PRODUCTIVE RESPONSE OF THE LAYING HENS SUBJECTED TO THERMAL STRESS IN CONVENTIONAL CAGES SYSTEM
Tahsin Sady Hussen
The researches organized in 2009, aimed to assess the productive response of the laying hens, accommodated in conventional pyramidal cages within standard temperature and thermal stress (overheat) conditions, due to inappropriate technical endorsements in small size farms. There were used 1000 Lohmann Brown laying hens, during the peak period of the laying cycle (age 25-28 weeks). The flock was divided into two groups: standard temperature group (ST), which comprised 500 hens, kept at 17-18ºC and overheated microclimate group (OH) - 500 hens, kept at 27-29ºC temperatures. Quantitative and qualitative production traits have been analyzed: eggs yield and laying intensity throughout the 4 weeks period, shell thickness and proportion of eggs with normal/abnormal shell. Shell quality was studied on 100 eggs/group weekly. The results indicated performance levels close to the hybrid management guide specifications, for the fowl accommodated at normal temperature (92.03% laying intensity, 0.392 mm shell thickness, 99.21% eggs with intact eggshell), while the hens subjected to higher temperatures presented lower laying levels (89.72%), thinner eggshell (0.367 mm), consequently more eggs with shell unconformities (rough and cracked shell, shell less eggs - 4.40%). It is suggested to improve microclimate conditions, though an increase of ventilation rate and to use a feed additive (sodium bicarbonate or vitamins), in order to protect hens against heat stress and regain production levels.
Key words: hens, heat stress, eggs, yield, shell, quality