Effect of encapsulated nitrate as an alternative source of nitrogen, with or without elemental sulphur, on nutrient intake and digestibility of beef cattle

For many years, nitrate has been used as a ruminant feed additive to produce ammonia (Sokolowski et al., 1959). Ammonia is the major source of nitrogen for protein synthesis by rumen microbiota (Leng et al., 2008); and microbial protein provides the amino acids needed for animal growth, reproduction and milk production (Godwin et al., 2014). Therefore, the inclusion of nitrate could be an economical replacement for part of the protein in feedlot rations. We evaluated the effects of encapsulated nitrate supplementation on nutrient intake and digestibility of steers. Five Nellore steers (317 kg ? 45 kg BW) fitted with ruminal cannulas were used in a 5 x 5 Latin square design experiment. The five experimental diets were prepared and fed once daily: T1) control, which had soybean meal as the main protein source; T2) soybean meal was replaced by 0.8% urea on a DM basis; T3) 0.8% urea on a DM basis plus 0.24% elemental sulphur (9:1); T4) soybean meal was replaced by 2% Encapsulated nitrate (EN) on a DM basis; T5) 2 % Encapsulated nitrate on a DM basis plus 0.24% elemental sulphur (9:1). All diets were isonitrogenous (15.5% CP) and isoenergetic (70% TDN) consisted of chopped Tifton hay and concentrate (50:50 on DM basis). The amount of NDF provided in each treatment was 46.71% ? 0.31%. Feed refusals were collected and weighed before feeding for all d of each experimental period. Feces were collected for 5 d to estimate the digestibility of dietary constituents. Feed and faecal dry matter (DM), organic matter (OM), neutral detergent fibre (NDF) and crude protein (CP) contents were determined. The variables were analysed as a Latin square design (confidence interval = 95%) using software R. DM, OM, NDF intake were not affected by the treatments (P>=0.08). CP intake did not differ between treatments T1, T2, T3 and T5. In contrast, CP intake was greater for T1 than T4 (P=0.01). DM and OM digestibility were higher for T1 compared to T3 (P=0.04 and P=0.02, respectively). NDF and CP digestibility were not affected by treatment (P>=0.13). According to the above, not observed statistical difference for NDF, DM, OM intake, and NDF, DPB digestibility. Thus, the NE and S may be included in the diet of Nellore steers to partially replace the source of true protein.