Semen analysis parameters from a captive population of the endangered Chacoan peccary (Catagonus wagneri) in Paraguay

•First report of semen parameters in the endangered Chacoan peccary.•Testis size, ejaculate volume and ejaculate pH are similar to the collared peccary.•Total number of spermatozoa per ejaculate was low.•Ejaculates contained many morphologically abnormal spermatozoa with poor motility.•Poor semen quality may be inherent to the species or specific to this population. Baseline information about the reproductive physiology of an endangered species is vital to captive breeding programs. This study analyzed reproductive parameters from eleven captive Chacoan peccaries (Catagonus wagneri) (mean age: 10.5 ± 1.2 years old) in Paraguay. After immobilization, testis length, width and firmness (hard to flaccid, 1–3) were assessed, followed by electroejaculation and analysis of semen. Samples were examined for percentage and progressive motility, total cell count, percentage live spermatozoa and morphology. Mean (±SEM) testis volume and firmness were 24.7 ± 1.8 cm3 and 2.1 ± 0.1, respectively. Mean ejaculate volume was 2.9 ± 0.7 ml with a pH of 7.7 ± 0.3. Few male peccaries had motile spermatozoa (n = 5/9) with a mean percentage and progressive motility of 18.3 ± 8.5% and 0.6 ± 0.3, respectively. The mean percentage of live spermatozoa was 25.1 ± 5.6%. Male peccaries had a low percentage of normal spermatozoa (12.4 ± 2.5%). The mean total count of spermatozoa per ejaculate was also quite low at 1.58 ± 1.01 million total spermatozoa per ejaculate. Spermatozoa defects were predominantly primary (77.7%) with the most common spermatozoa defects being tapered head (19.0 ± 7.4%), diadem/crater (17.7 ± 2.8%), and excess residual cytoplasm (9.6 ± 2.5%). Male age was not correlated with semen parameters (percent live: r=-0.19; motility percentage: r = 0.01; percent normal spermatozoa: r = 0.38; total count: r = 0.29; p>0.05). Evaluation of additional males from this population as well as other captive populations at various time points during the year is warranted.