Resumen El objetivo fue el ajuste de un modelo no lineal (MNL) para evaluar la curva de crecimiento en bovinos Limousin, en pureza de raza (PRZ) y cinco grados de cruzamiento (GPZ; 1/2, 3/4, 7/8, 15/16, 31/32 de Limousin). Se analizó el peso vivo, el intervalo de peso al nacer a 500 días de edad. Se evaluaron cuatro MNL: Brody, Bertalanffy, Gompertz y logístico. Se estimaron parámetros de crecimiento: peso adulto (PAD); tasa de crecimiento (TAC); edad (EPI; meses) y peso (PPI; kg) al punto de inflexión; edad (meses; E50M) para alcanzar 50% de madurez y madurez a 15 meses (GM15). Con el MNL seleccionado en PRZ se caracterizó la curva de crecimiento en GPZ. El modelo de mejor ajuste fue Bertalanffy. El PAD para machos PRZ fue 566.1, para GPZ estuvo en el intervalo de 446.9 a 527.4; para hembras, en GPZ estuvo en el intervalo de 374.5 a 419.9, en PRZ fue 443.0. Los MNL presentaron correlaciones por debajo de -0.75 entre PAD y TAC. En vaquillas de PRZ, EPI se estimó a 3.7 con 131.2 para PPI; en GPZ, EPI y PPI estuvieron en los intervalos de 2.9 a 3.7 y 110.9 a 124.4, respectivamente. E50M para hembras, en PRZ fue a 10.6 y para GPZ en el intervalo de 8.9 a 10.5. GM15 para hembras, en GPZ el promedio fue 90.5 % en PRZ fue de 87.9 %. Los machos en PRZ alcanzan E50M a partir de 13 meses.

Abstract The objective was to fit a non-linear model (NLM) to evaluate the growth curve in purebred (PB) Limousin cattle and in five degrees of crossbreeding (DCBs: 1/2, 3/4, 7/8, 15/16, 31/32 Limousin). Live weight, the birth weight interval at 500 d of age, was analyzed. Four NLMs were evaluated: Brody, Bertalanffy, Gompertz, and logistic. Growth parameters were estimated: adult weight (ADW); growth rate (GR); age (AIP; months) and weight (WIP; kg) at inflection point; age (months; A50M) to reach 50 % maturity and degree of maturity at 15 mo (DM15). The growth curve in DCB was characterized using the NLM selected for BP. The best-fitting model was Bertalanffy. The ADW for purebred (PB) males was 566.1, for crossbred (CB) males it was in the range of 446.9 to 527.4; for CB females it was in the range of 374.5 to 419.9, and for PB females, it was 443.0. The NLMs exhibited correlations below -0.75 between ADW and GR. In PB heifers, AIP was estimated at 3.7, and WIP, at 131.2; in CB heifers, AIP and WIP were in the ranges of 2.9 to 3.7 and 110.9 to 124.4, respectively. A50M for PB females was 10.6, and for CB females, within the range of 8.9 to 10.5. DM15 for CB females, the average was 90.5 %, and 87.9 % for PB females. PB males reach A50M at the age of 13 mo.

ABSTRACT The aim of this study was to compare the productive performance and profitability of the fattening of Kathadin male and female lambs (n=97) in confinement treated with Zeranol (ZNL), androgens (AND) and ZNL+AND under a 2x4 factorial design. The lambs treated with ZNL received 0.2 mg/kg of body weight (BW) every 28 d, those treated with AND received Nandrolone Decanoate + Trenbolone + Boldenone Undecinelate, via IM in doses of 0.3 mg/kg + 0.4 mg/kg + 0.3 mg/kg of BW, respectively, every 28 d, those treated with ZL+AND received the same doses of the mentioned drugs, while those in the control group received 0.5 ml of saline solution. Final body weight (FBW), daily weight gain (DWG), feed conversion (FC) on dry basis (DM) and wet basis (WM), and voluntary intake (VC) in DM and WM were evaluated. The FBW was different (p<0.05) between treatments in males and females. The DWG was higher (p<0.05) for females treated with AND compared to those treated with ZNL and AND+ZNL, being the latter similar to those of the control group. Females treated with AND registered a lower (p<0.05) VC compared to those treated with ZNL and AND+ZNL. Net utility, benefit: cost ratio and profitability were better in animals treated with AND. The administration of AND represents a viable alternative to make more efficient the confinement fattening systems of lambs.

