Abstract
The genesis of methods for defining the nutritional value of feeds and the nutrient requirements of animals, and their development in the late 19th and early 20th centuries in Europe and the USA are outlined. Current energy and protein feeding systems for ruminants are described. Particular reference is made to the Australian systems which are applicable to grazing animals as well as to those given prepared feeds, and enable the effective nutritional management of animals at pasture by means of the decision support tool GrazFeed. The scheme for predicting intakes by cattle and sheep from pastures allows for the effects of selective grazing on the composition of the feed eaten, and for reduction in herbage intake when a supplementary feed is consumed. For herbage of any given concentration of metabolizable energy (ME) in the feed dry matter the changes with season of year in the net efficiency of use of the ME for growth and fattening and in the yield of microbial crude protein, g/MJ ME, which both vary with latitude, are defined. An equation to predict the energy requirements for maintenance (MEm) of both cattle and sheep includes predictions of the additional energy costs incurred by grazing compared with housed animals and the cost, if any, of cold stress. The equation allows for the change in MEm with feed intake. A flexible procedure predicts the composition of liveweight gain made by any given breed or sex of cattle and sheep at any stage of growth, and the variation with rate of gain. Protein requirements for maintenance, production including wool growth, and reproduction, are related to the quantities of microbial true protein and undegraded dietary protein truly digested in the small intestine. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 4 : 609-624)
Highlights
In 1573 in Tudor England the ‘Five Hundreth Pointes ofGood Husbandrie’ written by Thomas Tusser included the couplet “From Christmas to May/Weak cattle decay”
In addition the complications are many (Leitch, 1972). These include retention from the Starch Equivalent (SE) system of correction factors, though V numbers are applied to the calculated energy values of rations as a whole and not to individual feeds as in SE; the factors vary with digestible energy (DE)% and the crude fibre (CF)% correction formerly applied to fodders is not used (Nehring and Haenlein, 1973; Schiemann, 1977)
In the USA, tables on the composition and nutritional value of feeds (e.g. NRC, 1996) continue to list Total Digestible Nutrient (TDN) but this system has been superseded by definitions of the energy requirements of animals and the value of feeds in net energy (NE) terms
Summary
Good Husbandrie’ written by Thomas Tusser included the couplet “From Christmas to May/Weak cattle decay”. The problem of providing feed for animals during the winter period in northern latitudes that these words illustrate began to diminish with the introduction of new crops and improved farming techniques. Improvements in farming practices, including the rotation of crops, increased food supplies for the human population and reduced fears of famine. Continuity of feed supplies for animals became reasonably assured and so there could be continuity in the selection and breeding. Of improved livestock which, in turn, focused attention on methods of feeding that would enable expression of their production potential. Whereas the average weights of cattle and sheep at the Smithfield Market for meat animals in London in 1710 were 170 and 13 kg respectively, in 1795 they had increased to 360 and 36 kg (Ernle, 1936). This paper outlines the genesis of energy and protein feeding systems, their development in the late 19th and early 20th centuries, and describes current systems with particular reference to the Australian systems
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