[Animal housing climatic quality in various harmful conditions in broiler production to avoid heat stress in summer].

There is an ongoing debate about the optimum stocking density of broiler birds. The figures which are discussed range between 25 kg/m2 and 43 kg/m2. The Ministry for Agriculture, Forestries and Food of Lower Saxony issued a decree which limits the stocking density to 30 kg/m2 in winter and 27 kg/m2 in summer time. Among other rules a day-night-rhythm in lighting has to be installed and the maximum allowable ammonia concentration is limited to 20 ml/m3. In a field study, involving 5 institutions of the Hannover School of Veterinary Medicine and the University of Göttingen, the effects of the decree on animal behaviour, health, hygienic conditions and economy was investigated in two identical conventional broiler barns in winter (trial 1) and summer (trial 3) and in two identical louisiana-type barns in summer (trial 2). This paper reports on the comparison of the air quality parameters in the experimental barns (E) and control barns (C) and concentrates on mean values only. The following differences were observed. (1) The mean air temperatures between the E-barns and C-barns didn't differ by more than 1 degree C. (2) The mean relative humidity of the air was in barn E 3.6% lower than in barn C (trial 1), the differences of the mean values in the other two trials were below 1% r. h. (3) The mean ammonia (NH3) concentrations were generally higher in the E-barns (trial 1: E = 17.9, C = 13.4, trial 2: E = 14.5, C = 10.9, trial 3: E = 7, C = 4.8 ml/m3) than in the C-barns. The NH3 threshold of 20 ml/m3 was frequently exceeded in trial 1 and 2 reaching peaks up to 46 ml/m3. (4) No hazardous concentrations of carbon dioxide (CO2), nitrous oxide (N2O), dimethyl amine (HN(CH3)2) and methane (CH4) were observed. The highest CO2 concentrations were found in trial 1 barn C (2816 ml/m3), 300 ml/m3 more than in barn E. In trials 2 and 3 the CO2 concentrations were slightly higher (trial 2: 200, trial 3: 40 ml/m3) in the C-barns than in the E-barns. The highest N2O concentrations were found in the louisiana-type barns (trials 2: E = 2.3, C = 1.8 ml/m3). In trial 1 (E = 0.5, C = 0.6 ml/m3) and trial 3 (E = 0.2, C = 0.2 ml/m3) the mean concentrations were by factors 3 to 10 lower. Small amounts of HN(CH3)2 were found in trial 1 only (E = 0.2, C = 0.3 ml/m3). The mean CH4 concentrations were higher in the C-barns (trial 2: E = 12.6, C = 14.6, trial 3: E = 19, C = 19.6 ml/m3). (5) The mean inspirable dust concentrations didn't differ very much between the trials an the barns. Highest inspirable dust amounts were found in trial 1 (E = 3.3, C = 3.8 mg/m3) followed by trial 2 (E = 2.8, C = 2.7 mg/m3) and trial 3 (E = 2.5, C = 2.3 mg/m3). A similar tendency was seen in the respirable dust (trial 1: E = 0.4, C = 0.6, trial 2: E = 0.4, C = 0.4, trial 3: E = 0.4, C = 0.3 mg/m3). The results of this study indicate that a reduction of bird density to 30 kg live weight per m2 will not have an immediate and strong effect on improving air quality. In particular heat stress in summer remains a problem. Therefore a brief list of measures to reduce heat stress for broilers in included.