Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The present study aimed to determine the prevalence of Bluetongue Virus (BTV) in sheep, by the real-time Reverse Transcription-polymerase chain reaction (RT-PCR) technique. Three hundred sixty-six sheep from the ten provinces of the Peru region were evaluated. The methodology used was the collection of blood samples from the jugular vein of the sheep, then the process of extraction and purification of RNA was carried out with the QIAmp® kit, then the reverse transcription to obtain the cDNA, and finally perform the real-time RT-PCR, for which the SuperScript III platinium One-step qRT-PCR kit was used, with the primers and probes being directed to segment 10 of the NS3 gene of BTV. The results of the real-time RT-PCR test revealed two positive sheep with a value of cycle threshold (Ct) of 35.21 and 35.57, with a prevalence of 0.54 % of BTV-positive sheep in the extensive production system, with environmental conditions that favor the development of the Culicoides vector. It is concluded that, by means of the real-time RT-PCR technique, the presence of BTV in this region of Peru is confirmed, which makes future studies necessary to determine the detection of other potential serotypes of BTV in the Peruvian Amazon in order to improve the control strategies of the disease.

Family sheep production is common in rural Mexico. It is an important element of subsistence systems in these areas but is generally rustic. Better understanding of rustic sheep production is a first step in developing strategies and programs to support family producers. Family sheep production units in two municipalities in the Mixteca region of Oaxaca, Mexico, were characterized in terms of production system, market access and land use. A mixed methodology was applied, employing a structured questionnaire addressing socioeconomic and productive variables, and participatory observation in 29 family sheep producers. All the surveyed producers see sheep farming as their main income source. Most (86 %) use a subsistence system, and all use family labor. The main feeding strategy was grazing of communal land, and production was largely intended for sale of live animals to intermediaries or in local markets for eventual processing for meat, and/or for self-use. Most (83 %) of the production units included a pen built from regional materials, and these pens were most frequently on the family property. Implementation of management plans and animal health and safety measures were minimal. Analysis of these productive systems identified how producers manage sheep production. Management strategies respond to the environmental services available on communal lands, and involve family-type production which fulfills economic, social, environmental and cultural functions, but provides low productivity. Unit productivity and producer livelihood could be improved by implementing measures such as pasture rotation and adopting technological innovations. Broadening producer access to government programs and creating public policy that promotes development in marginal rural areas could greatly improve productivity and consequently reduce poverty and food insecurity.

In mammalian semen, viscosity has been shown to have a negative influence on its conservation. In bird semen, studies on the physical characteristics of ejaculates are limited, particularly viscosity has not been studied. The media for cryopreservation do not consider viscosity to maintain sperm viability. Therefore, the objective of this study was to evaluate the effect of viscosity on the medium to maintain its viability after thawing. The parameters of basic evaluation, maturation and acrosome reaction were determined, evaluating the presence and distribution of Ca2+ through co-incubation with chlortetracycline. Twenty-five (25) evaluations of seminal pool were performed, cryopreserved in Lake medium supplemented with 6 % dimethylacetamide and with 0 % (Control), 10 %, 30 % and 45 % ficoll, to adjust the viscosity of the medium to conditions similar to those of semen and oviductal fluid and to a higher degree of viscosity. Sperm motility was lower (P£0.05) in aliquots with a higher percentage of ficoll. The percentage of live spermatozoa was similar (P>0.05) in the control and all aliquots with different percentage of ficoll. Sperm maturation presented a higher (P£0.05) percentage of non-capacitated spermatozoa when 10 % ficoll was used. Conversely the percentage of spermatozoa with acrosome reaction was also lower (P£0.05) when 10 % ficoll was used. The results of this study show that variations in the degree of viscosity of the medium can maintain or increase sperm viability after thawing.

The negative impact of heat stress (HS) in dairy cattle results in considerable economic losses at world level, as it reduces the milk production, reproductive efficiency, and productive life in the cows. In addition, the continuous genetic improvement results in highly productive cows, which are, however, less tolerant to HS because they produce greater metabolic heat. This, together with global warming, will turn HS into a hard-to-control challenge for the daily industry. In response dependent on the degree of HS, the dairy cattle carry out a series of physiological, metabolic and behavioral adjustments as thermoregulatory mechanisms for removing excess body heat and reducing the endogenous production of body heat, in order to maintain the normothermia. However, fertility and milk secretion decrease as a direct effect of hyperthermia and an indirect effect of lower dietary nutrient intake. Food and water intake are closely associated to the reduction of the productivity of dairy cattle exposed to HS. Notably, the impact of HS on productivity of dairy cattle varies among breeds, among which Bos taurus, particularly the Holstein breed, are less tolerant to HS. The identification of genes associated to thermotolerance utilized in selection programs using genetic markers to breed high milk-producing cows in warm climates is currently being studied. Therefore, the purpose of this review is to carry out a comprehensive analysis of the effects of HS on milk production, activation of thermoregulatory mechanisms and feed intake behavior in dairy cattle.

