EFFECT OF DIETARY-PROTEIN LEVEL ON LIPID DEPOSITION IN BROILERS DURING THE FINISHING PERIOD

Male and female broilers were fed from 3 wk of age with one of 2 experimental diets containing 20 or 23% of crude protein and 3 170 kcal metabolisable energy (ME)/kg. Twenty-five birds per treatment were slaughtered at 5 or 7 wk of age to study the influence of dietary protein concentration on lipid deposition both in abdominal cavity and in the rest of the carcass. Though the higher protein diet did not modify the weight gain, it improved the feed conversion and reduced the fattening of birds. This effect was obtained 2 wk after experimental food distribution. The reduction in fattening was more pronounced in females than in males using abdominal fat ratio as a criterion. On the other hand, the lipid proportion in the rest of the carcass was more reduced in males than in females when birds were fed 23% protein (11.3 versus 7.7% at 7 wk of age). Linear regression equations between abdominal fat and lipid content in the carcass confirmed that the decreasing of lipid content obtained with a higher protein concentration in the diet depended on the adipose compartment and on the sex of broilers. The carcass lipid content cannot be determined accurately from abdominal fat alone and is consistently affected by the composition of the diet.