Genome-wide association studies and functional annotation of pre-weaning calf mortality and reproductive traits in Nellore cattle from experimental selection lines.

Background: Reproductive efficiency is crucial for the long-term economic sustainability of beef cattle production. Pregnancy loss and stillbirth are complex reproductive traits that do not yet have their genomic background fully understood, especially in zebu breeds (Bos taurus indicus). Hence, this study aimed to perform a genome-wide association study (GWAS) and functional annotation for conception success (CS), pregnancy loss (PL), stillbirth (SB), and pre-weaning calf mortality (PWM) in Nellore cattle.

Injectable progesterone in 13-month-old prepubertal Nellore heifers: effects on in vitro embryo production and pregnancy rate.

The aim of this study was to evaluate the effect of injectable progesterone administration before ovum pick-up (OPU) on in vitro embryo production (IVEP) and pregnancy rate in prepubertal Nellore heifers. Twenty-three Nellore females, 13.04 ± 0.

Assessing different metrics of pedigree and genomic inbreeding and inbreeding effect on growth, fertility, and feed efficiency traits in a closed-herd Nellore cattle population.

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 relationship matrix H (FH), and ROH of different length (FROH); and calculate Pearson correlations between the different metrics in a closed Nellore cattle population selected for body weight adjusted to 378 days of age (W378). In addition to total FROH (all classes) coefficients were also estimated based on the size class of the ROH segments: FROH1 (1-2 Mb), FROH2 (2-4 Mb), FROH3 (4-8 Mb), FROH4 (8-16 Mb), and FROH5 (> 16 Mb), and for each chromosome (FROH_CHR).

Relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls: a cross sectional study.

The aim of this study was to investigate the relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls selected for postweaning weight. Data from the andrological evaluation of 836 bulls born between 2000 and 2019, including 583 Nellore animals (Bos indicus) and 253 Caracu animals (Bos taurus), were used. The bulls were divided into categories of age at the time of assessment: category 1 consisted of animals aged 20 to 23 months (22 ± 0.

Use of auxiliary techniques for assessing the reproductive capacity of natural service Nellore bulls.

The aim of this study was to investigate whether parameters obtained by computer-assisted sperm analysis (CASA), infrared thermography (IRT), and testicular B-mode and Doppler ultrasound can be used as indicators of fertility in natural service Nellore bulls. Twenty-nine Nellore bulls were evaluated on days 66 (-D66), 38 (-D38), and 10 (-D10) before the beginning of natural service mating. In all assessments, semen samples were collected and sperm kinetics were evaluated by CASA, thermographic imaging of the scrotal and ocular region, testicular B-mode ultrasound, and Doppler ultrasound of the spermatic cord.

Effect of Nellore (Bos indicus) donor age on in-vitro embryo production and pregnancy rate.

The aim of this study was to evaluate the effect of age of Nellore (Bos indicus) donors on the efficiency of in vitro embryo production (IVEP) and pregnancy rate. Thirty-six donors, including 11 female calves (13 ± 0.61 months), 17 prepubertal heifers (25 ± 0.