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Animal Science Journal (2015) 86, 415–421
doi: 10.1111/asj.12315
ORIGINAL ARTICLE Digestible and metabolizable energy in corn grains from different origins for growing pigs Chan S. PARK,1 Ah R. SON,1 Dong Y. KIL2 and Beob G. KIM1 1
Department of Animal Science and Technology, Konkuk University, Seoul and 2Department of Animal Science and Technology, Chung-Ang University, Anseong, Republic of Korea
ABSTRACT An experiment was conducted to determine the digestible energy (DE) and metabolizable energy (ME) concentrations in nine sources of corn grains fed to growing pigs and to compare the energy values among their countries of origin. A total of nine sources of corn grains including five sources of yellow corn from the United States (USY), two sources of yellow corn from South Africa (SAY), and two sources of white corn from South Africa (SAW) were used. Nine barrows with an initial body weight of 37.1 ± 8.6 kg were allotted to a 9 × 9 Latin square design with nine diets and nine periods. The DE concentration in SAY (3347 kcal/kg) was greater (P < 0.001) than in USY (3269 kcal/kg), but was less (P < 0.001) than in SAW (3436 kcal/kg) on an as-fed basis. Similarly, the ME concentration in SAY (3291 kcal/kg) was greater (P < 0.001) than in USY (3209 kcal/kg), but was less (P < 0.001) than in SAW (3386 kcal/kg). In conclusion, the DE and ME concentrations in nine sources of corn grains are different among their countries of origin.
Key words: corn grains, digestible energy, metabolizable energy, swine.
INTRODUCTION Corn is one of the major cereal grains in swine diets around the world and a large quantity of corn with various varieties (e.g. yellow corn and white corn) is produced in many countries. Moreover, new varieties have been continuously developed and their nutritive values for pigs have been evaluated (Bohlke et al. 2005; Pedersen et al. 2007; Linneen et al. 2008; Li et al. 2013). Sauber and Owens (2001) suggested that corn grains harvested from various countries may have different energy and nutrient compositions due to the differences in production environments, genetics, or both, which may result in different feeding values. Many researchers determined the digestible energy (DE) and metabolizable energy (ME) concentrations in corn grains fed to pigs as corn grains are the main energy source in swine diets (Stein et al. 2004; Baker & Stein 2009; Kim et al. 2009). Thus, accurate information on the energy values of corn grains is critical in formulating swine diets, particularly when corn grains are imported from overseas. The comparative energy values of different varieties of corn (Adeola & Bajjalieh 1997; Pedersen et al. 2007; Linneen et al. 2008; Oliveira et al. 2011) or of the same corn varieties harvested in different regions of the country (Opapeju et al. 2007) are available. However, to our knowledge © 2014 Japanese Society of Animal Science
comparative data for the energy values of corn grains from different countries of origin as swine feed ingredients are not available. We hypothesized that corn grains produced in different countries would have different energy values when fed to pigs. The objectives were to determine the DE and ME concentrations in nine sources of corn grains from different origins and to compare the energy values among their countries of origin.
MATERIALS AND METHODS Ingredients and diets Nine sources of corn grains, including five sources of yellow corn from the United States (USY), two sources of yellow corn from South Africa (SAY) and two sources of white corn from South Africa (SAW) were used (Tables 1,2). Experimental diets were formulated to contain 97.5% of each corn source as the sole source of energy (Tables 3,4). Limestone, dicalcium phosphate, salt and vitamin-mineral premix were included in diets to meet or exceed the nutrient requirement estimates (National Research Council 1998).
Correspondence: Beob G. Kim, Department of Animal Science and Technology, Konkuk University, Seoul 143-701, Republic of Korea. (Email: [email protected]) Received 14 April 2014; accepted for publication 17 July 2014.
416 C. S. PARK et al.
Table 1 Analyzed nutrient composition of nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Composition
Dry matter GE, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
86.5 3759 7.18 2.27 1.70 1.66 0.10 0.26 7.54 1.94
87.0 3865 7.02 2.62 1.76 1.36 0.05 0.24 7.52 2.05
86.6 3955 7.94 2.74 2.55 1.82 0.11 0.30 8.26 2.35
86.4 3898 7.41 2.73 1.74 1.68 0.17 0.28 7.91 1.93
86.7 3977 7.67 3.64 2.56 1.78 0.13 0.29 8.39 2.81
88.0 3914 7.29 3.06 2.18 1.55 0.10 0.23 8.35 2.28
87.0 3887 9.16 3.30 2.44 1.78 0.12 0.27 9.97 2.94
88.2 3892 7.21 3.15 2.36 1.76 0.21 0.21 7.62 2.31
87.1 3908 7.10 3.17 2.54 1.09 0.04 0.20 8.74 2.51
ADF, acid detergent fiber; GE, gross energy; NDF, neutral detergent fiber; SAW, white corn from South Africa; SAY, yellow corn from South Africa; USY, yellow corn from the United States.
