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Objective: To correlate the Breeding Soundness Evaluation (BSE) of Charolais and Charbray bulls in the warm sub-humid climate and its effect on the pregnancy rate and calving interval of herds to estimate differences between breeds. Design/Methodology/Approach: BSE was carried out on N = 90 Bulls, Charolais (n = 33) and Charbray (n=57), evaluated in situ during the period of 2017 to 2019. Variables for the bull (age, body condition, libido, and scrotal circumference), semen (concentration, motility, and volume), herd (pregnancy rate and calving interval), and environment (rainy and dry season) were analyzed with the one-way ANOVA, Factorial, Multiple regression and Multivariate analysis. Results: Charolais and Charbray bulls show similar results in the BSE (p>0.05) in a warm sub-humid climate. Study Limitations/Implications: Yearly seasons (rainy or dry) do not affect (p<0.05) the BSE rating. Libido is associated (p<0.05) with age (R= -0.42), sperm motility (R=0.67), sperm concentration (R=0.66) and pregnancy rate (R=0.63). Findings/Conclusions: Variables with high association (p<0.05) with pregnancy rate were libido (R=0.63), motility (R=0.60), sperm concentration (R=0.51) and age (R= -0.50); variables with high association (p<0.05) with calving interval were: age (R=0.74) and libido (R=-0.33). Charolais and Charbray bulls show similar reproductive efficiency in herds under a warm sub-humid climate in Veracruz. [ABSTRACT FROM AUTHOR]

With the aim of assessing bull fertility before or during its use for reproduction under tropical weather conditions where heat stress is present, and correlating it to herd parameters, BSE was carried out to determine which genetic groups of bulls have better reproductive performance. 223 bulls from different genetic groups, Zebu bulls (N = 72), European bulls (N = 58), and Crossbred Bulls (N = 93), were evaluated in situ over a two-year period, 2018–2019. Bull (age, corporal conditions, libido, and scrotal circumference), semen (concentration, motility and volume), herd (pregnancy rate and calving intervals) and environmental variables (THI, season, sampling month and spermatogenesis month) were analysed with One-Way ANOVA, as well as with factorial, multiple regression, and multivariate analysis. Zebu and European bulls have a higher libido than crossbreed bulls (p <.05), and it decreases with age (p <.05). High-libido bulls (>7) show high correlation (R = 0.70 p <.05) with herd parameters; BCS affects libido (p <.05). Sperm concentration is correlated to herd parameters (R = 0.82 p <.05). European bull sperm concentration and motility showed a decrease in autumn and winter (p <.05) in comparison to other genetic groups. Libido and semen variables are more associated with herd parameters than with other bull characteristics. Environmental variables are not associated with herd parameters (p >.05). Heat stress did not directly affect bull reproductive performance; Zebu bulls and crossbreeds showed better herd parameters (p <.05). Bull breeding soundness examination and herd proficiency. Herd proficiency of local genetic groups of bulls in tropical conditions. Breeding soundness examination in tropical environment conditions. [ABSTRACT FROM AUTHOR]