Dairy cow feeding : comparison of the different methods of prediction of dry matter intake

Abstract

The different methods of predicting the dry matter intake can be grouped into 3 main types :

1 / multiple regression equations, generally empirical and produced from experimental data,

2 / the system of two predictions, one linked to a physical regulation of intake (rumen fill), the other to an energetic regulation (energy balance) of which only the lesser value is conserved for the prediction of dry matter intake,

3/ the system based on Fill Unit of roughages and the substitution of concentrates to roughages.

The comparison of these different systems shows that the factors which are the most difficult to take into account remain those of the diversity of feed and their respective proportions in the ration, together with that of the beginning of lactation. The majority of these systems are more for establishing optimum ration calculations of feed recommendations rather than really predicting ingested quantities, taking into account all the possible factors of variation. They are closely linked to feeding practices (complete diet rich in by-products and concentrates in the U.S.A., individual adjustments in concentrate supply with rations composed mainly of roughages in Europe). The Fill Unit system proposed by INRA does have certain limits in the prediction of the fill value of feed (separation of roughages and concentrates, numerous equations) and in its use at the beginning of lactation. At the present time, this is the tool which enables the greatest diversity of situations to be described, whilst conserving a calculation method which is easy to use in practice and which has possibilities of being developed.