One of the strategies to genetically improve reproductive traits, despite their low inheritability, has been the identification of candidate genes. Therefore, the objective of this study was to detect candidate genes associated with fecundity through the fixation index (F_ST) and runs of homozygosity (ROH) of selection signatures in Katahdin ewes. Productive and reproductive records from three years were used and the genotypes (OvineSNP50K) of 48 Katahdin ewes. Two groups of ewes were identified to carry out the genetic comparison: with high fecundity (1.3 ± 0.03) and with low fecundity (1.1 ± 0.06). This study shows for the first time evidence of the influence of the CNOT11, GLUD1, GRID1, MAPK8, and CCL28 genes in the fecundity of Katahdin ewes; in addition, new candidate genes were detected for fecundity that were not reported previously in ewes but that were detected for other species: ANK2 (sow), ARHGAP22 (cow and buffalo cow), GHITM (cow), HERC6 (cow), DPF2 (cow), and TRNAC-GCA (buffalo cow, bull). These new candidate genes in ewes seem to have a high expression in reproduction. Therefore, future studies are needed focused on describing the physiological basis of changes in the reproductive behavior influenced by these genes.

Braunvieh is an important dual-purpose breed in the Mexican tropics. The study of its genetic diversity is key to implementing genetic improvement programs. This study was conducted to determine genetic diversity of reproductive traits in a Mexican Braunvieh beef cattle population using single nucleotide polymorphisms in candidate genes. Information from 24 genes with 52 intra-genic loci reported in literature to be associated with productive life, pregnancy rate and cow and heifer conception rate of 150 Braunvieh males and females was considered. Observed heterozygosity (Ho) revealed high genetic diversity for the studied traits, Ho = 0.42 +/- 0.087, relative to that of other populations of the same breed. Cluster analyses were carried out using the Ward and K-means algorithms. These analyses revealed high genetic diversity that was observed in the biplot of non-metric multi-dimensional scaling. It was found that clustering strategy allowed visualisation of distant groups by genotype but not by favourable alleles in all the loci. We found that the genes CSNK1E, DNAH11, DSC2, IBSP and OCLN affected most of the traits in our study and they were highly informative. Therefore, they represent a potential resource for selection and crossbreeding programs of the traits studied in Braunvieh. The analyses showed that the Mexican Braunvieh population has a high level of genetic diversity, arguably due to decades-long adaptation to the Mexican tropics.

En el estudio se compararon umbrales de frecuencia del alelo menor durante el control de calidad de los genotipos, utilizando polimorfismos de nucleótido simple para predecir valores genómicos de características de crecimiento en bovinos Suizo Europeo. El análisis se realizó con 28,973 y 18,994 registros de pesos al nacimiento y destete, 12,835 polimorfismos de nucleótido simple y 300 animales. Las características se analizaron bajo el enfoque de evaluación genómica en un solo paso. Los criterios de comparación fueron: 1) jerarquización de valores genómicos: se estimaron coeficientes de correlación Spearman y Pearson entre valores genómicos predichos con frecuencia estándar del alelo menor (0.05) y niveles menores; 2) habilidad de predicción de los modelos: se realizó validación cruzada con cuatro repeticiones y se obtuvo el promedio de los coeficientes de correlación de los fenotipos reales contra predichos; y 3) coeficiente de regresión simple: los valores genómicos obtenidos con frecuencia del alelo menor estándar e inferiores, fueron las variables independiente y dependiente, respectivamente. El efecto del nivel de frecuencia del alelo menor en la jerarquización de los valores genómicos no fue importante (correlaciones mayores que 0.99, <2.2x10-16). La habilidad predictiva del modelo fue similar: 0.7 promedio. Los coeficientes de regresión fueron cercanos a uno (0.99, <2x10-16). Los resultados sugieren que una frecuencia del alelo menor entre 0.0 y 0.05, no altera las predicciones de valores genómicos en poblaciones pequeñas. Sin embargo, estos resultados son preliminares y susceptibles a cambios si el estudio se repite con un número de marcadores y animales mayor.

Genomic evaluation improves accuracy and enables shorter generation intervals, accelerating genetic changes, possibly strengthening the antagonism between performance and less-selected traits. Our objective was to evaluate the impact of genomic selection for performance on foot structure in Angus cattle. Variance component estimation was done under the Bayesian approach (variance components estimation [VCE]) with partial or no genotypes, and with a new method based on predictivity (PRED) using all genotypes, to examine changes in genetic parameters over time. The performance trait groups were growth (GT), carcass (carcass traits [CT]), ultrasound carcass (uCT), and marbling (MT). Foot structure traits (FT) were foot angle (FA) and claw set (CS). Genetic parameters through VCE over 5-yr intervals and using genotypes were obtained. From 2011 to 2015 to 2019 to 2022, changes in heritability were observed for CS (0.12 ± 0.01 to 0.16 ± 0.01), FA (0.18 ± 0.02 to 0.14 ± 0.01), carcass weight (0.30 ± 0.03 to 0.35 ± 0.04), marbling (0.43 ± 0.02 to 0.60 ± 0.04), and ultrasound backfat thickness (0.32 ± 0.01 to 0.38 ± 0.01). Changes in genetic correlations were found for CS-carcass weight (0.25 ± 0.15 to −0.04 ± 0.08), CS-rib eye area (0.20 ± 0.11 to −0.12 ± 0.08), and CS-weight at ultrasound scanning (0.12 ± 0.06 to 0.0 ± 0.03). For PRED, estimates from two 2-yr slices showed that most GT and uCT heritabilities were lower than those from the last VCE interval (e.g., birth weight: 0.34 vs. 0.26). In comparison, FT heritabilities were higher (e.g., CS: 0.16 vs. 0.29). In general, all genetic correlations from PRED ranged from −0.15 to 0.10, whereas the values were between −0.15 and 0.05 in the last interval based on VCE. The predictivity method provides updated genetic parameters for young animals, whereas VCE estimates refer to the base population. Including genotypes had a strong impact on some estimates. Our results indicate that heritability estimates in recent generations for strongly selected traits have decreased compared to older generations. However, genetic correlations between foot structure and performance traits have consistently remained close to zero, likely due to the differences in selection intensity between these traits. While no strong antagonistic correlations were found, selecting multiple traits is crucial to maintain conformation while improving performance. Since the population structure changes due to genetic or environmental factors, updating the genetic parameters is vital for achieving expected genetic gains.

Mastitis is a disease that causes significant economic losses, since resistance to mastitis is a difficult trait to be improved due to its multifactorial occurrence. Therefore, our objective was to characterize a Mexican Braunvieh cattle population for genetic resistance and susceptibility to mastitis. We used 66 SNP markers for 45 candidate genes in 150 animals. The average heterozygosity was 0.445 ± 0.076, a value higher than those reported for some European breeds. The inbreeding coefficient was slightly negative for resistance to subclinical (−0.058 ± 0.055) and clinical (−0.034 ± 0.076) mastitis, possibly due to low selection for the immunological candidate genes that influence these traits. The genotypic profiles for the candidate loci per K-means group were obtained, as well as the group distribution through the graphics of the principal component analysis. The genotypic profiles showed high genetic diversity among groups. Resistance to clinical mastitis had the lowest presence of the heterozygous genotypes. Although the percentage of highly inbred animals (>50%) is up to 13.3%, there are highly heterozygous groups in terms of the studied traits, a favorable indicator of the presence of genetic diversity. The results of this study constitute evidence of the genetic potential of the Mexican Braunvieh population to improve mastitis-related traits.