This Is AuburnElectronic Theses and Dissertations

The impact of increasing dietary amino acid density and feed allocation during the first three weeks of life for broilers vaccinated against coccidiosis




Cloft, Sara

Type of Degree

Master's Thesis


Poultry Science


The objective of this research was to ameliorate growth depression and meat yield reductions associated with coccidiosis vaccination. Coccidiosis vaccination induces an enteric challenge to develop immunity from Eimeria infection. To achieve the research objective, 2 experiments were conducted providing diets with increased digestible (d) amino acid (AA) density during the starter period. The first experiment evaluated effects of starter diets formulated to either 1.15% dLys density or 1.25% dLys density in 3 different starter feed allotments to vaccinated broilers from 1 to 21 d of age on growth performance and meat yield during a 6 wk production period. The second experiment compared growth performance and meat yield responses of vaccinated broilers provided 6 dietary treatments resulting from combinations of pre-starter and starter diets from 1 to 19 d of age during a 6 wk production period. Combinations consisted of 3 pre-starter diets formulated to 1.35 % dLys density, 1.25% dLys density or 1.15% dLys density and 2 starter diets formulated to 1.25% dLys density or 1.15% dLys density. In experiment 1, vaccinated broilers fed the 1.25% dLys AA diet consumed 5.4 g more cumulative dAA, which translated to a 38 g increase in total breast meat weight (P = 0.002) compared with those given the 1.15% dLys AA diet. Additionally, increasing the starter feed allocation beyond the 0.45 kg/bird allotment reduced cumulative feed conversion ratios by 6.5 points and increased carcass weights by 98 g. In experiment 2, feeding the 1.35% dLys AA density pre-starter diet increased cumulative dAA intake by 11.9 g, translating to a 40 g increase in total breast weight ( P = 0.016) compared to broilers provided the 1.15% dLys AA density pre-starter diet. Growth performance and meat yield responses of broilers fed the 1.35% dLys density pre-starter diet were similar to those observed when feeding the 1.25% dLys diet from 1 to 19 d, which as likely due to the similar dAA intake between the 2 treatments. In both experiments, broilers fed the 1.15% dLys AA density displayed growth depression compared with non-vaccinated broilers fed the same dAA density. These results provide strategies for integrators utilizing coccidiosis vaccination to ameliorate growth performance and meat yield reductions.