Reducing the crude
protein level in broiler feeds

Similar to other species, a large part of the dietary nitrogen intake is not retained by the broiler but is excreted into the environment. Using standard diets, only 45% of dietary nitrogen intake is retained by the broiler body, and the rest is excreted into the litter with about 40% converted to ammonia leading to a deterioration in litter quality and so a deterioration in health status of the birds. A high CP level in the feed is moreover reported as a predisposing factor for necrotic enteritis. An excess of protein would also lead to a physiological need for an increase in water consumption to achieve efficient nitrogen excretion. As a consequence, high CP diets lead to higher levels of nitrogen and water excretion compared with low CP diets, leading to deterioration in litter quality and the birds’ environment.

Reducing dietary CP levels is thus a key solution to control nitrogen excretion and ammonia emission in poultry husbandry. Besides environmental benefits, low CP diets also impact upon bird health by reducing the occurrence of digestive disorders and by improving health status of the animal environment.

The impact of a significant CP level reduction in broiler feeds on growth performance was studied (Figure 4). The birds were offered a normal or a low CP diet differing by about 4.5 points in dietary CP. The diets were formulated to satisfy the broiler requirements and to contain the same amount of indispensable amino acids on a digestible basis per unit of ME.

Figure 4. Effect of lowering the dietary crude protein (CP) level on the growth performance and water intake of 3-week broilers (0.4-0.7 kg). ADG: average daily gain; FCR: feed conversion ratio.

It was possible to reduce the dietary CP level by 4.5 points with an adequate indispensable amino acid supplementation without impacting upon the performance of the birds.

These results confirm that it is possible to manipulate the dietary CP levels in broiler feeds without impacting upon performance as long as the indispensable amino acids supply is maintained at the bird requirements. This enables to maintain a good health status for the birds without depleting growth and carcass performance.

Reducing the dietary CP level and supplementing the diet with the corresponding limiting feed-grade amino acids reduces nitrogen excretion and limits the frequency and the severity of gut disorders. The use of low CP diets has no detrimental effect on performance when amino acids are correctly supplied, i.e. when the ideal amino acids profile is balanced and when the correct energy system is used.

For further information, please read our technical bulletins: numerous experimental results are reported.