Abstract
The hypothesis examined in this study was that extra dietary lysine (Lys) above the recommended standard exerts beneficial effects on the defence reactions, growth performance and nutrient utilization in Ascaridia galli-infected chickens. Therefore, 1-day-old female Lohmann Selected Leghorn chickens were at first fed standard Lys diet (8.5 g Lys/kg DM). At 4 weeks of age, the birds were allocated to groups 1 and 3, both being continued on standard Lys diet, whereas birds in groups 2 and 4 were switched to extra Lys diet (10.5 g Lys/kg DM). Birds in groups 3 and 4 were additionally infected at this age (4 weeks) with 250 embryonated eggs of A. galli. All the birds were slaughtered 7-week-post-infection (p.i.) at an age of 11 weeks. Infected birds on standard Lys diet consumed more feed and reached a similar level of Lys intake as birds on extra Lys diet 7-week-p.i. Utilization of feed, crude protein, and Lys for body weight (BW) gain was adversely affected in infected birds on standard Lys diet (P<0.001). Extra Lys diet reduced the incidence of infection (P<0.05), but worm counts, worm length, faecal egg counts and female worm fecundity were not different between the infected groups (P>0.05). Extra Lys diet led to higher final BW in uninfected and infected birds (P<0.05). It is concluded that extra Lys above the normal recommended standard supports the defence reactions and compensates the negative effect of infection on growth performance and nutrient utilization in A. galli-infected birds.