To assess the effects of season and genotype on fresh semen quality for freezing and subsequent use for AI, 32 healthy, mature (>4 to <6 years old) and habituated bulls (Bos indicus n = 14, Bos taurus n = 5, Crossbred taurus x indicus n = 6, and tropically adapted Bos taurus composites n = 7) were evaluated at a Venezuelan AI center for 12 months in which four distinct seasons (Hot-dry, Transition, Hot-humid, Cool-rainy) occur. Ejaculates were collected weekly from Bos taurus (n = 260), Bos indicus (n = 669), tropically adapted Bos taurus composites (n = 389), and crossbred Bos taurus x Bos indicus (n = 340) bulls. Routine AI Center assessments were conducted i.e., ejaculate volume (EV), sperm mass-motility (MM), total sperm number/ejaculate (TSE), sperm concentration/mL (SC), pre-freezing (PREF), and post-freezing minimum criteria rate for AI use (POSTF). Genotype affected EV (P < 0.0001), TSE (P < 0.0001), and SC (P < 0.0001) but not MM (P>0.05). Season affected EV (P < 0.001), TSE (P < 0.0001), SC (P < 0.01), and MM (P < 0.05). There were genotype x season interactions for EV, MM, TSE, and SC. The PREF averaged 74.0% during the study, although was less (P < 0.0001) during the hot-humid season than the other seasons. Even though, percent ejaculates considered unsuitable for freezing differed (P < 0.03) among the Hot-dry (20.2%), transition (30.9%), Hot-humid (32.4%), and Cool-rainy (24%) seasons. For POSTF, there were no seasonal differences (P>0.05). It is concluded that in tropical regions, season and genotype can affect bull semen variables, particularly those which affect the success of semen freezing and AI.

评估季节和基因型对冷冻和随后用于 AI 的新鲜精液质量的影响，32 头健康、成熟（> 4 至< 6 岁）和习惯的公牛（Bos indicus n = 14，Bos taurus n = 5，杂交种）taurus x indicus n = 6 和适应热带的Bos taurus复合材料n = 7) 在委内瑞拉 AI 中心进行了 12 个月的评估，其中发生了四个不同的季节（干热、过渡、湿热、凉雨）。每周从Bos taurus ( n = 260)、Bos indicus ( n = 669)、热带适应Bos taurus复合体 ( n = 389) 和杂交Bos taurus x Bos indicus ( n = 340) 公牛。进行常规 AI 中心评估，即射精量 (EV)、精子质量运动 (MM)、总精子数/射精量 (TSE)、精子浓度/mL (SC)、冷冻前 (PREF) 和冷冻后AI 使用的最低标准率 (POSTF)。基因型影响 EV ( P  < 0.0001)、TSE ( P  < 0.0001) 和 SC ( P  < 0.0001) 但不影响 MM ( P > 0.05)。季节影响 EV ( P  < 0.001)、TSE ( P  < 0.0001)、SC ( P  < 0.01) 和 MM ( P < 0.05)。EV、MM、TSE 和 SC 存在基因型 x 季节相互作用。在研究期间，PREF 平均为 74.0%，尽管 在湿热季节比其他季节要少（P < 0.0001）。尽管如此，被认为不适合冷冻的射精百分比 在干热 (20.2%)、过渡 (30.9%)、湿热 (32.4%) 和凉雨 (24%) 季节之间存在差异 ( P < 0.03)。对于POSTF，没有季节性差异（P > 0.05）。得出的结论是，在热带地区，季节和基因型会影响公牛精液变量，特别是影响精液冷冻和 AI 成功的变量。