Equivalência de fósforo usando um estudo de meta-análise e transcriptômica em frangos de corte alimentados com fitase

Abstract

The present study was carried out in three stages: in the first part, a bibliographical survey was carried out of pertinent assays to the requirement of available phosphorus (aP) of broilers in two breeding periods (1 to 21 days old and 1 to 42 days old) also work that used phytase in the diets. Weight gain and bone ash responses of the animals were considered as variables. These data were cataloged, grouped, selected, filtered and standardized, and two aP equivalence equations were determined when the phytase is add in feed. The second part was validated the equations obtained in the first part. Two experiments were carried out with male Cobb 500 broilers, with 15 birds per replicate and each treatment with six replicates. The treatments consisted of three levels of phytase inclusion (450/900/1350 FTU) and a reduction of the respective aP equivalence values. In the experiment 1 and 2, the positive control was formulated with 0.37% of aP and 0.79% of calcium (Ca) at 1 to 21 days old and 0.27% of aP and 0.57% of Ca at 22 to 42 days old. The same Ca4 levels were used for all treatments. In the third part, an experiment (3) was carried with male Ross 700 for liver transcriptomic analysis. Two periods were considered from 1 to 21 and 22 to 41 days old with six replicates of 15 birds each. The birds received aP deficient diets supplemented with 500 and 1500 FTU/kg plus a positive control. All diets had the same Ca level. The aP equivalence are 0.10/0.14/0.19% for 1 to 21 days old and 0.09/0.14/0.19% for 1 to 42 days old. No difference (P> 0.05) to weight gain (WG), feed conversion ratio (FCR) and alkaline phosphatase concentration (FAK) between the birds fed with control diet and birds fed with treatments supplemented with phytase and reduced levels of aP were observed. At the same age the birds fed with 450/900FTU/kg considering 0.19% of aP equivalence had better (P <0.05) bone ash (ASH) in tibia compared to the birds fed control diet. The same result for birds fed with 450FTU/kg and 0.14% of aP equivalence. From 22 to 42 days old, no difference was observed (P> 0.05) in the ASH, however, the birds fed control diet had worst WG, FCR and FAK results comparing with some of phyatse treatments. At experiment 2 from 1 to 42 days of age, no WG difference (P>0.05) between the birds fed control diet and phytase treatments. The birds fed with 450FTU/kg and 0.19% of aP equivalence had lower feed intake (FI) and better ASH compared to the birds fed control di et. At the same aP equivalence, birds supplemented with 1350FTU/kg had lower FI and FCR comparing with those fed control diet. In experiment 3 at 1 to 21 days old the birds fed 500FTU/kg had worst performance results comparing with the birds fed control diet. At 42 days old, no difference (P>0.05) between treatments supplemented with phytase (500 or 1500 FTU/kg) and control treatment. The transcriptomic investigative results show a reduction in the expression of genes related to the translocation of small molecules when broilers were fed with 1500 FTU/kg, compared to the birds fed control diets. The results (experiment 1 and 2) suggest that both equations can be used for the determination of aP equivalence values for broiler chickens feeds, and also, the phytase may influence the liver gene expression of broilers.