Feed is the largest cost item in any intensive livestock enterprise. Selecting the right combination of feed ingredients to provide a diet giving optimum animal production at least cost is a complex problem. When working out diets, there are over 40 individual nutrients to consider, not only their actual concentrations, but also the ratios with other nutrients.

The pig is enormously versatile in the range of feeds which it can use. This should be exploited by considering the supply and price of a wide variety of feeds.

Computer feed formulation programs are used to design diets that meet the pigs’ nutritional needs at optimum cost. Nevertheless, you still need to have an understanding of pig nutrient requirements, the value of individual ingredients and ingredient tolerance levels when calculating diets, otherwise problems can quickly develop.

Composition and nutritional value of feed ingredients.

There are several approaches that can help overcome the problem of variability in the composition and feeding value of ingredients. Generally, the best method is chemical analysis. Private and some government laboratories offer these services. In most cases, relatively simple measurements of e.g. protein, are performed and from these values, the levels of the more important amino acids are estimated.

Most recently, near-infrared (NIR) spectroscopy has been introduced to allow quick determination of digestible energy (DE).

Lysine is a critical nutrient but its measurement is difficult. It is known, however, that the lysine level is related to its protein level and can be predicted.

Chemical assays are not yet available to quickly measure the biological availability of nutrients and so average values must be used to estimate the amount of available nutrients in various feeds.

Ingredient constraints.

The extent to which an ingredient may be used in a particular diet is subjective. Constraints on ingredient use may be associated with their specific influence on palatability, digestibility, toxicology, palatability, availability, compatibility with other ingredients, variability in quality or simply disappointment with previous involvements. Blood meal for example, is often constrained to levels of less than 4% in pig diets because of its unpalatability.

A guide to the inclusion levels of certain feed ingredients is given in Table 1.

Table 1. A guide to inclusion levels of some feed ingredients

Nutrient constraints.

The requirement for some nutrients is dependent on the supply of others. This is particularly the case with amino acids and energy supply. For example, lysine needs are best expressed relative to the DE content. Similarly, the levels of other essential amino acids are considered in relation to lysine and to one another so that an optimum balance of the essential amino acids can be maintained.

Calculating diets.

Working out a diet with a calculator involves a lot of trial and error. Fortunately, there are now many good computer programs which simplify least-cost diet calculations.

To work out a diet, the feed formulation program matches the combination of feeds which meets the nutrient specifications at least cost.

There are many benefits to using a computer to formulate least-cost diets. The diets can be calculated quickly and easily. This is particularly valuable where there are a large number of feed ingredients available. The program is better able to asses all nutrients when judging the value of feed ingredients and so the final cost of the feed will be lower generally than by manual formulation.

Feed calculation programs also provide information about the price sensitivity of ingredients and nutrients used in working out a diet. The price sensitivity analysis gives an indication of which ingredient or nutrient specifications cost money to meet and shows the potential saving if these were to be relaxed or alternatively the cost of tightening them further.

Information is also provided on the price an excluded ingredient would have to be before it would be included in the diet. This information is very important to have when making buying decisions.

Feed calculation programs should be used by those familiar with nutrition as unsatisfactory calculations are possible. One problem with some least-cost programs is that, in order to reach a solution, a “filler” may be included. In some cases, this can lead to unnecessarily high levels of limestone or free amino acids being included in the diet.

Swill feeding.

Swill feeding is illegal in Australia because of the serious risk of introducing a devastating exotic diseases such as foot-and-mouth disease.

Swill feeding includes using food (or food scraps) containing or possibly having had contact with animal matter (e.g. from restaurants, hospitals and domestic households) as feed for pigs, poultry or ruminants. Even a tiny amount of leftover meat or dairy product could contain a dangerous virus. Once a disease agent is introduced in this way, it could rapidly spread to susceptible local livestock. Countries importing Australian meat and livestock products would immediately ban further imports.

Swill feeding has been implicated in overseas outbreaks of disease including the devastating European foot-and-mouth outbreak of 2001.

Many viruses are highly resistant to chilling, freezing and curing. Experience has shown that even boiling swill may not destroy all disease organisms.

If you suspect stock are being fed swill contact your local veterinarian, stock inspector or contact the toll free Disease Watch Hotline on 1800 675 888.

Author:

Sara Willis