Important! This text corresponds to the INRA-AFZ 2002 Tables and has not been updated yet.
In France, the first specific tables for horses, based on new nutritional concepts (net energy and digestible proteins expressed, respectively in Unités Fourragères Cheval – UFC, Forage units for horses – and in Matières Azotées Digestibles Cheval – MADC), were developed and published by INRA in 1984 (“Le Cheval”) and in 1990 (“Alimentation des chevaux”). The present tables are an evolution of these previous works, based on the same concepts but updated with recent data, thus improving the tools and the methods to predict energy and nitrogen values of horse feeds (Martin-Rosset et al., 1996).
The energy value of feeds is expressed in UFC. This energy unit corresponds to the net energy value of one kilogramme (as fed) of a reference barley, used for maintenance in the horse (INRA, 1984 and Vermorel and Martin-Rosset, 1997).
Origin of the data and characteristics of the data file
A group of 51 individual results of chemical composition and digestibility of feed materials were used to estimate the energy values. The majority of these data come from work performed in France (INRA), in the Netherlands (PR, Praktijkonderzoeck Rundvee, Schapen en Paarden, in collaboration with INRA), in Germany, in the United Kingdom, in Italy and in the United States of America. The file contains chemical composition data (ash, crude fibre and crude protein) and at least one of the following digestibility parameter: dry matter (DMd), organic matter (OMd) or energy (Ed) digestibility. OMd is essential for the determination of energy values. Although it is measured in most experiments, it was sometimes missing and was estimated by regression from the DMd. In a few rare cases, OMd and Ed were estimated from pig and ruminants values published in the present tables.
Development of equations to predict the energy value of feed materials
The UFC values for 51 feed materials were calculated using the factorial method, also called analytical method, which is distinctive for the net energy system of INRA. The relationships were established by regression between the reference UFC value previously calculated and the chemical composition with or without digestible organic matter (DOM) or digestible energy (DE) used as independent variables. The most precise calculated energy values were of course those including digestible elements in the prediction model (DOM or DE). These relationships use the following abbreviations: CF (crude fibre), CP (crude protein), CC (cytoplasmic carbohydrates, i.e. starch and sugars), OM (organic matter) and DOM (digestible organic matter), all expressed in % dry matter. DE is the digestible energy expressed in MJ/kg dry matter.
Concentrates (n = 51)
UFC = 0.815 – 0.947 CF / 100 + 0.0345 CP / 100 + 0.582 CC / 100 (r = 0.96; RSD = 0.06)
UFC = 0.131 – 0.628 CF / 100 – 0.282 CP / 100 + 1.340 DOM / 100 (r = 0.98; RSD = 0.04)
UFC = - 0.730 – 0.722 CP / 100 + 0.572 OM / 100 + 0.0941 DE (r = 0.99; RSD = 0.03)
UFC = - 0.134 + 0.274 CF / 100 – 0.362 CP / 100 + 0.316 CC / 100 + 0.0755 DE
(r = 0.99; RSD = 0.02)
Forages (n = 47)
UFC = - 0.056 + 0.562 CC / 100 + 0.0619 DE (r = 0.99; RSD = 0.01)
UFC = - 0.124 + 0.254 CC / 100 + 1.330 DOM / 100 (r = 0.99; RSD = 0.01)
Calculation of the energy values of feed materials
The energy values of the feed materials were first calculated using the INRA reference method (INRA, 1984; Vermorel and Martin-Rosset, 1997) when the digestibility was known. The digestibility values of 59 feed materials in the tables were derived from the same literature data that had served previously to establish the UFC system and notably the UFC value for concentrates. An additional 21 recent values obtained between 1984 and 1990, essentially by INRA, were also used. As it has already been indicated, the digestibility values for a small number of feed materials were taken from the pig or ruminant values presented in this book, when crude fibre and ADF was lower than 15 % dry matter or higher than 15 % dry matter respectively.
Energy digestibility (Ed) was calculated from OMd using a general equation established in collaboration in 1994 between INRA in France and PR in the Netherlands using a data file of 75 feed materials (concentrates and forages) for which Ed had been measured.
Ed (%) = 0.034 + Δ + 0.9477 OMd (%) (r = 0.99; RSD = 1.1)
with Δ = +1.1 for concentrates
Δ = -1.1 for forages
Digestible energy (DE) is calculated from gross energy (GE):
DE = GE x Ed / 100
Metabolisable energy (ME) can be predicted from digestible energy using regression equations between the ME/DE ratio and the chemical composition of the feed materials. These equations were established by INRA, using a data file of 81 results.
In the following equations, CF, CP and CC are expressed in % dry matter.
