Onset of reproductive capacity in unowned free-roaming cats

Abstract

Purpose was to investigate if an underlying biological cause exists for the reproductive success in unowned free-roaming (UFR) cats. These cats were presented for surgical sterilization during late summer/early fall. After castration of UFR toms, presence of penile spines was recorded, slides were made from vas deferens secretions for sperm morphology analyses, and testes were hemi-sectioned, formalin-fixed, paraffin-embedded, sectioned, stained with hematoxylin and eosin, and seminiferous tubule diameters were measured. After ovariohysterectomy of UFR queens, total ovarian-uterine weights were recorded. Ovaries were hemi-sectioned, formalin-fixed, paraffin-embedded, sectioned, stained, and follicles were counted. Presence of penile spines did not differ (p = 0.07) between toms 2 - 6 (n = 13) and > 6 months (n = 16). Percentage of normal sperm morphology did not differ (p = 0.39) between toms 2 - 6 (n = 11; 77 ± 11%) and > 6 months (n = 9; 81 ± 13%). Seminiferous tubular diameter increased (p < 0.01) in toms 2 - 2.5 (n = 6; 88.1 ± 10.9 µm), 3 - 4 (n = 6; 109.8 ± 8.9 µm), 5 - 6 (n = 6; 142.2 ± 16.9 µm), and > 6 months (n = 6; 237.9 ± 52.5 µm). There was no association (R2 = 0.20; p = 0.07) between age and total ovarian-uterine weight of queens. Number of primary, secondary, and tertiary follicles recorded did not differ (p = 0.08) between queens 2 - 4 (n = 13) and 5 - 6 (n = 4) months. The largest follicle diameter did not differ (p = 0.14) between queens 2 - 4 (581.6 ± 53.7 µm) and 5 - 6 months (469.4 ± 113.9 µm). Results may explain why UFR cat populations continue to increase despite investments in extensive trap-neuter-return efforts. Selective pressure responses to shortened lifespans may contribute to onset of earlier reproductive capacity in UFR cats.