Abstract This study establishes the serological frequency against Neospora caninum on day zero and the presence of N. caninum DNA surveyed throughout the gestation of Bubalus bubalis females in a bovine buffalo system in the central zone of the state of Veracruz, Mexico. Blood samples were taken from 11 females in 6 different sampling periods and analyzed for N. caninum antibodies detection on day zero. DNA detection by PCR was performed on all sampling periods. The gestation months of the females were recorded for five trimesters by ultrasonography, as well as births and pregnancy losses. Recorded seropositivity and positivity for agent DNA were 90.9% (95% CI 58.7-9.7) and 36.3% (95% CI 10.9-69.2), respectively, on day zero. N. caninum DNA was detected between 18.1% (95% CI 2.3-51.7) and 45.4% (95% CI 16.7-76.6) over the five trimesters of observation, with three births and three abortions recorded. The studied water buffalo population had a high presence of N. caninum antibodies; however, the detection of N. caninum DNA remained below 47% in the females. The association was only observed in the detection of DNA with pregnant females (P 0.007). Our results support the hypothesis of the resistance of water buffaloes to infection and the onset of clinical signs against infection by N. caninum even upon a high possibility of infection and reinfection described in this production system in Mexico.

RESUMEN Antecedentes En México la nutria neotrópical (Lontra longicaudis annectens, Olfers, 1818) se encuentra ampliamente distribuida y sus poblaciones están amenazadas. Objetivos Estimar la densidad y abundancia de la nutria de río neotropical en el Sistema Lagunar de Alvarado (SLA), Veracruz. Métodos El SLA tiene una extensión de 51,960.52 hectáreas y está compuesto por lagunas costeras, lagunas interiores y ríos. Por medio de la técnica de muestreo a distancia con transectos sistemáticos, se estimó la distribución, densidad y abundancia de la nutria neotropical en el SLA. Resultados Se obtuvieron un total de 25 avistamientos independientes de nutrias, siendo los ríos Limón, Blanco y Culebrilla donde se registraron con mayor frecuencia. Se estimó una abundancia de 934 (% C.V.= 20.45) nutrias para todo el SLA, con una densidad de 0.179 organismos / km2 (% C.V.= 20.45). Conclusiones Este estudio contribuye a determinar una primera estimación directa de la densidad, para esta especie en una región de México. La importancia de este estudio es la precisión con la que se estima la población de nutrias, lo que permite tener una información más robusta para tomar decisiones y acciones para el manejo y conservación de la especie

ABSTRACT Background In Mexico, the neotropical otter (Lontra longicaudis annectens, Olfers, 1818) is widely distributed, and its populations are threatened. Objectives To estimate the density and abundance of neotropical river otters in the Alvarado Lagoon System (SLA), Veracruz. Methods The SLA has an extension of 51,960.52 hectares and is made up of coastal lagoons, interior lagoons, and rivers. We employed the distance sampling technique with systematic transects to estimate the distribution, density, and abundance of the Neotropical otter in the SLA. Results A total of 25 independent otter sightings were obtained; the Limón, Blanco, and Culebrilla rivers are the areas with the most significant sights. An abundance of 934 (% C.V.= 20.45) otters was estimated for the entire SLA, with a density of 0.179 organisms/km2 (% C.V.= 20.45). Conclusions This study contributes to determining the first direct estimation of density for this species in a region of Mexico. The importance of this study is the precision with which the otter population was estimated, which allows for more robust information to make decisions and to take actions for the management and conservation of the species.

Crossbred dairy cows differ in productive and reproductive traits compared to purebred Holsteins. The objectives of this study were to breed Holstein, Jersey, Montbeliarde and Swedish Red using a breed rotational crossbreeding system and evaluate some productive and reproductive performance. Imported Holstein cows were used H (n = 200) as the basis for crossbreeding. The genetic groups obtained in first lactation were: 1) H (n = 44); 2) F1J (50% Holstein and 50% Jersey, n = 58); 3) F1M (50% Holstein and 50% Montbeliarde, n = 72); 4) HJS (25% Holstein, 25% Jersey and 50% Swedish Red, n = 53). Percentage of cows removed was higher (P = 0.05) in H (15%) than crossbred cows (5%). Days open period was greater (P = 0.03) in H (160.8 ± 21.7) than F1J (108.6 ± 9.5), F1M (121.6 ± 9.1) and HJS (121.6 ± 11.8) Projected calving interval was higher (P = 0.03) in H (443.8 ± 21.7 days) than F1J (388.4 ± 9.4), F1M (401.0 ± 8.8), HJS (402.9 ± 13.7). Holstein cows (10,040.9 ± 232.2 kg) produced more milk (P = 0.0001) than F1J (9.050 ± 161.4), F1M (8,866.0 ± 157.4) and HJS cows (8,856.3 ± 160.0). All variables were similar between the crosses (P = 0.10) Services per conception were similar (P = 0.10) in all groups. In conclusion, crossbred cows, regardless of the genotype, had lower percentage of cows removed from the herd, less days open and calving interval than Holstein. However, Holstein cows produced more milk than crossbreds.

La heterosis en ganado lechero cambia los parámetros productivos y reproductivos comparados con el ganado Holstein puro. El objetivo fue realizar cruzamientos rotativos con Holstein, Jersey, Montbeliarde y Sueco rojo y medir algunos rendimientos productivos y reproductivos. En los cruzamientos se usaron como base, vacas Holstein importadas (H; n = 200). Los grupos genéticos obtenidos de primera lactancia fueron: 1) H (n = 44), 2) F1J (50% Holstein y 50% Jersey; n = 58), 3) F1M (50% Holstein y 50% Montbeliarde; n = 72), 4) HJS (25% H, 25% J y 50% Sueco rojo S; n = 53). El porcentaje de vacas destinadas al rastro fue mayor (P = 0.05) en H (15%) que en las cruzas (5%). El periodo de días abiertos se prolongó (P = 0.03) en vacas H (160.8 ± 21.7), comparadas con las F1J (108.6 ± 9.5), F1M (121.6 ± 9.1) y HJS (121.6 ± 11.8). El intervalo de partos proyectado se incrementó (P = 0.03) en H (443.8 ± 21.7 días), comparado con las cruzas F1J (388.4 ± 9.4), F1M (401.0 ± 8.8), HJS (402.9 ± 13.7). Las vacas H (10,040.9 ± 232.2 kg) produjeron más (P = 0.0001) leche que las F1J (9,050 ± 161.4), F1M (8,866.0 ± 157.4) y HJS (8,856.3 ± 160.0). Todas las variables fueron similares entre las cruzas (P = 0.10). Los servicios por concepción fueron similares (P = 0.10) en todos los grupos. En conclusión, las vacas con heterosis, sin importar el genotipo, tuvieron un menor porcentaje de rastro, días abiertos e intervalo de partos que las Holstein, aunque éstas tuvieron una mayor producción.