REGULAR ARTICLES Level of Leucaena leucocephala silage feeding on intake, rumen fermentation, and nutrient digestibility in dairy steers Nguyen Thien Truong Giang 1 & Metha Wanapat 1 & Kampanat Phesatcha 1 & Sungchhang Kang 2 Received: 11 November 2015 /Accepted: 18 April 2016 # Springer Science+Business Media Dordrecht 2016 Abstract The objective of this experiment was to determine effects of Leucaena silage (LS) feeding on feed intake, nutri- ent digestibility, and rumen fermentation in dairy steers. Four rumen fistulated dairy steers, 167 ± 12 kg body weight (BW), were randomly assigned to receive dietary treatments accord- ing to a 4 × 4 Latin square design. Treatments were as follows: T1= 100 % untreated rice straw (RS), T2 = 70 % RS+ 30 % LS, T3 = 40 % RS + 60 % LS, and T4 = 100 % LS, respective- ly. All animals were fed rice straw and LS ad libitum with concentrate mixture supplemented at 0.2 % BW. The results found that dry matter intake and nutrient digestibility were the highest in dairy steers fed 60 % LS (P < 0.05). Ruminal tem- perature and pH were not affected by LS feeding (P > 0.05) while ruminal ammonia nitrogen and blood urea nitrogen con- centration were linearly increased with increasing levels of LS feeding (P < 0.01). On the other hand, total volatile fatty acids and propionate (C 3 ) were improved by LS feeding especially in steers fed 60 % LS (P < 0.05) whereas acetate (C 2 ) produc- tion and C 2 /C 3 ratio were decreased. Moreover, methane pro- duction was reduced together with increasing LS feeding level (P <0.05). Based on this study, it could be concluded that 60 % LS feeding could enhance feed intake, digestibility, and rumen fermentation end-product while reducing methane production in dairy steers. This study suggested that LS could be used as high-quality roughage for ruminant feeding in the tropical region. Keywords Dairy steers . Leucaena silage . Methane . Rice straw . Rumen fermentation Introduction Leucaena (Leucaena leucocephala) can be a locally excellent choice for alternative protein resources for ruminants due to its high protein, palatability, digestibility, and availability. Its amino acid content is well balanced as compared to alfalfa. According to Garcia et al. (1996), Leucaena contained protein at high level of 29.2 % in leaf and 22.03 % in stem and leaf. In addition, it does not cause bloat, probably due to its secondary compounds such as tannin content (Gupta et al. 1992). This compound has positive effect without reducing dry matter intake if animal is fed small amount. Condensed tannins bind to dietary protein to form tannin-protein complex which can avoid protein degradation in rumen and increase protein by- pass in the lower gastrointestinal tract, resulting in high pro- tein absorbed into animal body (Wanapat et al. 2015; Barry and Duncan 1984). In addition, it also contains sulfur content which is necessary condition for sulfur using bacteria to grow, especially for cellulolytic degradation bacterial species. However, it also has drawback because of mimosine toxicity. Mimosine is a toxic non free amino-acid, and degraded by rumen microbe enzymes into 3-hydroxy-4(1H)-pyridone (DHP) (Hegarty et al. 1964) which is toxic for both ruminants and non-ruminants, resulting in production of goiters, loss of hair, and reduced fertility. According to Hegarty et al. (1976), animal fed with Leucaena, DHP is absorbed into blood and acts as a potent goitrogen. * Metha Wanapat metha@kku.ac.th 1 Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand 2 Agricultural Unit, Department of Education, National Institute of Education, Phnom Penh, Cambodia Trop Anim Health Prod DOI 10.1007/s11250-016-1060-3