The objective was to compare the prevalences of antibodies against different serovars of Leptospira interrogans among the states of Puebla, Tabasco and Veracruz, as well as among some of their municipalities, and to determine if the health status of the cows influences their fertility. Blood samples were taken from 423 cows (Bos taurus x Bos indicus and Bos indicus) from 24 ranches in 11 municipalities in the aforementioned states. The prevalences of the Hardjo and Inifap serovars were higher (P<0.05) in the state of Veracruz than in the state of Puebla, but the prevalence of the Wolffi serovar was higher (P<0.05) in the state of Puebla than in the state of Veracruz. The prevalences of the Hardjo and Palo Alto serovars were higher (P<0.05) in the state of Tabasco than in the state of Puebla, but there were no differences between these two states in the prevalences of the Inifap and Wolffi serovars (P>0.05). The number of serovars in the state of Veracruz was higher (P<0.05) than in the state of Puebla, but the number of serovars in Tabasco was intermediate; in addition, there was an important variation (P<0.05) between municipalities and between ranches in the prevalence of the different serovars. Overall, the serovar with the highest frequency was Inifap, while the serovar with the lowest frequency was Tarassovi. The health status of the cows did not influence the pregnancy rate (P>0.05); however, vaccination of cattle against Leptospira interrogans is recommended in order to decrease the risks associated with this bacterium in cattle and humans.

Este estudio se llevó a cabo para evaluar el tiempo para el establecimiento de gramíneas forrajeras tropicales en el bioma del “Cerrado”, con base en rasgos morfogenéticos y estructurales. Se distribuyeron tres cultivares (Paiaguás, Ipyporã y Marandu) de Brachiaria brizantha (Sin. Urochloa brizantha) y dos cultivares (Quênia y Tamani) de Panicum maximum (Sin. Megathyrsus maximus) en un diseño de bloques al azar con cuatro repeticiones. Los rasgos morfogenéticos y estructurales del pasto se evaluaron desde el día 35 hasta el día 65 después de la siembra, a intervalos de siete días. La altura del dosel aumentó linealmente con el período de establecimiento, en todos los cultivares. En los cultivares de Megathyrsus, la densidad de macollos disminuyó a medida que avanzaba el período experimental, mientras que el número de macollos en los cultivares de Urochloa aumentó. Los cultivares Ipyporã y Marandu tuvieron las tasas más altas de aparición foliar. Las tasas de elongación foliar más bajas se presentaron en los cultivares Paiaguás, Ipyporã y Tamani, y las tasas de elongación más altas en el cv. Quênia. Como resultado, el cv. Quênia mostró los valores más altos de longitud foliar final (64.9 cm) y masa de lámina foliar (3,352.9 kg MS ha-1). La mayor tasa de senescencia del cv. Tamani (2.1 cm macollo-1 d-1) dio como resultado que el mayor porcentaje de material muerto (1,815.5 kg ha-1) se encontrara en la masa de forraje de este cultivar. Los cultivares Paiaguás, Marandu y Tamani se establecieron a los 44 d, mientras que los cv. Quênia e Ipyporã se establecieron a los 51 y 58 días después de la siembra, respectivamente, en el Cerrado brasileño.

Measuring forage mass (FM) in the pasture, prior to grazing, is critical to determining the daily allocation of forage in pastoral animal production systems. FM is estimated by cutting forage in known areas, using allometric equations, or with the use of remote sensors (RS); however, the accuracy and practicality of the different methods for estimating FM is variable. The objective was to obtain predictive models using environmental and pasture management variables to predict FM. Regression models were fitted to estimate FM based on variables of pasture management (PM) or measurements obtained by RS, such as reflectance, air temperature, and rainfall. A mixed pasture grazed by beef cattle was studied for three years. With 80 % of data, models were built by ordinary least squares (OLS) or by machine  learning (ML) algorithms.  The remaining 20 % of the data was used to validate the models using the coefficient of determination and average bias between estimated and observed values. The base model of study was the relationship between pasture height before grazing and FM, this model was fitted using OLS; the r2 was 0.43. When models that included PM variables were fitted, the r2 was 0.45 for OLS and 0.63 for ML. When fitting models with PM and RS variables, the r2 was 0.71 for OLS and 0.96 for ML. ML-fitted model ensembles reduced the bias of FM estimates of the examined pasture. Overall, ML models better represented the relationship between pasture height before grazing and FM than OLS models, when fitted with pasture management variables and RS information. ML models can be used as a tool for daily decision-making in pastoral production systems.

