by: Murray Snowdon
Many soybeans grown today are fed to livestock as full-fat beans. This is a change from the traditional practice of extracting the oil for human consumption and feeding the remaining meal to livestock. With varieties now available that will mature in the Maritimes, farmers are showing considerable interest in the place that soybeans might play in their cropping and feeding programs.
The same excellent amino acid profile found in soybean meal is found in full-fat soybeans but the level of protein and the individual amino acids are diluted by the 18% oil content as seen in Table 1.
TABLE 1. Typical Nutritive Value of Soybeans and Soybean Meal, As-Fed Basis
*Soybean meal is subjected to some heat during processing.
Although full-fat soybeans are, in effect, comprised of soybean meal and soy oil, soybean energy level is not as high as expected based on its component parts. The reasons for this discrepancy are not clear. Lower than expected fat digestibility is one probable factor. Improper processing or improperly formulated diets are other factors that probably account for some of the lower than expected energy values that have been reported.
Raw soybeans contain trypsin inhibitors that interfere with protein digestion. These must be destroyed by heat before feeding to swine or any other non-ruminants.
Because of the substantial variation within each soybean processing method, no one method has a clearcut advantage over the others in terms of end-product nutritional value. Some of the systems used in soybean processing are described below.
1. Propane Flame Roasting. This system exposes the bean directly to a flame. If roasting temperatures are too high, nutrient availability near the surface of the bean will be reduced while the centre of the bean may be left uncooked. Lower temperatures will reduce charring and fire risk, but also reduce throughput. Direct flame roasting offers the advantage of burning off a portion of any mycotoxins present and can also be used to dry and roast in one operation.
2. Fluidized bed. In this process, the product being cooked is suspended in, and surrounded by a heat transfer medium. In most cases the heating medium is air, where the beans bounce or float as they flow through the unit. Usually beans are not charred in this process. This method also removes a portion of any mycotoxins present, although in this case it is by air movement rather than by burning. This method can also be used to dry beans.
3. Dry extrusion. In this process, beans are dried and ground before forcing them through a die. The friction in this process creates sufficient heat to destroy most of the trypsin inhibitor. Extrusion releases oil from the cells making the extruded product oily to the touch. Extruded beans often give better performance than roasted beans in swine diets, due in part to the ease of digestion of this free oil. In ruminant diets however, this free oil is more likely to impair rumen function.
4. Micronizing. This method exposes the beans to dry heat by microwaves from infra-red burners.
5. Pelleting. Pelleting will not destroy trypsin inhibitors and cannot be used as a substitute for heating. Pelleting does however improve soybean utilization by monogastrics, making the inclusion of roasted beans in commercial feeds an attractive option.
Some type of heating is necessary to lower trypsin inhibitor levels before feeding soybeans to pigs and chickens. Although heat processing is not necessary for ruminants, some of the advantages listed below make roasting or extruding worth considering.
2. Improved undegraded intake protein (UIP or "by-pass" protein) levels in ruminants.
3. Increased energy density if part of the hull is removed.
4. Roasted beans can be safely fed in ruminant diets that contain urea since roasting destroys the urease enzyme.
5. Improved carbohydrate digestibility.
6. Improved storage characteristics.
Because of the large number of variables involved -soybean variety, moisture content, heating method and time-temperature combinations, processors must establish their own processing parameters. The end use - ruminant or monogastric - is also a major factor in determining roasting procedures.
Measuring Adequacy of Roasting
Many methods are available to monitor the adequacy of soybean processing. Choice of test depends on type of animals being fed, cost of testing and turnaround time.
1. Trypsin Inhibitor Level. For monogastrics, especially young animals, the trypsin inhibitor of the raw bean must be dramatically reduced. On farm colorimetric tests are available to estimate trypsin inhibitor activity - see # 3 below.
Some labs are set up to do more precise measurements of trypsin inhibitor activity for processors interested in fine-tuning their roasting procedures.
2. Urease Test. Unless urea is included in the diet, urease is not a major problem, but its presence indicates that trypsin inhibitor is also still present. This test can be conducted in a lab or is available as a colorimetric home kit. It gives a reasonable indication of sufficient heating, but cannot detect overheating.
3. ADIN or ADFN. Acid detergent insoluble nitrogen is a test often used in silages to detect heat damage and reduced protein digestibility. It is used for the same purpose in soybeans. It can be used on its own or can be subtracted from protease insoluble protein to give a good measure of "digestible by-pass protein."
