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International Journal of Poultry Science

.: Home > International Journal of Poultry Science > 2007 > Volume 6 Number 3 > G. Rahimi1 and M. Hassanzadeh2

Effects of Different Protein and Energy Contents of the Diet on Growth Performance and Hormonal Parameters in Two Commercial Broiler Strains

G. Rahimi1 and M. Hassanzadeh2
1Department of Animal Sciences, Faculty of Agricultural Sciences, University of Mazandaran, Sari, Iran 2Department of Poultry Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
Abstract :

The present study was carried out to investigate the influence of energy and protein contents of the diet on growth performance and to evaluate further interactions of dietary manipulation and genotype on
endocrine parameters in broiler chickens. 1200 day-old male and female broiler chicks from 2  commercial broiler strains (Hybro and Ross) were fed ad libitum from day 1 onwards by 4 different diets either with a highor low energy combined with a high or low crude protein content. Body weight and feed intake were measured weekly. Venous blood samples were taken (10 birds/sex /line/diet group) weekly from day 14 on, for plasma Growth Hormone (GH), Triiodotyronine (T ) and Thyroxin (T ) content. Relative growth rate 3 4 was higher in broiler chickens which fed the low energy diet compared to high energy diet during the first week of age, while from week 1 on, a reverse effect of energy on relative growth rate was found. The effect of energy and protein on feed intake was significant (p<0.05), while no interaction between energy and protein was found. Within high energy diet, birds fed low protein diet showed a tendency for higher T levels, 3 while on low energy diet, broiler chicks fed high protein level showed a tendency for higher plasma T3 concentrations, probably explaining the presence of a significant energy×protein interaction. Protein content of the diet, significantly (p<0.05) affected plasma T levels while energy content had no effec. The higher GH 4 as well as T levels in the younger chicks may be an indicator of higher requirement of these hormones for 3 protein synthesis during the fast growth phase. It can be concluded that higher protein content of the feed could result in lower T , higher T and higher plasma GH levels. Possible causal mechanisms underlying 3 4 this phenomenon are discussed.

Keywords :
Diet, energy, protein, broilers, GH, T , T 3 4

Date Deposited : 14 Jul 2011 12:38

Last Modified : 14 Jul 2011 12:38

Official URL:

Volume 6, Number 3, - 2007 , ISSN 1682-8356

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