IntroductionCattle temperament is an important factor that affects the profitability of beef cattle enterprises, due to its relationship with productivity traits, animal welfare and labor safety. Temperament is a complex phenotype often assessed by measuring a series of behavioral traits, which result from the effects of multiple environmental and genetic factors, and their interactions. The aims of this study were to perform a genome-wide association study and detect genomic regions, potential candidate genes and their biological mechanisms underlying temperament, measured by flight speed (FS) test in Nellore cattle.Materials and MethodsThe genome-wide association study (GWAS) was performed using a single-step procedure (ssGBLUP) which combined simultaneously all 16,600 phenotypes from genotyped and non-genotyped animals, full pedigree information of 162,645 animals and 1,384 genotyped animals in one step. The animals were genotyped with High Density Bovine SNP BeadChip which contains 777,962 SNP markers. After quality control (QC) a total of 455,374 SNPs remained.ResultsHeritability estimated for FS was 0.21 ± 0.02. Consecutive SNPs explaining 1% or more of the total additive genetic variance were considered as windows associated with FS. Nine candidate regions located on eight different Bos taurus chromosomes (BTA) (1 at 73 Mb, 2 at 65 Mb, 5 at 22 Mb and 119 Mb, 9 at 98 Mb, 11 at 67 Mb, 15 at 16 Mb, 17 at 63 Kb, and 26 at 47 Mb) were identified. The candidate genes identified in these regions were NCKAP5 (BTA2), PARK2 (BTA9), ANTXR1 (BTA11), GUCY1A2 (BTA15), CPE (BTA17) and DOCK1 (BTA26). Among these genes PARK2, GUCY1A2, CPE and DOCK1 are related to dopaminergic system, memory formation, biosynthesis of peptide hormone and neurotransmitter and brain development, respectively.ConclusionsOur findings allowed us to identify nine genomic regions (SNP windows) associated with beef cattle temperament, measured by FS test. Within these windows, six promising candidate genes and their biological functions were identified. These results may contribute to a better comprehension into the genetic control of temperament expression in Nellore cattle.

The aim of this study was to estimate heritability for five temperament and two reproductive traits in Nellore cattle and to estimate genetic and phenotypic correlations among them. Temperament was evaluated using the movement (MOV), tension (TEN) and crush (CS) scores (measured with animals inside the squeeze chute) as well as the flight speed (FS) and temperament score (TS). Reproductive traits included i) heifer rebreeding (HR), which evaluates heifers' ability to become pregnant, given that they had calved once; and ii) stayability (STAY), which measures cows' ability to calve at least 3 offspring before reaching 65 months of age. We used Bayesian inference and Gibbs sampling in a two-trait analysis to estimate genetic parameters applying a linear model for FS and threshold models for MOV, TEN, CS, TS, HR and STAY. The animal model included contemporary group as a fixed effect, direct additive genetic and residual effects as random effects, and animal age at yearling as a covariate (with linear and quadratic effects). Heritability estimates for MOV, TEN, CS, FS, TS, HR and STAY were 0.14 ± 0.04, 0.11 ± 0.03, 0.09 ± 0.03, 0.22 ± 0.02, 0.19 ± 0.04, 0.13 ± 0.02 and 0.13 ± 0.02, respectively. The genetic correlation estimates were low to moderate and the highest values (in magnitude) were − 0.19 ± 0.21 (HR-CS), − 0.21 ± 0.15 (STAY-TEN) and − 0.24 ± 0.16 (STAY-CS), indicating that the selection to improve cattle temperament does not negatively affect HR and STAY. These results indicate that all traits had sufficient genetic variability to respond to direct selection; however, given the low estimated heritability, we expect to see only long-term genetic changes. Genetic correlations showed that there is no antagonism of temperament with fertility and longevity; however, we recommend including these traits as selection criteria in Nellore breeding programs to obtain satisfactory genetic changes.