Table 2 Nutrient variability among nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Item
Dry matter Gross energy, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
Mean
87.1 3895 7.55 2.96 2.20 1.61 0.11 0.25 8.25 2.35
SD
0.6 62 0.67 0.41 0.37 0.24 0.05 0.04 0.77 0.36
Maximum
88.2 3977 9.16 3.64 2.56 1.82 0.21 0.30 9.97 2.94
Minimum
86.4 3759 7.02 2.27 1.70 1.09 0.04 0.20 7.52 1.93
CV, %
0.73 1.58 8.85 13.9 16.9 15.0 48.6 14.2 9.36 15.4
Means for sources USY
SAY
SAW
86.7 3897 7.44 2.80 2.06 1.66 0.11 0.27 7.92 2.22
87.5 3900 8.23 3.18 2.31 1.66 0.11 0.25 9.16 2.61
87.6 3900 7.16 3.16 2.45 1.43 0.13 0.20 8.18 2.41
ADF, acid detergent fiber; CV, coefficient of variation; NDF, neutral detergent fiber; SAW, white corn from the South Africa; SAY, yellow corn from the South Africa; SD, standard deviation; USY, yellow corn from the United States.
Table 3 Ingredient composition of experimental diets containing nine sources of corn grains (%, as-fed basis)
Ingredient
Diet
Ground corn Limestone Dicalcium phosphate Salt Vitamin-mineral premix†
97.5 0.6 1.0 0.4 0.5
†Provided the following quantities per kg of complete diet: vitamin A, 25 000 IU; vitamin D3, 4000 IU; vitamin E, 50 IU; vitamin K, 5.0 mg; thiamin, 4.9 mg; riboflavin, 10.0 mg; pyridoxine, 4.9 mg; vitamin B12, 0.06 mg; pantothenic acid, 37.5 mg; folic acid, 1.10 mg; niacin, 62 mg; biotin, 0.06 mg; Cu, 25 mg as copper sulfate; Fe, 268 mg as iron sulfate; I, 5.0 mg as potassium iodate; Mn, 125 mg as manganese sulfate; Se, 0.38 mg as sodium selenite; Zn, 313 mg as zinc oxide; butylatedhydroxytoluene, 50 mg.
Animal care and experimental design The protocols for the present experiment were reviewed and approved by the Institutional Animal Care and Use Committee at the Konkuk University. Nine crossbred barrows (Landrace × Yorkshire × Duroc) with an initial body weight (BW) of 37.1 ± 8.6 kg were used. All pigs were individually housed in the metabolism cage (0.48 m × 1.49 m). Pigs were randomly allotted to a 9 × 9 © 2014 Japanese Society of Animal Science
Latin square design with nine diets and nine periods using a spreadsheet program (Kim & Kim 2010). To prevent the metabolic disorder caused by deficient amino acids in diets, a commercial diet was provided for 7 days after the periods 3 and 6.
