The heat stress for workers employed in laying hens houses

In laying hens houses, microclimatic conditions, in general, are regulated according to the physiological needs of livestock but these are not always favorable to workers involved even occasionally on the farm. The optimal values of the internal air temperature indicated in the literature for these structures are between 15 and 20°C although some authors propose wider ranges of variation. The critical values reported in the literature of the air temperature are from 30°C with the beginning of the first decrease of performance of production which become increasingly larger with increase of the temperature up to lethal consequences over 45°C. The optimum relative humidity is between 60 and 70%. Especially in Mediterranean areas the optimal temperatures are abundantly exceeded due to the high values of solar radiation, coming to 1000 W m -2 , and similarly for the high values of air temperature that during the summer can reach 40°C. Although in the laying hens houses, as well as in other livestock species, the presence of the operator in areas designated for the animal has been greatly reduced due to the widespread use of mechanization (collecting eggs, distributing feed and water, etc.), this is still necessary in many cases: monitoring, maintenance, collection of eggs laid outside the nest, the removal of animals deceased, repairing breakdowns, etc... and exposes the operator to a number of risks including heat stress. The aim of this paper is to evaluate the heat stress for workers that operate in laying hens houses located in the Mediterranean environment. The research was conducted in a modern farming for 14,000 Lohmann Brown laying hens located in a City of the Alto Lazio (Montefiascone) during the warmer summer period (from June 15 th ,2012 to August 15 th ,2012) with the relief of the main climatic parameters (air temperature and relative humidity) and subsequent determination of the main indices of heat stress assessment provided by the main technical standards: UNI EN ISO 7730 for the determination of the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) in moderate environments and UNI EN 27243 for the calculation of the wet bulb globe temperature (WBGT) in hot severe environments. The results indicate a high risk of worker exposure to heat stress. To minimize the risk we have to act on clothing and especially on the exposure time.