RESUMEN El objetivo del estudio fue comparar el desempeño productivo y la rentabilidad de una engorda de corderos machos y hembras Kathadin (n=97) en confinamiento tratados con Zeranol (ZNL), andrógenos (AND) y ZNL+AND bajo un diseño factorial 2x4. Los corderos tratados con ZNL recibieron 0.2 mg/kg de peso vivo (PV) cada 28 d, los tratados conAND recibieron Decanoato de nandrolona + Trembolona + Undecinelato de boldenona, vía IM en dosis de 0.3 mg/kg + 0.4 mg/kg + 0.3 mg/kg de PV, respectivamente, cada 28 d, los tratados con ZL+AND recibieron las mismas dosis de los fármacos mencionados, en tanto que los del grupo control recibieron 0.5 ml de solución salina. Se evaluó el peso vivo final (PVF), ganancia diaria de peso (GDP), conversión alimenticia (CA) en base seca (BS) y base húmeda (BH), y el consumo voluntario (CV) en BS y BH. El PVF fue diferente (p<0.05) entre tratamientos en hembras y machos. La GDP resultó mayor (p<0.05) para hembras tratadas con AND en comparación con las tratadas con ZNL y AND+ZNL, siendo las últimas similares a las del grupo control. Las hembras tratadas con AND registraron un menor(p<0.05) CV en comparación con las tratadas con ZNL y AND+ZNL. La utilidad neta, relación beneficio: costo y rentabilidad fueron mejores en los animales tratados con AND. La administración de AND representa una alternativa viable para hacer más eficiente los sistemas de engorda de corderas y corderos en confinamiento.

Abstract: The aim was to evaluate the post-weaning growth of Pelibuey lambs under different types of feeding, considering the cost-benefit ratio (RCB) and profitability. Thirty lambs of 13.14 ± 2.87 kg and 60 days old were used, individual housing, for a period of 49 days. Three feedstuffs were evaluated: Starter (I), Weaning and growing (DyD), and I plus DyD, in a ratio of 50: 50% (I+DyD), with 10 repetitions each. ANOVA was used to evaluate the effect of the type of feeding on daily weight gain (GDP), daily feed consumption (COA), feed conversion (CA) and final weight (PF). Except for CA (P < 0.05), the type of feeding did not significantly affect PF, GDP and COA (P > 0.05). The RCB and profitability were slightly higher with feed I+DyD compared to I and DyD. In conclusion, I+DyD was productive and economically more profitable than I and DyD.

Resumen: El objetivo fue evaluar el crecimiento post-destete de corderos Pelibuey bajo diferentes tipos de alimentación, considerando la relación costo-beneficio (RCB) y la rentabilidad. Se utilizaron 30 corderos de 13.14 ± 2.87 kg y 60 días de edad, alojados individualmente, por un periodo de 49 días. Se evaluaron tres alimentos: Iniciador (I), Destete y Desarrollo (DyD), e I más DyD, en proporción de 50:50% (I+DyD), con 10 repeticiones cada uno. Se usó ANOVA para evaluar el efecto del tipo de alimentación sobre la ganancia diaria de peso (GDP), el consumo diario de alimento (COA), la conversión alimenticia (CA) y peso final (PF). Excepto para CA (P < 0.05), el tipo de alimentación no afecto PF, GDP y COA (P > 0.05). La RCB y la rentabilidad fue mayor con el alimento I+DyD en comparación con I y DyD. El tratamiento I+DyD fue más productivo y económicamente más rentable que I y DyD.

