The purpose of the present study was to evaluate the response of laying hens to the low-phosphorus diets based on different kinds of cereal grains and supplemented with microbial phytase. Laying performance, feed intake, egg shell quality as well as bone strength parameters and Ca, P, Mg and Zn contents in the bones were involved as experimental parameters. At the age of 17 weeks, 288 Lohmann Brown pullets were assigned to the six dietary treatments, each treatment consisting of 12 cages with 4 birds per one. Until the beginning of the laying period the pullets were fed a standard diet containing 145 g of crude protein and 11.3 MJ ME, 4 g non-phytate P and 10.6 g of Ca per kg feed. The experimental diets provided from the first day of laying were based on maize (diets I, II, III) or on a combination of maize, barley and wheat (diets IV, V, VI) and contained about 165 g CP and 11.2 MJ ME/kg. In diets I, III or IV and VI the level of non-phytate phosphorus was decreased to 1.41 g/kg while in control diets (III or V) the amount of non-phytate P was 3.0 g/kg. In low-P diets III and VI microbial 6-phytase was included at the level of 450 FTU/kg diet.
The phosphorus level in diets did not affect the laying rate during the experimental period of 53 weeks. The higher P-level in feed enhanced egg shell strength only (P<0.01). Supplementation of low-P-diets with phytase did not affect the performance of hens, such as feed intake and egg quality, however it improved the egg shell strength as compared to low-P unsupplemented groups. Regarding strength and elasticity of the tibia, the P-level and phytase supplement were without visible effects. The best parameters that characterize the bone quality were obtained by addition of 3 g of non-phytate P level per kg of diets.Svrha ovog istraživanja bila je ocijeniti odgovor kokoši nesilica na obroke s niskim fosforom na bazi raznih vrsta žitarica s dodatkom mikrobijelne fitaze. Nesenje, unos hrane, kakvoća ljuske jaja kao i parametri čvrstoće kosti i sadržaj Ca, P, Mg i Zn u kostima bili su obuhvaćeni kao pokusni parametri. U dobi od 17 tjedana 288 pilenki Lohmann Brown izabrano je za šest hranidbenih tretmana, a svaki tretman sastojao se od 12 kaveza po 4 pilenke. Do početka nesenja pilenke su hranjene standardnim obrocima koji su sadržavali 145 g sirovih bje¬lančevina i 11.3 MJ ME, 4 g nefitinskog P i 10.6 g Ca po kilogramu hrane. Pokusni obroci su se prvog dana nesenja temeljili na kukuruzu (obro¬ci I, II, III) ili na kombinaciji kukuruza, ječma i pšenice (obroci IV, V, VI) i sadržavali su oko 165 g CP i 11.2 Mj ME/kg. U obrocima I, III ili IV i VI razina nefitinskog fosfora smanjena je na 1.41 g/kg dok je u kontrolnim obrocima (III ili V/) količina nefitinskog P bila 3.0 g/kg. U obrocima s niskim P (III i VI) uključena je mikrobijelna 6-fitaza na razini od 450 FTU/ kg obroka.
Razina fosfora u obrocima nije djelovala na postotak nesivosti u pokusu od 54 tjedna. Više razine P u hrani povećale su samo čvrstoću ljuske jajeta. (P < 0,01). Dodavanje fitaze u obroke s niskim P nije dje¬lovalo na unos hrane i kakvoću jaja, međutim poboljšalo je čvrstoću ljuske jajeta u usporedbi sa skupinama s niskim P bez dodataka. Što se tiče čvrstoće i elastičnosti goljenice, razina P i dodavanje fitaze nije imalo vidljivih učinaka. Najbolji parametri koji karakteriziraju kakvoću kosti dobiveni su dodavanjem 3 g nefitinskog P na kg obroka