4. Lipase Test. This test, available for on-farm use, gives an indication of UIP level. Since lipase enzymes survive more heat than urease, they can be used as a marker for high temperature processing; through a colorimetric test they can be used to estimate UIP or "by-pass" value.
5. PDI Test. PDI is a measure of protein dispersibility in water. As heat exposure increases, PDI decreases. Although the test has some limitations, it is a quick and relatively inexpensive method of testing roasting adequacy for ruminants. This test is used widely in the U.S.
6. Visual Appraisal. When no other means is available, beans can be evaluated by their colour and taste. Beans should be golden brown with few if any blackened beans, and should have no bitter or raw taste.
Using Peterson's arithmetic constants to relate soybean's energy and protein value to corn and soybean meal puts the dollar value of raw soybeans between 85 and 90% of soybean meal. Roasted beans, will be worth between 90 and 95% of soybean meal.
To obtain a precise value for an individual farmer, a least cost formulation based on a set of ration specifications and a list of available feeds is required.
In high energy diets, beans are worth more since they replace fat in a formulation. In diets for dairy cows or rapidly growing cattle, beans are worth a further premium because of their UIP value and may have a calculated dollar value greater than soybean meal. In low productivity situations, where beans compete with less expensive protein and energy sources, soybeans will be worth less.
Being aware of the factors that affect the value of a feed make wise buying and selling decisions easier. Because most beans are heat processed before feeding, this article will deal primarily with roasted soybeans.
DRY MATTER LEVEL AND SHRINK
Roasted beans contain much less moisture than raw beans, a major factor in bean pricing. Even beans that have already been dried will lose further moisture when roasted. Beans often exit a roaster with only 3 to 8% moisture content, compared to 10 to 14% in most "dry" feeds. This means that beans arriving at the roaster at 14% moisture might leave at 4% moisture, an "apparent" loss of 10% of the original weight. In reality, this is not a loss to the purchaser or owner of the beans since they only lose water and get a more nutrient-dense feed ingredient.
The dry matter level of roasted beans will depend on a number of factors including dry matter level when they enter the roaster, the temperature of the roaster and the time the beans spend in the roaster. As well, the beans will be at their driest immediately following roasting but may pick up some moisture as they sit in storage, depending on weather conditions at the time.
In addition to water loss, there is also loss of dirt, dust, pods and hulls during handling and roasting. The actual amount of loss will vary with the beans in question, the individual roasting operation and what, if any, deliberate attempts are made to remove these materials. If beans are roasted on a custom batch basis and each customer has their own beans returned to them, any shrinkage encountered will be an actual shrink. If however, each customer's beans are not kept separate, then the processor must adjust (i.e. pencil shrink) the weight of beans that are returned to each customer. Most roasting operations assume that total shrink, including water, equals about 13% for beans at 86% dry matter. At 13% shrink, 100 tonnes incoming would yield 87 tonnes of roasted beans. If the 100 tonnes of 86% dry matter raw beans were purchased at $270 per tonne, the resulting 87 tonnes of roasted beans would have to sell for $310 per tonne to cover the 13% shrink. Of this $40 increase in price, $28 is due to moisture loss and the balance due to actual dry matter loss (hulls etc.)
Roasting charges may vary from one location to another; some of this variation is accounted for in shrink charges, but fuel costs, volumes processed, capital cost and level of market competition also contribute to differences in roasting charges.
If $35 per tonne of raw beans was charged for roasting, then $40 per tonne would have to be added to the roasted bean to cover roasting. Adding this to the $310 (calculated previously), puts the final price at $350 per roasted tonne, for beans that entered the roaster at $270. This does not include any other handling, carrying or mark-up charges. Remember that a large portion of this price increase is simply because water has been removed and the initial dollar value of the beans must be applied to a smaller tonnage.
Although often beneficial, roasting is not a necessity for beans fed to ruminant animals. Farmers who grow beans but do not have ready access to a roaster may want to consider the option of feeding their beans raw. A livestock specialist should be consulted about possible rations for raw beans.
EXAMPLE PRICE BREAKDOWN PER TONNE OF ROASTED SOYBEANS
** Other possible charges such as transportation to and from the roaster and carrying charges may still apply to the above price.
TEMPERATURE OF ROAST
Beans roasted for increased "by-pass" protein in dairy diets require considerably more heating than those roasted for pigs. If the roasting operator passes these costs directly along to his dairy customers, then they would pay more than swine customers for roasted beans. Another factor that could contribute to a higher cost of beans roasted to higher temperatures is the higher dry matter level in beans that have been roasted to higher temperatures.