ABSTRACT This study aimed to evaluate the lactation curve of female Murrah buffaloes, using mixed nonlinear models (NLM), across three lactation periods (180 d, 210 d, and 240 d). A total of 5334 data on daily milk production (kg) were analyzed. The data were collected every seven days in the interval of one to 250 days of lactation, corresponding to 221 lactations and 145 females, with calvings from 2017 to 2019. The data came from a herd located in the Centro municipality, Tabasco, Mexico. Five NLM were evaluated: Wood (WOD), Wiltmink (WIL), Cobby (COB), Brody (BRO), Sikka (SIK). The best fit model was selected based on the mean prediction error, mean absolute percentage error (MAPE), prediction error variance, coefficient of determination (R2), concordance correlation coefficient (CCC), Akaike (AIC) and Bayesian (BIC) information criteria. A regression analysis was performed between the observed and predicted values. All the NLM had a R2 above 0.91. They tend to underestimate the predictions, without residual autocorrelation. The MAPE showed an average value of 23.5%. The best fit model was WOD, followed by SIK and BRO. For WIL and COB, the mixed model did not improve the fitting. The shortest lactation period showed the best fit, followed by the 210 d and 240 d periods. The relationship between observed:predicted values fluctuated from 0.65 to 1.00, with an average value of 0.94. The use of NLM transcended in the AIC and BIC. The evaluated models showed goodness of fit, with good predictability, but low values in accuracy and precision of prediction.

Abstract Preweaning growth of lambs and ewe productivity are vital indicators of sheep production system success. An evaluation was done of the effects of birth season and year, birth type, sex and parturition number on preweaning growth and ewe productivity in Pelibuey sheep in a semi-extensive system in the humid tropics of Mexico. Data were from the production records of 323 ewes over a 7-yr period (2011-2017). Birth weight (BW), weaning weight (WW, at 60 d) and litter weight at weaning (LWW) were evaluated. Other evaluated factors included ewe prolificacy, preweaning mortality and lamb weight per ewe in a 240-d cycle (LW240d). All the factors affected (P≤0.05) the response variables. Lambs from multiple births had lower (P<0.05) BW and WW, but higher (P<0.05) LWW, LW240d, and mortality than lambs from single births. Lambs born in the dry season had higher (P<0.05) BW and WW, and ewes had higher LWW and LW240d, than in other seasons. Compared to multiparous ewes (≥3 parturition), primiparous ewes had lighter lambs (P<0.05) at birth and weaning, as well as lower (P<0.05) prolificacy, LWW and LW240d. Birth year affected (P<0.05) BW, WW, mortality and productivity characteristics. Preweaning growth performance was best in lambs born from multiparous sheep with a single parturition in the dry season. However, ewe productivity was highest in the dry season in multiparous ewes with two parturitions a year.

Resumen El objetivo fue evaluar los efectos de época y año de nacimiento, tipo de parto, sexo y número de parto sobre el crecimiento predestete y la productividad de las ovejas en ovinos de raza Pelibuey que producen bajo un sistema semi-extensivo en el trópico húmedo de México. Se usaron datos de 323 ovejas Pelibuey a partir de registros de producción de 2011-2017. Se evaluaron los pesos al nacimiento (PN) y al destete (PD, a 60 d), así como los pesos de camada al destete (PCD). Adicionalmente, se evaluó prolificidad, mortalidad hasta el destete y kilos de cordero producido por oveja en un ciclo de 240 días (PC240d). Todos los factores afectaron (P≤0.05) las variables de respuesta. Los corderos procedentes de partos múltiples tuvieron menor (P<0.05) PN y PD, pero mayor (P<0.05) PCD, PC240d y mortalidad que los corderos procedentes de partos simples. Los corderos nacidos en época de seca tuvieron mayores (P<0.05) PN y PD, mientras que las ovejas tuvieron mayores PCD y PC240d, comparado con otras épocas del año. Las ovejas primíparas tuvieron corderos más livianos (P<0.05) al nacimiento y al destete, así como menor (P<0.05) prolificidad, PCD y PC240d que las ovejas multíparas (≥3 partos). El año de nacimiento afectó (P<0.05) PN, PD, tasa de mortalidad y características de productividad. En conclusión, se observó un mejor desempeño en el crecimiento predestete para corderos Pelibuey nacidos de ovejas multíparas y con parto simple en la época de seca. Sin embargo, la productividad de la oveja fue mejor con la presencia de partos dobles, en tiempo de sequía, y con el aumento en número de partos.

