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Meta-analysis on apparent amino acid digestibility in Eimeria-challenged broiler chicken

2021 CPRF,Nutrition
Caused by apicomplexan protozoa Eimeria, avian coccidiosis is responsible for major economic losses in the global poultry industry. Sub-clinical Eimeria infections impair digestive tract capacity and barrier function leading to poor growth and feed efficiency. The objective of this study was to use a meta-analysis approach to evaluate and quantify the effect of an Eimeria infection on the apparent ileal digestibility (AID) of amino acids (AA) in broiler chickens. A database composed of 6 articles with a total of 21 experiments was built to look at effect of challenge and type of challenge (a mix of Eimeria spp. vs E. acervulina), while a sub database of 3 articles with a total of 15 experiments was used to evaluate the effect of dose of E. acervulina-challenged birds. For the overall database, regression models were fitted with the mixed model procedure in Minitab 19 with fixed effects of challenge, species, and their interactions. For the sub database, the mixed model procedure was used to fit regression models and identify a linear or quadratic response to dose. Challenge decreased AID (P<0.05) of both dispensable and indispensable AA except for Trp. Specifically, the largest depression was observed for Cys, Thr, Tyr, Ala, and Val with the magnitude of difference of 8.7, 5.4, 5.2, 5.1, and 4.9%, respectively for challenged vs. unchallenged birds. The type of challenge affected (P<0.05) AID of AA with exception of Cys, Tyr, Ala, Ser, Leu, Asp, Gly, and Pro. E. acervulina challenge had larger negative effects on AID of Ile, Leu, and Val. Moreover, increasing E. acervulina dose linearly decreased (P<0.05) AID of all indispensable and dispensable AA except for Trp and quadratically decreased AID of all AA except Cys, Met, Arg, and Trp. The largest linear decrease due to effect of E. acervulina dose was seen in AID of Cys, followed by Ala, Val, Thr, and Ile. Although, AID of Trp was not affected by E. acervulina challenge, mixed Eimeria species challenge decreased (P<0.05) AID of Trp. In conclusion, the effect of Eimeria on AID of Thr was supported by the increased secretion of mucin associated with an Eimeria infection while Cys played a role in oocyst sporulation. In addition, the effect of Eimeria on branched chain AA was likely due to their involvement in the proliferation and production of immune associated cells and proteins. Overall, the results confirmed that an Eimeria infection negatively impacted AA digestibility/utilization. The ranking of the most affected AA suggested grounds for nutritional intervention during sub-clinical field Eimeria infections or vaccination programs.
Tags :
aminoacids,digestibility,eimeria challenge
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