SOYBEAN
(FULL-FAT) UTILIZATION
For several years, there has been interest in using whole unextracted,
full-fat soybeans in livestock rations. Because soybeans contain both
a high quality protein (38-42%) and a rich source of oil (18-22%), they
have the potential to supply major amounts of protein and energy to
livestock and poultry rations. Numerous studies have been conducted
which demonstrates that properly processed whole soybeans may be used
efficiently in livestock and poultry rations (46).
The decision to use full-fat products in ration
formulations usually is dependant upon economics. The best way to determine
if whole soybeans are economical is to formulate least-cost rations
using linear programming techniques. It is possible using the following
formula (57) to determine if whole soybeans are a more economical source
of supplemental protein and energy compared to soybean meal:
A is the cost advantage, or disadvantage, for using cooked whole soybeans. Y is the local cost per ton of 44% soybean meal and 0.8636 is the protein relationship between whole soybeans (38% protein) and 44% meal. If the price comparison is made between whole soybeans and dehulled soybean meal, or the protein content of the soybean differs from 38%, this factor should be adjusted. W is the percentage of oil in the whole soybeans (usually around 18%) and 1.292 is the relation of the energy value of soybean oil to animal fat. This factor may be adjusted to make comparison between other fat sources. Z is the local cost per pound of the animal fat. These two segments calculate the relative value of the protein and energy supplied by whole soybeans. From this is subtracted S, the price per ton of whole soybean, plus PC, the processing cost for a ton of soybeans. The processing cost will vary with the type of machinery used and volume of soybeans processed.
In general, full-fat soybeans may replace soybean meal in swine and poultry diets with similar performance anticipated. The decision on which soybean product to use needs to be based on the product's composition, availability and unit costs.
There has been considerable interest in using full-fat roasted soybeans in rations of high-producing dairy cows. In the early stages of lactation, the dairy cow is unable to consume enough energy and protein to support maximum milk production. Full-fat roasted soybeans have been proposed as a method to increase caloric and protein intake (58-59).
Stern and co-workers (60) reported studies where lactating Holstein cows were fitted with a rumen cannula in the proximal duodenum and terminal ileum to measure protein degradation in the rumen, amino acid flow and absorption in the small intestine. Soybean meal, whole soybeans and whole soybeans extruded at various temperatures were studied. Feeding diets containing extruded whole soybeans increased the availability of essential amino acids compared to diets containing soybean meal or whole soybeans. Absorption from the small intestine of the individual amino acids was generally greater for the extruded whole soybean diets.
Ground raw soybeans were compared to soybean meal in a series of swine gestation-lactation studies (61). Performances of the two protein sources were similar. It would appear that older animals can tolerate the anti-nutritional factors in soybeans. This is not the case for growing-finishing pigs. Crenshaw and Danielson (62) reviewed the literature, the oldest reference was 1930, and concluded that feeding raw soybean to growing-finishing pigs will reduce performance regardless of initial age or weight. Rudolph and co-workers (15) reported significantly lower nitrogen and amino acid digestibilities at the end of the pig's small intestine for an extruded whole soybean with little heat treatment.
In summary, properly processed soybean meal is universally accepted as the most important supplemental protein ingredient in livestock and poultry feeds. Soybean meal complements cereal grains in meeting the animals' requirements needed for economical and efficient production
