Design of farming systems for low input conditions: principles and implications based on scenario studies with feed allocation in livestock production

This study addresses the issue of designing farming systems for low input c onditions. By focusing on the problem of feed (=resource) allocation in liv estock systems it provides clues for the design of alternative agricultural systems and systems in general. Linear programming (LP) is used to examine system behaviour under conditions of varying feed resource qualities, for individual animal production levels that range from 0.75 to 3.00 times main tenance. Milk yield, animal numbers and amounts of feed offered or refused are measures of system performance in two hypothetical Cases representative for actual fanning systems. Case 1 considers available feed as one aggrega ted resource, with an average nutritive value ranging from that of straw to that of high quality forage. It establishes the individual animal output l evel that is required to achieve maximum total system output from a given f eed resource. In Case 2, animals of different production levels are allowed to select between two feed resources that, through proper definition of th e their proportions on offer, on average represent the same feed quality sc ale as in Case 1. The possibility of selection, however, allows the nutriti ve value of the actual intake to differ from the average nutritive value of feed offered. Better feed and higher (potential) individual animal output tend to increase total system output in terms of milk, by reducing the numb er of animals, Nevertheless, the term 'damning objective' is introduced to express that high targets for subsystem output reduces total system output if subsystem requirements exceed resource availability. Moreover, heterogen eity of (feed) resources can increase system output by using more productio n units with lower individual output. The results are tested against farmer s' practice and situations reported in literature. Implications for the des ign of sustainable systems and further research are discussed.