Comparative Effects of Supplemental DL-2-hydroxy-4-[methylthio] Butanoic Acid and DL-methionine in Diet on Egg Production and Quality in Laying Hens

This study was conducted to compare the effects of DL-2-hydroxy-4-[methylthio] butanoic acid (HMB) and DL-methionine (DLM) on egg production performance and egg quality of laying hens. Two hundred and eighty-eight commercial laying hens were assigned to 3 dietary treatment groups and fed the experimental diets from 34 to 46 weeks of age. The bioefficacy of HMB relative to DL-methionine (DLM) was set at 88% (weight/weight), therefore 0.115% of HMB and 0.101% of DLM were added to a basal diet. DLM and HMB supplementation increased body weight, feed intake, hen-day egg production, egg weight, FCR and egg mass (P<0.01). These supplementations also increased yolk and albumen weight (g/egg) (P<0.01), while DLM slightly decreased albumen weight (% of egg). Consequently, Haugh unit was poor by DLM supplementation but did not by HMB supplementation (P<0.05). DLM supplementation significantly increased fat content in egg (g/egg and % of egg), though level of estradiol in blood was elevated by HMB supplementation. In conclusion, HMB supplementation (as 88% bioefficacy of DLM) can be used as an effective methionine source. However, mechanism of protein and fat synthesis and/or degradation of laying hens may be differed when different form of methionine is supplied.