Caída en la producción láctea, signos respiratorios agudos y muertes asociadas a estrés calórico en bovinos lecheros de Uruguay

espanolEn marzo de 2017 se registro un episodio clinico de estres calorico en un tambo de vacas Holando en el suroeste de Uruguay. Tras la ingesta de la racion matutina, 6 de 189 vacas lactantes manifestaron disnea, ortopnea y respiracion con la boca abierta. Cinco vacas se recuperaron, una murio durante el episodio y otra habia muerto la noche anterior. No se encontraron lesiones en el tracto respiratorio. Los indices de temperatura y humedad (ITH) ambiental maximos fueron 83,5; 83,5 y 83,0, los dias 27 y 28 de febrero y 1 de marzo, indicando una ola de calor, con estres calorico moderado. No se detectaron ergoalcaloides en la racion. Los signos de comienzo abrupto, la ausencia de lesiones en el tracto respiratorio y los ITH moderadamente elevados por tiempo prolongado, indicaron un episodio agudo de estres calorico con desenlace fatal. En el analisis retrospectivo se observo que el episodio clinico estuvo precedido de una reduccion de la produccion lactea desde el 15 de febrero al 2 de marzo, seguido de una recuperacion parcial de la produccion entre el 3 y el 15 de marzo, en asociacion con una reduccion del ITH. Este reporte marca la necesidad de implementar medidas adecuadas para prevenir y controlar el estres calorico durante el verano en tambos de Uruguay. Palabras clave: Bovinos Holando, Clima, Enfermedades Productivas, Lecheria, Signos Respiratorios. EnglishOn March 2017, a clinical episode of heat stress in Holstein cows was diagnosed in a dairy farm from southwest Uruguay. After the consumption of the morning feed, 6 of 189 cows presented dyspnea, orthopnea, and open-mouth breathing. One cow died during the manifestation of these clinical signs, the other five cows recovered a few minutes afterwards. Another cow died the night before. There were no lesions in the respiratory system. The maximum Temperature Humidity Index (THI) recorded on February 27-28 and March 1 was 83.5, 83.5 and 83.0, respectively, indicating a heat wave and moderate heat stress. No ergoalkaloids were detected upon toxicological evaluation of the feed. The sudden onset of clinical signs, the lack of lesions in the respiratory tracts, and the moderately elevated THI registered for a prolonged period, indicated an acute clinical episode of heat stress with fatal outcome. The retrospective analysis of the daily THI and average milk production revealed that the clinical episode was preceded by a marked subclinical reduction of milk production from February 15 to March 2, associated with a high THI registered in that period. This was followed by a partial recovery of milk production between March 3 and March 15, in association with a concomitant reduction of the THI and, therefore, of heat stress. This report highlights the need for applying adequate mitigation strategies to prevent and control heat stress during summer in dairy cows in Uruguay. Keywords: Climate, Dairy Farming, Holstein Cattle, Production Diseases, Respiratory Signs