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Dimethylglycine (DMG) is a naturally occurring tertiaryamino acid in the intermediary metabolism of betaine inliving organisms. Dietary supplementation in broiler diets results in improved apparent faecal digestibility of thecrude protein and carbohydrate fraction. This is hypothesisedto result from an emulsifying effect of DMG in theintestinal tract, which allows non-fat nutrients to be moreefficiently absorbed, rendering more nutrients available forutilisation (Kalmar et al., 2010; Prola et al., 2013). DietaryDMG has also been shown to improve carcass characteristicsby decreasing fat deposition and increasing meatyield. These changes are linear in the range between 0and 1 g Na DMG/kg feed and are more pronouncedwith increased level of dietary polyunsaturated fatty acids(Kalmar et al., 2011). Kalmar et al. (2011) suggestedenhanced utilisation of dietary fat as an energy source asa possible underlying basis. Namely, dietary fat is utilisedas a source of energy, instead of being deposited as bodyfat. Consequently, less protein is used to provide energy,which promotes lean growth. Therefore, dietary DMG notonly reduces feed costs, but also has potential environmentalbenefits because of improved protein utilisation,which has been demonstrated by reduced N excretion intourine (Kalmar et al., 2010). Possibly, DMG also influenceshepatic gene expression by affecting DNA methylation, ashas been demonstrated for other methylamine derivates(Emmert et al., 1996; Niculescu et al., 2006). Effects ofdietary DMG on hepatic gene expression are currentlyunder investigation.The aim of this study was to assess the efficacy ofdietary supplementation with DMG at a level of 1 g NaDMG/kg to improve broiler performance. Three broilertrials were conducted at different European locations, atwhich distinct broiler strains and basal diets were used 6 replicate male pens and 6 replicate female pens pertreatment. A 3-phase feeding programme was used with astarter diet from day 1 until day 14, a grower diet from day15 until day 28, and a finisher diet from day 29 until day39. Each floor pen was 2.2 1.8 m (length width) andhad softwood shaving litter as bedding. Lighting schedulewas 24 h light during the first 3 d, followed by 23 hlight:1 h darkness until day 7, and then 18 h light:6 hdarkness until slaughter. Ambient temperature waskept at 28 1C during the first 2 wk, and after day 15,it was reduced by 0.5 1C per day until 22 1C was reached.Additionally, the temperature at the surface of the beddingwas monitored and maintained at about 34 1C by infra-redheaters until day 21. Relative humidity was 60.073.5%. Allbirds were vaccinated against coccidiosis (Paracox; EssexPharma GmbH, Munich, Germany) at 9 d of age by individualoral application at the dose level of 0.1 mL/broiler chicken
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