Growth Models for Commercial Pork Production
In the real world, it is a challenge to figure out the best feeding or management strategy for individual grower-finisher operations. Many factors influence this strategy, including pig performance potentials, physical farm layout, feed intake, environmental conditions, potential feed ingredients, feed processing, and payment systems. To complicate things even further, the best strategy may change over time as environmental or economic conditions within the industry change.
A pig growth model can integrate all of the existing knowledge of nutrient utilization for growth and animal-environment interactions into a single computer program. In this way, models can be effective tools for identifying the most appropriate strategy for individual grower-finisher units, by simulating alternative management and feeding strategies and assessing how they measure up.
Over the past 15 years, a model has been developed by the International Pig Growth Modeling Group, a collaboration between researchers at the University of Guelph, Massey University (New Zealand), Wageningen Agricultural University (The Netherlands), and Agribrands International. A recent paper in the Canadian Journal of Animal Science described the principles involved in the development and application of computerized pig growth models for commercial pork production.
According to researchers, the majority of the pig growth models being used in the industry today are based on energy and amino acid utilization. This makes sense since the efficiency of pork production hinges on these factors and feed is the single greatest cost in raising pigs - energy and amino acids account for more than 80% of the nutrient cost in practical pig diets.
In order to predict economically important production traits, the specifics of an operation need to be reflected accurately within the framework of the model. To accomplish this, the program needs to incorporate information on initial and final body weights, available nutrient levels in feed ingredients and diets, number of rations fed, physical layout of the operation, carcass evaluation and payment systems, prices of products and resources, and production goals. Other information, that is important to ensure the accuracy of the growth model but more difficult to quantify, includes protein deposition rates and the amount of feed consumed at various stages of growth.
One of the greatest challenges facing growth modelers is the prediction of feed intake at various stages of growth, or the establishment of the feed intake curve. Feed intake is influenced by many things, including the animal itself (body weight, sex, health status), the feed being consumed (form, quality and composition), the surrounding environment (environmental temperature, water quality and availability, feeder and pen design), and by interactions between these factors. Estimates of feed intake help nutritionists formulate the right level of dietary nutrients once the daily nutrient requirements have been established. Feed intake is also closely related to growth rate, feed conversion, carcass value and, ultimately, profitability. Independent data has shown that there is a large variation in feed intake on commercial farms in Canada, supporting the need to continuously track feed intake at different stages of growth.
According to researchers, there are many practical applications of models in commercial pig production. Models can be used as an educational tool to demonstrate the basic principles of nutrient utilization for growth in pigs. More in-depth knowledge of the interactions between factors helps a nutritionist understand why groups of animals, managed under varying conditions, may respond differently to similar diets and why different diets are necessary under various conditions.
Models can also be used to develop realistic production goals. If actual performance differs greatly from predicted performance, then models can be used to systematically evaluate why these differences are occurring.
Models can be useful in answering basic questions and examining "what-if" scenarios that may apply to many different facilities. For example, the effects of changes in the carcass grading system on the optimum shipping strategy can be measured. A nutritionist can use a growth model to make general feeding recommendations based on a limited number of observations, such as maximum protein deposition and observed levels of feed intake in grower-finisher pigs.
Growth models can be used to assess an infinite number of management and feeding strategies to decide on the most profitable strategy for an individual operation. In order to accomplish this, the various steps involved include:
According to the researchers, regardless of the model being used, effective communication with the producer is paramount to establishing the production goals of the operation. Bottom line is the best feeding and management strategy will depend on whether the goal is to maximize the animals' lean growth potential (for breeders), income per pig (for producers with a limited supply of weaner pigs), or income per pig place per year (when space is the limiting factor).
Source: de Lange, C. F. M., Marty, B. J., Birkett, S., Morel, P. and Szkotnicki, B. 2001. Application of pig growth models in commercial pork production. Can. J. Anim. Sci. 81: 1-8.
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