Einfluss einer zugabe von ascorbinsäure zum tränkwasser und von betain zum futter auf die leistung, die hämatologie und die gehalte an igg sowie hsp 70 bei pekingenten (Anas platyrhynchos domesticus) bei einer haltung unter hohen umgebungstemperaturen

Negative effects of heat stress on duck growth performance remain a critical issue in tropical countries. This experiment was conducted to determine the effect of betaine and ascorbic acid on ducks exposed to heat stress during the grower phase (21 to 42 days of age). A total of 270, 1-day old male Pekin ducks were randomly allocated to one of three dietary treatments, with 6 pens per group and 15 ducks per pen. During the period of 1 to 21 days of age, ducks were fed on a common starter diet and no heat stress was imposed. During the whole grower phase, heat stress was imposed to all ducks (11:00-17:00 h, 33-40°C; relative humidity 70%). The ducks received one of three treatments: (1) basal diet, (2) basal diet supplemented with 800 mg/kg betaine and (3) basal diet supplemented with 800 mg/kg betaine + 300 mg/kg ascorbic acid in water. Supplementing betaine or betaine PLUS ascorbic acid resulted in an increased (P< 0.05) body weight on day 42, a better feed efficiency during days 21-42, increased counts or concentrations of red blood cells, haematocrit, haemoglobin, platelet count and mean platelet volume and serum level IgG when compared to the heat stress control group. On the contrary, betaine or betaine plus ascorbic acid reduced (P< 0.05) serum corticosterone concentration and gene expression of heat shock protein HSP70 in the liver in comparison to the heat stress control group. In conclusion, betaine and ascorbic acid could improve growth performance and blood parameters of ducks under heat stress.