Feed materials with CP > 30 % on dry matter basis
100 ME/DE = 94.36 + 0.110 CF – 0.275 CP (r = 0.41; RSD = 1.75)
Sugar beet pulp
100 ME/DE = 89
Other feed materials
100 ME/DE = 84.07 + 0.165 CF – 0.276 CP + 0.184 CC (r = 0.67; RSD = 1.37)
Calculation of metabolisable energy:
ME = DE x 100 ME/DE
Efficiency of utilisation of metabolisable energy for net energy
The physiological situation used as reference in the UFC system is the maintenance (m). The efficiency of utilisation of ME is expressed by the coefficient km, where 0 < km < 1.
km can be predicted from the chemical composition of feed materials by taking into account, if necessary, the DOM for 5 groups of feed materials, using the equations established by INRA on a data file of 48 results (Vermorel and Martin-Rosset, 1997).
In the following equations, CP, CF, DOM and CC are expressed in % dry matter.
Cereals, legume seeds (excluding oil seeds) and molasses
100 km = 77.45 – 0.060 CP + 0.106 CC – 0.054 DOM (r = 0.99; RSD = 0.32)
Cereal by-products, corn gluten feed, dehydrated sugar beet pulp, dehydrated potato and soybean hulls
100 km = 94.41 – 0.237 OM – 0.022 CP + 0.121 CC (r = 0.98; RSD = 0.45)
100 km = 100.32 – 0.194 OM – 0.120 CP – 0.530 CF (r = 0.94; RSD = 0.76)
Oil seed meals
100 km = 67.03 + 0.0426 CP + 0.1566 CC (r = 0.95; RSD = 0.29)
Dehydrated alfalfa, dehydrated grass, wheat straw
100 km = 57.56 – 0.110 CF + 0.105 CP + 0.270 CC + 0.150 DOM
For forages, the following correction (Δ km) is applied. It takes into account the extra energy needed for ingestion (Vermorel and Martin-Rosset, 1997).
Δ km = - 0.20 CF + 2.50
km = km – Δ km
Net energy and UFC
NE (MJ/kg) = ME x km
One UFC corresponds to the net energy contained in 1 kg of standard barley (87% dry matter) used for maintenance, or 9.42 MJ/kg: 1UFC = 9.42 MJ NE.
UFC = ME x km / 9.42
Estimation of the UFC value using the chemical composition and the digestible components of feed materials
The UFC values of the feed materials were also calculated by using a set of equations previously described (p. 43). These equations take into account the chemical composition and the digestible components of the feed materials.
Calculation of digestible components
The DOM value was calculated from the organic matter and OMd. For the majority of feed materials, the DOM data come from measurements (literature and/or INRA). For dehydrated alfalfa and for dehydrated grass, OMd was predicted from the chemical composition given in the tables and INRA equations linking OMd and the crude fibre content (expressed in % dry matter):
Grass: OMd (%) = 81.51 – 0.792 CF (n = 19; r = 0.42; RSD = 6.3)
Alfalfa: OMd (%) = 90.52 – 0.995 CF (n = 25; r = 0.66; RSD = 3.7)
Digestible energy was calculated as indicated above.
Calculation of UFC values
4 groups of feed materials have been considered.
Cereal grains, cereal by-products (wheat milling by-products and gluten feed), legume and oil seeds (pea, lupin, faba bean, full fat rapeseed and full fat sunflower seed), oil seed meals (groundnut, rapeseed, linseed, sunflower, copra, sesame and soybean), dehydrated sugar beet pulp, dehydrated potato, carob and molasses.
- Feed materials with a known OMd
UFC = - 0.134 + 0.274 CF / 100 – 0.362 CP / 100 + 0.316 CC / 100 + 0.0755 DE
- Other feed materials (including oil seeds but except legume seeds and oil seed meals rich in cell walls)
UFC = 0.815 – 0.947 CF / 100 + 0.0345 CP / 100 + 0.582 CC / 100
Dehydrated alfalfa and dehydrated grass
UFC = - 0.056 + 0.562 CC / 100 + 0.0619 DE
UFC = - 0.730 – 0.722 CP / 100 + 0.572 OM / 100 + 0.0941 DE
UFC = - 0.124 + 0.254 CC / 100 + 1.33 DOM / 100
Comparison of energy values calculated by the analytical method and directly using prediction equations
The differences between the UFC values calculated either by the analytical method or the prediction equations, for the feed materials for which the digestibility could be accurately estimated, are very low (- 0.04 < Δ UFC < + 0.02) and are not significantly related to the chemical composition. They are consistent with those calculated from a separate data file containing 43 feed materials for which both chemical composition and digestibilities were available.