The aim of this study was to estimate the genetic associations between temperament and sexual precocity indicators in Nellore cattle. Temperament was evaluated at approximately 550 days of age, using three traits: i) movement score (MOV), recording the animals' movement inside the crush; ii) temperament score (TS) for assessing the reactions of animals in a corral pen; and iii) flight speed test (FS), recording the speed (in m/s) at which the animals exit the crush after being weighed. Three sexual precocity indicators were used: i) age at first calving (AFC, in days); ii) occurrence of precocious pregnancy (OPP, as a binary trait); and iii) yearling scrotal circumference (SC, in cm). The (co)variance and genetic parameters were estimated by Bayesian Inference via Gibbs sampling, assuming a linear animal model for FS, AFC and SC and a threshold animal model for MOV, TS and OPP in multitrait analyses. The mean posterior heritability estimates for MOV, FS, TS, AFC, OPP and SC were 0.11 ± 0.03, 0.27 ± 0.07, 0.16 ± 0.09, 0.09 ± 0.01, 0.44 ± 0.06 and 0.43 ± 0.02, respectively. The mean posterior correlation estimates were: 0.13 ± 0.14 (MOV-AFC), -0.03 ± 0.16 (MOV-OPP), 0.08 ± 0.10 (MOV-SC), 0.14 ± 0.11 (FS-AFC), -0.19 ± 0.15 (FS-OPP), -0.07 ± 0.08 (FS-SC), 0.09 ± 0.09 (TS-AFC), -0.03 ± 0.09 (TS-OPP) and -0.28 ± 0.08 (TS-SC). These results indicate that all the traits had sufficient genetic variability to respond to selection. The low magnitude of the genetic correlations indicated that selection for improvements in sexual precocity would not change the temperament of Nellore cattle. In order to obtain genetic progress in cattle temperament, direct selection for these traits is recommended.

a b s t r a c tThe aim of this study was to evaluate the effects of temperament on the quality and efficiency of handling and on the pregnancy rate of Nellore cows submitted to a fixed time artificial insemination (FTAI) protocol. Temperament and handling procedures were simultaneously assessed in 798 Nellore cows on the first (d0), ninth (d9) and 11th days (d11) of the FTAI protocol, using the flight speed (FS) and crush score (CS) tests. During the insemination process performed on d11 of the FTAI protocol, the following handling indicators were recorded: rough or overly aggressive handling of the cows by stockpersons (AGGRESSION), accidents (ACCIDENT), time to inseminate (TIME), and the degree of dirtiness on cows' perineal region (DIRTINESS). There was a significant effect of CS on TIME (P ¼ 0.013) and DIRTINESS (P ¼ 0.004), while FS tended to affect TIME (P ¼ 0.06) and the likelihood of AGGRESSION (P ¼ 0.07). Cows subjected to aggressive handling and/or accidents had a greater FS mean than cows that did not face such aversive situations (2.077 1.18 vs. 1.74 7 0.75 m/s, P¼ 0.0003). The chance of pregnancy (expressed in odds ratio) was greater in cows with low FS (OR ¼1.48) than in cows with high FS (defined as the reference class, with OR ¼1) (χ 2 ¼ 3.73, P¼ 0.05), and the low FS group had 10% more pregnant cows than the high FS group (with 52.59% vs. 42.62% pregnant cows, respectively). Pregnant cows had significantly lower FS means relative to non-pregnant cows on d0 (1.79 vs. 2.10 m/s, Po 0.001), d9 (1.67 m/s vs. 1.79 m/s, P¼ 0.038) and d11 (1.70 m/s vs. 1.90 m/s, P ¼0.004). We conclude that excitable temperament has an effect on the quality and efficiency of handling during FTAI, by increasing the time required for insemination, the dirtiness on cows' perineal region and the likelihood of aggressive actions by stockpersons. Also, cattle temperament measured by FS reduces the chance of pregnancy in Nellore beef cows.