Effects of Cold Stress and Ammonia Concentration on Productive Performance and Egg Quality Traits of Laying Hens

SIMPLE SUMMARY: In the cold season, in order to alleviate the adverse effect of the low temperature, restricting or reducing ventilation is one of the common methods to preserve indoor heat to ensure the suitable temperature for hens in many poultry houses with no heating equipment. However, ventilation is the most important means to discharge ammonia in the house and ensure the indoor air quality in poultry farms. Measure of limiting ventilation to save energy usually causes the accumulation of gaseous ammonia released by poultry manure, which results in an increased indoor ammonia concentration. Therefore, studying the performance of laying hens exposed to a long-term ammonia concentration is of great significance for ventilation management in winter. In addition, it is not clear how the interaction between low temperature and ammonia concentration affects the performance of laying hens. Therefore, this study aims to evaluate the effects of temperature, ammonia and their interaction on productive performance and egg quality of laying hens breeding from the start to the peak period of laying. The study is of great significance to the poultry industry regarding the ventilation management in winter from the perspective of controlling temperature and ammonia concentration. It is also a reference for ensuring layer productive performance and egg quality. ABSTRACT: In a cold climate, ensuring indoor air quality and heat preservation simultaneously has always been a difficult problem in the poultry house. The current study was carried out in order to determine the effects of chronic low temperature and ammonia concentration on productive performance and egg quality of commercial laying hens. 576 18-week-old Hy-line Brown hens were used in this study. Birds were housed in cages and received for 20-week exposure to low temperature and ammonia in six artificial environmental chambers. Birds were randomly assigned into six treatments: treatment 1 (T1, 20 °C, ≤5 ppm, control group), treatment 2 (T2, 20 °C, 20 ppm), treatment 3 (T3, 20 °C, 45 ppm), treatment 4 (T4, 8 °C, ≤5 ppm), treatment 5 (T5, 8 °C, 20 ppm) and treatment 6 (T6, 8 °C, 45 ppm). Daily feed intake (DFI), feed efficiency (FE), egg production (EP) and body weight (BW) were recorded and calculated from 19 weeks of age. Egg samples were collected at 22, 26, 30, 34 and 38 weeks of age and egg weight (EW), shell breaking strength (SBS), albumen height (AH), yolk weight (YW), shell weight (SW), shell thickness (ST) and Haugh unit (HU) were measured. The results of the present study indicated that low temperature and excessive ammonia decreased the EP of hens compared with those of the T1 birds. Low temperature increased DFI of hens thereby FE showed significant differences among treatments. During the early period of the experiment, low temperature treatment increased the BW of laying hens, but this trend of increase was suppressed by the treatment of ammonia with the prolongation of the experimental period. Egg quality was also affected by low temperature and excessive ammonia. At different experimental periods, egg quality traits of hens exposed to the cold and ammonia stress presented significant differences compared to those of control birds. The present study indicated that the effect of ammonia was more pronounced on hens than that of low temperature at the early and peak laying period in terms of several main traits of productive performance and egg quality under long term hens breeding.