Determinación del riesgo potencial de estrés térmico del ganado bovino en cuatro localidades del centro y sur de Chile

Datos climáticos del periodo diciembre a febrero de los años 1999 al 2007 provenientes de estaciones meteorológicas situadas en Curicó, Chillán, Temuco y Osorno fueron utilizados para calcular un índice temperatura-humedad ajustado por el efecto del viento y de la radiación (THIadj-max). Las variables climáticas utilizadas para calcular este índice incluyeron: velocidad del viento, temperatura máxima del aire, humedad relativa y un valor estimado de la radiación solar. Cuando los valores de THIadj-max fueron superiores a 75, estos días fueron considerados como indicadores de “alerta” y riesgo potencial de estrés térmico en el ganado. Adicionalmente, el impacto en la producción animal fue estimado sobre la base de pérdidas potenciales de producción de leche para cada localidad, utilizando dos ecuaciones para su estimación. Las localidades de la región central, Curicó y Chillán, presentaron valores promedios de THIadj-max similares (79,4 y 79,1, respectivamente), pero ambos superiores a las de la región sur (Temuco y Osorno 77,1 y 68,1, respectivamente; P 75 fue mayor en la región central. Asimismo, la producción de leche mostró un mayor potencial de pérdidas en las regiones centrales de Chile (1,5 a 4,3 y 1,2 a 3,6 L*vaca-1*d-1 para Curicó y Chillán, respectivamente). Por otra parte, las regiones del sur, Temuco y Osorno, presentaron menores pérdidas potenciales (0,9 a 2,6 y 0,1 a 0,6 L*vaca-1*d-1, respectivamente). En conclusión, el riesgo potencial de estrés térmico para el ganado bovino es mayor en Curicó y Chillán, es moderado en Temuco, y es mínimo en Osorno. Finalmente, la cuantificación del impacto directo que tiene el clima sobre la productividad y el bienestar de los bovinos en Chile necesita ser estudiada.Meteorological data from December to January of years 1999 to 2007 from weather stations located in four localities in Chile (Curicó, Chillán, Temuco and Osorno) were used to calculate the adjusted temperature-humidity index (THIadj-max). Climate variables used to calculate the index were: wind speed, air temperature, relative humidity and an estimated value of solar radiation. When the values of THIadj-max were greater than 75, those days were considered as alert and as potential risk of heat stress in cattle. Additionally, the impact of climate on animal production was assessed by means of potential losses in milk production for each locality estimated by two equations. The localities of Curicó and Chillán presented similar values of THIadj-max (79.4 and 79.1, respectively), and both were higher than those for Temuco and Osorno (77.1 and 68.1, respectively, P 75 was greater in the Central region. In addition, the estimated mean milk production loss was greater in the Central regions (1.5 to 4.3 and 1.2 to 3.1 L*cow-1*d-1 for Curicó and Chillán, respectively). Conversely, the Southern regions, Temuco and Osorno, presented lower potential losses with 0.9 to 2.6 and 0.1 to 0.6 L*cow-1*d-1, respectively. In conclusion, the potential risk of heat stress of cattle seems greater in Curicó and Chillán, moderate in Temuco and minimum in Osorno. Additional research is needed in the order to quantify the impacts of environmental conditions in productivity and welfare of cattle in Chile

Factores climáticos que afectan el desempeño productivo del ganado bovino de carne y leche

