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Influence of Hen Age on the Response of Turkey Poults to Cold Stress, Escherichia coli Challenge, and Treatment with a Yeast Extract Antibiotic Alternative¹

G. R. Huff^*,2, W. E. Huff^*, N. C. Rath^*, F. Solis de los Santos, M. B. Farnell and A. M. Donoghue^*

^* USDA, Agricultural Research Service Poultry Production and Product Safety Research, Fayetteville, AR 72701; Department of Poultry Science, University of Arkansas, Fayetteville 72701; and Department of Poultry Science, Texas A&M University, College Station 77843

² Corresponding author: grhuff{at}uark.edu

Two battery experiments were conducted to evaluate a commercial yeast extract feed supplement, Alphamune, in a cold stress-Escherichia coli challenge of 1-wk-old turkeys. Experiment 1 used 1-d-old male poults that were the progeny of 33-wk-old hens in their second week of lay. Experiment 2 used male poults of the same genetic line from 40-wk-old hens in their eighth week of lay. Poults were fed a standard unmedicated turkey starter diet or the same diet with either a low level (504 g/t) or a high level (1,008 g/t) of yeast extract. Challenged birds were exposed to intermittent cold stress during wk 1 to 3 and to a respiratory E. coli challenge at 1 wk of age. In both experiments, BW at wk 1 was increased by feeding yeast extract. In experiment 1, challenged, control-fed birds had decreased BW at wk 3 and feed conversion was protected by both levels of yeast extract supplementation. In experiment 2, challenge had no effect on control-fed birds; however, yeast extract decreased the BW of challenged birds. In experiment 1, total leukocyte numbers were decreased by challenge of control-fed birds only, and there was no effect of challenge on the heterophil/lymphocyte ratio. In experiment 2, total leukocyte numbers were decreased and the heterophil/lymphocyte ratio was increased in challenged, control-fed birds. Percentage mortality was not affected by challenge in experiment 1; however, in experiment 2, mortality was increased by challenge of control-fed birds and those fed the lower level of yeast extract. These results suggest that hen age should be considered when designing studies to evaluate antibiotic alternatives and in making decisions for incorporating such alternatives into production.

Key Words: turkey • yeast extract • hen age • Escherichia coli • cold stress

¹ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.

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