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9
Diet Formulation
Formulation of swine diets requires an understanding of the nutrient requirements and of the feed ingredients that can supply those nutrients. Tables 10-1 through 10-13 give summaries of nutrient requirements of various classes, weights, and levels of performance of pigs. Tables 11-1 through 11-11 give the composition of various feed ingredients and their relative values as nutrient sources. These guides can be used to formulate nutritionally adequate diets that, when fed at the recommended level, will allow pigs to perform optimally.
From a nutritional standpoint, there is no "best" formula in terms of the ingredients that are used in the diet. Therefore, ingredients should be selected on the basis of availability, price, and quantity and quality of the nutrients that they contain. Corn, grain sorghum, barley, and wheat are the primary energy-supplying ingredients in diets for swine weighing 10 kg or more. These cereal grains are severely deficient in several essential amino acids, minerals, and vitamins. Soybean meal, other oilseed meals, and animal protein meals are generally added as sources of supplemental amino acids to the grain, but they too are deficient in many of the essential minerals and vitamins. Table 9-1 compares the nutrient content of corn and of an unsupplemented corn—soybean meal diet with the nutrient requirements of a 40-kg growing pig.
Swine diets can be formulated using rather simple mathematical procedures with a hand-held or desk calculator when a few ingredients are used in the diet. However, more sophisticated formulation procedures are needed to more precisely meet the dietary requirements on a bioavailable nutrient basis and when using larger numbers of ingredients that differ in their nutrient bioavailability. These formulation procedures often require computer programs and the expertise of a professional nutritionist.
The nutrient requirements generated by the models and the feedstuff composition tables in this publication allow the user to formulate diets on the basis of bioavailable (true or apparent ileal digestible) amino acids and bioavailable phosphorus. The procedures used to formulate diets on a bioavailable nutrient basis, though more complex, are similar to those used to formulate diets on a total nutrient basis. The following section gives examples of the calculation procedures. For the sake of simplicity, the procedures address formulation of a diet on a total nutrient basis, using corn and soybean meal as the primary feed ingredients.
Formulating A Corn—Soybean Meal Diet
Diets can be formulated on a total nutrient basis or on an available nutrient basis. For the example given below, the formulation is on a total nutrient basis.
In swine diets formulated with corn and soybean meal, the two ingredients contribute about 97.5 percent of the total diet. The remaining 2.5 percent consists of mineral supplements and carrier mixes containing vitamins, trace minerals, and additives. Corn and soybean meal are each similarly high in digestible energy (DE) concentration. Any combination of these two ingredients will result in a relatively high-energy diet.
Formulation
The first step in diet formulation is presented in Equation 9-1, where C is the percentage of corn and S is the percentage of dehulled soybean meal in the diet.
Lysine is the first-limiting amino acid in corn—soybean meal diets. Because of this, one can manipulate the propor-
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TABLE 9-1 Nutrients in Corn and Corn + Soybean Meal (Dehulled) Compared with the Nutrient Requirements of a 40-kg Growing Pig of High-Medium Lean Growth Rate (325 g of carcass fat-free lean/day)
Nutrient
Corn
Corn + Soybean Meal (74.1%:23.4%)
Requirement (40-kg pig)
Indispensable amino acids (%)
Arginine
0.37
1.09
0.35
Histidine
0.23
0.47
0.29
Isoleucine
0.28
0.71
0.49
Leucine
0.99
1.59
0.86
Lysine
0.26
0.90
0.90
Methionine + cystine
0.36
0.60
0.52
Phenylalanine + tyrosine
0.64
1.46
0.83
Threonine
0.29
0.65
0.59
Tryptophan
0.06
0.20
0.16
Valine
0.39
0.82
0.62
Mineral elements
Calcium (%)
0.03
0.10
0.60
Phosphorus, total (%)
0.28
0.37
0.50
Phosphorus, available (%)
0.04
0.07
0.23
Sodium (%)
0.02
0.02
0.10
Chlorine (%)
0.05
0.05
0.08
Magnesium (%)
0.12
0.16
0.04
Potassium (%)
0.33
0.75
0.23
Sulfur (%)
0.13
0.20
—a
Copper (mg/kg)
3.0
6.9
4.0
Iodine (mg/kg)
0.03
0.04
0.14
Iron (mg/kg)
29
63
60
Manganese (mg/kg)
7.0
13.6
2.0
Selenium (mg/kg)
0.07
0.12
0.15
Zinc (mg/kg)
18
26
60
Vitamins
Vitamin A (IU/kg)
213
170
1,300
Vitamin D (IU/kg)
0
0
150
Vitamin E (IU/kg)
8.3
6.7
11
Vitamin K (mg/kg)
0
0
0.50b
Biotin (mg/kg)
0.06
0.11
0.05
Choline (g/kg)
0.62
1.09
0.30
Folacin (mg/kg)
0.15
0.43
0.30
Niacin, available (mg/kg)
0c
5.2
10.0
Pantothenic acid (mg/kg)
6.0
8.0
8.0
Riboflavin (mg/kg)
1.2
1.6
2.5
Thiamin (mg/kg)
3.5
3.3
1.0
Vitamin B6 (mg/kg)
5.0
5.2
1.0
Vitamin B12 (µg/kg)
0
0
10.0
Ascorbic acid
0
0
—d
Linoleic acid (%)
1.9
1.6
0.1
a The requirement is unknown but is met by the sulfur from methionine and cystine.