The effect of climate on dairy and beef cattle is variable and complex because it affects the environment in which the animals are raised and reproduced. Its influence on animal welfare and production have been recognized and studied since 1950's. Climate affects livestock directly and indirectly, since it modifies the quality and/or quantity of food available, the requirements of water and energy, and the amount of energy consumed and the use of it. The animals cope with these adverse conditions of climate by altering physiological and behavioral mechanisms in order to maintain their body temperature within a normal range. As a result it is possible to observe changes in the food intake, behavior and productivity. These changes are magnified under extreme conditions of heat or cold, implying drastic reductions in the indices of production, such as average daily gain and daily milk production. Most of the research conducted in this area has been done mainly in controlled environmental chambers, with emphasis on the animal response and its productivity. Currently, the major scientific focus is on the development of thermal stress indices as practical tools for cattle handling under unfavorable environmental conditions. The objectives of this review are to describe and discuss the most important climatic factors affecting cattle performance as well as the major mitigation alternatives. It also presents a brief overview of the research carried out in Chile and possible lines of research in this field.El efecto del clima en el ganado bovino es variable y complejo, ya que condiciona el medioambiente en el que los animales viven y se reproducen. Sus influencias en el bienestar y producción animal han sido reconocidas y estudiadas desde 1950. El clima afecta al ganado directa e indirectamente, ya que modifica la calidad y/o cantidad de alimentos disponibles, los requerimientos de agua y energía, la cantidad de energía consumida y el uso de ésta. Los animales hacen frente a las condiciones adversas del clima mediante la modificación de mecanismos fisiológicos y de comportamiento para mantener su temperatura corporal dentro de un rango normal. Como consecuencia, es posible observar alteraciones en el consumo de alimento, comportamiento y productividad. Estos cambios se acentúan bajo condiciones extremas de frío o calor, implicando drásticas reducciones en los índices productivos, tales como tasa de ganancia de peso y producción diaria de leche. La mayor parte de la investigación en esta área ha sido realizada principalmente en cámaras de ambiente controlado, con énfasis en la respuesta fisiológica y productiva del animal. Actualmente, el principal esfuerzo de investigación se concentra en el desarrollo de índices de estrés térmico que permitan mitigar los efectos negativos del clima en la productividad y supervivencia del ganado. Los objetivos de esta revisión son describir los principales factores ambientales que afectan la productividad del ganado y establecer las bases para la cuantificación del impacto climático en la producción de carne y leche en Chil

Effect of substrate on the in vitro protein digestibility of extracts generated by Saccharomyces cerevisiae

Se evaluó el efecto del tipo de sustrato a fermentar por Saccharomyces cerevisiae (Sc) sobre la digestibilidad in vitro de la proteína cruda (Divcp y Div2h), de la proteína verdadera (Dtp) y la tasa de degradación de proteína (kdcp) en diferentes extractos proteicos producidos por esta levadura. Estos fueron generados a través de un método biotecnológico (fermentación en estado sólido). Se utilizaron como sustratos (tratamientos del experimento) paja de trigo, TWS; paja de cebada, TBS; rastrojo de ají, TCS; cascara de avena, TOH y almidón-glucosa en polvo, TSP (control). Para el cultivo de Sc con los sustratos a evaluar, se agregaron 2 mL de una solución de inóculo de Sc (6,7×106 sporas mL-1) a 12 mL de medio de cultivo, junto con 2 g de sustrato vegetal (materia seca), más una fuente de nitrógeno. La incubación fue mantenida por 7 días bajo condición aeróbica, a una temperatura constante de 26 °C (pH 5). El contenido promedio de PC de la biomasa de levadura generada fue de 45%. Luego de realizar la extracción de la biomasa de Sc, se midió la digestibilidad in vitro de sus proteínas en dos fases (pepsina/tripsina-pancreatina). Los resultados permitieron observar un efecto del tipo de sustrato fermentado (P≤0,001) sobre la Divcp y Dtp (P≤0,01). La mayor digestibilidad (Divcp) fue obtenida con TSP (78,9% PC) y la menor con TCS (67,1% PC). También, se pudo apreciar diferencias entre los tratamientos (P≤0,01) para la velocidad de degradación (kdcp). La medición de un 71,8% (promedio) para Divcp, 16,4% h-1 (promedio) para kdcp, y un contenido satisfactorio de PC, permiten sugerir que este extracto de Sc posee el potencial para llegar a constituir una alternativa como suplemento proteico para nutrición animal.The in vitro crude protein (CP) digestibility (Divcp), true protein digestibility (Dtp) and degradation rate (kdcp) were measured in different protein extracts of Saccharomyces cerevisiae (Sc) yeast. These extracts were generated through a biotechnological method (solid state fermentation). Wheat straw (TWS), barley straw (TBS), chili stubble (TCS), oats hull (TOH) and starch-glucose powder (TSP; control) were used as substrates for fermentation by Sc, and their effect on the aforementioned kinetic parameters in the generated cellular biomass was evaluated. In 12 mL cultivation medium, 2 mL Sc solution inoculum (6.7×106 spores mL-1) was added together with 2 g vegetable substrate (dry) and additional nitrogen source, and the mixture was incubated for 7 days at a constant temperature (26°C at pH 5) under aerobic conditions. The average CP content of the yeast biomass (DM) was of 45%. The Divcp and Dtp were analyzed (two phases: pepsin/trypsin-pancreatin) after the extraction of the yeast biomass, and an effect of the fermented substrate on these values (P≤0.001 and P≤0.01, respectively) was observed. The greatest digestibility (Divcp) was obtained with TSP (78.9% CP) and the lowest with TCS (67.1% CP). In addition, differences in the kdcp between the treatments were also observed (P≤0.01). The high contents of CP, Divcp (71.8% on average) and kdcp (16.4% h-1 on average) suggest that Sc yeast biomass has the potential to become an alternative for the production of animal protein supplements

