Application of mixed design models in impact of high Ammonia concentration on Plasma Immunoglobulins and Newcastle virus vaccine titer in broilers

High Ammonia concentration in broiler's houses contributed a reduction in performance, lowering in resistance and increased mortality. Four out of five Hubbard broiler groups (5 × 60) were subjected to 60 ppm ammonia for 2; 4; 6; 8 hours per day; respectively for 5 successive weeks. The impact of high ammonia concentration on biochemical; immunological and bacteriological status was assessed in 900 (150 sera, 150 plasma, 150 swab and 450 organ) samples collected post exposure. Data were analyzed using traditional and mixed model ANOVA considering repeated measures. Effect size estimates were quantified using Eta and partial Eta-squared. Broilers showed 10, 18, 32 and 41.2% mortalities at 2, 4, 6 and 8 hrs of exposure; respectively. A highly significant decline (P ˂ 0.01) was recorded in immune organs’ weight. Plasma immunoglobulins revealed a highly significant decrease (P ˂ 0.01) at 8 hrs of exposure. Newcastle virus vaccine titer revealed a highly significant decrease (P ˂ 0.01) in 4, 6 and 8 hrs of exposure. Effect size statistics revealed that mixed model ANOVA was advantageous in exhibiting the biological value of studied effects. The longer the period of exposure to ammonia beyond permissible limits, the larger negative influences can be detected. Management practice in broiler farms should include preventive measures to reduce ammonia concentrations as well as researchers should keep in mind a quantitative estimate for each effect size when conducting experimental studies.