Relationship among fluctuating asymmetry, morphological traits, and sperm quality in layers.
The aim of the present study was to analyze the relationship between fluctuating asymmetry and the mean value of several bilateral traits (toe, leg, wing, and wattle lengths, and leg width) and sperm quality variables (volume, appearance, concentration, motility, morphological abnormalities, and acrosome and membrane integrities) in different breeds of layers. In total, 165 roosters were sampled at 36 wk of age. There was no significant correlation between fluctuating asymmetry and sperm quality variables. There was a positive association (P < 0.01) between sperm motility and concentration, and between sperm concentration and volume. Sperm motility was positively correlated (P < 0.001) with morphologically normal sperm. The membrane integrity did not correlate with motility. This study shows different results for the association between sperm quality variables and morphological traits. There was a negative association (P < 0.05) between toe length and membrane integrity and between leg length and sperm motility. In disagreement with the expected results, wattle length did not correlate with any sperm quality parameter. In general, roosters with longer legs had longer toes and wings, whereas those with longer wattles had longer toes, legs, and wings. Breed effect was significant for the sperm motility index (P < 0.001), concentration and membrane integrity (P < 0.05), and morphologically normal sperm (P < 0.01). Spanish breeds had similar sperm quality variables to the White Leghorn population, although the Blue Andaluza (a Spanish breed) showed smaller values for sperm motility index and concentration and membrane integrity. Breed effect was not significant for any fluctuating asymmetry, with values ranging from 1 to 6% of the trait value; however, breed effect was significant for all of the morphological traits (P < 0.001). The CV was higher for ejaculate volume and concentration, intermediate for semen appearance, motilities, and morphologically normal sperm, and smaller for membrane and acrosome integrity. In conclusion, the results suggest that fluctuating asymmetry is of limited use for assessment of rooster sperm quality. Some morphological traits (toe length, leg length, and leg width) might be associated with some sperm quality variables (motility and membrane integrity).