<![CDATA[Abstract This research aims to see the effect of giving Mannan Oligosaccharides (MOS) and citric acid at different levels on the protein efficiency ratio of broiler chickens. The research was carried out in a poultry experimental cage at the Faculty of Animal Husbandry, Jambi University using 200 Day Old Chicks (DOC) chickens. In this research, the experimental method was used with a completely randomized design (CRD) consisting of 5 treatments with 4 repetitions. The treatments are P0: without MOS and without citric acid (control), P1: giving 0.25% MOS + 1% citric acid through drinking water, P2: giving 0.25% MOS + 2% citric acid through drinking water, P3: administering 0.5% MOS + 1% citric acid through drinking water, and P4: administering 0.5% MOS + 2% citric acid through drinking water. Data were processed using analysis of variance (ANOVA) and Duncan's advanced test. The results showed that the administration of Mannan Oligosaccharides (MOS) with citric acid had a significant difference (P<0.05) on drinking water consumption, ration consumption, protein consumption, body weight gain and protein efficiency ratio. It was concluded that the protein efficiency ratio with administration of 0.5% Mannan Oligosaccharide (MOS) and 1% citric acid in drinking water was the same as administration without treatment (control). The use of 2% citric acid in drinking water has a significant effect on reducing the protein efficiency ratio of broiler chickens. Keywords: Citric acid; Mannan oligosaccharide (MOS); Protein efficiency ratio Abstrak Penelitian ini bertujuan untuk melihat pengaruh pemberian Mannan Oligosakarida (MOS) serta asam sitrat pada level yang berbeda terhadap rasio efisiensi protein ayam broiler. Penelitian dilakukan di kandang percobaan ternak unggas Fakultas Peternakan Universitas Jambi dengan menggunakan 200 ekor ayam Day Old Chicks (DOC). Dalam penelitian ini digunakan Metode experiment dengan rancangan acak lengkap (RAL) yang terdiri dari 5 perlakuan 4 pengulangan. Adapun Perlakuan tersebut yaitu P0: tanpa MOS dan tanpa asam sitrat (kontrol), P1: pemberian 0,25% MOS + 1% asam sitrat melalui air minum, P2 : pemberian 0,25% MOS + 2% asam sitrat melalui air minum, P3: pemberian 0,5% MOS + 1% asam sitrat melalui air minum, dan P4: pemberian 0,5% MOS + 2% asam sitrat melalui air minum. Data diolah menggunakan analisis sidik ragam (ANOVA) dan uji lanjut Duncan. Hasil penelitian menunjukkan bahwa pemberian Mannan Oligosakarida (MOS) dengan asam sitrat berbeda nyata (P<0,05) terhadap konsumsi air minum, konsumsi ransum, konsumsi protein, pertambahan bobot badan, dan rasio efisiensi protein. Disimpulkan bahwa rasio efisiensi protein dengan pemberian 0,5% Mannan Oligosakarida (MOS) dan 1% asam sitrat dalam air minum sama dengan pemberian tanpa perlakuan (kontrol). Penggunaan asam sitrat sebanyak 2% dalam air minum berpengaruh nyata terhadap penurunan rasio efisiensi protein ayam broiler. Kata kunci: Asam sitra; Mannan oligosakarida (MOS); Rasio efesiensi protein]]>
