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Unformatted text preview: © 2010 Poultry Science Association, Inc. 2010 J. Appl. Poult. Res. 19 :101–111 doi: 10.3382/japr.2009-00042 Performance of two 1970s and Ross 308 broiler strains fed drug-free low-protein and recommended-protein diets T. A. Woyengo ,* A. Golian ,† C. Bennett ,‡ H. Muc ,* and W. Guenter * 1 * Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2; † Faculty of Animal Science, Ferdowsi University of Mashhad, Mashhad, Iran 48978; and ‡ Manitoba Agriculture, Food and Rural Initiatives, Livestock Knowledge Centre, Winnipeg, Manitoba, Canada R3T 5S6 Primary Audience: Nutritionists, Commercial Poultry Producers, Veterinarians SUMMARY The objective of this study was to compare the performance of a modern commercial broiler strain (Ross 308; RS) with that of two 1970s broiler strains (broiler strains 1 and 2) fed a drug- free low-protein or recommended-protein diet. All chicks were vaccinated on d 1 against coc- cidiosis using the edible immunocox gel vaccine (Vetech Laboratories Inc., Guelph, Ontario, Canada). Six hundred straight-run chicks of each strain were divided into 10 groups of equal weight and randomly placed in 30 floor pens. Five pens of each strain were randomly assigned to the recommended-protein or low-protein dietary regimen. The low-protein grower diet was used as the finishing diet (d 30 to 63). The BW gain (BWG) and FCR of the RS birds were bet- ter ( P < 0.05) than those of broiler strain 1 birds by 35.6 and 12.2% and those of broiler strain 2 birds by 53.4 and 12.3%, respectively. The BWG and FCR up to 30 d of age were depressed ( P < 0.05) regardless of the strain when the low-protein diets were fed to birds. The low-protein diets, however, depressed ( P < 0.05) the overall (d 63) BWG of only the RS birds (3,992 vs. 3,771 g/bird). Therefore, the 1970s broiler strains compared with the RS strain had slower growth and performance, but were less sensitive to a decrease in dietary protein. The faster growth rate of the modern RS broiler strain compared with the 1970s strains was due to genetic improvement of the RS strain. Key words: broiler , dietary protein , 1970s strain , modern strain , performance DESCRIPTION OF PROBLEM The use of low-level therapeutic antibiotics to enhance growth performance in the poultry industry is a concern to consumers because some claim it may lead to antimicrobial resistance . In response, an examination of methods to mini- mize or eliminate the use of growth promoters in the poultry industry is needed. A drug-free poul- try meat market has recently gained attention in Europe and North America [2–4]. Governments in Europe are encouraging drug-free production methods, with the objective of satisfying con- sumer demand and encouraging the export of drug-free meat products ....
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