Buyers should be confident that the beans they are buying have been adequately, but not excessively heated for the animals that they are feeding.
In feeding situations where extra energy is required, soybeans will be worth more. The oil in soybeans (up to 20% of the dry matter), allows an animal to consume more calories without eating more feed. In high energy demand situations such as chicken broiler, lactating cow, and lactating sow diets this extra energy can be quite valuable in boosting animal performance. In these situations, the oil in beans can be priced against fat sources such as tallow.
A benefit of soybeans, particularly to a farmer, but less so to a feed manufacturer is the ease at which fat can be added to a diet by using soybeans compared to any other on-farm method. The dollar advantage of this is difficult to quantify.
When feeding animals in a low state of productivity, such as replacement dairy heifers, the fat provided by beans is not worth as much and it will likely be cheaper to feed more grain to obtain energy, than it would be to incorporate soybeans into the diet.
Since oil content varies with variety and growing conditions, some buyers include oil level in their pricing formula.
Since soybeans are purchased first and foremost as a source of protein, protein level is obviously an important factor. As with oil levels, variety and growing conditions can affect protein level.
There is some confusion about the expected protein level in Maritime soybeans. Part of this confusion stems from the fact that people often quote protein levels at different dry matter levels. For example, beans that are 40% protein on a dry matter basis would be 34% as-fed if harvested at 85% dry matter. After leaving the drier they could be up to 36% at 90% dry matter and up to 38% after leaving a roaster at 96% dry matter. Most New Brunswick soybeans contain between 39 and 43% crude protein on a dry matter basis.
In situations where extra by-pass protein is required, the by-pass level in well roasted beans will add to their value. The premium that this adds depends on the other sources of by-pass that are available at the time. As with fat, high productivity animals such as early lactation cows, are the animals most likely to benefit. Roasted beans will have "by-pass" protein levels of 45-55% compared to 25-30% in raw beans.
In Wisconsin the roasted soybean market is large and well established, with about 45 roasting facilities processing 1/3d of the State's soybean crop. Beans are fed almost exclusively to dairy cattle and sell for a premium over 48% SBM. At the time of writing (September, 1994), SBM is selling at Wisconsin mills for about $308 and roasted beans for $370 (values have been converted to Canadian dollars per metric tonne). This contrasts sharply with Maritime prices; at the P.E.I. elevators this week, soybean meal is selling for $385 and roasted beans for $329. As you can see, beans in Wisconsin are demanding a dollar premium over SBM while here they are being sold for less than SBM.
For safe storage soybeans should contain no more than 14% moisture. Apart from concerns with moisture content, the high oil content of soybeans raises other storage concerns. Ground, raw beans are the least stable form and are susceptible to storage breakdown especially in warm weather. Adequate heating of soybeans reduces natural enzyme levels and will make the beans more stable in storage.
POTENTIAL BENEFITS OF SOYBEANS IN LIVESTOCK DIETS
1. Soybeans are especially valuable when they can replace soybean meal and fat in feeding situations that require high energy levels.
2. When adequate dietary energy levels can be reached without fat, soybeans have to compete with grain energy, and will be worth less than when they compete with fat sources.
3. If the animals being fed are already performing at their genetic potential, extra energy from soybeans will not give a growth response, but should improve feed efficiency.
4. Properly roasted soybeans can be used as a source of UIP (bypass protein) for ruminants. This lowers the need for less palatable protein sources such as meat meal and blood meal. Using beans as a concentrated energy source and as a replacement for high cost animal source proteins will maximize their dollar value in a diet.
5. The oil in soybeans helps to reduce dust levels in ground rations.
1. Inadequately heated beans that contain significant amounts of trypsin inhibitor will reduce the performance of swine, poultry, and young calves.
2. Overheating beans will increase the portion of "bound protein," which cannot be digested by either ruminants or monogastric animals. A lab measurement of ADIN (acid detergent insoluble nitrogen) is used as an indicator of bound protein.
3. Incorporating a high level of soybeans into a diet requires ration rebalancing in order to maintain a proper ratio of energy to other nutrients, especially protein, in the diet.
4. Since the oil in ground soybeans can become rancid, regular grinding will be necessary especially in warm weather.
5. Swine diets containing high levels of soybeans may result in a softer carcass fat.
6. Lactating cows fed high levels of soybeans will produce milk fat that is less saturated and more susceptible to oxidation.
7. Feeding very high levels of soybeans to dairy cows may often lower fat test, partially through the negative effects of the soy oil on rumen fermentation and fibre digestion.
