The word "ruminant" comes from the Latin ruminare, which means "to chew over again". From this the origin of a word, people can vividly feel the process of how are ruminant acquired food.

Rumen is one of the most important parts for the ruminants, which help ruminant acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The microbes in it can provide ruminants with protein used for growth and maintain activity. Both the exogenetic and endogenous nitrogen make significant contributions to the ruminal N pool which is necessary for the rumen microbial growth.

Even though ruminant is important, many researchers believe that it should be paid more attention to the endogenous nitrogen (EN) contribution in the small intestine of ruminants. There is a tendency towards acknowledging that the endogenous protein makes up a considerable fraction of duodenal N flow, and determination of EN along the gastrointestinal tract allows for a better adjustment of both supply and requirement for N and amino acids (AA) in ruminants.

In order to make a more accurate estimation of true N digestibility and know how much dietary N is needed to cover the requirement for EN and endogenous AA (ENAA) loss by the knowledge of EN loss, PhD. ZHOU Chuanshe and his group from Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) ,led by professor TAN Zhiliang, carried out an experiment. They chose four goats fitted with ruminal, duodenal and ileal cannulas as the experiment animals, the goats were randomly assigned to one of four treatments in a 2*2 factorially arrangement with two dietary ruminal degraded protein(RDP)to ruminal undegraded protein(RUP) ratios and two feed intake levels. Scientists found that the dietary ratio of RDP to RUP can significant affect the ileal flows of endogenous leucine,phenylalanine and cysteine, the feed intake had significant effects on the intestinalre-absorption of endogenous isoleucine, leucine, lysine and tyrosine. The dietary ratio of RDP to RUP and feed intake had significant interaction effects on the intestinal re-absorption of endogenous threonine.

So far, there were few studies been conducted to examine the effect of dietary ratio of RDP to RUP and feed intake on the flow of EN and ENAA in ruminants. Zhou's research showed that there were no significant differences in the duodenal flow of EN and total ENAA within the range of dietary ratios of RDP to RUP for growing goats. The endogenous losses were insensitive to the feed intake in this research, when the feed intake changed from 0.63 kg/d to 0.50 kg/d, the duodenal and ileal flow of endogenous N decreased respectively by about 22% and 9%. In summary, the duodenal and ileal flows of EN and total ENAA were not significantly affected by the dietary ratio of RDP to RUP and feed intake.

This research had received financial support from National Natural Science Foundation of China (No.31001024, No.31320103917), Ministry of Science and Technology of the People`s Republic of China (No. 2012BAD14B17), Chinese Academy of Sciences (No. KFJ-EW-STS-071) and Hunan Provincial Science and Technology Department (2013TF1006).

The article has been published on Archives of Animal Nutrition, details could be found at http://www.tandfonline.com/doi/abs/10.1080/1745039X.2015.1093872?journalCode=gaan20 

Contact: TAN Zhiliang

E-mail: zltan@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences