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 ¼ 72), European bulls (N ¼ 58), and Crossbred Bulls (N ¼ 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 ¼ 0.70 p < .05) with herd parameters; BCS affects libido (p < .05). Sperm concentration is correlated to herd parameters (R ¼ 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). HIGHLIGHTS 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.

Objetivo: El objetivo fue analizar el costo del Intervalo Interparto (IIp) en la producción de ganado vacuno del sureste de México, y predecir las posibles pérdidas económicas en las granjas tropicales. Diseño/metodología/aproximación: Se analizaron granjas tropicales correspondientes a 1,200 bovinos de las razas: Simmental, Simbrha, Brahman y cruzas F1, en pastoreo. Se utilizó el ANOVA unidireccional para comparar los costos entre las razas. La regresión lineal se utilizó para obtener la relación entre la edad de la vaca y el IIp. Resultados: El costo de un día sin preñez alcanzó los US $ 0,99 (± 0,05), y una vaca que no parió durante un año representó una pérdida, para el productor, de US $359.00 (± 11,72), en relación con los costos de producción. Limitaciones del estudio/implicaciones: Los ingresos obtenidos de la venta de un becerro al destete y la leche generada, ascendieron a US $734.10 (± 16.98) dólares. Hallazgos/conclusiones: No se encontraron diferencias significativas entre las razas (p <0.05) y el IIp, sin embargo, hubo una relación positiva (r = 0.9326, r2 = 0.8698, p <0.05) entre el IIp y el incremento de la edad de la vaca.

El objetivo fue realizar una evaluación económica de la eficiencia reproductiva y productiva en unidades de producción (UP) con bovinos criollos de Nunkiní en Campeche, México. Se evaluó en 10 UP la tasa de gestación, intervalo interparto, natalidad, becerros destetados, ingresos y rentabilidad. Las UP mostraron baja eficiencia reproductiva (tasa de gestación de 41.0% ± 1.95%), elevado intervalo interparto (577.0 d ± 3.64 d), bajos índices de natalidad (37.7% ± 2.03%), becerros destetados (75.40% ± 39.30%), ingresos de USD 1359.17 (p > 0.05), y una estructura de costos fijos y variables de USD 850.57 y USD 1750.58. Las secciones con mayor impacto en los costos fueron la alimentación (34.14%) y mano de obra (30.38%), los cuales afectaron de manera negativa la rentabilidad (-48.28%). En conclusión, las UP evaluadas presentaron una baja rentabilidad como consecuencia de la baja eficiencia reproductiva y productiva del pie de cría.

Cattle production plays an important role in economic development and food security. Developed countries have achieved optimum levels of production through the implementation of technologies that have allowed efficient use of resources. In contrast, in the developing countries, despite their suitable means of production, such as large tracts of land dedicated to livestock, and programs of nutrition and health, farmers have not widely adopted reproductive and productive supplementation. Therefore, this chapter explores the main critical factors that limit the transfer of technology in bovine production systems, analyzing the interaction between the models, actors, and means of production.

Objective: To correlate the Breeding Soundness Evaluation (BSE) of Charolais andCharbray bulls in the warm subhumid climate and its effect on the Pregnancy rate andCalving 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 2017 to 2019. Bull (age, body condition, libido, and scrotal circumference), Semen (concentration, motility, and volume), Herd (Pregnancy rate and Calving interval) and environment variables (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&gt;0.05) in awarm subhumid climate.Limitations/implications: Year season (Rainy or Dry) do not affect (p&lt;0.05) the BSErating. Libido is associated (p&lt;0.05) with age (R=-0.42), sperm motility (R=0.67), spermconcentration (R=0.66) and pregnancy rate (R=0.63). Findings/conclusions: Variables with high association (p&lt;0.05) with pregnancy ratewere libido (R=0.63), motility (R=0.60), sperm concentration (R=0.51) and age (R=-0.50); variables with high association (p&lt;0.05) with calving interval were: age (R=0.74)and libido (R=-0.33). Charolais and Charbray bulls show similar reproductive efficiencyin herds under a warm subhumid climate in Veracruz.