Abstract This study aimed to determine the frequency for the seizure of livers with damages attributed to the presence of Fasciola sp. and associated risk factors. It was conducted a prospective observational study with daily visits, for 12 months, to a municipal slaughterhouse in the Sierra area in the state of Tabasco. Of the seized livers, 25.8 % tested positive for the parasite presence; seizure was the same in male and female animals (X2= 0.011, gl= 1, P<0.05). The highest proportion of seized livers was observed during the rainy season (9.36 %). This study concludes that the prevalence of fascioliasis in the Jalapa area has not decreased in recent years and is related to animal origin. Fascioliasis is a disease that must be monitored to detect the factors that allow it to remain in a geographic region, in order to establish and propose strategic control and preventive measures adapted to the particular conditions of endemic areas.

Resumen El objetivo fue determinar la frecuencia por decomiso de hígados con daños atribuidos a la presencia de Fasciola sp y los factores de riesgo asociados. Se realizó un estudio prospectivo observacional en el que se efectuaron visitas diarias durante un periodo de 12 meses, a un rastro municipal en la zona Sierra del estado de Tabasco. El 25.8 % de los hígados fueron positivos a la presencia del parásito, siendo el decomiso por sexo igual para machos y hembras (X2 = 0.011, gl= 1, P<0.05). La mayor proporción de decomiso, se concentró en la época de lluvias (9.36 %). Se concluye que la prevalencia de la fasciolosis en la zona de Jalapa no ha disminuido en los últimos años y está relacionada con el origen del animal. La fasciolosis es una enfermedad que debe ser monitoreada para detectar los factores que permiten su permanencia en una región geográfica, con el fin de poder establecer y plantear medidas estratégicas de control y de prevención adaptadas a las condiciones particulares de las zonas endémicas.

ABSTRACT: The objective of the study was to evaluate productivity variables in the preweaning period of Pelibuey (n = 28) and Katahdin (n = 21) ewes kept under humid tropic production conditions. The ewes were placed together with their offspring in individual pens from lambing to weaning. Preweaning dry matter consumption (DMC) and weaning productivity did not differ (p > 0.05) between breeds, but the Pelibuey ewes had greater (p < 0.05) weight loss than the Katahdin ewes (-3.01 vs 0.76 kg). Double-birth ewes showed greater (p < 0.05) weight loss (0.46 kg vs. -2.70 kg), preweaning DMC (1.91 vs 2.17 kg day-1) and weaning productivity. The weaning productivity of the Pelibuey and Katahdin ewes is similar under humid tropic conditions, although the Pelibuey ewes lost more weight. The number of lambs at birth improved productivity in Pelibuey and Katahdin ewes.

RESUMEN: El objetivo del estudio fue evaluar variables de productividad en el periodo pre-destete de ovejas Pelibuey (n = 28) y Katahdin (n = 21) mantenidas en condiciones de producción del trópico húmedo. Las ovejas se colocaron junto con sus crías en corrales individuales del parto al destete. El consumo de materia seca (CMS) pre-destete y la productividad al destete no difirió (p > 0.05) entre razas, pero las ovejas Pelibuey tuvieron mayor (p < 0.05) pérdida de peso que las ovejas Katahdin (-3.01 vs 0.76 kg). Las ovejas de parto doble presentaron mayor (p < 0.05) pérdida de peso (0.46 kg vs. -2.70 kg), CMS pre-destete (1.91 vs 2.17 kg día-1) y productividad al destete. La productividad al destete de las ovejas Pelibuey y Katahdin es similar bajo las condiciones de trópico húmedo, aunque las ovejas Pelibuey perdieron mas peso. El número de corderos al parto mejoró la productividad en las ovejas Pelibuey y Katahdin.

