Plant-Based Semen Extenders in Aquaculture and Livestock: A Systematic Review of Antioxidant and Antimicrobial Mechanisms with Emphasis on Cucumber-Juice (Cucumis sativus) for Clarias gariepinus in Resource-Limited Settings

Abstract

Bacterial contamination of semen is a recognized cause of reduced sperm function in many vertebrates, but the acute impacts of naturally occurring bacteriospermia on teleost semen under hatchery conditions are inadequately characterized. This study evaluated the short-term effects of indigenous mixed bacterial flora on pooled Clarias gariepinus semen and assessed whether two common dilution ratios (1:1 and 1:2) mitigate bacterial damage.  Pooled semen from six male broodstock was assessed at baseline, immediately following dilution (0 h), and at 3 and 6 h post-dilution during chilled storage (4°C). Sperm motility, viability, and concentration were measured using standard laboratory techniques. Bacterial species present in semen were isolated and identified using culture-based methods and biochemical profiling. Data were analyzed using descriptive statistics with effect size calculations and bootstrap confidence intervals.  Baseline motility and viability were high (77.5% and 74.0%, respectively). Four bacterial species were identified in semen samples: Staphylococcus aureus, Klebsiella sp., Proteus spp., and Serratia sp during the study. By 3 h post-dilution, both dilution groups exhibited complete loss of motility (0%) . Viability declined to 34.0% (1:1 dilution) and 33.0% (1:2 dilution) at 3 h, and further to 12.5% and 10.0% respectively by 6 h. The 1:1 dilution showed a marginal advantage in preserving viability, but neither dilution prevented rapid sperm incapacitation. A positive correlation was observed between fish body weight and testes weight (r = 0.67, bootstrap 95% CI: -0.12 to 0.94).Naturally occurring mixed bacterial contamination rapidly and severely impairs Clarias gariepinus semen during short-term storage. Dilution alone is not protective. The experimental findings emphasize the critical importance of aseptic handling, individual male screening, and development of evidence-based extenders to preserve fertilization capacity in fish hatcheries.