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Feed Intake in Ration Balancing

John Maltman, Swine Specialist

Properly balancing rations is dependent on a couple of key items. Initially, target values for the ration are set usually in percentage of lysine and a set value for energy per kilogram of feed. The values chosen are appropriate for the age and weight of the pig as outlined in a table of values.

The new NRC 1998 publication has updated values for pigs of various lean tissue deposition rates.

While this approach gives a well-balanced ration, results from farm to farm can vary widely. A ration that works well on one farm could produce substandard results on another farm.

Upon examination, the most frequently overlooked elements in the equation are those that impact on feed intake. By formulating a ration to specific nutrient levels we are actually expecting the pig to consume a specific amount of each nutrient each day. The pig must eat a specified number of grams of lysine and other amino acids and calcium, phosphorous, etc. to achieve maximum growth.

Any large reduction in intake translates into reduced growth. Similarly large excesses in consumption can complicate digestion. This is particularly noticeable with young pigs during the transition phase. During this period a piglet’s body is totally dedicated to animal protein and energy sources coming from sows’ milk.

What we want to do is transition the piglet’s system from animal protein and energy to plant protein and energy. At weaning, the piglet’s body has not developed adequate amounts of enzymes for plant starch digestion or stomach acid for plant protein digestion. Through the introduction of highly digestible plant material blended with highly digestible animal source protein and energy, two things are accomplished. Growth can continue, since the pig’s body can deal with animal source protein and energy. Secondly, the pig must develop sufficient enzymes and stomach acid to deal with the presence of plant material in the diet. In a warm, dry, sanitary environment, appropriate digestion of plant material can occur within 10 days. Once transition occurs, a higher amount of plant material can be added in a step-wise fashion until no animal protein sources are necessary. Economics often dictates when animal protein such as herring meal will be removed from the ration.

The step-wise approach is taken so as not to overwhelm the developing amounts of stomach acid that is vital in several ways. Hydrochloric acid (HCL) breaks up the long protein molecules into smaller pieces (peptides) which can later be further split up by enzymes and then absorbed from the small intestine. This process is dependent on the acid working on the protein and also creating an acid environment (pH2 to pH4) to prevent harmful bacteria from multiplying.

If feed intake is as predicted, all goes well. However if our genetics are generous eaters then higher levels of all nutrients are consumed. In the early days after weaning, this is desirable but we need to be conscious of the fact that high daily intakes of calcium can neutralize stomach acid.

This causes stomach acid levels to be reduced. With lower acid levels in the stomach, digestion is not as complete and harmful bacteria in the intestine have a food source to work on and a more favourable pH. For example, E-coli is well known to cause scours in pigs but it has difficulty functioning when pH levels are below pH4. Normal stomach conditions prevent these bacteria from multiplying but excessive dietary protein or excessive calcium levels can allow a flare-up of scours. Ration acidifiers can assist in keeping intestinal contents at proper pH levels, but attention should be directed at watching daily intakes of the various nutrients. Lowering calcium in the ration does not negatively affect growth of young pigs but can reduce scours where this is a problem.

Poor growth can also be a result of poor intake. Where conditions combine to reduce daily intake, it is necessary to reformulate to increase nutrient density. Even the properly formulated ration will disappoint if intake is not as expected, regardless of age or weight category.

Before discarding a ration as "no good" be sure to check intake to see if the pig is receiving the predicted amounts of nutrients daily.

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