Sperm mobility phenotype is a highly heritable, component of male fertility in commercial broilers. Our genome wide association studies have identified several chromosomal regions contributing to mobility phenotype. One region contains the candidate gene KCNMA1 which codes for a calcium activated potassium channel known to be expressed in sperm. The gene includes 28 exons spanning more than 430 kbp of chromosome 6. Targeted re-sequencing of regions of this gene have identified Single nucleotide Polymorphism (SNPs) differentially represented in high and low mobility lines. One SNP in exon 27 was developed for TaqMan based SNPlotype assays. Application of this test to our experimental lines as well as commercial birds with low mobility indicates that this region is largely homozygous in the low mobility line and the commercial samples, whereas the high mobility line has much higher genetic diversity. Sequence analysis of additional regions should identify additional SNPs for analysis of our lines. We are developing additional DNA samples representing crosses of high and low mobility birds to determine the contributions of this region to sperm mobility phenotype.