Two experiments were conducted to evaluate the effect of alum on ammonia emission,live performance,and health of broilers.In experiment 1,the effect of alum （0,2,and 4%） supplementation on the emission of ammonia was measured.The effects of alum-treated litter and stocking density （12,16,and 20 birds m-2） on the live performance and incidence of footpad and hock dermatitis were investigated in experiment 2.Alum supplementation in chicken excreta significantly decreased pH from 8.06 to 5.27 and 3.62 by 2 and 4% alum treatments,respectively.Ammonia emission rate was reduced 73.0 and 75.8% by 2 and 4% alum treatments,respectively.The suppressed litter urease activity was detected in 4% alum treatment.Alum-amended litter （1 kg m-2） decreased atmosphere ammonia concentrations by 30% in broiler house.Alum-amended litter maintained a lower pH until 35 d of age.Body weight （BW） gain was decreased by alum treatment in the period of 4-7 wk of age.Higher stocking density （20 birds m-2） increased BW gain in the first 3 wk of age but decreased BW gain during the period of 4-7 wk of age.Neither alum nor stocking density treatments had a significant effect on feed intake and feed efficiency.Alum-treated litter had no detrimental effect on the development of footpad and hock burns.In contrast,high stocking density （20 bird m-2） increased the incidence of footpad and hock lesion.The result suggests that the decreased litter pH and suppressed bacterial urease activity by alum treatment is responsible for the decreased ammonia emission.At high stocking density,the increased litter moisture content should be responsible,at least partially,for the development of footpad and hock lesions.
ZHANG Hong-fang JIAO Hong-chao SONG Zhi-gang LIN Hai
