Effects of Adding Methionine in Low-Protein Diet on Production Performance, Reproductive Organs and Chemical Liver Composition of Laying Hens under Tropical Conditions

Abstract: This study was conducted to determine the effects of adding DL-methionine (Met) in low-protein diet (Low-CP; 14 % CP) on egg production, reproductive organs, abdominal fat and chemical liver composition of laying hens under tropical conditions. Four hundred and eighty commercial laying hens (Isa-brown) during 24-44 weeks of age were fed with the Low-CP diet containing 0.26, 0.30, 0.38 or 0.44 % Met. Dietary protein 16 % CP with 0.38 % Met was offered as the positive control group. The results showed that hen-day egg production, egg mass and feed conversion ratio of hens received Low-CP diet with 0.26 % Met was the worst among experimental groups (P<0.01). Increasing Met to 0.44 % could improve hen-day egg production and egg weight as same as the control group, although FCR and egg mass of all Low-CP diet with various levels of Met were still significantly poorer (P<0.05). Interestingly, adding synthetic Met to Low-CP diet resulted in significant reduction of mortality rate compared to the Low-CP diet without adding Met and the control group (P<0.05). Hens received Low-CP diet with 0.44 % Met had lower yolk egg percentage than 0.26 % Met group. Moreover, higher eggshell thickness, ovary weight, oviduct weight and abdominal fat weight in supplementing Met groups were observed (P<0.05). However, adding Met could not achieve development of reproductive organs compared to the control. Liver fat and abdominal fat contents were linearly increased with the Met supplementation, while the liver protein was inversely reduced (P<0.05). In conclusion, the adding Met in Low-CP diet may give advantage to the hen raised under hot climate, particularly in case of mortality rate and eggshell thickness. Key words: Low-protein, methionine, laying-hen, production performance, tropica