Growth of mallards fed phosphamidon for 13-day periods during three different developmental stages

Mallard ducklings (Anas platyrhynchos) were exposed to a 13-day dietary treatment of 0, 0·5 or 5·0 ppm phosphamidon at one of three successive age intervals (5–17 days, 18–30 days, or 31–43 days) during a 10-week growth period. Weekly measurements of body weight, wing length, primary feather length, and bill length revealed slower development of primary feathers in those birds treated from 5 to 17 days; treatment effects on body weight and wing length from 6 to 8 weeks of age were observed among those birds treated from 18 to 30 days of age. Some differences in growth patterns among birds treated with the same phosphamidon level, but at different growth stages, were attributed to the varying size of the group with which a duckling was housed at different times in the growth process. No brain cholinesterase depression was observed in any group either 24h after phosphamidon treatment was terminated or at 10 weeks of age.