Influence of climatic factors on the development of pneumonia in lambs
Introduction
Respiratory problems are common and relevant diseases of sheep in all the major sheep-rearing countries. They cause mortality in lambs, reduced growth and an important economic impact in drug costs and condemnations in abattoirs (Jones et al., 1982, Moreno, 1994, Cano et al., 1995, Goodwin et al., 2004). Lamb pneumonia is regarded as a complex disease, involving interaction among host, (immunological and physiological), multiple agents, (bacterial, viral, mycoplasma) and environmental factors (Brodgen et al., 1998). There is a lack of epidemiological surveys, although, in some studies, the abattoir pathology data have been used to evaluate the influence of environmental factors on the pneumonia (McIlroy et al., 1989, Moreno, 1994, Luzon, 1999). How the design of the animal installations impact the economy of the sheep flocks is one of the questions farmers frequently ask. In this report, we summarise an investigation into mortality rates in lambs with special reference to the influence of the climate factor in the development of pneumonia in lambs on four farms in Aragon, a traditional lamb producing area located in the northeast of Spain.
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Materials and methods
This study was performed on four farms producing young lambs for meat. In this area, lambs are slaughtered when their live weight is between 21 and 25 kg (2–3 months old). The farmers follow a traditional husbandry system, housing sheep in the farm buildings towards the end of pregnancy, just 1 month before birth. Most of them were managed under accelerated lambing, such as the Cornell STAR system. In this husbandry system they carry out 3–5 lambing periods per year and 1.5–1.9 lambs are sold
Results
The evaluation of the causes of death in this study showed pneumonia to be the second most frequent cause (28.7%), preceded by deaths due to digestive disorders (29.2%). These two causes were followed by starvation (22.9%). Respiratory and digestive processes varied according to the year and the flock studied, but, on all the farms, there was a remarkable increase of pneumonic pathology in the year 2003. Dramatic climatic differences were recorded in 2003 compared to the two previous years.
Discussion
The lamb mortality rates due to respiratory problems obtained in this study were similar to others previously registered in the same type of lamb product and in the same geographic region (Luzon, 1999). However, in the present study, we have observed the mortality causes in more detail from birth to slaughter according to age. Thus, we observed that there were variations during the life of the animal and this fact may have important consequences in the analysis of the impact of respiratory
Acknowledgements
The authors thank to the farmers: J. Oliva, V. Oliva, J. Bravo and J. Sanz for allowing us to use their farms for this study.
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