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Research Article | 29 Oct 2026

Effects of repeated ejaculation on sperm kinematics, seminal plasma biochemical composition, and protein molecular-weight profiles in tropical Saanen bucks

Annisa Rahmi1,2, Ni Wayan Kurniani Karja3, Mokhamad Fakhrul Ulum3, Syahruddin Said4, Rahadian Pratama5, Abdullah Baharun2, and Raden Iis Arifiantini3 Show more
VETERINARY WORLD | Article No. 34 | pg no. 4857-4873 | Vol. 19, Issue 10 | DOI: 10.14202/vetworld.2026.4857-4873
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ABSTRACT

                      
Background and Aim: Ejaculation frequency is an important consideration in natural mating and semen collection programs because repeated ejaculation may alter seminal plasma composition and sperm function. However, integrated information on these responses in Saanen bucks maintained under tropical conditions remains limited. This study evaluated how repeated ejaculation affects fresh semen quality, sperm kinematics, seminal plasma biochemical components, and protein molecular-weight profiles in tropical Saanen bucks.
Materials and Methods: Six Saanen bucks aged 2–3 years underwent a 7-day sexual rest period before semen collection. Five successive ejaculates (E1–E5) were collected from each buck within a single day, yielding 30 ejaculates. Fresh semen quality was assessed using standard laboratory procedures, and sperm motility and kinematics were evaluated using computer-assisted sperm analysis. Seminal plasma biochemical components were quantified spectrophotometrically, whereas protein molecular-weight fractions were characterized using one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Associations between ejaculation frequency and semen or biochemical variables were evaluated using Pearson’s correlation analysis.
Results: Ejaculation frequency did not affect most conventional semen quality parameters, including total and progressive motility, sperm viability, plasma membrane integrity, and acrosome integrity (p > 0.05), whereas semen pH differed significantly (p < 0.05). Among sperm kinematic variables, distance, average path, and amplitude of lateral head displacement differed significantly, while velocity-related parameters remained relatively stable. Five major seminal plasma protein fractions of approximately 15, 20, 30, 35, and 50 kDa were identified, with the approximately 15-kDa fraction showing the greatest relative abundance. Ejaculation frequency was negatively correlated with semen color (r = −0.488, p = 0.005), total protein (r = −0.945, p = 0.015), albumin (r = −0.964, p = 0.008), cholesterol (r = −0.937, p = 0.019), and triglycerides (r = −0.969, p = 0.006).
Conclusion: Repeated ejaculation up to five times within a day largely preserved conventional fresh semen quality in tropical Saanen bucks but was associated with changes in sperm movement characteristics and marked reductions in key seminal plasma biochemical components. These findings indicate that seminal plasma composition may be more sensitive than conventional semen traits to increased ejaculation frequency and should be considered when optimizing breeding and semen collection schedules.
                      
Keywords: ejaculation frequency, seminal plasma biochemistry, seminal plasma proteins, sperm kinematics, sperm motility, sperm quality, Saanen bucks, tropical environment.