Nutrition management of growing pigs

Nutritional management of pigs to optimise growth demands pig-specific, time-specific and place-specific determination and provision of nutritional requirement. These elements need to be incorporated into response prediction models that operate in a real-time (not retrospective) closed-loop control environment. This implies appropriate means for the on-line measurement of response to change in nutrient provision, and the simultaneous means for manipulation of feeding level and feed quality. The paper describes how response prediction modelling and response measurement may now be achieved. Optimisation may be pursued with mixed objectives, including those of production efficiency and environmental protection. Introduction; managing the nutritional environment The potential benefits of optimising pig response to nutrients by the targeting of specific production objectives rather than the satisfaction of generalised ‘nutrient requirements’ were proposed by Whittemore and Elsley (1974), and recently reaffirmed by Jean dit Bailleul et al., (2000). Both reports differentiate between biological and economic performance, and place the understanding of nutrient dispositioning at the centre of any ability to optimise production response. Present considerations are as much directed to the management of the environment as of production performance. It may be calculated that some 5 kg of excreta are voided daily by pigs. For each pig place on a farrow-to-finish production unit, the annual output of N, P and K respectively is about 7.5 kg, 3 kg and 4.5 kg. This may be considered as a potential organic fertiliser or a potential pollutant (Whittemore, 1995). Losses are usually in the order of greater than 30 % for N, and around 10 % for P and K. Figure 1 Components of nutrition management in the growing pig As indicated in Figure 1, the prediction of nutrient response needs knowledge at three levels. First, the yield of nutrients from dietary substrates: feed evaluation. Second, the uses to which the nutrients will be put. Third, the way these two levels interact to produce output in terms of retentions and excretions; that is, model algorithms and structures. Nutrition management also needs further knowledge of the value of the response in the market place, and the means to balance monetary with nonmonetary value. Explicit in nutrition management is the means to accurately measure and control inputs, and to accurately measure and timeously respond to outputs. Optimisation necessitates control responses within the time period of the production process itself. Retrospective determination of inefficiency is inefficient in itself, and past history is no certain guide to future events in the production of pigs. The growth of the pig requires therefore to be managed toward the optimum end point throughout its growth course by an Integrated Management System (IMS). Real time measurement of response to nutrient supply, the comparison of that response with the predicted expectation, and the immediate on-line adjustment of nutrient supply are all seminal to management. This is the ‘closed-loop’ paradigm. In this respect the rules are no different to other dynamic management cycles of Design, Implement, Measure, Emend... Emendation to meet target outputs can only result from measurement of response. In the context of the production of pigs, both measurement and design emendation have till now been unavoidably retrospective. ANIMAL NUTRIENT FLOW NUTRIENT SUPPLY FROM FEEDS