Zoonosis, cambio climático y sociedad

La sociedad contemporánea se enfrenta a uno de los retos más grandes de la historia humana, el calentamiento global, mismo que acarrea enormes consecuencias, tales como los disturbios climáticos, así como los patrones de las enfermedades de origen animal transmisibles al hombre. Precisamente ante este escenario las instituciones educativas de nivel superior deben dar cumplimiento a su responsabilidad y ser las generadoras de alternativas de solución mediante el trabajo especializado de investigación; y para ello, la pesquisa científica es la mejor de las alternativas a nuestro alcance para comprender y encarar estos desafíos.Universidad Autónoma del Estado de México y Ediciones y Gráficos Eón, S.A. de C.V

Effect of substrate on the in vitro protein digestibility of extracts generated by Saccharomyces cerevisiae

The in vitro crude protein (CP) digestibility (D-ivcp), true protein digestibility (D-tp) and degradation rate (kd(cp)) were measured in different protein extracts of Saccharomyces cerevisiae (Sc) yeast. These extracts were generated through a biotechnological method (solid state fermentation). Wheat straw (TWS), barley straw (TBS), chili stubble (TCS), oats hull (TOH) and starch-glucose powder (TSP; control) were used as substrates for fermentation by Sc, and their effect on the aforementioned kinetic parameters in the generated cellular biomass was evaluated. In 12 mL cultivation medium, 2 mL Sc solution inoculum (6.7x10(6) spores mL(-1)) was added together with 2 g vegetable substrate (dry) and additional nitrogen source, and the mixture was incubated for 7 days at a constant temperature (26 degrees C at pH 5) under aerobic conditions. The average CP content of the yeast biomass (DM) was of 45%. The D-ivcp and D-tp were analyzed (two phases: pepsin/trypsin-pancreatin) after the extraction of the yeast biomass, and an effect of the fermented substrate on these values (P <= 0.001 and P <= 0.01, respectively) was observed. The greatest digestibility (D-ivcp) was obtained with TSP (78.9% CP) and the lowest with TCS (67.1% CP). In addition, differences in the kd(cp) between the treatments were also observed (P <= 0.01). The high contents of CP, D-ivcp (71.8% on average) and kd(cp) (16.4% h(-1) on average) suggest that Sc yeast biomass has the potential to become an alternative for the production of animal protein supplements

Determination of potential risk of heat stress of cattle in four locations of Central and Southern Chile

Meteorological data from December to January of years 1999 to 2007 from weather stations located in four localities in Chile (Curico, Chillan, Temuco and Osorno) were used to calculate the adjusted temperature-humidity index (THIadj-max). Climate variables used to calculate the index were: wind speed, air temperature, relative humidity and an estimated value of solar radiation. When the values of THIadj-max were greater than 75, those days were considered as 'alert' and as potential risk of heat stress in cattle. Additionally, the impact of climate on animal production was assessed by means of potential losses in milk production for each locality estimated by two equations. The localities of Curico and Chillan presented similar values of THIadj-max (79.4 and 79.1, respectively), and both were higher than those for Temuco and Osorno (77.1 and 68.1, respectively, P 75 was greater in the Central region. In addition, the estimated mean milk production loss was greater in the Central regions (1.5 to 4.3 and 1.2 to 3.1 L*cow(-1)*d(-1) for Curico and Chillan, respectively). Conversely, the Southern regions, Temuco and Osorno, presented lower potential losses with 0.9 to 2.6 and 0.1 to 0.6 L*cow(-1)*d(-1), respectively. In conclusion, the potential risk of heat stress of cattle seems greater in Curico and Chillan, moderate in Temuco and minimum in Osorno. Additional research is needed in the order to quantify the impacts of environmental conditions in productivity and welfare of cattle in Chile

Environmental factors affecting daily water intake on cattle finished in feedlots