8. Feeding soybeans, like other fat or oil sources, will often reduce milk protein percentage.
9. If enough oil from soybeans is fed to upset rumen function, dry matter intake will drop. In this situation, animal energy intake may drop despite the high energy level in the diet. Disrupted rumen function also impairs fibre digestion meaning that less feed value will be extracted from the forages in the diet.
In a recent summary of research on feeding soybeans to swine, 90% of the trials reported an improvement in feed efficiency while 55% reported an improvement in rate of gain. The following guidelines should increase the chances of success in feeding full-fat soybeans to swine.
1. Take into account that soybeans contain about 75% of the protein level found in 48% soybean meal and cannot substitute for soybean meal on an equal weight basis.
2. Limit soybeans to approximately 15-20% of swine grower-finisher diets and 25% in sow diets. The exact inclusion rate will depend in part on the level of oil in the other diet ingredients.
3. Add an extra 5 I.U. of vitamin E per kilogram of diet, for each percentage unit increase in dietary fat.
4. Boost dietary protein level to maintain a proper protein to energy ratio and to compensate for the lower dry matter intake expected on a soybean supplemented diet.
5. Ensure that roasting is adequate and trypsin inhibitor levels are low.
6. Overheating soybeans can cause problems. A lab measurement of protein solubility is recommended if appearance of the beans, or pig performance suggests a problem. If overheating has occurred, dietary protein level must be increased to compensate.
Interpreting the published soybean feeding data is difficult. Numerous trials have reported disappointing results, i.e. no production response when compared to soybean meal. Others have reported excellent response to soybeans. Type of forage, degree of soybean heating and grinding, feeding level and animal productivity can all have dramatic effects on response. Feeding adequately processed beans at moderate levels in a diet balanced for fibre, by-pass protein and mineral levels is the best way to ensure success.
1. Although it is not necessary to roast soybeans for ruminants, roasting can be used as a method of drying with the added benefits of reduced mycotoxin level, increased UIP levels and increased safe upper feeding limits.
2. Feeding raw beans may lower feed intake and usually will not boost milk production when compared to soybean meal. There is little effect on fat test, but milk protein level is often depressed when raw beans are fed.
Roasted beans usually will not affect feed intake, and generally do boost milk production, especially in early lactation. The effects of roasted beans on milk composition are similar to raw beans. Fat test can go either up or down but the effect is usually small. Protein test is often lower when roasted beans are fed.
Extruded beans give good milk response, but are more likely than roasted to lower milk fat test.
3. Dairy cows should not be fed more than 3.5 kg per day of roasted beans or 2 kg of raw soybeans.
4. Beef cattle diets should contain no more than 5% added fat from soybeans. For example, an animal consuming 7 kg of dry matter could be fed about 1.7 kg of soybeans.
5. When feeding high levels of soybeans or any other fat source, dietary levels of calcium and magnesium should be increased by about 15% over normal feeding levels.
6. Since rumen microbes cannot digest fats or oils, provide enough readily available carbohydrates (i.e. grain) to maintain rumen productivity.
7. To allow the animal to make good use of the soybean oil, which will be digested post-ruminally, dietary levels of UIP (by-pass protein) should be increased. One common guideline is to add 1 percent of dietary UIP for each 3 percentage units of added dietary fat.
8. If roasted soybeans are used to replace other by-pass protein sources, ensure through lab testing that the beans have been heated sufficiently to provide the desired UIP level.
9. If soybeans are fed whole, protein "by-pass" value will be increased but the possibility of beans passing through the animal undigested is also increased. If beans are finely ground, protein by-pass will be reduced and the possibility of the fat interfering with rumen function is increased.
Usually rolling or coarse grinding is the best compromise, but farmers may wish to begin by feeding whole beans. Providing few are seen in the manure, grinding is not necessary. If beans are passing through the cow, coarse grinding or rolling will be necessary.
The value of soybeans will vary with each feeding situation. Rations for high performance animals, that routinely call for added fat and/or increased levels of "by-pass" (UIP) protein will put maximum value on beans. Low productivity situations that do not normally call for fat or elevated levels of "by-pass" will put a lower dollar value on beans.
Most least cost formulations will value soybeans very near to or considerably above the value of 48% SBM, depending on diet and other feeds available. Soybean meal will continue to be the feed which will have the biggest effect on full-fat soybean price. Grain and fat prices will also affect the price, but to a lesser extent.
Soybeans represent a good source of energy and protein that can be grown in the Maritimes. Soybeans can be fed to most classes of livestock, but feeding guidelines need to be followed if optimum feed efficiency and animal performance are to be achieved.