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Avaliação dos impactos de fatores climáticos nos padrões de mortalidade em explorações de bovinos
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Authors
Advisor(s)
Abstract(s)
Os bovinos são animais homeotérmicos e como tal têm uma Zona de Conforto Térmico. Fora desta sofrem stress térmico para manter a sua temperatura corporal. Este é observado em consequência de eventos climáticos extremos e tem efeitos negativos a nível produtivo, reprodutivo, metabólico e, no pior dos cenários, culmina na morte dos animais.
O conhecimento da zona de conforto térmico dos bovinos e efeitos da temperatura são de interesse primário, pois permitem aplicar medidas preventivas adaptadas ao ambiente local e ajustar as condições de produção dos bovinos. Além disso, é importante perceber de que forma é que o stress térmico influencia a taxa de mortalidade e em que proporção.
Neste estudo fez-se uma caracterização da variação da taxa de mortalidade ao longo do ano para as 7 regiões em que o país foi dividido, analisando-se dados relativos a um período de 4 anos (2015-08-15 a 2019-08-15). Avaliou-se e quantificou-se também a relação do THI (Índice de Temperatura-Humidade) com o Risco Relativo, ou seja, a relação exposição-resposta tendo em conta os desfasamentos temporais, através de Modelos Não Lineares com Desfasamento Distribuído (DLNM). Para tal consideram-se todas as explorações bovinas presentes em Portugal continental, que no período em estudo, tinham informação relativa à sua localização e que apresentavam continuidade de registos no Sistema Integrado de Recolha de Cadáveres de Animais (SIRCA), assim como os bovinos nelas presentes. Os registos das mortes foram obtidos da base de dados do SIRCA e os dados climáticos das estações meteorológicas localizadas em Portugal continental.
Verificou-se que a taxa de mortalidade apresenta sazonalidade ao longo do ano, sendo que a faixa etária dos animais entre 1 e 60 dias é a que apresenta valores mais elevados. Valores de THI a partir de 75 e abaixo de 45, têm efeitos imediatos e desfasados no tempo (até 25 dias), com risco de morrer de 1,2 a 3 vezes mais, respetivamente.
ABSTRACT - Cattle are homeothermal animals and as such they have a thermal comfort zone. Beyond this, they experience thermic stress to maintain their body temperature. Thermic stress is observed in association with extreme weather events. It has negative effects, by affecting production, reproduction, metabolism and, in worse case, it ends with death. The knowledge of cattle comfort zones and temperature effects are of primary interest, as they allow the application of preventive measures adapted to the local environment and adjust the production conditions of the cattle. Furthermore, it is important to understand in which way is thermic stress affecting mortality rate and in what proportion. Thus, in this study, we characterized the variation of mortality rate through the year, in 7 regions that the country was divided, by analysing data for a period of 4 years (2015-08-15 a 2019-08-15). We described and quantified the relationship between THI (temperature-humidity index) with relative risk, in other words, the exposure-response relationship, considering delayed effects, through distributed lag non-linear models (DLNM). For this purpose, all bovine holdings present in mainland Portugal during the study period are considered to have information regarding their location and which had continuity of records in the Integrated Animal Corps Collection System (SIRCA), and the cattle present in them. The death records were obtained from the SIRCA database and the climatic data from the weather stations. It was found that the mortality rate presents seasonality throughout the year, with the age group of animals between 1 and 60 days being the one with the highest values. THI values from 75 and below 45, have immediate and lagged effects (up to 25 days), with a risk of dying 1.2 to 3 times more, respectively.
ABSTRACT - Cattle are homeothermal animals and as such they have a thermal comfort zone. Beyond this, they experience thermic stress to maintain their body temperature. Thermic stress is observed in association with extreme weather events. It has negative effects, by affecting production, reproduction, metabolism and, in worse case, it ends with death. The knowledge of cattle comfort zones and temperature effects are of primary interest, as they allow the application of preventive measures adapted to the local environment and adjust the production conditions of the cattle. Furthermore, it is important to understand in which way is thermic stress affecting mortality rate and in what proportion. Thus, in this study, we characterized the variation of mortality rate through the year, in 7 regions that the country was divided, by analysing data for a period of 4 years (2015-08-15 a 2019-08-15). We described and quantified the relationship between THI (temperature-humidity index) with relative risk, in other words, the exposure-response relationship, considering delayed effects, through distributed lag non-linear models (DLNM). For this purpose, all bovine holdings present in mainland Portugal during the study period are considered to have information regarding their location and which had continuity of records in the Integrated Animal Corps Collection System (SIRCA), and the cattle present in them. The death records were obtained from the SIRCA database and the climatic data from the weather stations. It was found that the mortality rate presents seasonality throughout the year, with the age group of animals between 1 and 60 days being the one with the highest values. THI values from 75 and below 45, have immediate and lagged effects (up to 25 days), with a risk of dying 1.2 to 3 times more, respectively.
Description
Dissertação de Mestrado Integrado em Medicina Veterinária
Keywords
Stress térmico Taxa de mortalidade DLNM Índice Temperatura-Humidade Bem-Estar animal Bovinos Thermic Stress Mortality Rat DLNM Welfare Welfare Cattle
Pedagogical Context
Citation
Vicente JS 2020. Avaliação dos impactos de fatores climáticos nos padrões de mortalidade em explorações de bovinos [dissertação de mestrado]. Lisboa: FMV-Universidade de Lisboa.
Publisher
Universidade de Lisboa, Faculdade de Medicina Veterinária