Tri-State Swine Nutrition Guide

Bulletin 869-98

Feed Ingredients

Feed grains only meet part of the nutrients that are required in the diets of pigs. Therefore, other feed components are needed to balance the diet. Combining the grains and other ingredients into a final diet mixture to meet the pig's nutritional needs requires information about the nutrient content of each feed grain, knowledge about their nutritional limitations, and the suggested feeding level. Variations in crop growing conditions, storage length, and crop variety may produce wide compositional variations among and within individual grains. Average compositional values of commonly used feeds are presented in Table 15 and can to be used as a guide in formulating diets for swine. Suggested incorporation rates of various grains and by-products are presented in Table 16, with the composition of commonly used mineral sources listed in Table 2.

Test weight is perhaps the quality attribute of grains that can best reflect their overall nutritional value. Although most of the test-weight variation is due to the starch component, it is a general reflection of growing conditions and nutrient content of the grain. Common test-weights are normally expressed in the United States as lb./bushel [corn (56), oats (32), sorghum (56), wheat (60), and barley (48)]. Grains having lower test weights than that indicated in the parentheses contain more fiber, less starch, and have a lower digestible energy value than normal test-weight grains. The percentage of crude protein of low test-weight grains may, in fact, be higher than that of the normal test weight. This is because in low test-weight grains, the starch content is reduced and the protein is, therefore, at a higher proportion to the other components. Low test-weight grains usually result from early frost conditions, a situation that also encourages the development of mycotoxins. Pig growth rate is usually not affected until test weight is extremely low. Feed conversions are generally poorer due to the grain's higher fiber content. Poorer performance responses noticeably occur when test weights (lb./bushel) are between 70 to 80% of normal. Because of potential differences in test weights, volumetric feed mills should be calibrated frequently to assure that the diet contains the correct proportion of feed components.

Dietary fats and oils contain 2.25 times more energy than carbohydrates (starch). This means that 1 lb. of fat added to a diet will be approximately equivalent to the energy present in 2.25 lb. of corn starch. The addition of fat to a diet thus results in improved feed conversion because the diet contains a more concentrated form of energy. Although the addition of fat to market pig diets improves feed conversion, body-fat deposition is often increased, particularly in barrows during the latter stages of the finisher period.

Choice white grease and soybean oil are considered higher-quality fats compared to yellow grease. Many of the fat products commercially available for feeding pigs are blends of various animal and vegetable sources. Several contain high amounts of free fatty acids and other impurities that reduce their quality. High-quality animal fat sources and animal-vegetable fat blends should contain no more than 1% moisture, 0.5% impurities, 3.5% unsaponifiable material, or 5% total MIU (moisture, impurities, and unsaponifiable material). The presence of water in a fat mixture can accelerate equipment deterioration and/or the development of rancidity in either the stored fat or in the final diet mixture. Diets that contain rancid products will result in a low feed acceptability that subsequently reduces pig gains and feed conversion ratios. Antioxidants such as ethoxyquin, butylated hydroxyanisole (BHA), or butylated hydroxytoluene (BHT) are generally added to fat sources to prevent the development of rancidity.

The most common and cheapest energy source for pig diets in the tri-state area is yellow dent corn, but other grains and by-products are also available and are often economical. It is essential that an analysis of the grain or feed product be conducted prior to feeding to ascertain its nutrient composition and quality. Analyses for moisture, protein (and possibly lysine) and test weight are generally adequate for grains. Suggested incorporation rates of various grains and by-products are presented in Table 16.

In addition to regular yellow dent corn, several new varieties of corn (high-oil, high-lysine, low-phytic acid) have or will become available in the near future. The varieties of high-oil corn have a 6 to 9% oil content and a lysine content of 0.28 to 0.30%, whereas regular yellow dent corn averages 3.5% oil and 0.25% lysine. The germ component of the high-oil corn kernel, which is proportionally higher than in regular corn, accounts for most of the additional oil and lysine. Consequently, an increased digestible energy content of about 5% and a 7% improvement in feed conversion is frequently reported when feeding trials have compared these high-oil corn varieties with regular corn.

The high-lysine corn varieties generally have a higher but also a wider variation in their lysine content than regular corn. The use of high-lysine corns generally does not result in improved pig gains but can result in a lower feed cost. When high-lysine corn is fed, there should be a reduction in the dietary level of supplemented protein and/or synthetic lysine added per ton. The total dietary lysine level should be the same for both types of diets.

Much of the phosphorus in the cereal grains and soybean meal is bound with phytic acid and is poorly digested by the pig. Consequently, a large quantity of phosphorus is excreted in swine manure. Low phytic-acid corn varieties have about 35% of their phosphorus bound in phytic acid compared to 70% for regular corn. The newer varieties of low-phytate corns allow for more phosphorus to be in an inorganic form; thus, the phosphorus in these corns is more effectively digested and absorbed by the pig with less being excreted.

Soybean meal is the most economical and commonly used swine protein (amino acid) supplement used in the tri-state area. Although soybean meal quality can be variable and its protein (amino acid) content can be influenced by crop growing conditions, it generally has a more consistent quality than most other protein sources used for swine diets. Dehulled 48% crude protein (CP) soybean meal is the processed meal without the soybean hulls being added back to the meal, whereas 44% CP soybean meal has the soybean hulls returned to the meal after the oil has been extracted. The 44% CP soybean meal has a fiber content of 7.5%, compared to the 3.5% fiber in dehulled soybean meal. The decision to use 44 or 48% crude protein soybean meal should be based on the cost per unit of protein, not on the price per ton. Both sources of soybean meal have the same proportion of the amino acids, but differ in the total percentage of amino acids (as fed basis). Table 16 shows recommended usage rates of various protein sources normally used in pig diets.

Whole (full-fat) soybeans are frequently used to increase the energy content of swine diets. The use of roasted or extruded full-fat soybeans generally adds 3 to 4% oil to the final diet mixture (the diet normally contains from 2 to 3% oil from the cereal grain contribution). Due to the oil in the whole soybean, the intact bean has a lower protein and lysine content. Consequently, a higher level of the whole bean must be included in the diet compared to diets that have soybean meal as the protein supplement. Because of the presence of several anti-nutritional factors in raw whole soybeans, the bean must be heat-processed by being roasted or extruded prior to being used in swine diets. Many extruders and roasters can produce an excellent full-fat soybean product, but there is a wide variation in the technical ability of equipment operators to produce a quality product. Economic analyses have generally not favored on-farm roasting or the extruding of soybeans. With the higher oil content in the final diet mixture, feed intake will be slightly lower when the roasted whole soybean is added. Raw soybeans containing mycotoxins should be avoided and not fed to swine, particularly to young pigs and reproducing animals.

There are many grain and industry by- products that can be used in pig diets. Commonly used plant by-products include corn gluten meal, corn gluten feed, hominy feed, brewers products, distillers dried grains, and various mill feeds such as wheat, bran, shorts, and middlings. Animal by-products would include meat and bone meal, blood meal, fish meals, milk products, and various animal fats. These by-products have varying nutrient compositions, but each has a nutritional limitation. Some of these by-products are valuable protein or amino acid supplements, whereas others are good energy sources (Table 15).