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 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

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

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

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

Cycle-specific female preferences for visual and non-visual cues in the horse (<i>Equus caballus</i>)

<div><p>Although female preferences are well studied in many mammals, the possible effects of the oestrous cycle are not yet sufficiently understood. Here we investigate female preferences for visual and non-visual male traits relative to the periodically cycling of sexual proceptivity (oestrus) and inactivity (dioestrus), respectively, in the polygynous horse (<i>Equus caballus</i>). We individually exposed mares to stallions in four experimental situations: (i) mares in oestrus and visual contact to stallions allowed, (ii) mares in oestrus, with blinds (wooden partitions preventing visual contact but allowing for acoustic and olfactory communication), (iii) mares in dioestrus, no blinds, and (iv) mares in dioestrus, with blinds. Contact times of the mares with each stallion, defined as the cumulative amount of time a mare was in the vicinity of an individual stallion and actively searching contact, were used to rank stallions according to each mare’s preferences. We found that preferences based on visual traits differed significantly from preferences based on non-visual traits in dioestrous mares. The mares then showed a preference for older and larger males, but only if visual cues were available. In contrast, oestrous mares showed consistent preferences with or without blinds, i.e. their preferences were mainly based on non-visual traits and could not be predicted by male age or size. Stallions who were generally preferred displayed a high libido that may have positively influenced female interest or may have been a consequence of it. We conclude that the oestrous cycle has a significant influence on female preferences for visual and non-visual male traits in the horse.</p></div

Distribution of EBVs and dEBVs for conformation traits in FM horses.

a<p>Minimum and maximum estimated breeding values (EBV). The average estimated breeding value for animals born between 1998 and 2000 was set to 0.</p>b<p>Minimum and maximum deregressed breeding values (dEBV). Deregressed EBVs were used for association analysis.</p

Significantly associated SNPs with dEBV for height at withers using a mixed-model approach.

a<p>EquCab 2.0 assembly.</p>b<p>corresponding homologous human position, build 37.</p>c<p>trait-increasing allele/trait-decreasing allele; (frequency of the trait-increasing allele).</p>d<p>corresponding list of p-values of 1-d.f. (additive or allelic) test for association between SNP and trait; the Bonferroni-corrected threshold for a 5% genome-wide significance level is p_BONF = 1.31×10⁻⁶.</p>e<p>corresponding list of empirical p-values derived from permutations with 40,000 replicates.</p

Age, body height, body weight, body condition score (range: 1–5), mane density score (1 = sparse, 2 = medium, 3 = dense), mean libido score (0 = no libido, to 4 = high libido) and mean pooled attractiveness rank ± SD (1 = very attractive, to 7 = not attractive) with and without blinds in oestrous and dioestrous tests of the seven stallions used in the study.

<p>Age, body height, body weight, body condition score (range: 1–5), mane density score (1 = sparse, 2 = medium, 3 = dense), mean libido score (0 = no libido, to 4 = high libido) and mean pooled attractiveness rank ± SD (1 = very attractive, to 7 = not attractive) with and without blinds in oestrous and dioestrous tests of the seven stallions used in the study.</p