of age, of 24,890 Nellore cattle, offspring of 375 sires and 16,917 dams from five herds in the state of Mato Grosso, Brazil, were used in order to describe the variability of the weight development by random regression models. The model evaluated as the most suitable used the covariance fu...