Sperm mobility: A primary determinant of fertility in the domestic fowl (Gallus domesticus)

Previous research demonstrated that sperm mobility is a quantitative trait of the domestic fowl. The trait is quantified by measuring the absorbance o f an Accudenz solution after overlay with a sperm suspension and brief incu bation at body temperature. In the present work, average and high sperm mob ility phenotypes (n = 30 males per phenotype) were selected from a base pop ulation. Differences were found between sperm oxygen consumption (p < 0.000 1), acylcarnitine content (p < 0.05), linear velocity (p < 0.001), and stra ightness (p < 0.001), a trajectory variable measured with the Hobson SpermT racker. Oxygen consumption and stearoylcarnitine content of sperm from the high-mobility phenotype were twice those observed with sperm from average m ales, implying a pivotal role for mitochondria. On the basis of these resul ts, a graded relationship was predicted between fertility and sperm mobilit y. Males (n = 48) were chosen at random from another base population, sperm mobility was measured per male, and each ejaculate was used to inseminate 8-12 hens (8 x 10(7) viable sperm per hen). When fertility was plotted as a function of sperm mobility, data points approximated a skewed logistic fun ction. The hypothesis that vaginal immunoglobulins constitute an immunologi cal barrier to sperm transport was tested and rejected. Therefore, we concl uded that sperm mobility is a primary determinant of fertility in the fowl.