MANOVA on average peripheral blood testosterone levels during exposure to stallions or to mares.

<p>MANOVA on average peripheral blood testosterone levels during exposure to stallions or to mares.</p

Semen characteristics.

<p>Semen characteristics (means ± 95% CI over averages of three ejaculates per stallion) after exposure to mares (A, C) or to stallions (B, D), plotted separately for mean sperm number (A, B), mean VCL (C, D), and each for stallions who were first exposed to other stallions and then to mares, and for stallions who were first exposed to mares and then to other stallions. The numbers of stallions per treatment are indicated in the figure (one stallion had to be euthanized before the last semen collection–see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143185#sec002" target="_blank">Methods</a>). See Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143185#pone.0143185.t001" target="_blank">1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143185#pone.0143185.t002" target="_blank">2</a> for statistics.</p

Semen characteristics versus testosterone levels.

<p>Semen characteristics versus mean peripheral plasma testosterone levels (“T”; in nmol/L). Mean sperm number (A) after exposure to mares versus T during exposure to mares (tau = 0.45, p = 0.04), and (B) after exposure to stallions against T during exposure to stallions (tau = -0.31, p = 0.19). (C) Mean VCL after exposure to mares against T during exposure to mares (tau = 0.18, p = 0.41), and (D) after exposure to stallions against T during exposure to stallions (tau = 0.49, p = 0.04). The analogous correlations between T and the other sperm velocity measures were never significant (|tau| always < 0.30, p always > 0.17). Stallions were either first exposed to stallions and then to mares (triangles) or vice versa (circles). The lines give the regressions to emphasize the direction of significant correlations.</p

MANOVA on the mean sperm velocity measures VSL (straight line velocity), VCL (curvilinear velocity), and VAP (average path velocity) after exposure to stallions or to mares.

<p>MANOVA on the mean sperm velocity measures VSL (straight line velocity), VCL (curvilinear velocity), and VAP (average path velocity) after exposure to stallions or to mares.</p

Testosterone levels.

<p>Correlation between average peripheral plasma testosterone levels (“T”; in nmol/L) while exposed to mares or to stallions (Kendalls’ tau = 0.58, p = 0.009). Stallions were either first exposed to stallions and then to mares (triangles) or vice versa (circles). The line gives the regression.</p

Data Burger et al. ProcB

"sim" = MHC similar; "dissim" = MHC dissimilar; "Testost" = peripheral testosterone blood level; "µ" = mean; "ELA" = MHC antigens of horses; "VSL", "VCL", and "VAP" = sperm velocity measure