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Economic optimum nutrition of growing pigs.

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In two trials, a total of 504 boars and 504 gilts were used to determine the most profitable feeding strategy for the Topigs TN60 strain under current economic circumstances, using margin over feed cost as the objective function. The trials started when the pigs were 10 weeks old and were terminated after a 12-week trial period in each case. In the first trial the EFG Pig Model and Optimiser was used to assess the current feeding strategy used on the Baynesfield Estate, and to determine how the optimum strategy might change under different economic scenarios. An added objective was to evaluate the Pig Growth Model by comparing the predictions made by the model with the actual outcomes of the trial. Significant differences in gains, feed intake and carcass parameters were measured across sexes and feed treatments, and hence margin over feed cost, under the different economic scenarios applied. The Growth Model accurately predicted the optimum feeding strategy although the predicted feed intakes were marginally lower than those measured in the trial. The response to a series of feeds differing in balanced protein was measured in the second trial, the main objective being to develop equations that would describe the response of boars and gilts of this strain to dietary protein. These equations could then be used in the future to calculate the optimum economic level of dietary protein as economic circumstances on the farm changed. The results of both the simulation exercise and the trial provided strong evidence that the optimum economic level of dietary protein differs for gilts and boars, and that this difference widens as profitability in the enterprise is reduced, either through an increase in the cost of feed ingredients or when pork prices decline. Uniformity in body and carcass weight was increased with dietary protein content. The results of both trials provide convincing evidence that gilts and boars should be reared separately, and fed different dietary protein levels, if margin over feed cost is to be maximized, and that the economic optimum feeding strategy is not static but varies with economic circumstances.


Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.