Period of Boar Ejaculate Collection Contributes to the Yearly Intra-Male Variability of Seminal Plasma Cytokines

Abstract

The concentrations of cytokines in seminal plasma (SP) fluctuate over time in healthy males, weakening their practical usefulness as diagnostic tools. This study evaluated the relevance of intra-male variability in SP cytokines and to what extent the period of the year when ejaculate is collected contributes to such variability. Thirteen cytokines (GM-CSF, IFNγ, IL-1α, IL-1β, IL-1ra, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-18, and TNFα) were measured using the Luminex xMAP® technology for 180 SP samples of ejaculate collected over a year from nine healthy and fertile boars. The SP samples were grouped into two annual periods according to decreasing or increasing daylight and ambient temperature. Intra-male variability was higher than inter-male variability for all cytokines. All SP cytokines showed concentration differences between the two periods of the year, showing the highest concentration during the increasing daylength/temperature period, irrespective of the male. Similarly, some cytokines showed differences between daylength/temperature periods when focusing on their total amount in the ejaculate. No strong relationship (explaining more than 50% of the total variance) was found between annual fluctuations in SP-cytokine levels and semen parameters. In conclusion, the period of the year during which ejaculates were collected helps explain the intra-male variability of SP-cytokine levels in breeding boars.

Measurable Cytokine Concentrations in Pig Seminal Plasma Are Modified by Semen Handling and Storage

“…This may have been caused by the clear differences observed between ejaculates/males in the measured SP concentrations, consistent with previous studies that highlighted clear variability between male breeding pigs in the concentrations of SP cytokines. [ 38 , 39 , 40 ]. Similar high variability in cytokine concentrations was also observed in the SP of healthy men [ 30 , 31 ].…”

“…Only in this way would it be possible to correctly compare results between different clinical trials, since the cut-off concentrations between the physiological and pathological reproductive conditions may differ between storage conditions. Before deciding which condition for SP storage is better, it is important to consider that some cytokines are at very low measurable levels in the SP of healthy boars, as evidenced in this study and others [ 38 , 39 , 40 ]. Therefore, the conditions chosen should be those that guarantee the highest measurable levels for the cytokines of interest.…”

Extracellular vesicles in seminal plasma: A safe and relevant tool to improve fertility in livestock?

“…Surprising? Not really, considering inter-or intra-male variations in composition and relative amounts of these molecules and even the effects of handling (Padilla et al, 2020;Parrilla et al, 2020). Inter-male variation has led to ambiguous statistical relations, either positive or negative (Novak et al, 2010;De Lazari et al, 2020;Kang et al, 2019;Pavaneli et al, 2019;de Andrade et al, 2022).…”

Seminal Plasma: Relevant for Fertility?

“…The evidence gathered via association studies, at least regarding livestock fertility, show for proteins [ 11 , 33 , 35 , 36 , 43 ] or cytokines [ 41 , 70 ] either positive, negative or ambiguous statistical relations. This variation is not surprising, considering inter- or intra-male variations in composition and the relative amounts of these molecules and even the effects of handling [ 43 , 58 , 109 ]. Such variations, together with specific differences in experimental layout, are present among the plethora of contradictory reports [ 36 , 94 , 131 , 211 , 212 ].…”

“…The SP is basically formed by secretions of epithelial cells and thus contains electrolytes, protein and steroid hormones, sugars and proteins/peptides, including enzymes [24]. The relative proportions of these components certainly varies among species, the year [43,58] and the type of ejaculate in question. Classical examples of the latter are when either all components are ejaculated at once (e.g., poultry and ruminants) or in relative different proportions (e.g., humans, stallion, boar, etc.).…”