Effects of high dietary copper concentration on growth performance, processing characteristics, amino acid digestibility, and ileal microflora composition of broilers
Type of DegreeMaster's Thesis
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Subtherapeutic antibiotics have been added to diets to improve growth performance of broilers. Pressure from the food service industry is reducing the use of this practice, so the broiler industry is evaluating alternatives to antibiotics. One potential alternative is feeding high concentrations of dietary Cu. Previous research has shown increases in BW gain and decreases in feed conversion ratio (FCR) when feeding high concentrations of Cu, but the mode of action is unknown. One hypothesis is that Cu may improve the digestibility of amino acids (AA). Two experiments were designed to examine the interaction between AA density and Cu concentration on growth performance, processing characteristics, and AA digestibility of broilers. In experiment 1, 1,600 chicks were grown until 33 d of age and fed 8 dietary treatments throughout experimentation. Positive and negative control treatments received moderate AA density diets with 14 mg/kg Cu. Positive control birds received diets supplemented with diclazuril and were not vaccinated against coccidiosis. All other birds were vaccinated against coccidiosis. Experimental diets were arranged as a 2 × 3 factorial of moderate (95% of primary breeder guidelines) and low (88% of primary breeder guidelines) AA density and 3 Cu programs, where birds were fed 135-135-135, 270-135-135, or 270-270-135 mg/kg of supplemental Cu in the starter, grower, and finisher periods, respectively. Broilers fed 270 mg/kg of Cu in the starter and grower periods and 135 mg/kg of Cu in the finisher period had lower FI and FCR (P < 0.040) and higher carcass weights and yields (P < 0.035) than broilers fed 135 mg/kg of Cu in all phases. Next generation sequencing showed no changes (P ≥ 0.07) in ileal microbiota composition. In experiment 2, 672 male chicks were provided with 6 dietary treatments from 1 to 14 d of age. Experiment 2 employed the same positive and negative control treatments as experiment 1, and a 2 × 2 factorial arrangement of moderate or low AA density and supplementation with 135 or 270 mg/kg of Cu. Apparent digestibility of Cys was decreased (P < 0.010) from 63.4% in broilers fed no supplemental Cu to 51.2 and 56.0% in broilers fed diets supplemented with 135 or 270 mg/kg of Cu, respectively. An interaction between AA density and Cu concentration was observed where birds fed moderate AA diets had higher digestibility of Lys, Val, His, and Arg (P < 0.040) when fed diets containing 270 mg/kg of supplemental Cu, with no differences between the treatments receiving low AA density diets. Approximately 24% of broilers in the United States are raised to over 3.4 kg, but information is sparse on feeding high concentrations of Cu to these broilers, particularly from 2.8 to 4.0 kg BW. Therefore, experiment 3 was conducted to evaluate effects of feeding high concentrations of Cu to broilers from 29 to 53 d of age. All birds were provided common starter and grower diets containing 135 mg/kg of Cu in the starter and grower periods (1 to 19 and 20 to 28 d of age), and were given 0-0, 135-0, 270-0, 135-135, or 270-270 mg/kg of supplemental Cu in the finisher 1 and finisher 2 periods (29 to 41 and 42 to 53 d of age). No treatment differences (P ≥ 0.08) were observed for growth performance. Total breast weight (pectoralis major and minor muscles) was increased by 32 g (P = 0.010) in birds fed 270-270 mg/kg of supplemental Cu compared with broilers fed 135-0 mg/kg of Cu, and total breast meat yield was increased 0.4% (P = 0.017) in birds fed 270-270 mg/kg of Cu compared with birds fed 0-0 mg/kg of Cu. These studies indicated that feeding broilers high concentrations of Cu beyond the starter and grower periods may improve growth performance and carcass characteristics.