Feeding and sample collection Daily feed allowance was calculated as 2.5 times the estimated maintenance requirement for energy (i.e. 106 kcal ME/kg BW0.75; National Research Council 1998) based on BW of pigs measured at the end of the each period. Daily feed allowance was divided into two equal meals and was fed to pigs at 08.00 and 16.00 hours. Water was freely available to the pigs. Each period lasted 7 days. The initial 3 days were considered as an adaptation period. Feces were collected following the marker-to-marker method as described by Adeola (2001). Chromic oxide was added in the morning meal at 0.5% as an indigestible marker and provided on days 4 and 8 of each period. The collection of fecal samples was initiated and terminated when chromic oxide visually appeared in the feces. The collection of urine was initiated on day 4 at 14.00 hours and terminated on day 8 at 14.00 hours. At the end of the each period, a subsample of urine was filtered by cotton sheet and collected in a 200 mL bottle. Fecal and urine samples were immediately stored at −20°C for further analyses. Animal Science Journal (2015) 86, 415–421
ENERGY VALUES IN CORN GRAINS
417
Table 4 Analyzed nutrient composition of experimental diets containing nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Composition
Dry matter GE, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
86.5 3689 7.22 1.88 2.14 3.18 0.45 0.32 7.92 2.28
87.0 3798 6.81 2.43 1.94 3.33 0.56 0.38 7.05 2.59
86.7 3731 7.69 2.36 2.03 3.49 0.55 0.40 7.24 2.48
86.3 3690 7.06 2.30 1.62 3.29 0.60 0.41 6.28 2.21
86.5 3746 7.39 2.66 1.97 3.18 0.48 0.35 7.34 2.50
87.4 3838 7.16 3.26 2.06 3.07 0.50 0.37 7.87 3.02
87.2 3824 9.41 3.07 3.12 3.76 0.50 0.35 7.12 3.08
87.7 3835 7.17 3.27 2.39 3.26 0.53 0.34 7.51 2.21
87.8 3838 7.25 3.05 2.22 3.06 0.45 0.39 6.85 2.81
ADF, acid detergent fiber; GE, gross energy; NDF, neutral detergent fiber; SAW, white corn from South Africa; SAY, yellow corn from South Africa; USY, yellow corn from the United States.
Chemical analysis Nine sources of corn grains and experimental diets were analyzed for dry matter (DM; Association of Official Analytical Chemists 2005; method 930.15), crude protein (CP; Association of Official Analytical Chemists 2005; method 990.03), ether extract (EE; Association of Official Analytical Chemists 2005; method 920.39), crude fiber (Association of Official Analytical Chemists 2005; method 978.10), ash (Association of Official Analytical Chemists 2005; method 942.05), neutral detergent fiber (NDF; Goering & van Soest 1970), acid detergent fiber (Association of Official Analytical Chemists 2005; method 973.18), calcium (Association of Official Analytical Chemists 2005; method 978.02) and phosphorus (Association of Official Analytical Chemists 2005; method 946.06). Frozen fecal samples were dried at 55°C in a forced-air drying oven until constant weight. Frozen urinary samples were thawed and 3 mL of subsample was added in the cotton ball and lyophilized for further analysis as reported by Kim et al. (2009). Experimental ingredients, diets, fecal samples and lyophilized urinary samples were analyzed for gross energy (GE) using an adiabatic bomb calorimeter (C2000; IKA, Staufen, Germany).
Calculation and statistical analysis The DE concentrations of experimental diets were calculated by the difference between the total GE intake and fecal GE output. The ME concentrations of experimental diets were calculated by the difference between the total DE intake and urinary GE output (Kil et al. 2013). The DE and ME concentrations in corn grains were calculated by dividing the proportion of each corn grain (97.5%) in the experimental diets. Data were analyzed by the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC, USA). The corn source was used as the fixed variable and the animal and period were used as random variables. The CONTRAST statement was also used to determine significant differences in energy values of corn among different countries of origin. Least squares of means for each dependent variable were calculated and separated by the PDIFF option with Tukey’s adjustment. With this option, letters indicating significant differences were generated using a macro program (Saxton 1998). The experimental unit was the pig and the significance was declared at an α level of 0.05. Animal Science Journal (2015) 86, 415–421
RESULTS Chemical composition Mean, standard deviation (SD), and coefficient of variation (CV) for nutrient compositions of nine sources of corn grains were calculated, and mean values for nutrient compositions of three countries of origin were also calculated (Table 2). Mean values for the GE concentrations in USY, SAY and SAW were fairly comparable. The concentrations of CP ranged from 7.02% to 9.16%. The concentrations of EE in USY were slightly less than those in SAY and SAW (2.80% vs. 3.18% and 3.16%). Variation of the GE concentrations in nine sources of corn grains (CV = 1.58%) was relatively less compared with other nutritional compositions.
Energy utilization of diets containing various corn grain sources Energy digestibility of diets containing USY sources 1 and 2, and SAW sources were greater (P < 0.05) than all other diets except diets containing USY source 4 and SAY source 1, which were not different from diets containing SAW source 2 (Table 5). Energy digestibility of diets containing SAY source 1 was greater (P < 0.05) than diets containing USY source 3 and SAY source 2. Energy digestibility of the diets containing SAW was greater than the diets containing USY (P < 0.001) and SAY (P < 0.001). Values for the DE concentration of diets containing SAY source 1 and SAW sources were greater (P < 0.05) than other diets except diets containing USY source 2, which was not different from diets containing SAY source 1 and SAW source 2. The DE concentration of diets containing SAY was greater (P < 0.001) than diets containing USY, but was less (P < 0.001) than diets containing SAW. Values for the energy retention rate of pigs fed diets containing USY source 1 and SAW sources were greater (P < 0.05) than those of pigs fed diets © 2014 Japanese Society of Animal Science
© 2014 Japanese Society of Animal Science
Values are expressed as least squares mean. Means within a row without a common superscript letter differ (a < b < c < d < e < f, P < 0.05). †Each least squares mean represents nine observations. DE, digestible energy; GE, gross energy; ME, metabolizable energy; SAW, white corn from South Africa; SAY, yellow corn from South Africa; SEM, standard error of means; USY, yellow corn from the United States.