Resumo Fungos nematófagos das fezes de búfalo de água e do solo no sudeste do México foram isolados, e a atividade predatória in vitro contra larvas infectantes de Haemonchus contortus (L3) (HcL3) foi avaliada.Os fungos foram isolados por aspersão de solo e de fezes em placas de agar água. Foram preparadas seis séries de 10 placas de Petri contendo uma cultura de 7 dias de idade de cada fungo e uma série sem fungos como controle. Quinhentos HcL3 foram adicionadas a cada placa. As placas foram incubadas à temperatura ambiente. O número médio de HcL3 recuperadas foi considerado para estimar a taxa de redução larval. Quatro isolados de fungos nematófagos corresponderam a Arthrobotrys oligospora, var microspora (estirpes 4-276, 269 e 50-80) e um isolado identificado como A. oligospora, var. oligospora (isolados 48-80 de fezes de búfalo de água. Do solo, dos cinco isolados três corresponderam a A. musiformis (Bajío, Yumca e Macuspana isolados), e dois isolados foram identificados como A. oligospora (isolados de Comalcalco e Jalapa de Méndez). A atividade predatória de isolados de fezes de búfalo de água variou entre 85,9 e 100%. Enquanto isso, os fungos do solo variaram entre 55,5 e 100% (p≤0,05). Os fungos nematófagos obtidos podem ter importantes implicações nesse controle de parasitos de importância na indústria pecuária.

Abstract Nematophagous fungi from the feces of water buffalo and soil from southeastern Mexico were isolated, and their in vitro predatory activity against Haemonchus contortus infective larvae (L3) (HcL3) was assessed. The fungi were isolated by sprinkling soil or feces on water agar plates. Six series of 10 Petri dishes containing a 7-day-old culture of each fungus and a series without fungi as the control were prepared. Five hundred HcL3 were added to each plate. The plates were incubated at room temperature. The average of recovered HcL3 was considered to estimate the larval reduction rate. Four nematophagous fungi isolates corresponding to Arthrobotrys oligospora, var microspora (strains 4-276, 269 and 50-80) and one identified as A. oligospora,var. oligospora (isolates 48-80) were obtained from water buffalo feces. From the soil, five isolates were isolated; three corresponded to A. musiformis (Bajío, Yumca and Macuspana isolates), and two isolates were identified as A. oligospora (Comalcalco and Jalapa de Méndez isolates). The predatory activity of isolates from water buffalo feces ranged between 85.9 and 100%. Meanwhile, the fungi from the soil ranged between 55.5 and 100% (p≤0.05). The nematophagous fungi obtained could have important implications in the control of parasites of importance in the livestock industry.

ABSTRACT We evaluated the effect of some environmental factors on age at first lambing (AFL) and lambing to conception interval (LCI) of Pelibuey ewes under the humid tropical conditions of Mexico. Ewes grazed on Tanzania (Panicum maximum), Bermuda (Cynodon dactylon), and Brachiaria grass (Brachiaria humidicola) and received hay in the corral in the months of grass scarcity. Reproduction was continuous during the year. Data of 839 lambings from 334 ewes registered from 2009 to 2017 were analyzed using survival analysis procedures. The statistical model for AFL included the effects of year, season, and litter size at lambing, whereas that for LCI included year and season plus parity number of ewe and litter size at weaning. The overall means ± SD for AFL and LCI were 551.6±144.8 and 145.4±113.1 days, and their medians were 510 and 98 days, respectively. Only year of lambing had a significant effect on AFL, whereas LCI was affected by year, parity number, and litter size at lambing (P<0.05). Both AFL and LCI means did not show any trend with advancing years. The largest AFL and LCI means and medians corresponded to the first-parity ewes. In addition, single birth ewes had the longest LCI means and median. Therefore, year of lambing affects AFL, whereas year of lambing, parity number, and litter size at weaning affect LCI of Pelibuey ewes, indicating that these factors should be considered in the development of sound strategies to improve sheep production.

