Effect of protein restriction on performance, nutrient digestibility and whole body composition of male Lohmann Dual chickens

As killing of day old male chickens of layer breeds becomes a greater concern in the public discussion, dual-purpose chicken hybrids, producing both eggs and meat, are of high interest. A trial was conducted to determine the effect of protein restriction on performance, nutrient digestibility and whole body composition of male dual-purpose chickens from 1 to 77 days of age. Three isoenergetic diets were formulated to provide three levels of protein, respectively, in each phase: 23.0, 22.1 and 20.4% CP in the starter phase (1 to 14 d); 21.6, 20.3 and 19.2% CP in the grower period (15 to 28 days) and 19.4, 18.6 and 17.5% CP in the finisher diet (29 to 77 days). A total of 480 male Lohmann Dual chickens were randomly allocated into 24 experimental pens, the diets were offered ad libitum to 8 replicates with 20 chickens. Weight gain , feed intake and feed conversion rate were not affected in the overall feeding period. Weight gain and feed intake differed only by dietary protein content in the grower period (P =0.017; P =0.038), but this did not affect overall performance. Within the groups data followed a normal distribution, but analysing the individual weights of the animals showed a split development with a clear difference in the growth rate of high and low performing birds. However, no difference between the feeding regimes could be detected within the groups of high and low performing birds. Nutrient digestibility was similar between groups. All data showed differences between control and the two low protein groups, but not between low protein groups, except for total digestibility of crude protein. Whole body composition was similar between the groups and dietary protein restriction did not influence protein, fat, calcium and phosphorus levels. In conclusion, the data indicate that the dietary protein level can be reduced for the tested chicken strain, which would result in economic and environmental benefits without negative impact on animal performance and carcass quality .