0.574 0.688 < 0.001 0.172 < 0.001 < 0.001 < 0.001 0.141 0.695 0.242 < 0.001 < 0.001 0.017 0.198 0.018 < 0.001 0.079 < 0.001 < 0.001 < 0.001 0.700 0.899 0.003 < 0.001 < 0.001 < 0.001 0.12 0.45 12 0.03 56 0.7 0.03 0.50 16.5 13.5 0.6 0.02 0.00
3 2 1
Diet intake, kg/day 1.57 1.54 1.57 1.55 1.55 1.53 1.57 1.53 1.55 5.82ab 5.86ab 5.71a 5.79ab 5.87ab 5.99b 5.87ab 5.95ab GE intake, Mcal/day 5.81ab 158ab 202d 180bcd 189cd 171abc 201d 152a 160ab Fecal output, g/day 163ab 4.71c 4.57ab 4.69bc 4.65bc 4.69bc 4.72c 4.63bc 4.69bc Feces GE, Mcal/kg 4.50a 747ab 924d 846bcd 877cd 801abc 951d 703a 752ab Fecal GE output, kcal/d 735a 87.1d 84.0a 85.0abc 84.6ab 86.4bcd 84.0a 87.7d 86.9cd Energy digestibility, % 87.2d 3.28cd 3.13a 3.14a 3.17ab 3.32de 3.21bc 3.36e 3.34de Diet DE, Mcal/kg 3.22bc Urine output, kg/day 2.15 2.37 2.55 2.22 2.70 2.20 1.81 2.28 2.74 Urine GE, kcal/kg 60.4 70.9 64.3 53.4 33.1 51.0 71.1 61.4 53.5 108.1c 84.5abc 79.8ab 70.6a 102.4bc 87.0abc 72.6a Urinary GE output, kcal/day 95.8abc 104.6bc 85.3bc 82.2a 83.6ab 83.2a 85.2bc 82.3a 86.3c 85.8c Energy retention rate, % 85.6c 3.21cd 3.07a 3.09ab 3.12abc 3.27ef 3.15bcd 3.31f 3.29f Diet ME, Mcal/kg 3.16cd abc ab a abcd bcd cd ab bcd 0.98 0.98 0.98 0.98 0.99 0.98 0.98 0.99d ME : DE 0.98
4
5
1
2
1
2
SEM SAW SAY USY Item
Energy digestibility and retention of pigs fed experimental diets containing nine sources of corn grain (as-fed basis†) Table 5
0.301 0.534 0.035 0.005 < 0.001 0.077 < 0.001 0.001 < 0.001 0.012 < 0.001 0.275 < 0.001 < 0.001 0.644 0.168 0.149 0.552 < 0.001 0.094 < 0.001 0.481 < 0.001 < 0.001 < 0.001 0.091
USY vs. USY vs. SAY vs. SAY SAW SAW
P-value
P-values for contrast
418 C. S. PARK et al.
containing USY sources 3, 4 and 5, and SAY source 2, but were not different from pigs fed diets containing USY source 2 and SAY source 1. The energy retention rate of pigs fed diets containing SAW was greater than pigs fed diets containing USY (P < 0.001) and SAY (P < 0.001). The ME concentrations of diets containing SAY source 1 and SAW sources were greater (P < 0.05) than other diets. The ME concentrations in diets containing USY sources 1 and 2 were greater (P < 0.05) than those in diets containing USY sources 3 and 4, but were not different from diets containing USY source 5 and SAY source 2. The concentrations of ME in diets containing SAW were the greatest (P < 0.001) and those in diets containing USY were the least (P < 0.001). The ME : DE of diets containing SAW was greater than diets containing USY (P < 0.001) and SAY (P = 0.017).