The genetic study on sheep breeds with naturally high ovulation rate (OR) and prolificacy, has allowed to detect the participation of several genes. Among them there are the ones related to the transforming growth factor-beta superfamily (BMPRIB, GDF9 and BMP-15), as well as to other genes with major effect, such as the distal-less homeobox 3' (FecL), estrogen receptor (ESR), prolactin receptor (PRLR) and inhibin receptor (INHA and INHB). However, sheep homozygous for the majority of the allelic variants in BMP-15 or GDF9 are sterile, for which it is important the understanding of the genetic and molecular basis of these polymorphisms, for their use in rational programs of genetic improvement on prolificacy. Polymorphism in the melatonin gene (MTNR1) has been associated with non-reproductive seasonality in sheep. Selecting several sheep breeds for these characteristics has significantly reduced the seasonal anoestrus, showing reproductive activity during spring and summer. It seems that these genes in some breeds may be interacting additively and an allelic variant in a breed may not be present in other, or two be present at the same time; therefore, the understanding of the genetic mechanisms that affect ovulation rate and prolificacy are important for the selection of reproductive traits.

El estudio genético en razas de ovejas que naturalmente presentan altas tasas de ovulación (TO) y de prolificidad, ha permitido detectar la participación de varios genes. Entre ellos están los relacionados a la superfamilia del factor de crecimiento transformante β (BMPRIB, GDF9 y BMP-15), así como de otros genes con efecto mayor, tales como el "distal-less homeobox 3" (FecL), el receptor de estrógenos (ESR), el receptor de prolactina (PRLR) y el de las inhibinas (INHA y INHB). Sin embargo, las ovejas homocigotas para la mayoría de las variantes alélicas en BMP-15 o GDF9 son estériles, por lo que es importante el entendimiento de las bases genéticas y moleculares de estos polimorfismos, para su uso en programas racionales de mejoramiento genético con énfasis en la prolificidad. El polimorfismo en el gen de la melatonina (MTNR1) se ha asociado con la no estacionalidad reproductiva en ovejas. La selección en varias razas de ovejas para estas características ha reducido significativamente el anestro estacional, mostrando actividad reproductiva durante la primavera y el verano. Sin embargo, parece ser que estos genes en algunas razas pueden estar interactuando aditivamente, y una variante alélica en una raza puede no aparecer en otra, o bien dos al mismo tiempo, por lo que son variados los mecanismos genéticos que afectan la tasa ovulatoria y prolificidad.

The aim of this study was to evaluate the productivity and profitability of two commercial sources of progesterone therapy as part of a hormonal induction treatment in a heifer dual purpose herd. A second objective was to determine the productivity and profitability of a recombinant bovine somatotropin (ST) application during induced lactation. Forty four Holstein heifers x Zebu crosses were used. Four treatments and two control groups were evaluated. For economic analysis all components of total cost (TC) of the companies were considered, further there was a simulation which was designed for three natural lactations after the hormonal induction, based on two scenarios in which different body weights were considered as different periods. Artificial induction of lactation yielded a 100% success rate in the four groups of animals with no statistical differences between them (P > 0.05). The best cost-benefit ratio (CBR) was recorded by CIDR treatment without ST. Although the four treatments showed economic viability, those without ST had a better ratio (B / C) than those supplemented with ST. As for the net present value (NPV), the benefits updated showed that the profits were higher when ST was not applied and, mainly, in the CIDR treatment. The internal rate of return (IRR) reveals that most of the treatments have a yield above 20%.

