Comparison between predicted total digestible nutrients and actual total digestible nutrients using nutrient digestibility of rice straw and timothy in ruminants

This study attempted to compare total digestible nutrients (TDN) calculated as Rohweder, NRC, and Waldo and Peiqiang methods and TDN measured as digestibility of in vivo appearance. Rohweder method showed that the TDN of rice straw and timothy were 54.32% and 57.79%, respectively. In NRC method, the digestibility of neutral detergent fiber (NDF) and TDN of rice straw were 50.76% and 53.15%, respectively. When NRC method was applied in Timothy, the digestibility of NDF and TDN were 51.53% and 55.22%, respectively. Waldo and Peiqiang method calculated the results through the rumen in situ test. NDF digestibility of rice straw and timothy was 44.61% and 51.82%, which was different from the results of NRC method. In addition, TDN was predicted to be 48.85% for rice straw and 55.41% for timothy. In the in vivo apparent digestibility experiment, the digestibility of NDF and TDN in rice straw was 41.10% and 44.79%, respectively. In timothy, the digestibility of NDF and TDN were measured as 51.29% and 58.18%, respectively. As a result of a series of studies, rice straw was found in Rohweder and NRC methods showed higher TDN than other methods. In this study, there was a difference in rice straw by measurement method, but there was no difference in timothy. Therefore, when evaluating the value of feed in order to provide roughage to ruminant, calculation methods must be modified and supplemented. In addition, TDN should be considered to apply several evaluation methods instead of one method.