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Published online by Cambridge University Press: 27 February 2018
Since the 1980’s, two feed evaluation systems, the NRC and the INRA, have been proposed, suggesting allowances for energy and protein (Cuddeford, 1998). NRC recommendations include suggestions for digestible energy (DE) and digestible crude protein (DCP in 1978) and later crude protein (CP in 1989). INRA, (from 1984-1990), have firstly suggested the Net Energy System (NE), also referred to as the UFC system in French, (so called, as the NE system relies on expressing the NE value of a feed relative to a reference feed [barley], or Horse Feed Unit). The INRA have also gone on to recommend the Horse Digestible Crude Protein system (HDCP, or MADC in French). Whilst the INRA and NRC systems have both proposed nutritional requirements, the NRC is exclusive in its use of a protocol called the ‘factorial method’.The factorial method was initially contrived to allow for the determination of physiological expenditure, where the efficiencies of the nutrients were known and relevant. Other influences could then be considered by implementing feed trials to determine allowances which would take into account most environmental factors. Both the NRC and the INRA have proposed a range of Dry Matter Intake (DMI) values, which intend to meet the nutritional requirements of differing types of horses. DMI values provided by the INRA have been drawn directly from feeding experiments conducted over the last 30 years. Ingestibility of the main types of forages have also been extensively measured in horses, using feeding trials devoted to that purpose. The following chapter will review existing methods and suggest a progression strategy towards a common rationing system.