5781 INTRODUCTION Forage production is dependent on soil type and cli- matic conditions (Sotomayor-Ríos and Pitman, 2001). In many countries, relatively low CP concentration (<10% of DM; NRC, 2001) and relatively large water require- ments (Rezaei et al., 2014) are the main limiting factors for producing corn silage. Therefore, it is necessary to consider unusual plants with great yield, CP concentra- tion, and digestibility and reduced water requirements as alternative feeds (Rezaei et al., 2014). Recently, certain species of amaranth (Amaranthus sp.) have been consid- Chemical composition, fermentation characteristics, digestibility, and degradability of silages from two amaranth varieties (Kharkovskiy and Sem), corn, and an amaranth–corn combination 1 N. Karimi Rahjerdi,* Y. Rouzbehan,* 2 H. Fazaeli,† and J. Rezaei* *Department of Animal Science, Faculty of Agriculture, Tarbiat Modares University, P.O. Box 14115-336, Tehran, Iran; and †Animal Science Research Institute, P.O. Box 1483, Karaj 315, Iran ABSTRACT: Amaranth (Amaranthus sp.) is a C 4 plant adapted to poor soils and regions with limited rainfall and high temperatures. The plant is character- ized by a yield of up to 85 t/ha, CP concentration of up to 28.5% of DM, and DM digestibility of 59 to 79%, which may vary depending on the species and vari- ety. The potential of this plant as a forage source for ruminants has not been completely considered. This study aimed at assessing the nutritive value of silages from corn (Zea mays), 2 amaranth (Amaranthus hypo- chondriacus) varieties (var. Kharkovskiy and Sem), and an amaranth–corn combination by chemical com- position, silage fermentation characteristics, in vivo digestibility, and in situ DM degradability. Treatments evaluated were ensiled corn var. hybrid SC 704 (EC), ensiled amaranth var. Kharkovskiy (EK), ensiled amaranth var. Sem (ES), ensiled corn–amaranth var. Kharkovskiy mixture, and ensiled corn–amaranth var. Sem mixture. Five sheep were used in a 5 × 5 Latin square design experiment to determine in vivo digest- ibility. The nylon bag technique was used to determine the in situ DM degradability using 3 ruminally fstulat- ed sheep. Compared with EK, ES had greater ash-free NDF (NDFom) and CP concentrations. In comparison with EC, the ensiled amaranths and corn–amaranth mixtures had a greater (P < 0.001) concentration of CP but less concentrations of NDFom, ADL (P < 0.001), and water-soluble carbohydrates (P = 0.034). Silage pH and ammonia-N concentration were the least (P < 0.001) for EC and greatest for ES. The EC had greater (P < 0.001) concentrations of lactic and acetic acids but less (P < 0.001) concentrations of propionic and butyric acids compared with the other silages. The in vivo DM digestibility (P = 0.035) and ME (P = 0.030) of EK and ES were greater than those of EC. Effective degradability of DM in EK and ES was less (P < 0.001) than with the other silages. Overall, mixing amaranth with corn improved concentration of CP and digest- ibility of the mixed corn–amaranth silages and has the potential of completing corn in ruminant diets. Key words: amaranth, in situ degradability, in vivo digestibility, silage © 2015 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2015.93:5781–5790 doi:10.2527/jas2015-9494 1 The authors wish to gratefully acknowledge Ali Mokhtassi- Bidgoli from Tarbiat Modares University for his assistance with agronomic management and statistical analysis of data, and Mr. Gary Easton for his English language correction of the manu- script. A special thanks to Mr. Ali Karimzadeh from ‘Panje Talaee Cultivation and Industry’ (Tehran, Iran), which works on amaranth production, for his kind support in supplying seeds of the amaranth varieties and producing forage for this research. 2 Corresponding author: rozbeh_y@modares.ac.ir Received July 4, 2015. Accepted October 5, 2015. Published December 18, 2015