Turkey sperm mobility influences paternity in the context of competitive fertilization

We have devised a novel means of investigating competitive fertilization in turkeys, using microsatellite genotyping to identify male parentage. Our r esults demonstrate that sperm mobility is a mechanism responsible in part f or paternity efficiency in turkeys. Sperm mobility is composed of several p arameters in which sperm motility is a component. Differences between ejacu lates in the number of sperm penetrating into a dense, insert, nontoxic sol ution were measured and used to classify males into high, average, or low s perm mobility phenotypes. Microsatellite genotyping was used to determine p arentage of poults after equal numbers of sperm from in males (either high or average phenotype, n = 5, mixed with low phenotype, n = 5) were insemina ted simultaneously. In a separate study, the numbers of sperm hydrolyzing t he perivitelline layer of eggs were compared between hens inseminated with sperm from high-, average-, or low-phenotype males. Overall, heterospermic inseminations resulted in consistently fewer offspring produced by low-mobi lity phenotype males. This correlated with physiological data in which seme n from the low-mobility males had reduced numbers of sperm at the fertiliza tion site as determined by sperm hole counts in the perivitelline layer of eggs. This is the first illustration of a measurable sperm trait predictive of paternity success in a competitive fertilization trial in turkeys, a sp ecies that is predominately reproduced by artificial insemination of multip le-sire pools.