Energy values in corn grains On an as-fed basis, the DE concentrations of SAY source 1 and SAW sources were greater (P < 0.05) than those of USY sources 1, 3, 4 and 5, and those of SAY source 2 (Table 6). The concentration of DE in SAY was greater (P < 0.001) than that in USY, but was less (P < 0.001) than in SAW. Values for the ME concentration in SAY source 1 and SAW sources were also greater (P < 0.05) than those of USY sources 1, 3, 4 and 5, and those of SAY source 2. Similar to the DE concentration, the ME concentration in SAW was the greatest (P < 0.001) and that in USY was the least (P < 0.001) among three different corn origins. Similar results were also observed when DE and ME concentrations of corn were expressed on a DM basis.
DISCUSSION Chemical composition The GE concentrations in corn grains used in this experiment were within the range of previously reported values (Sauvant et al. 2004; National Research Council 2012; Cervantes-Pahm et al. 2013; Liu et al. 2013; Rojas et al. 2013). Although the mean values for the GE concentration were quite similar among their countries of origin, values ranged from 3759 kcal/kg in USY source 1 to 3977 kcal/kg in USY source 5. Cromwell et al. (1999) reported that nutrient compositions in various sources of corn grains were affected by growing environment. In addition, Opapeju et al. (2007) reported that the nutrient composition was different between two genotypes of corn gains grown in the same area. Therefore, differences in the GE concentration of corn grains used in our study may be a consequence of different environmental conditions, genotype or other unknown factors. Animal Science Journal (2015) 86, 415–421
Animal Science Journal (2015) 86, 415–421
Values are expressed as least squares mean. Means within a row without a common superscript letter differ (a < b < c < d < e < f, P < 0.05). †Each least squares mean represents nine observations. DE, digestible energy; GE, gross energy; ME, metabolizable energy; SAW, white corn from South Africa; SAY, yellow corn from South Africa; SEM, standard error of means; USY, yellow corn from the United States.
– < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 – 30 28 4488 3930d 3879e 4412 3937d 3874e 4468 3787ab 3710abc 4588 3749a 3689ab 4441 3868bcd 3789cd 4343 3838bc 3768bcd
4566 3712a 3632a
4510 3724a 3662a
4448 3891cd 3838de
– < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 3908 3422de 3378f 3892 3449e 3394f 3887 3294bc 3227bcd 3914 3400de 3354ef 3977 3249ab 3197abc 3898 3219a 3165ab 3865 3366cd 3297de
As-fed basis GE DE ME Dry matter basis GE DE ME
3759 3298bc 3238cd
3955 3215a 3146a
5 1
2
3
4
1
2
1
2
– 26 24
SEM SAW SAY Energy values for nine sources of corn grains (kcal/kg)†
USY Item
Table 6
– < 0.001 < 0.001
SAY vs. SAW USY vs. SAW USY vs. SAY
P-value
P-values for contrast
ENERGY VALUES IN CORN GRAINS
419
Energy utilization of diets containing various corn grain sources The energy digestibility of nine sources of corn grains was within the range of previously reported values (Opapeju et al. 2007; Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). The different energy digestibilities in various sources of corn grains observed in this experiment may be associated with the variability in fiber contents. It has been reported that the concentration of NDF in diets or ingredients was negatively correlated with the energy digestibility (Le Goff & Noblet 2001). Values for the energy retention rate in corn grains agree with previous values (Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). Due to the relatively lower concentration of CP in corn grains, differences between the energy digestibility and retention rate were less than other feed ingredients, such as soybean meal (Rojas & Stein 2013), corn gluten meal and distillers dried grains with solubles (Rojas et al. 2013). Consequently, the ME : DE for corn grains was also greater than other feed ingredients high in CP (National Research Council 2012). Significant differences were not observed among the energy digestibility and retention rates of diets containing USY and SAY. However, the energy digestibility and retention rates of diets containing SAW were greater than those of diets containing USY and SAY. The reason for this observation remains unclear; however, compared with yellow corn, white corn may contain more available starch and lipids that are the major sources of energy in corn. Cowieson (2005) suggested that the digestibility of starch may be negatively affected by the amylase inhibitor, resistant starch, and phytate concentrations in diets fed to chickens. The EE digestibility may also be an important factor. The forms of oil in feed ingredients vary, and thus, digestive capacity to EE in feed ingredients depends on its storage form of oil (Kim et al. 2013).
