Preliminary study to determine the threonine requirement of specific humoral immune response in rearing ducks

Dietary threonine supply is reported to determine the quality of immune response in challenged animals, however, few data on threonine requirement of ducks is available. Therefore, the aim of the present trial was to study specific humoral immune response of ducks fed surplus threonine (+15 or +30%) above to the recommendation of the breeding company. For that purpose a total of 1050, 7 weeks old breeding ducks were used in the trail. The birds were assigned into 3 groups and fed with a commercial growing duck breeder diet supplemented with different doses of threonine. Dietary threonine levels were 0.59, 0.68 and 0.77 g per kg of feed. The body weight and feed intake of the birds were controlled weekly. All birds were immunized by live, freeze dried duck plague virus (Duck herpesvirus 1 ) at 16 and 20 weeks of age. Blood samples for virus neutralization (VN) tests were taken from 14 birds per treatment just before the first immunization (week 16), 2 weeks after (week 18) and 2 weeks after the 2nd immunization (week 22). Our data show that the specific humoral immune response to duck plague virus tended to be higher in birds fed surplus 15% threonine (P = 0.083). Higher supply, however, resulted in no difference in VN test compared to the group fed with the recommended dietary threonine level. Therefore it can be concluded that elevated dietary threonine supply boosts the immune defense of rearing ducks, however, the supplementation of surplus dietary threonine needs some caution.