Effects of urea plus nitrate pretreated rice straw and corn oil supplementation on fiber digestibility, nitrogen balance, rumen fermentation, microbiota and methane emissions in goats
Zhang, X., Medrano, R.F., Wang, M., Beauchemin, K.A., Ma, Z., Wang, R., Wen, J., Bernard, L.A., Tan, Z. (2019). Effects of urea plus nitrate pretreated rice straw and corn oil supplementation on fiber digestibility, nitrogen balance, rumen fermentation, microbiota and methane emissions in goats, 10(1), http://dx.doi.org/10.1186/s40104-019-0312-2
Plain language summary
This is a collaboration with Chinese researchers. Rice straw is an abundant crop residue in rice producing areas, such as China and Southeast Asia. However, rice straw has low nutritive value, which limits its wide and
efficient use in ruminant diets, because of the high content of indigestible structural polysaccharides and low crude protein content. Enteric methane from ruminants is an important source of greenhouse gas and represents a loss of 2–14% of dietary energy. Feeding straw results in greater methane emissions per unit of feed digested than high quality forage, because it has a slow passage rate and prolonged residency time in the rumen. Before promoting the use of rice straw in ruminant diets, strategies are needed to improve its digestibility and decrease its methane emissions. The study examined the use of urea to pretreat rice straw to enhance its nutritional quality by destroying fiber structure and increasing non-protein nitrogen content. We combined urea with nitrate, because nitrate has been identified as a possible strategy to reduce methane emissions. We also used oil, because it is another option to decrease methane emissions from ruminants.We concluded that a combination of rice straw pretreated with urea plus nitrate and corn oil supplementation of the diet improved fiber digestibility and lowered enteric methane emissions without negative effects on nitrogen retention by the animals. These strategies improved the utilization of rice straw by goats.
Background: Urea pretreatment is an efficient strategy to improve fiber digestibility of low quality roughages for ruminants. Nitrate and oil are usually used to inhibit enteric methane (CH ) emissions from ruminants. The objective of this study was to examine the combined effects of urea plus nitrate pretreated rice straw and corn oil supplementation to the diet on nutrient digestibility, nitrogen (N) balance, CH emissions, ruminal fermentation characteristics and microbiota in goats. Nine female goats were used in a triple 3 × 3 Latin Square design (27 d periods). The treatments were: control (untreated rice straw, no added corn oil), rice straw pretreated with urea and nitrate (34 and 4.7 g/kg of rice straw on a dry matter [DM] basis, respectively, UN), and UN diet supplemented with corn oil (15 g/kg soybean and 15 g/kg corn were replaced by 30 g/kg corn oil, DM basis, UNCO). Results: Compared with control, UN increased neutral detergent fiber (NDF) digestibility (P < 0.001) and copies of protozoa (P < 0.001) and R. albus (P < 0.05) in the rumen, but decreased N retention (-21.2%, P < 0.001), dissolved hydrogen concentration (-22.8%, P < 0.001), molar proportion of butyrate (-18.2%, P < 0.05), (acetate + butyrate) to propionate ratio (P < 0.05) and enteric CH emissions (-10.2%, P < 0.05). In comparison with UN, UNCO increased N retention (+34.9%, P < 0.001) and decreased copies of protozoa (P < 0.001) and methanogens (P < 0.001). Compared with control, UNCO increased NDF digestibility (+8.3%, P < 0.001), reduced ruminal dissolved CH concentration (-24.4%, P < 0.001) and enteric CH emissions (-12.6%, P < 0.05). Conclusions: A combination of rice straw pretreated with urea plus nitrate and corn oil supplementation of the diet improved fiber digestibility and lowered enteric CH emissions without negative effects on N retention. These strategies improved the utilization of rice straw by goats. 4 4 4 4 4 4