The objective was to analyze the relationship between the antibiotic-resistance profile and the biofilm formation of S. aureus isolates from bovine mastitis. Thirty (30) isolates of S. aureus from cases of subclinical mastitis in dairy farms in semi-intensive production and backyard production systems, located in the states of Guanajuato and Michoacán, Mexico, were analyzed. An antibiogram was performed by the Kirbi-Bauer disc-diffusion method. Biofilm formation was determined by the violet crystal staining method. For the evaluation of antibiotic resistance genes and biofilm formation, genomic DNA was obtained from a colony for the identification of the genes: blaZ, mecA, tetK, tetM, gyrA and gyrB, and icaA and icaD. The results showed that 100 % of the isolates were resistant to penicillin and dicloxacillin, followed by cefotaxime (86.6 %), ampicillin and cephalotin (83.3 %) and ceftazidime (80.0 %), while a 36.6 % resistance to oxacillin was observed. It was identified that all isolates of S. aureus had the ability to form biofilm with a range between 20 to 98 %. It was also observed that isolates with a high multi-resistance presented a greater formation of biofilm, establishing a significant positive correlation. In conclusion, S. aureus isolates from bovine mastitis presented high levels of antibiotic resistance; as well as an important biofilm-forming capacity, demonstrating the existence of a positive correlation between these two factors.

The objective of this study was to estimate the degree of technical efficiency and identify the factors of inefficiency of beef cattle production in the Sierra Norte of Puebla, Mexico. The data were generated by surveying a statistical sample of 180 bovine production units (BPUs). Technical efficiency was estimated using the Stochastic Production Frontier and the explanation of inefficiency was estimated with a multiple linear regression model. The results indicate that the size of the BPU is positively correlated with efficiency; the small BPU group showed an average efficiency of 0.72, the medium ones 0.75 and the large ones 0.85. Feed and labor costs can be reduced, while maintaining the same level of production. The significant (P≤0.05) explanatory variables of inefficiency are schooling, technical assistance, experience, and administrative management.

La restricción de la ingesta de nutrientes por parte de las vacas de carne durante la gestación puede influir en el potencial de crecimiento posparto de la progenie, por lo que el objetivo del presente estudio fue evaluar los efectos de la restricción nutricional y de la nutrición adecuada o la sobrealimentación durante el último tercio de la gestación de las vacas cruzadas (Charolais x Nellore) criadas en el bioma pampeano, sobre el rendimiento productivo de la progenie hasta los 15 meses de edad. Ochenta y tres (83) vacas se dividieron en tres tipos de tratamiento: vacas de control en pastos naturales bajo restricción nutricional (RES); suplementación para satisfacer el 100 % de las necesidades (REQ); suplementación por encima de las necesidades (ALTO). Los terneros nacidos de vacas con tratamiento REQ y ALTO tuvieron un mayor peso corporal al nacimiento que los terneros de las vacas con tratamiento RES (39.28, 39.13 vs 34.58 kg), sin que esto haya influido en el rendimiento postnatal. Las hembras de las vacas con tratamiento REQ y ALTO presentaron un mejor rendimiento postnatal y, en consecuencia, un mayor peso a los 12 meses de edad en comparación con las crías de las vacas con tratamiento RES (300.71 y 311.79 frente a 259.47 kg). Estos terneros alcanzaron el 60 % del peso adulto temprano (358 y 345 vs 405 d) y tuvieron un mayor porcentaje de reproducción a los doce meses de edad (73.98 y 84.08 vs 34.08 %) que las hembras nacidas de las vacas con tratamiento RES. La suplementación de las vacas para satisfacer el 100 % de las necesidades, así como la sobrealimentación durante el último tercio de la gestación, mejora el rendimiento de las crías a los doce meses de edad, y los machos y las hembras responden de forma diferente a los insultos nutricionales de la madre durante este periodo.