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Assessment of factors influencing body composition of broiler chickens

University of British Columbia

Seven experiments, involving 14,760 growing male and female broilers, were conducted to test the effect of genotype, dietary protein, amino acid profile and cereal, and lighting programs on body lipid content at market weight. Among three pure strains of broiler chickens obtained from a Canadian breeder (Shaver), the Cornish 2 strain grew the fastest and contained the highest body fat (p<0.05). The White Rock strain grew most slowly, and the Cornish 1 strain was intermediate. Among three commercial strains obtained from Shaver, all had very similar growth rates and carcass lipid content. Birds fed a high-protein (HP) diet had a significantly lower body lipid content (p<0.001), and a significantly (p<0.001) decreased energy retention as compared with those fed a low-protein (LP) diet. With the increase of body energy retention per kg W[sup 0.75], an increasing proportion of retained energy was directed to body fat. An LP diet may reduce nitrogen excretion but it may result in a fat carcass. It was found that three LP diets with different essential amino acid profiles did not result in increased body lipid deposition, but they significantly reduced nitrogen excretion as compared with the control diet (NRC, 1994). Barley and wheat diets significantly reduced body fat deposition as compared with a corn diet without affecting final body weight. These results were supported by the observation that the higher the barley or wheat percentage in a diet, the lower the body fat content. Addition of wheat bran to a corn diet also reduced body fat deposition. Body lipid deposition and liver fatty acid synthesis rate were significantly lower in barley-fed birds than in corn-fed birds, with an intermediate level in wheat-fed birds. It can be concluded that barley or wheat in a diet can reduce liver fatty acid synthesis, resulting in lower body lipid content. Three increasing lighting programs (INC 2, INC 3 and INC 4) reduced early feed intake and body weight gain and resulted in complete or near complete compensatory growth in body size at 6 wk of age. The birds reared under INC 2, INC 3 and INC 4 contained significantly higher body water and protein contents (p<0.05) but lower body lipid content (p<0.11) than those reared under the control lighting program (16L: 8D). These results indicate that bird body lipid accretion can be effectively reduced by genetic selection, dietary (protein, amino acid, cereal) manipulation and environmental (lighting) control.

Thesis/Dissertation

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2009-07-23

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http://hdl.handle.net/2429/11223

Animal Science

University of British Columbia

UBCV

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