The differences are of the same order of magnitude whether the UFC values were calculated by equations using chemical composition alone or in association with digestible elements such as DOM or DE.
Therefore, the UFC values of 81 feed materials in the tables have been calculated using either of the following methods:
- Equations associating chemical composition criteria with a digestible element, DE, when OMd could be established with adequate precision (59 feed materials)
- Equations based on the chemical composition of feed materials for which DOM or DE could not be established with precision (22 feed materials).
Comparison with other tables
The vectors for the chemical composition of the feed materials and their digestibility values in the present tables were compared with the previous INRA tables (INRA, 1984; INRA, 1990).
The chemical composition and digestibility values sometimes differ significantly for feed materials common to the old and new tables, so that UFC values can be different. In addition, the energy value of the reference barley increased slightly from 9.21 MJ/kg (INRA, 1984) to 9.42 MJ/kg based on the latest INRA research (Vermorel and Martin-Rosset, 1997).
The present tables are more complete (81 feed materials) than the previous INRA tables (33 feed materials). This was made possible by using prediction equations based exclusively on the chemical composition. However, we did not wish to extend this method to all the feed materials in the new tables, since it was important to remain within the validity range of the equations.
The Dutch feed tables (CVB, 2000) use a net energy system that is very similar to the INRA system (Ellis, 2002). The German (DLG, 1995) and North American (NRC, 1989) tables use the digestible energy system. This system overestimates energy values, especially when cell walls and/or crude protein values are high (Martin-Rosset and Vermorel, 2002).
Definition and principle
The nitrogen value of feed materials represents the quantity of amino acids from dietary and microbial origin absorbed in the digestive tract. It is expressed in digestible crude protein for the horse, MADC (INRA, 1984; INRA, 1990; Tisserand and Martin-Rosset, 1996).
The nitrogen value depends on the crude protein content in the feed material, on its digestibility (Nd) and on the proportion of amino acids absorbed in the small and large intestines. It is expressed by a coefficient k that is specific for each group of feed materials:
MAD = CP x Nd
MADC = DCP x k
Digestibility of nitrogen (Nd) in the digestive tract and calculation of digestible crude protein (MAD)
The MAD values were established according to the type of feed material.
In the following equations, MAD is expressed in g/kg dry matter and CP is expressed in % dry matter.
MAD = - 4.94 + 8.533 CP (r = 0.93; RSD = 7.7)
MAD = - 29.95 + 8.673 CP (r = 0.93; RSD = 9.2)
MAD = - 25.96 + 8.357 CP (r = 0.97; RSD = 7.1)
Other feed materials
For the other feed materials, the MAD values were established either by in vivo measurements taken from the literature and/or from INRA, or, in a very limited number of cases, from the pig or ruminant values presented in this book, when crude fibre and ADF was lower than 15 % dry matter or higher than 15 % dry matter respectively.
Calculation of the MADC value of feed materials
The coefficient k depends on the type of feed material.
k = 1 for concentrates
MADC = MAD
k = 0.85 for dehydrated forages
MADC = MAD x 0.85
k = 0.80 for straw and by-products rich in lignin
MADC = MAD x 0.80
The k values depend, firstly, on the true digestibility of crude protein in the small and large intestines and, secondly, on the recovery of amino acids of microbial and dietary origin absorbed in the large intestine. The true digestibility values were validated with INRA results using the mobile nylon bag technique (in the small and large intestines) on 37 feed materials (21 forages and 16 concentrates; Macheboeuf et al., 1995; Martin-Rosset and Tisserand, 2002) and in the USA by ileal flow markers (Coleman et al., 2000)
Comparison with other tables
The values of total crude protein, of nitrogen digestibility and MADC published in the tables were compared with those of previous INRA tables.
The MADC values are slightly different due to the changes in crude protein content. The precision of estimations of total (totality of digestive tract) and partial (small intestine vs. large intestine) digestibilities has been improved due to the new data. The tables are also more complete.
The Dutch (CVB, 2000) and German (DLG, 1995) tables express the nitrogen value in MAD. In the North American tables, the nitrogen value is expressed as crude protein. The MAD and CP systems overestimate the nitrogen value of feed materials, notably for forages, and to a lesser extent for concentrates, when the levels of NDF and above all ligno-cellulose (ADF) are high (Marin-Rosset and Tisserand, 2002).
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- CVB, 2000. Veevoedertabel 2000. Chemische samenstelling, verteerbaarheid en voederwaarde van voedermiddelen. Centraal Veevoederbureau, Lelystad, The Netherlands.
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