Records from 7 studies conducted during 1999 to 2005 were utilized to assess the effects of environmental factors on daily water intake (DWI) of finishing cattle. Data from unshaded feedlot pens (up to 24 pens utilized per study; 6 to 9 animals.pen(-1)) containing predominantly Angus crossbred cattle were obtained by dividing total water intake by the number of animals utilizing that waterer. Each waterer was shared by 2 pens; therefore, data were derived from a database containing 72 experimental units comprising 144 pen records. Climatic data were compiled from weather stations located at the feedlot facility. The database included daily measures of mean ambient (Ta), maximum (Tmax), and minimum (Tmin) temperature (degrees C), precipitation, relative humidity (%), wind speed (m.s(-1)), solar radiation (SR, W.m(-2)), and temperature-humidity index (THI), as well as DMI (kg.d(-1)) and DWI (L.d(-1)). Simple and multiple regression analyses were conducted by season and for the overall data set. Results confirmed that DWI increases during the summer (P < 0.01). When seasons were combined and analyzed by linear regression, the best predictors of DWI were THI (r(2) = 0.57), Ta (r(2) = 0.57), Tmin (r(2) = 0.56), and Tmax (r(2) = 0.54). In multiple regression analyses, smaller coefficients of determination (R-2 < 0.25) were found within summer and winter seasons. Across season, the largest R-2 (0.65) were obtained from the following prediction equations: 1) DWI = 5.92 + (1.03.DMI) + (0.04.SR) + (0.45.Tmin); and 2) DWI = -7.31 + (1.00.DMI) + (0.04.SR) + (0.30.THI). In conclusion, Ta, Tmin, and THI were found to be the primary factors that influence DWI in finishing cattle, whereas SR and DMI were found to have a smaller influence on DWI

Simulation of the nitrogen use efficiency in pasture-finished steers in southern Chile

The high content of crude protein (CP) of pastures in southern Chile creates a nutritional imbalance that results in large amount of nitrogen (N) being excreted into the environment. Two regression equations and a dynamic model, available from the literature, were utilized to simulate the N use efficiency (NUE) in pasture-finished steers. A medium frame animal (Angus breed) with an initial and final body weight (BW) of 350 and 500 kg, respectively, was used to estimate nutrient requirements and excretions. Average DMI was fixed at 2.2% of animal BW with 150 days on feed (October to February). Energy and protein requirements, as well as the retained protein, were estimated by using Beef NRC software (tabular system level 1), while the nutritional characteristics of the pasture were obtained from studies based in Chile. The quality of the pastures was good enough to allow daily weight gain (GDP) of 1.0 kg/d. However, metabolizable protein balance was positive across the whole finishing period (average of 149 g/d). Total production of microbial protein increases with time because of the greater DMI, even when the PC content in forage decreases with time. This also explains the lower contribution of DIP during the last months of the finishing period. The estimated N intake was 123 g/d, whereas N excretion was 106 g/d. In summary, the combination of high levels of CP of Chilean southern pastures and the low NUE of the finishing cattle (13.4 - 16.3%), represent a strong challenge in terms of contamination and production

Effect of High Potency Growth Implants on Average Daily Gain of Grass-Fattened Steers

Simple Summary Improving efficiency in beef cattle production requires the adoption of technologies that are low cost but high in return. High potency growth-promoting implants (HGPs) are widely used under feedlot conditions but there are few reports of their use under grazing conditions. We conducted a trial to assess whether the use of high potency HGPs have advantages for grass-finished cattle. Our results were similar to those reported for feedlot cattle, showing that the quality of the pastures was good enough to take advantage of the HGP technology, generating a marginal income that justifies the use of technology under grazing conditions. High potency growth promoter implants (HGPs) are widely used under feedlot conditions but there are few reports under grazing conditions. The study's goal was to assess the effect of HGPs on the average daily gain of steers fattened in pastures. A total of 57 crossbreed steers (Hereford x Angus)-initial body weight = 356.65 kg +/- 5.04 (SEM)-were randomly allocated to one of three groups: Control without HGP (n = 19), Synovex group (n = 17), and Revalor group (n = 21). The fattening period was 67 days using paddocks of Lolium perenne L. and Trifolium repens L. Body weight was recorded three times in the period. The data were analyzed using an analysis of covariance with a level of significance of 5%. The average daily gain (ADG) (1.55 +/- 0.07 and 1.48 +/- 0.09 kg/d) and the total weight gain (103.4 +/- 4.9 and 99.2 +/- 5.8 kg) were similar for Revalor and Synovex, respectively (p > 0.05). Moreover, HGP groups showed higher ADG and total weight gain (p < 0.01) than the control group (ADG = 0.93 +/- 0.08 kg/d and a total weight gain of 62.2 +/- 5.2 kg). Final body weights were 527.8 +/- 8.5 kg and 512.2 +/- 9.9 kg for Revalor and Synovex, respectively; and 479.9 +/- 10.1 kg for Control. In conclusion, grazing-finished steers showed better performance when high potency HGPs were used, improving the ADG and final live body weight, generating a marginal income that justifies the use of the technology under grazing condition