The effects of different levels of pennyroyal (Menta pulegium L.) and ration crude protein on performance and blood metabolites of laying hens

This experiment was conducted to evaluate the effects of different levels of pennyroyal and ration crude protein levels on performance, egg quality and blood metabolites of laying hens. Experiment was conducted as a factorial (3*3) (0, 1, 2% pennyroyal) and crude protein (NRC, 10, 20% lower than NRC recommendation) in a completely randomized design with 432 of Hy- line (W36) laying hens in 9 treatments and 4 replicates (with 12 hen in each replicate) for 12 weeks from 25-37 weeks of hens age. Using of 2% pennyroyal and ration crude protein and interaction between them negatively affected the performance of laying hens. The use 2% pennyroyal increased the percentage of eggshell. The egg production, egg mass and feed intake reduces in using pennyroyal and low crude protein diets. In interaction effects the best performance was observed in diet with no pennyroyal and NRC crude protein level. Using pennyroyal with low crud protein diets reduced the egg production percentage, egg mass, feed intake and increased the feed conversion. Interaction between pennyroyal and ration crude protein significantly affected the eggshell strength and Haugh unit. 2% pennyroyal reduced the blood uric acid level and 10% lower crude protein than NRC recommendation reduced blood total crude protein percentage. By reducing 20% ration crude protein, the percentages of hetrophlis increased and lymphocytes decreased. The overall results showed that in laying hens using pennyroyal, 10% and 20% crude protein lower than NRC recommendation have adverse effects on their performance.