Research Open Access Effects of beta-benzene hexachloride in-ovo on the embryonic growth and development of domestic mallard ducks (Anas platyrhynchos domesticus L.) Abstract This was the first study conducted to test if varying levels of ß-Benzene Hexachloride affects the embryonic growth and development of Mallard using in-ovo procedure. In a sanitized environment, 200 fertile eggs at day 0 (n=200) were exposed to varying concentrations of β-Benzehexacholorohexane (β-BHC). The five treatments with four replications (10 eggs rep -1) were the sham-injected control (T1), positive control (T2), 150 ppb (T3), 300 ppb (T4) and 600 ppb (T5) of β-BHC. All treatments except T1 were administered by in-ovo using sterilized olive oil as vehicle. The embryonic weight and body length were determined on days 7, 14, 21 and 28. On the day of hatching (day 28), movement and feeding behaviors were documented using DSLR camera. The results revealed that the significant decrease in embryonic weight and length were observed at 600 ppb ß-BHC. Likewise, eggs treated with 300 and 600 ppb β-BHC manifested splay leg incidence. The reduced total hatchability of 300 and 600 ppb β-BHC may be attributed to leg weakness. Therefore, 300 ppb β-BHC present in duck eggs is critical.