b The requirement is generally met by microbial synthesis.
c The niacin in cereal grain is unavailable.
d The requirement is met by metabolic synthesis.
tions of corn and dehulled soybean meal to meet the required concentration of this amino acid and be reasonably sure that the requirements for all the other essential amino acids will be met and that the amount of nonessential amino acid nitrogen will be adequate. To formulate a corn—soybean meal diet for a 40-kg pig, one may use the equation:
where A is the percentage of lysine in corn, C is the percentage of corn in the diet, B is the percentage of lysine in soybean meal, 97.5 - C is the percentage of soybean meal in the diet, and L is the lysine requirement of the 40-kg pig, expressed as a percentage of the diet.
Values for A, B, and L are then inserted into Equation 9-2, leaving only one unknown (C). The percentages of corn and soybean meal in the diet can then be solved as follows: 0.26C + 3.02(97.5 - C) = (0.90 × 100), where C is 74.1 percent corn in the diet. Because S is 97.5 - C, then S is 23.41 percent soybean meal in the diet.
The next step is to add an ingredient to supply inorganic phosphorus to complete the requirement (0.50%) for total phosphorus. If dicalcium phosphate, which contains 18.5
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percent phosphorus, is selected, Equation 9-3 will show the percentage of dicalcium phosphate (DP) to include in the diet.
The next step is to add an ingredient to supply calcium to complete the requirement for calcium (0.60%). If ground limestone, which contains 38 percent calcium, is selected, Equation 9-4 will show the percentage of ground limestone (GL) to include in the diet.
One can completely fortify the swine diet by adding 0.25 percent sodium chloride; a vitamin premix that supplies the vitamins deficient in the corn—soybean meal mixture (vitamins A, D, E, K, B12, riboflavin, niacin, pantothenic acid); a trace mineral premix that supplies the trace minerals that may be deficient (iron, zinc, copper, manganese, iodine, and selenium); and if desired, a premix that contains one or more antimicrobial agents. The fortified diet is
TABLE 9-2 Fortified Swine Diet
Nutrient
Percent
Corn
74.44
Soybean meal, dehulled
23.40
Dicalcium phosphate
0.71
Ground limestone
0.90
Sodium chloride
0.25
Vitamin premix
0.10
Trace mineral premix
0.10
Antimicrobial premix
0.10
Total
100.00
shown in Table 9-2. The diet is made to total 100 percent by increasing the amount of corn to 74.44 percent.
Formulation on a true or apparent digestible lysine basis is essentially the same as described above except that the true or apparent digestible lysine values for corn and soybean meal are used in the calculations. These values are obtained by multiplying the total lysine concentrations in Table 11-4 by the amino acid digestibility coefficients in Tables 11-5 or 11-6. For example, to meet the apparent digestible lysine requirement (0.73%) of the same 40-kg pig in the previous example, the apparent digestible lysine in corn (0.26% total lysine × 66% apparent digestibility of lysine = 0.17% apparent digestible lysine) and soybean meal (3.02% × 85% = 2.56%) are used. Similar procedures are used to formulate diets on an available phosphorus basis. Based on the composition and bioavailability data in Table 11-1, the bioavailable phosphorus requirement (0.23%) of the 40-kg pig is met by using the bioavailable phosphorus in corn (0.28% total phosphorus × 14% bioavailability = 0.039% bioavailable phosphorus), soybean meal (0.69% × 23% = 0.16%), and dicalcium phosphate (18.5% × 100% = 18.5%).
Representative terms from entire chapter:
nutrient basis
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