Use of nutraceuticals in the stallion: Effects on semen quality and preservation

Nutritional supplements are widely used in the equine industry with the aim of improving horse health, sports or reproductive performances. Over the years, a number of studies have focused on investigating the effects of several dietary compounds on the quality and preservation of stallion semen. This paper reviews the literature available on the use of nutritional supplementation for the improvement of reproductive performance and semen quality in equine species, critically appraising the benefits and negative effects of several compounds found in complementary feeds such as PUFAs from different sources, vitamins and antioxidants, carnitine and botanical extracts. Different nutraceuticals have been highlighted to improve stallion fertility by providing optimal levels of antioxidants, with the most promising results obtained by the combination of PUFAs and antioxidants that resulted to be essential for the maintenance of normal reproductive functions and the reduction of cryodamage in cooled and frozen equine semen.

Effects of L-Carnitine on Equine Semen Quality During Liquid Storage

l-Carnitine (LC) plays a key role in sperm metabolism, easily providing energy through β-oxidation, which positively affects motility. The objective of this study was to investigate the association between blood plasma and seminal plasma LC levels, as well as the effect of LC as an additive in a skimmed milk-based extender during sperm storage at 5°C. In the first experiment, semen and blood samples from 14 Quarter Horse stallions were used. The LC content in blood plasma and seminal plasma was determined by spectrophotometry and their relationships with seminal parameters were evaluated. In the second experiment, ejaculates (n = 16) from four Quarter Horses were used. Each ejaculate was split into four treatment groups with different LC concentrations: 0 (control), 0.5, 1.0, and 2.0 mM. Sperm motility, integrity of plasma and acrosomal membranes, intracellular reactive oxygen species content, and plasma membrane stability were evaluated immediately after samples reached 5°C (0 hour) and after 24, 48, and 72 hours. There was a positive correlation (p < 0.05) between LC levels in seminal plasma with both sperm concentration and plasma and acrosomal membrane integrity. Furthermore, the addition of LC (1 and 2 mM) preserved the motility of equine sperm stored at 5°C. It was concluded that the concentrations of LC with seminal plasma present correlate to semen parameters and the addition of LC to skimmed milk-based extender preserves the motility of equine sperm stored at 5°C for up to 48 hours.

Comparison of cushioned centrifugation and SpermFilter filtration on longevity and morphology of cooled-stored equine semen

This study compares two methods for seminal plasma removal by evaluating sperm recovery rates, and motility and morphology of cooled-stored semen. Ejaculates were divided into three groups: control, filtration and cushioned centrifugation. Semen was extended to 25 million sperm/ml using a skim-milk-based extender and stored at 5°C for all groups. Sperm motility (total motility (%TM) and progressive motility (%PM)) was determined at 0, 24, 48 and 72 hours by a computer-assisted sperm analyser. Sperm morphology was assessed using differential interference microscopy. Overall, %TM of the centrifugation group was significantly higher than the filter group, but not significantly different than the control. No significant difference in %TM or %PM was detected for the control group and filter. Cushioned centrifugation was a superior method to obtain progressively motile sperm compared with control (P=0.03) and filter groups (P<0.001). No significant difference was found for the per cent of normal sperm cells and detached heads between the groups. This study demonstrated that cushioned centrifugation was a superior method to remove seminal plasma while preserving %TM and enhancing %PM for stallions under cooled storage over three days. However, as the differences appear to be negligible, the SpermFilter may represent an alternative for farms lacking a centrifuge.