Title:	Decoding bull fertility under tropical conditions: multivariate predictive modelling from 25,512 field spermiograms.
Authors:	FASSANO, C. J. LIMA, P. H. L. de SOUZA, F. A. LARA, N. S. de BERGSTEIN-GALAN, T. G. NOGUEIRA, E. KOZICKI, L. E.
Affiliation:	CLOVIS JUK FASSANO, PONTIFÍCIA UNIVERSIDADE CATÓLICA DO PARANÁ; PEDRO HENRIQUE LOMBA DE LIMA, PONTIFÍCIA UNIVERSIDADE CATÓLICA DO PARANÁ; FERNANDO ANDRADE SOUZA, UNIVERSIDADE FEDERAL DO PARANÁ; NATALIA SIQUEIRA DE LARA, UNIVERSIDADE FEDERAL DO PARANÁ; TÁCIA GOMES BERGSTEIN-GALAN, UNIVERSIDADE FEDERAL DO PARANÁ; ERIKLIS NOGUEIRA, CNPGC; LUIZ ERNANDES KOZICKI, PONTIFÍCIA UNIVERSIDADE CATÓLICA DO PARANÁ.
Date Issued:	2026
Citation:	Reproduction in Domestic Animals, v. 61, e70190, 2026.
Pages:	16 p.
Description:	ABSTRACT - This large-scale study evaluated 25,512 Nellore bulls raised under tropical field conditions to elucidate multivariate determinants of breeding soundness and to derive a data-driven risk stratification framework based on BSE outcomes. Macro- and microscopic semen traits (e.g., progressive motility, sperm morphology including major defects, scrotal circumference, vigour and mass activity), recorded clinical alterations and epidemiological factors (age and seasonality) were integrated using multivariable modelling and internal validation. Logistic regression identified progressive motility, proportion of major defects and scrotal circumference as independent predictors of BSE-based unfitness, with a cross-validated ROC AUC of 0.84 (95% CI 0.83–0.85), indicating high discriminative performance. Principal component and clustering analyses revealed three reproducible phenotypic profiles (optimal, intermediate and critical) combining functional, morphological and anatomical attributes. These components were synthesised into a Breeding Soundness Risk Index (BSRI) showing consistent calibration and stability under five-fold crossvalidation, enabling objective stratification of bulls by probability of BSE-based unfitness. Advancing age and seasonal heat load were associated with increased odds of BSE-based unfitness, consistent with cumulative thermal and physiological stress under tropical management. Collectively, these results support progressive motility, major sperm defects and scrotal circumference as cornerstone indicators of breeding soundness in large-scale field settings, and the BSRI provides an objective, field-applicable score to support sire selection and management decisions under tropical conditions
Thesagro:	Esperma Fertilidade Gado Nelore Inseminação Artificial
NAL Thesaurus:	Artificial insemination Beef cattle Breeding soundness Bulls Multivariate analysis Nellore Sperm motility
ISSN:	1439-0531
DOI:	https://doi.org/10.1111/rda.70190.
Type of Material:	Artigo de periódico
Access:	openAccess
Appears in Collections:	Artigo em periódico indexado (CNPGC)