Understanding the factors affecting semen quality is important for optimizing male reproductive efficiency. The present study aimed to evaluate the seminal quality associated with breed, age, season, and sperm counting chamber in boar ejaculates. A total of 22 sexually mature and healthy boars from maternal and sire commercial breeds were utilized as semen donors, with an average age (mean ± standard deviation) of 21.0 ± 7.2 months. Boars were housed individually in well-ventilated pens and fed a standard breeder mix. Semen samples were collected from each boar in dry and rainy season. The boars were grouped according to age into three categories: <12 months, 12-24 months, and >24 months. Only ejaculates with at least 75 % morphologically normal sperm and more than 8.5 x 109 total sperm per ejaculate were used. The samples were analyzed using the Computer-Assisted Semen Analysis (CASA) ISAS®v1 system. Results showed that younger boars (<12 months) exhibited higher total and progressive sperm motility and faster swimming patterns compared to older boars. The percentages of total motility and fast spermatozoa were increased by rainy season. The kinematics variables showed significant differences (P<0.05) between sperm counting chambers. Duroc and Landrace breeds presented spermatozoa with greater total motility, while terminal sire line breeds showed accelerated linear progressiveness (P<0.05). Overall, the impact of various factors on seminal and kinematic variables in boar ejaculates, including age, season, genetic breed composition, and sperm counting chamber enables to better understand the semen quality of boar ejaculates. This highlights the importance of optimizing swine reproductive management practices in sexually active boars.

[Objetive] The objective of the present study was to characterize different sperm subpopulations based on morphometric parameters of frozen-thawed semen in two bovine subspecies using a CASA system. [Methodology] The experiment was carried out at the Costa Rica Institute of Technology from May to December 2023. Spermatozoa from 10 bulls (five animals of each species Bos taurus and Bos indicus) were evaluated after thawing of the semen doses by an ISAS^®v1, computer-assisted sperm analysis (CASA)-Morph system. Sub-populations of head morphometric spermatozoa were characterized using multivariate procedures such as principal components (PCs) analysis and clustering methods (k-means model) [Results] The ejaculate of male exhibits significant heterogeneity and comprises diverse sperm subpopulations with differing morphometric patterns. Three different sperm subpopulations were identified from three PCs: t head size, head shape, and symmetry of the sperm head and the degree to which it was pyriform. The proportions of the different sperm subpopulations varied in the two-bovine subspecies; Bos taurus and Bos indicus. Results indicated that subpopulations SP1, SP2, and SP3 were different for PC criteria and these differences were relevant. The variability in sperm morphometry assessments underscores the need to standardize semen evaluation protocols [Conclusions] These findings highlight the importance of knowing the diversity in sperm morphometry between subspecies to both improve in vitro evaluation tests and to distinguish subspecies.