The aim of the present trial was to study the effect of two different dietary phosphorus (P) levels on the laying performance in long-term (17 months) egg production and egg shell quality in terms of strength and thickness from the 7th to 17th month of laying. In case of eggshell quality parameters the time effect as well as the interaction between dietary P levels and time were also examined. Sixty Tetra-SL layers were fed diets with two different levels of P (4.9 or 4.4 g/kg total phosphorus) at constant 38.5 g/kg calcium level. In the course of the trial egg production %, egg weight, feed intake and body weight were recorded. At every 4th weeks 20 eggs per treatment were broken to deretmine the strength and thickness of eggshell. Results showed that the examined two levels of dietary P did not affect the percentage of egg production and the feed conversion ratio (kg feed/kg egg mass). The egg weight significantly increased and eggshell strength was significantly lower when hens received the lower dietary P feed. During the laying period, both the eggshell strength and thickness gradually decreased as laying period time went on. In conclusion phosphorus content of the layer diet can be lowered, without reducing the egg production, nevertheless approaching the end of the long laying period, higher P-content feed suggested, whereby eggshell strength can be improved.

hen; diet; phosphorus; long laying period; eggshell quality

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia