the World Wide Web at:The online version of this article, along with updated information and services, is located on www.asas.org by Rodrigo Arias on November 15, 2011 jas.fass.org Downloaded from ABSTRACT: 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 (°C), precipitation, relative humidity (%), wind speed (m·s ) 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.

SUMMARYThe 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.Palabras clave: estrés, ganado de leche y carne, bienestar animal, factores climáticos. INTRODUCCIONAlgunos de los principales resultados de la actividad antropogénica han sido el incremento de los niveles atmosféricos de CO 2 , las alteraciones de las propiedades biológicas y químicas del suelo, así como el continuo uso y cambio de uso de la tierra (Vitousek 1994). En su conjunto estos hechos han provocado cambios climáticos a través del planeta aumentando las temperaturas mínimas y máximas para el período 1951 -1990 (Karl y col 1993. Esta asimetría entre mínimas y máximas ha sido detectada a través de todas las estaciones del año en el planeta, particularmente en las regiones del hemisferio norte. Asimismo, diversos modelos climáticos pronostican cambios en el clima del mundo, con un aumento en la concentración de CO 2 atmosférico, incrementos de temperaturas y cambios en la distribución de las precipitaciones (Klohn y Faurès 2006). Las estimaciones de incremento en la temperatura superficial media global son de un rango de 1,5 a 4,5 °C (Khalifa 2003). Todo esto tendría profundos efectos en la producción agropecuaria y de alimentos tanto para los animales como para el ser humano. Schimmelpfennig y col (1996) reportaron la existencia de numerosos informes que indican potenciales daños a los animales en función de los cambios de clima proyectados. El efecto del clima en la producción animal ha sido estudiado desde hace aproximadamente medio siglo, lográndose importantes avances en el entendimiento de los aspec...

No abstract

RESUMENEl objetivo del estudio fue evaluar los efectos de las condiciones climáticas del verano sobre la producción de leche, actividad animal y temperatura timpánica (TT; n = 15), utilizando variables climáticas y tres índices de comodidad térmica. Los datos se analizaron considerando hora del día y categorías del índice comprensivo del clima (CCI). Se estimaron modelos de regresión simple para predecir la tasa de respiración (RR) de las vacas (α = 0,05). Los índices termales fueron normales y pobres predictores de RR (r 2 < 0,35; P < 0,001). La proporción de animales en pastoreo, echados y rumiando se redujo (P < 0,002) en 9,4; 1,7%; y 5,4 cuando el valor de CCI ≥ 25, mientras que los animales en pie y bajo sombra aumentaron 7,4 y 6,3%. Además se registró una correlación positiva entre RR y CCI. Las vacas tuvieron mayores TT en las categorías de CCI "moderado" y "suave" vs. "normal", así como también para PM vs. AM. El mayor valor de TT se observó en los días con máximos valores en los índices térmicos. Hubo diferencias tanto en la producción de leche como en los valores de CCI entre AM vs. PM (P < 0,001). Sin embargo, no hubo diferencias en la producción de leche entre las categorías de CCI (P = 0,19). Aunque las vacas mostraron signos de estrés por calor la producción diaria de leche no disminuyó al asociarlas a las categorías de CCI, demostrando que los animales fueron capaces de enfrentar las condiciones climáticas estivales.Palabras clave: comodidad térmica, cambio climático, bienestar animal. SUMMARYThe objective of the study was to assess the effects of summer weather conditions on animal performance and behaviour in southern Chile. Data of milk yield, animal activity, tympanic temperatures (TT; n = 15), and three comfort thermal indices were collected in La Araucanía Disctrict. Time of day and comprehensive climate index (CCI) categories were considering as influential factors. Simple regression models were estimated to predict the respiration rate of cows as an estimator of thermal comfort. Daily values of thermal indices were poor predictors of respiration rate, as well as climatic variables (r 2 < 0.35; P < 0.001). During days with CCI ≥ 25 there was a reduction (P < 0.002) in the proportion of animals on grazing (9.4%), lying (1.7%), and ruminating (5.4%). The proportion of animals standing and under shade increased 7.4 and 6.3%, respectively. Respiration rates were positively correlated with greater CCI values. The TT was higher for CCI categories "moderate" and "mild" vs. "normal" also for PM vs. AM. The highest TT was observed on days that had higher values of the thermal indices, especially CCI. There were differences for milk production and CCI values between AM vs. PM (P < 0.001). However, no differences for milk production were observed between CCI categories observed (P = 0.19). In conclusion, although cows showed signs of heat stress daily milk production did not show differences among CCI categories, showing that they were able to cope adverse climatic conditions of summer in southern Chi...

No abstract