Case–control approach application for finding a relationship between candidate genes and clinical mastitis in Holstein dairy cattle

Abstract

Mastitis is a major source of economic loss in dairy herds. The objective of this research was to evaluate the association between genotypes within SLC11A1 and CXCR1 candidate genes and clinical mastitis in Holstein dairy cattle using the selective genotyping method. The data set contained clinical mastitis records of 3,823 Holstein cows from two Holstein dairy herds located in two different regions in Iran. Data included the number of cases of clinical mastitis per lactation. Selective genotyping was based on extreme values for clinical mastitis residuals (CMR) from mixed model analyses. Two extreme groups consisting of 135 cows were formed (as cases and controls), and genotyped for the two candidate genes, namely, SLC11A1 and CXCR1, using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), respectively. Associations between single nucleotide polymorphism (SNP) genotypes with CMR and breeding values for milk and protein yield were carried out by applying logistic regression analyses, i.e. estimating the probability of the heterogeneous genotype in the dependency of values for CMR and breeding values (BVs). The sequencing results revealed a novel mutation in 1139 bp of exon 11 of the SLC11A1 gene and this SNP had a significant association with CMR (P < 0.05). PCR-RFLP analysis leads to three banding patterns for CXCR1c.735C>G and these genotypes had significant relationships with CMR. Overall, the results showed that SLC11A1 and CXCR1 are valuable candidate genes for the improvement of mastitis resistance as well as production traits in dairy cattle populations.

Association of SlC11A1 gene and production traits using logistic regression

“…Differences in EBVs for production traits when comparing the heterozygous genotype to both homozygous genotypes of SLC11A1 SNP are given in Table 1. In spite of the positive significant effect of SLC11A1 gene on clinical mastitis resistance, which has been previously shown (BAGHERI et al, 2016), no significant relation was found between this gene and production traits (protein and fat yield and protein and fat percentage). It should be kept in mind that selection of specific alleles of important genes may improve udder health; however, correlated response for other economic traits should not be ignored.…”

“…Polymerase chain reaction-mediated single strand conformation polymorphism (PCR-SSCP) results showed a polymorphism due to a mutation at position 1139 (NM_174652.2:c.1139 C > G). More information on SSCP variants has been presented in BAGHERI et al (2016). Differences in EBVs for production traits when comparing the heterozygous genotype to both homozygous genotypes of SLC11A1 SNP are given in Table 1.…”

“…Hence, it is suggested that both health and production traits to be considered simultaneously in selection breeding programs. There are several genes that simultaneously have positive effects on production traits and health traits such as clinical mastitis resistance (BAGHERI et al, 2013;BAGHERI et al, 2016), which can be simply used in selection strategies for dairy cattle programs. On the other hand, some genes have positive effects on production traits, while increasing the incidence of clinical mastitis cases (HERINGSTAD et al, 2007).…”

“…A moderate variation in the coding sequence of SlC11A1 gene in cows has been found and it was shown that it would be a sign of selection pressure on this gene (GERNAND et al, 2012). BAGHERI et al (2016) have shown that SLC11A1 gene plays a critical role in mastitis resistance. Since, there is an antagonistic relation between udder health and production traits in dairy cattle, production traits should also be considered in selection programs for health traits, as well.…”

Predicting the effects of the single nucleotide polymorphism A122V on CXC chemokine receptor type 1 of Bos taurus (Artiodactyla: Bovidae) cattle by in silico analyses

“…Over the past decade, some reports in the literature have described a strong association between polymorphisms in the bovine CXCR1 gene and pathogen-specific incidence rate of clinical mastitis (VERBEKE et al, 2014;PAWLIK et al, 2015;BAGHERI et al, 2016). Recently, Pokorska et al (2016) identified single nucleotide polymorphisms located within the coding region and the 3'UTR site of the bovine CXCR1 gene that were significantly associated with the susceptibility of cows to clinical mastitis.…”