Accurate prediction of pregnancy following fixed-time artificial insemination (FTAI) remains challenging under commercial goat production conditions. This study compared multivariable logistic regression and Random Forest models for pregnancy prediction and used SHAP analysis to characterize predictor contributions. Data from 920 goats subjected to FTAI across four regions of Peru were analyzed using reproductive, hormonal, animal-level, and management variables. Logistic regression was developed after univariable screening, whereas Random Forest models used 500 trees with mtry values of 2, 3, and 4. Models were compared using stratified 10-fold cross-validation with identical folds. The mtry = 4 configuration yielded the highest Random Forest AUC. Logistic regression identified semen type, buck and doe breed, insemination site, and cervical mucus score as independent predictors. Chilled semen was associated with higher pregnancy odds, whereas superficial cervical insemination was associated with lower odds. Logistic regression outperformed Random Forest in discrimination (AUC, 0.761 vs. 0.654), accuracy (0.679 vs. 0.644), and specificity (0.882 vs. 0.782), whereas Random Forest showed higher sensitivity (0.369 vs. 0.278). SHAP analysis identified eCG dose, cervical mucus score, semen type, and insemination site as the most influential predictors. Overall, logistic regression provided superior and more consistent predictive performance, whereas Random Forest offered complementary sensitivity and captured nonlinear predictor contributions. These findings support logistic regression as the more effective predictive approach for pregnancy following FTAI under the conditions studied, with explainable machine learning providing complementary insight into prediction patterns.

Goat sperm cryopreservation remains a major challenge because freeze-thaw procedures induce structural and functional damage that compromises post-thaw sperm quality. Although antioxidant supplementation has been widely investigated to reduce oxidative stress, its effectiveness remains inconsistent and may depend on the cryopreservation protocol. This study was conducted in two phases. In Phase 1, three antioxidants-ascorbic acid (2.5, 5.0 and 10.0 mg/mL), cysteamine (50, 100 and 200 μM), and glycine (5, 10 and 20 mM)-were screened using semen from six bucks (three Alpine-French and three Murciano-Granadina). Post-thaw assessments via the AndroVision® CASA system (Minitube, Germany; software version 0.26), viability (eosin-nigrosine staining), plasma membrane integrity (HOST), and thermoresistance test (TTR) revealed no statistically significant effects of antioxidant treatment on motility and kinematic parameters (P > 0.05). However, numerical differences favored glycine at 20 mM, which yielded the highest estimated marginal means for total motility (60.35 ± 3.51%), progressive motility (59.97 ± 3.55%), and fast motility (47.74 ± 3.98%), surpassing the control group. The TTR proved more discriminative: ascorbic acid at 10.0 mg/mL produced the most severe decline, whereas cysteamine at 100 μM achieved the highest values among treated groups. In Phase 2, glycine at 20 mM-selected for its numerically favorable kinematic profile-was validated in an independent experiment comparing two cryopreservation protocols: Programmable and Manual. Evaluations included CASA motility and kinematic parameters, plasma membrane integrity, acrosome integrity, mitochondrial activity, thermoresistance test, cold shock resistance test, and gene expression analysis (SOD1, HSP70, CAT). Results demonstrated that the cryopreservation protocol exerted a significantly greater effect than antioxidant supplementation. The manual protocol consistently produced superior values for total motility, progressive motility, fast motility, kinematic parameters (VCL, VAP, VSL, BCF, ALH, HAC), acrosome integrity, and cold shock resistance (P < 0.05). In contrast, glycine supplementation at 20 mM did not significantly affect any evaluated parameter (P > 0.05), nor did the Protocol × Antioxidant interaction. Relative expression of SOD1, HSP70, and CAT did not differ between protocols, treatments, or their interaction (P > 0.26). Overall, these findings indicate that, under the conditions evaluated, optimization of the cryopreservation protocol had a greater impact on post-thaw sperm functional quality than glycine supplementation, highlighting the importance of optimizing cryopreservation procedures before evaluating antioxidants as complementary strategies.