Green Soybeans - Can They Be Fed?
Some of the soybeans harvested in Ontario in 2002 were unusual in the fact that they appeared normal except that they were green. In previous years there has been the occasional green soybean harvested in Ontario but that was due to an early frost that caught some soybeans prior to maturity. That was not the case this time.
Parts of Southern Ontario received very little or no rainfall during most of the 2002 growing season. The lack of rainfall, combined with long periods of extremely hot weather, created stressful conditions for all crops in these areas. In response to this stress many of the soybean plants "shut down" or quit growing prematurely, not allowing the soybeans to reach natural maturity. When harvested these beans were dry but the loads contained green and yellow soybeans. The percentage of green beans in a sample varied from field to field and within a field. The majority of the fields harvested had less than 15% green beans but some had up to 70% green soybeans.
Normally, as the soybean matures an enzyme called chlorophyllase would degrade the chlorophyll resulting in a yellow coloured bean. The green soybeans resulted when varying amounts of chlorophyll remained undegraded in the hull of the soybean and in some cases throughout the whole soybean.
Much of this chlorophyll is contained within the hulls and the oil of the soybean. This concerned soybean crushers since this chlorophyll could negatively impact the colour and quality of the soybean oil. As a result, the crushers were reluctant to purchase loads of soybeans containing more than 25-30% green soybeans. The elevators began offering discounted prices for green soybeans, especially for loads containing more than 30% green soybeans. Suggested discounts were up to $80 per tonne for loads with over 50% green soybeans.
An alternative to crushing these soybeans for the soybean oil and meal would be to feed them as full fat soybeans. The nutrient content of the green soybeans relative to the regular soybeans both on a raw and on a roasted basis was determined with the following results;The results of these analyses suggest that there are no nutritional differences between the green soybeans and the regular soybeans, both on a raw and roasted basis. It is unknown what effect, if any, the chlorophyll could have on product quality and colour when consumed by monogastrics. A research trial with a group of pigs is presently being carried out at the University of Guelph to investigate any such effects.
Full fat soybeans can be fed to monogastrics (swine and poultry) and to ruminants (cattle and sheep). They are lower in protein and, because of the high fat content, higher in energy than soybean meal. Heat treatment by roasting, extruding or micronizing destroys the anti-nutritional factors associated with soybeans and is necessary prior to including soybeans in monogastric rations with the possible exception of gestation diets for sows.
Ruminants can use either raw or roasted soybeans. Raw soybeans should not be mixed and fed with feeds containing urea as the urease in the raw soybeans can breakdown the urea to ammonia. The heat treatment of soybeans destroys the urease and will increase the percent of protein that is considered as bypass (UIP, RUP) protein.
It is recommended that any soybeans be analyzed prior to feeding and that the rations be balanced with the help of a knowledgeable nutritionist.
As for a suggested price for green soybeans - we'll leave that up to the buyer and the seller!
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