Energy allowances and feeding systems for ruminants / Ministry of Agriculture, Fisheries and Food, Department of Agriculture & Fisheries for Scotland, Department of Agriculture for Northern Ireland.

  • Ministry of Agriculture, Fisheries and Food
Date:
1975
Catalogue details

Licence: Open Government Licence

Credit: Energy allowances and feeding systems for ruminants / Ministry of Agriculture, Fisheries and Food, Department of Agriculture & Fisheries for Scotland, Department of Agriculture for Northern Ireland. Source: Wellcome Collection.

    46/92 page 36
    Normally, however, if a variety of foods is to be included in a ration and economic considerations taken into account, the use of the linear program- ming technique is desirable. LINEAR PROGRAMMING OF RATIONS FOR BEEF ANIMALS It should by now be apparent that the ME value of a food does not accur- ately represent its contribution to animal production, since the efficiency of utilisation of the ME for liveweight gain (k,), is influenced by the energy concentration (M/D), and therefore by the other foods in the ration. Diets for pigs and poultry are commonly formulated to specified energy concentrations, whilst complete diets for dairy cattle would be formulated to a given amount of ME (MJ). With beef cattle, both approaches must be used together. The ration must be defined by both terms, total ME and energy concentration (M/D), otherwise linear programming using ME alone as the energy constraint is unsound. The right hand side of the matrix must have values for both total ME and the chosen energy concentration (M/D). Alternatively a statement of dry matter intake (DMI) required can be used instead of M/D, since M/D = ME/DMI. The break-even prices and substitution rates which can be calculated for rations for low rates of gain will differ substantially from those found when rations for high rates of gain are formulated. An alternative approach is to use the variable net energy system now to be described. Variable Net Energy System for Ration Formulation This system is based on principles put forward by MacHardy (1965)!, and worked out in detail by Harkins, Edwards and McDonald (1974). It calcu- lates the net energy for each food at the level of animal production under study, thus making the system additive, and ideal for use in linear programme work. Replacement rates can be calculated for any situation, and it is of great value in desk formulation of multi feed rations without recourse either to linear programming or the use of equation (30) described earlier. The system states allowances in net energy and is based on two concepts, Animal Production Level (APL), and Net Energy for maintenance and production (NEmp), which were discussed at the end of Section I. For any given animal production level a food has a net energy dependent upon its metabolisable energy concentration. Tables may be constructed which allow the net energy (NEmp) values to be obtained if the production situation and metabolisable energy values (MEF) of the foods are known. ANIMAL PRODUCTION LEVEL This is defined as the ratio between the total net energy requirement and the net energy required for maintenance (E,,): E E Animal Production Level, APL = ee =|]4+— = (19) given that-En = 5.67 + 0.061 W (4) ‘Abst. 9th Int Cong. Anim. Prod., p25. ?Anim. Prod. 19, 141, 1974
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