The Montana Tropical ® Composite is a recently developed beef cattle population that is rapidly expanding in Brazil and other tropical countries. This is mainly due to its improved meat quality and adaptation to tropical climate conditions compared to Zebu and Taurine cattle breeds, respectively. This study aimed to investigate the genetic architecture of ultrasound-based carcass and meat quality traits in Montana Tropical ® Composite beef cattle. Therefore, we estimated variance components and genetic parameters and performed genome-wide association studies using the weighted single-step Genomic Best Linear Unbiased Prediction (GBLUP) approach. A pedigree dataset containing 28,480 animals was used, in which 1,436 were genotyped using a moderate-density Single Nucleotide Polymorphism panel (30K; 30,105 SNPs). A total of 9,358, 5,768, 7,996, and 1,972 phenotypic records for the traits Longissimus muscle area (LMA), backfat thickness (BFT), rump fat thickness (RFT), and for marbling score (MARB), respectively, were used for the analyses. Moderate to high heritability estimates were obtained and ranged from 0.16 ± 0.03 (RFT) to 0.33 ± 0.05 (MARB). A high genetic correlation was observed between BFT and RFT (0.97 ± 0.02), suggesting that a similar set of genes affects both traits. The most relevant genomic regions associated with LMA, BFT, RFT, and MARB were found on BTA10 (5.4-5.8 Mb), BTA27 (25.2-25.5 Mb), BTA18 (60.6-61.0 Mb), and BTA21 (14.8-15.4 Mb). Two overlapping genomic regions were identified for RFT and MARB (BTA13:47.9-48.1 Mb) and for BFT and RFT (BTA13:61.5-62.3 Mb). Candidate genes identified in this study, including PLAG1, LYN, WWOX, and PLAGL2, were previously reported to be associated with growth, stature, skeletal muscle growth, fat thickness, and fatty acid composition. Our results indicate that ultrasoundbased carcass and meat quality traits in the Montana Tropical ® Composite beef cattle are heritable, and therefore, can be improved through selective breeding. In addition, various novel and already known genomic regions related to these traits were identified, which contribute to a better understanding of the underlying genetic background of LMA, BFT, RFT, and MARB in the Montana Tropical Composite population.

Genetic improvement, without control of inbreeding, can go to loss of genetic variability, reducing the potential for genetic gains in the domestic populations. The aim of this study was to analyze the population structure and the inbreeding depression in Campolina horses. Phenotype information from 43 465 individuals was analyzed, data provided by the Campolina Breeders Association. A pedigree file containing 107 951 horses was used to connected the phenotyped individuals. The inbreeding coefficient was performed by use of the diagonal of the relationship matrix and the genealogical parameters were computed using proper softwares. The effective population size was estimated based on the rate of inbreeding and census information, and the stratification of the population was verified by the average relationship coefficient between animals born in different regions of Brazil. The effects of inbreeding on morphological traits were made by the use of inbreeding coefficient as a covariate in the model of random regression. The inbreeding coefficient increased from 1990 on, impacting effective population size and, consequently, shrinking genetic variability. The paternal inbreeding was greater than maternal, which may be attributed to the preference for inbred animals in reproduction. The average genetic relationship coefficient of animals born in different states was lower than individuals born within the same state. The increase in the inbreeding coefficient was negatively associated with all studied traits, showing the importance to avoid genetic losses in the long term. Although results do not indicate a severe narrowing of the population until the present date, the average relationship coefficient shows signs of increase, which could cause a drastic reduction in genetic variability if inbred mating is not successfully controlled in the Campolina horse population.

A B S T R A C TIn general, is said that functional traits have a positive genetic correlation with conformation in horses but, this hypothesis has never been investigated in the Brazilian Campolina breed. We aimed to estimate genetic parameters (heritabilities and genetic correlations) for these traits based on genealogical records from 107,951 animals, in which 43,159 were phenotyped. A total of 16 morphological traits (MT); one gaits score (GtS) and two traits related to conformation harmony (CH), were simultaneously analysed under a Bayesian multi-trait model framework. Genetic trends were estimated over the years of birth for animals born between 1951 and 2016. MT were all genetically positively associated (from 0.05 to 0.98). CH traits presented positive and negative genetic correlations, but all favourable to the selection goals. GtS was negatively associated with all MT, except for Chest Width (0.08). CH and GtS presented lower positive genetic correlation (0.10 and 0.01, for the ratio between Height at Withers and Height at Back, and ratio of Back-Loins Length over Body Length, respectively). Observed results indicated the existence of sufficient additive genetic variance (heritability estimates ranged from 0.07 to 0.43) for the studied traits, benefiting the implementation of a breeding program, if the desired is to select animals for morphology or gaits. All genetic trends were favorable despite of the phenotypic selection in the Campolina breed. These trends presented low regression coefficients, but the increase on average predicted breeding values for the investigated period was 137.9%.

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The DMRT3 gene has been described as the main gene influencing gait in horses; however, most studies have examined its effects by comparing information from trotted and gaited individuals. Within the Brazilian Mangalarga Marchador breed, animals can present two types of gaits (marcha batida and marcha picada), which differ in the movement form-diagonal (marcha batida) or lateral (marcha picada). We examined a possible association of the g.22999655C>A DMRT3 SNP with the type of gait, in this two-gaits breed. The relationship between individuals was calculated for the two phenotypic groups, as well as the inbreeding coefficient and its trend over generations. The allelic and genotypic frequencies were estimated based on genotype data from 310 horses (205 marcha ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 18 (1): gmr18217 F.O. Bussiman et al. 2 batida; 105 marcha picada).Two threshold models were used to determine the proportion of phenotypic variance explained by DMRT3 genotypes. The average coancestry for animals with marcha batida was 0.04 ± 0.00, whereas in marcha picada it was 0.05 ± 0.01 (higher than the population mean of 0.04 ± 0.00). The inbreeding coefficient was 1.71% and 3.48% for marcha batida and marcha picada animals, respectively. Effects of the DMRT3 gene ranged from 9.94 to 10.77% (as a proportion of phenotypic variance) when included as an uncorrelated random effect and as a covariable, respectively. The genotypic frequencies of the DMRT3 and the patterns of kinship and inbreeding could be a result of selection in this breed, resulting in statistical confusion between the DMRT3 effects and population structure.