Nutrient composition

Feed makes up 55-65 per cent of total pig production costs, and is the largest cost associated with pig production. Therefore, selecting the right combination of feed ingredients to calculate a diet that provides optimum animal production for the least cost is essential to maximise profitability. Accurate pig diet calculation requires reliable nutrient composition information. Diet formulation software with a reliable nutrient compositional database and reports from laboratory tests of particular batches of ingredients results in diets that meet pig nutrient needs.

Nutrient availability in feeds

Not all nutrients in an animal's feeds are available to it. some nutrients, Some nutrients are in non-readily digestible forms, either naturally or as a result of processing, and, during the digestive process, pass through the digestive tract without being absorbed. Other nutrients may be broken down by bacteria in the animal's gut and are of no use.

Consequently, a feed's total nutrient value is not as accurate as diet calculation based on an available nutrient value (that amount of the nutrient that the animal can use). Unfortunately, it is not easy to determine the available nutrient value. Several techniques for assessing availability have been developed. Most of these techniques have concentrated on determining lysine availability because of both its significant role as a first-limiting amino acid (most critically important nutrient) and its tendency to damage during the processing of feed ingredients. Slope ratios and digestibility assays are the main techniques developed for the pig but each method has several problems. When calculating pig diets, the value of available lysine derived from prediction equations (such as those in Table 1) or published results of digestibility or slope-ratio studies should be used. In Tables 2, 3, 4 and 5, which give a guide to nutrient composition, energy (as DE), phosphorus (as available P) and lysine (as available lysine) are given in available figures. The other amino acids are also presented as available figures on the assumption that their availability figure is similar to lysine's.

Feedstuff variability

The nutrient composition of feedstuffs can vary widely depending on:

• feed variety or cultivar
• seasonal conditions, such as drought or frost, during growth and near-harvest
• agronomic conditions, such as the level of irrigation and fertiliser application
• conditions and time of feed storage
• manufacturing processes.

Of the important nutrients, amino acid and digestible energy variations show the greatest impact on animal performance. Both require the further development of simpler and less expensive tests for rapid assessment as indicators of the value of a wider range of feed ingredients.

Table 1. Available lysine prediction equations (as-fed basis)

*where 'x' is the crude protein percentage of the grain

Digestible energy

Gross energy determinations from a bomb calorimeter provide information only about a feed's total energy content. The actual digestible energy (DE) value of a feed (i.e. that which the pig can use) can be truly determined only with a pig digestibility measurement.

Fortunately, a substantial portion of any large change in DE in most feed ingredients is closely related to significant changes in crude fibre content, especially in the processing of a feedstuff, such as oil extraction and de-hulling. Weather damage to grain crops can alter the feed's energy content.

More recent developments in the area of near infrared (NIR) analysis have provided calibrations to rapidly and cheaply provide a relatively accurate indication of the DE content of feed ingredients such as cereal grains. Ideally, this information would be included in the grain's description before being purchased but this area needs further development.

Feedstuff inclusion limits

The values in Tables 2, 3, 4, and 5 are a guide to the composition of different feed ingredients. It also provides recommendations for maximum dietary inclusion levels for these ingredients in pig diets - a guide to the maximum levels that can be used in practical diet formulation. They are based on the possible influence of the ingredient on the:

• diete palatability
• presence of inhibitory substances
• desirability of limiting fibre inclusion
• pelletability
• compatibility
• presence of other undesirable effects.

Table 2. A guide to feedstuff nutrient composition - grains and grain by-products (see footnote)

Table 3. A guide to feedstuff nutrient composition of animal protein meals (see footnote)

Table 4. A guide to feedstuff nutrient composition - vegetable protein meals (see footnote)

Some have toxic and antinutritional components, which may be lower in some varieties and reduced by processing. Also for variety of nutrient source.

Table 5. A guide to feedstuff nutrient composition of miscellaneous ingredients (see footnote)

Footnote

W/dam - Weather damaged
NL - No limit at likely conventional usage levels
* Usage level depends on degree of mould development
** No limit except for baconer (level in brackets)
*** No limit for triticale varieties low in growth inhibitors
**** Limit to 5 per cent for breeders or weaners, and 10 per cent for other pigs
@ 20 per cent for breeders and young growers, 25-30 per cent for finishers and 20 per cent for sows and gilts
# aa is amino acid