Effects of age, season, breed, and sperm counting chamber on boar semen quality variables in tropical conditions

In the porcine industry, male sperm quality plays a relevant role in the productivity and profitability of the productive system in the tropics. Understanding the factors affecting semen quality is important for optimizing male reproductive efficiency. The present study aimed to evaluate the seminal quality associated with season, breed, age, 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. The boars were housed individually in well-ventilated pens and fed a standard breeder mix. The boars were grouped according to age into three categories: <12 months, 12-24 months, and >24 months, and semen doses were collected from each boar during the dry and rainy seasons. Ejaculates with at least 75 % morphologically normal sperm and more than 8.5 x 109 total sperm per ejaculate were used. The semen doses were analyzed using Computer-Assisted Semen Analysis (CASA; ISAS® v1). The results showed that younger boars (<12 months) exhibited higher progressive and total sperm motility and faster swimming patterns than older boars. The estimation of total motility and fast spermatozoa increased during the rainy season. The kinematic variables showed significant differences (P < 0.05) between the sperm counting chambers. The Duroc and Landrace breeds presented spermatozoa with greater total motility, whereas the 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 us to better understand semen quality in boars. This emphasizes the importance of optimizing swine reproductive management practices in sexually active boars.