The effect of phase nutrition during starter period on production performances and nitrogen content in feces of broilers of different genotypes

Objective of the research was to investigate the effect of phase nutrition, i.e. different mixtures used in broiler nutrition with phase reduction of protein content during starter period on production peformances of fattening chickens of different genotypes and on nitrogen content in faeces. Differences between groups (treatments) were in the type of mixtures use din starter period, and according to the following program: T1 (control group) - nutrition consisted of mixtures with 23% of proteins in duration from day 1 to 21; T2 - from day 1 to 14, mixture containing 23% of protein was used, and from day 14 to 21, mixture with 20% of proteins; T3 - from day 1 to 7, mixture was used containing 23% of protein and from day 7 to 21, mixture with 20% of proteins; T4 - nutrition with mixture containing 20% of proteins in duration from day 1 to 21. During the trial period (from day 1 to 21) production parameters were followed. Nitrogen content was determined in a collective faeces sample. Results showed that chickens of different genotypes expressed different sensitivity to protein restriction. Comparing the trial groups with the control in the third week, in chickens of Ross 308 provenience significantly lower body weight was registered only in chickens of T4 group with the highest protein reduction. In Cobb 500 chickens, significantly lower body weight was determined in T3 and T4 trial groups. In case of both hybrids, in T2 group, slightly lower body weight was established, but without statistically significant difference compared to the control. Feed conversion in both genotypes was the highest in T3 and T4 treatments. The program of phase nutrition resulted in decrease of the nitrogen content in faeces. Based on obtained data it can be concluded that applied nutrition treatments with drastic protein reduction during starter period in both genotypes had negative effect on production performances. Therefore, the composition and dynamics of mixture changes must be taken into consideration when formulating the program of phase nutrition, in order to achieve both goals - decrease of protein content in feed with simultaneous diminished nitrogen excretion and achieving good results.