Abstract Coenzyme Q9 (COQ9), a coenzyme Q (CoQ) precursor, is an essential component of the mitochondrial electron transport chain that drives adenosine triphosphate production. COQ9 polymorphism 18:25527339 is characterized by substitution of guanine (allele G) for adenine (allele A), which modifies the function of the protein encoded by the gene. In Holsteins, allele A has been associated with better reproductive performance in terms of the conception rate, number of services per conception (SPC) and days open (DO). The signal transducer and activator of transcription (STAT) protein is a transcription factor activated in the presence of cytokines and growth factors. STAT5A polymorphism 19:42407732 in exon 8 has been associated with higher fertility and embryonic survival rates. The objective of this study was to determine the relationship of COQ9 and STAT5A polymorphisms with reproductive parameters [calving to first heat interval (CFHI), DO and SPC]. Blood samples were taken from 112 lactating Holstein from a herd in México for allele genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). To estimate the association between reproductive parameters and genotypes, a linear mixed-effect model was performed. The COQ9 AG genotype was associated significantly with lower SPC (P<0.05) but not with DO or CFHI. No significant association with any reproductive parameter was found for STAT5A. Our findings suggest that the COQ9 18:25527339 polymorphism is a useful molecular marker for improvement of reproductive performance in dairy herds.

Abstract Complex vertebral malformation (CVM) is an autosomal recessive genetic syndrome present in Holstein cattle. The disease results in direct economic losses for cattle ranchers due to abortions and deaths of newborn calves. The purpose of the study was to estimate the allelic and genotypic frequencies of CVM syndrome in three Holstein cow herds in western Mexico and determine whether an improving effect between CVM genotype and milk production exists. A total of 308 cows were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR/RFLP) assays. The cow’s genotypes and first- and second-lactation total milk yield adjusted to 305 days were compared using a mixed statistical model, and the genotypic frequencies were calculated. The total recessive allele frequency of the CVM was 0.06. Milk production by lactation did not differ between CVM carriers and normal cows. It is concluded that not a direct relationship was found between milk production and CVM carrier status in the Mexican herds sampled.

Resumen El complejo de malformación vertebral (CVM) es un síndrome genético autosómico recesivo presente en el ganado Holstein. La enfermedad causa pérdidas económicas directas para los ganaderos debido a los abortos y la muerte de becerros neonatos. El propósito del estudio fue estimar las frecuencias génicas y genotípicas del síndrome CVM en tres hatos de vacas Holstein en el occidente de México y determinar si existe un efecto mejorante entre el genotipo CVM y la producción de leche. Se genotiparon 308 vacas usando la técnica de reacción en cadena de la polimerasa con polimorfismos de longitud de fragmento de restricción (PCR/RFLP, por sus siglas en inglés). Se compararon los genotipos de las vacas y los promedios de producción de leche de primera y segunda lactancia ajustados a 305 días utilizando un modelo estadístico mixto, y se calcularon frecuencias génicas y genotípicas. La frecuencia total del alelo recesivo de CVM fue de 0.06. La producción de leche por lactancia no difirió entre los portadores CVM y las vacas normales. Se concluyó que no hay una relación directa entre la producción de leche y el genotipo de portador de CVM en los hatos mexicanos muestreados.