Los objetivos del presente trabajo fueron: 1) evaluar la productividad y rentabilidad de dos fuentes comerciales de progesterona como integrantes de un tratamiento lactoinductor en vaquillas de reemplazo de un hato de doble propósito y 2) determinar la productividad y rentabilidad de la aplicación de somatotropina bovina recombinante (ST) durante la lactación inducida. Se usaron 44 novillonas producto de cruzas Holstein x Cebú. Se evaluaron cuatro tratamientos y se manejaron dos grupos testigo. Para el análisis económico se consideraron todos los componentes del costo total (CT) de las empresas, adicionalmente se realizó una simulación en la que se proyectó para tres lactaciones naturales posteriores a la lactoinducción, basadas en dos escenarios en los que se consideraron diferentes pesos corporales como diferentes periodos. En los cuatro grupos de animales lactoinducidos, el 100% de las vaquillas respondió al tratamiento sin diferencias estadísticas entre ellas (P > 0.05). La mejor relación beneficio-costos (RBC) la registró el tratamiento CIDR sin ST. Si bien los cuatro tratamientos presentaron viabilidad económica, los tratamientos sin ST presentaron mejor relación (beneficio/costo) que aquellos tratamientos que sí fueron complementados con ST. En cuanto al valor actual neto (VAN), los beneficios actualizados de todos los años muestran que las utilidades que generaron los tratamientos fueron superiores cuando no se aplicó ST y, principalmente, en el tratamiento con CIDR. La tasa interna de rentabilidad (TIR) revela que la mayoría de los tratamientos tienen una rentabilidad arriba del 20%.

Bovine leptospirosis causes high economic losses in cattle mainly due to reproductive failure, as well as representing public health risk. Since the last century, antibody titers against several Leptospira serovars have been detected by the microscopic agglutination test (MAT) in Mexico. With the exception of very few cases, the presence of serovars causing leptospirosis in cattle and other animal species has not been demonstrated by isolation in Mexico, and in such cases characterization had to be done abroad by complex and slow immunological approaches, by comparison with a number of reference strains. The present study was conducted to perform the molecular characterization of Leptospira isolates by multiple locus sequencing typing (MLST). A hundred and ninety seven sera and kidneys samples were collected immediately after slaughter, from grazing cattle coming from the south-eastern states of Mexico. Anti-Leptospira antibodies were detected by the MAT and kidneys were inoculated into EMJH and Fletcher's specific medium. A seropositivity of 60.4% (119 out of 197), with titers from 1:100 up to 1:3 200 was detected. Four isolates (2.03%), referred as CAL4, CAL6, CAL7 and MOCA45, were characterized by serology, ribotyping and MLST as L. kirschneri serovar Grippotyphosa; L. interrogans serovar Hardjo; L. santarosai serovar Mini and L. santarosai serovar Tarassovi, respectively. With the exception of serovar Hardjo, the three other isolates belong to serovars and species not previously isolated in Mexico. These findings make it necessary to evaluate the potential distribution of such serovars among cattle and their role on animal production and public health.

La leptospirosis bovina causa grandes pérdidas económicas a la ganadería por problemas reproductivos y también es un riesgo de salud pública. En México, desde el siglo pasado se ha registrado la presencia de anticuerpos contra serovariedades de Leptospira por la técnica de aglutinación microscópica (AM), en bovinos y otras especies animales. En muy pocos casos, la enfermedad fue demostrada por el aislamiento de Leptospira, y en tales casos, su caracterización se basó en métodos inmunológicos lentos que requirieron la comparación con cepas de referencia y que fueron realizados fuera de México. En el presente trabajo se realizó la caracterización molecular mediante la secuenciación de locus múltiples (MLST), de aislados de Leptospira obtenidos de riñones de bovinos recolectados en rastro, procedentes de las zonas Golfo y sur de México. Se obtuvieron muestras de suero y riñones de 197 bovinos para realizar la AM, y el cultivo en medios específicos EMJH y Fletcher. Se detectó una seropositividad del 60.4% (119 de 197), con títulos desde 1:100 hasta 1:3,200 y se obtuvieron cuatro aislados de Leptospira (2.03%), denominados CAL4, CAL6, CAL7 y MOCA45. Los aislados fueron caracterizados por serología, ribotipificación y MLST, como L. kirschneri serovariedad Grippotyphposa; L. interrogans serovariedad Hardjo; L. santarosai serovariedad Mini y L. santarosai serovariedad Tarassovi, respectivamente. A excepción de la serovariedad Hardjo, los aislados pertenecen a especies y serovariedades no aisladas anteriormente en la República Mexicana, esto sugiere la necesidad de evaluar su diseminación entre bovinos y su potencial efecto en la producción animal y en la salud pública.