This study was aimed to evaluate the effect of low crude protein (CP) diets supplemented with arginine (Arg), threonine (Thr), and glutamine (Gln) separately or in combination on growth performance and oxidative status of broilers challenged with Eimeria Spp. A total of 780 14d-old male Cobb 500 broilers were randomly allocated into 10 groups (6 cages/ treatment,13 birds/ cage). Nine challenged groups (C) were orally gavaged with 12,500 oocysts of E. maxima, 12,500 oocysts of E. tenella, and 62,500 oocysts of E. acervulina, and one non-challenged control group (NC) was orally
gavaged with PBS. The control diet (20% CP) was fed to NC and one challenged group (CC). Low CP diets (17% CP) with amino acid supplementations were fed to the rest C (T1, No supplementation; T2, 1% Arg; T3, 1% Thr; T4, 1% Gln; T5, 1% Arg+1% Thr; T6, 1% Arg+1% Gln; T7, 1% Gln+1% Thr; T8, 1% Arg+1% Thr+1% Gln). Growth performance was recorded on 6 and 9d post-infection (DPI). The liver was collected on 6 DPI for oxidative status analyses. Data were analyzed by one-way ANOVA and Duncan’s multiple range test. At 6 & 9 DPI, feed intake (FI), body weight (BW), and body weight gain (BWG) were higher (P<0.05), and feed conversion ratio (FCR) was lower (P<0.05) in NC than all C. At 6 DPI, T3, T7, T8 had lower FI, BW, and BWG than other C. T6 had higher (P<0.05) BW and T2&T6 had higher BWG and lower FCR (P<0.05) than CC. At 9 DPI, FI was higher (P<0.05) in CC than all other C except T1. And T8 had lower FI, BW, and BWG than other treatment groups. The lipid oxidation product, malondialdehyde (MDA), in the liver was lower (P<0.05) in NC than all C. T8 had a higher (P<0.05) MDA content than T1&T6. The activity of superoxide dismutase was higher (P<0.05) in T1&T5 than in T3. The activity of glutathione peroxidase was lower (P<0.05) in T2&T6 than in CC&T1. The glutathione content was higher (P<0.05) in NC than C while no differences were observed among C.
In conclusion, under Eimeria infection, birds fed a normal diet and low CP diet tended to have the same growth performance. Thr supplementation in the low CP diet might adversely affect the growth performance while Arg supplementation could have a beneficial effect on growth performance and oxidative status of birds during an acute infection stage.