Quality of seminal fluids varies with type of stimulus at ejaculation.

The theory of ejaculate economics was mainly built around different sperm competition scenarios but also predicts that investments into ejaculates depend on female fecundity. Previous tests of this prediction focused on invertebrates and lower vertebrate, and on species with high female reproductive potential. It remains unclear whether the prediction also holds for polygynous mammals with low female reproductive potential (due to low litter size and long inter-birth intervals). We used horses (Equus caballus) to experimentally test whether semen characteristics are adjusted to the oestrous cycle of the mare a stallion is exposed to during few moments before ejaculation. We analysed 122 weekly semen samples collected from 16 stallions during exposure to either an oestrous or a dioestrous mare. Semen volume and the rate of motile sperm were higher when stallions were exposed to an oestrous than to a diestrous mare, while total sperm counts and sperm velocity remained unchanged. Sperm collected after exposure to an oestrous mare also showed reduced oxidative degeneration of cell membranes over a period of 48 hours. We conclude that stallions invest more into their seminal fluids when the chance of fertilization is elevated, and that this adjustment of ejaculate quality can happen very quickly

Characterization of Dimethylsulfoxide / Glycerol Mixtures: A Binary Solvent System for the Study of "Friction-Dependent" Chemical Reactivity

The properties of binary mixtures of dimethylsulfoxide and glycerol, measured by several techniques, are reported. Special attention is given to those properties contributing or affecting chemical reactions. In this respect the investigated mixture behaves as a relatively simple solvent and it is especially well suited for studies on the influence of viscosity in chemical reactivity. This is due to the relative invariance of the dielectric properties of the mixture. However, special caution must be taken with specific solvation, as the hydrogen-bonding properties of the solvent changes with the molar fraction of glycerol.Comment: 49 pages including appendix, 20 figures and 89 reference

Effect of Equi-Strath® on Leucocyte Occurrence in the Haired Skin of Horses

Strath®/Bio-Strath® is a plasmolyzed herbal yeast product with malt, honey and orange syrup. Its ability to support the immune system of the human being is well known and was tested in several studies. Equi-Strath®, the adapted product for horses was tested in this study. The aim of the study was to analyze the effects of Equi-Strath® on skin condition in the horse. The study included twenty healthy Franches-Montagnes stallions which were divided into two groups. The study group (SG, n = 10) received 0.06 ml/kg bodyweight of Equi-Strath®, the control group (CG, n = 10) the same amount of placebo, daily. The supplement and the placebo were given from week 1 until week 10 of the trial, orally. Skin biopsies were taken three times, once at the beginning of the study (week 0), once at half time (week 5) and once at the end of the study (week 10), followed by histological analysis including leucocytes count twice in five vision fields of each slide. No alterations of hair, adnexal structures or skin thickness were found. However, the number of perivascular lymphocytes turned out to be increased at the end of the study in 9 out of 10 animals of the study group, whereas number of lymphocytes in biopsies of the control group where increased only in 4 out of 10 animals. The increase of lymphocytes in the study group suggests an activation of the immune system due to the application of Equi-Strath®