Energy values in corn grains Mean values for the DE concentrations in USY, SAY and SAW were 3269, 3347 and 3436 kcal/kg on an as-fed basis, respectively, and those for the ME concentrations were 3209, 3291 and 3386 kcal/kg on an as-fed basis, respectively. These values agreed with the values reported previously (Sauvant et al. 2004; Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). However, the DE and ME concentrations in USY sources were slightly less than values suggested by the National Research Council (2012). Although the energy digestibility and retention rate of diets containing USY were not different compared to those of diets containing SAY, the concentrations of DE and ME in USY were less than those in SAY. Yin et al. (2002) also reported significantly different DE © 2014 Japanese Society of Animal Science
420 C. S. PARK et al.
concentrations in two sources of yellow corn grains with no different energy digestibility. The chemical structures of nutrients in yellow corn may be affected by differences in environment and soil conditions between these two countries. And consequently, the energy utilization was different between SAY and USY (Sauber & Owens 2001). Similar to the results of energy digestibility and retention rates, the concentrations of DE and ME in SAW were greater than those in USY and SAY. This may be due to the differences in the energy digestibility and retention rate among the countries of origin.
Conclusion The GE concentrations of nine sources of corn grains were fairly comparable despite their different countries of origin. However, the energy digestibility and retention rate of diets containing SAW were greater than those in diets containing USY and SAY. The energy digestibility and retention rates of USY were not different from those of SAY. The DE and ME concentrations in nine sources of corn grains were different between their countries of origin. The concentrations of DE and ME in USY were less than SAY, and those of SAW were greater than USY and SAY.
ACKNOWLEDGMENTS The authors express appreciation for the support from the Rural Development Administration (Suwon, Republic of Korea; PJ907038). A part of the present work resulted from the Konkuk University research support program.
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SAS Users Group International. pp. 1243–1246. SAS Institute, Cary, NC. Stein HH, Benzoni G, Bohlke RA, Peters DN. 2004. Assessment of the feeding value of South Dakota-grown field peas (Pisum sativum L.) for growing pigs. Journal of Animal Science 82, 2568–2578. Yin Y-L, Gurung NK, Jeaurond EA, Sharpe PH, de Lange CFM. 2002. Digestible energy and amino acid contents in Canadian varieties of sorghum, pearl millet, high-oil corn, high-oil–high-protein corn and regular corn samples for growing pigs. Canadian Journal of Animal Science 82, 385– 391.
© 2014 Japanese Society of Animal Science
Animal Science Journal (2015) 86, 415–421
doi: 10.1111/asj.12315
ORIGINAL ARTICLE Digestible and metabolizable energy in corn grains from different origins for growing pigs Chan S. PARK,1 Ah R. SON,1 Dong Y. KIL2 and Beob G. KIM1 1
Department of Animal Science and Technology, Konkuk University, Seoul and 2Department of Animal Science and Technology, Chung-Ang University, Anseong, Republic of Korea
ABSTRACT An experiment was conducted to determine the digestible energy (DE) and metabolizable energy (ME) concentrations in nine sources of corn grains fed to growing pigs and to compare the energy values among their countries of origin. A total of nine sources of corn grains including five sources of yellow corn from the United States (USY), two sources of yellow corn from South Africa (SAY), and two sources of white corn from South Africa (SAW) were used. Nine barrows with an initial body weight of 37.1 ± 8.6 kg were allotted to a 9 × 9 Latin square design with nine diets and nine periods. The DE concentration in SAY (3347 kcal/kg) was greater (P < 0.001) than in USY (3269 kcal/kg), but was less (P < 0.001) than in SAW (3436 kcal/kg) on an as-fed basis. Similarly, the ME concentration in SAY (3291 kcal/kg) was greater (P < 0.001) than in USY (3209 kcal/kg), but was less (P < 0.001) than in SAW (3386 kcal/kg). In conclusion, the DE and ME concentrations in nine sources of corn grains are different among their countries of origin.
Key words: corn grains, digestible energy, metabolizable energy, swine.
INTRODUCTION Corn is one of the major cereal grains in swine diets around the world and a large quantity of corn with various varieties (e.g. yellow corn and white corn) is produced in many countries. Moreover, new varieties have been continuously developed and their nutritive values for pigs have been evaluated (Bohlke et al. 2005; Pedersen et al. 2007; Linneen et al. 2008; Li et al. 2013). Sauber and Owens (2001) suggested that corn grains harvested from various countries may have different energy and nutrient compositions due to the differences in production environments, genetics, or both, which may result in different feeding values. Many researchers determined the digestible energy (DE) and metabolizable energy (ME) concentrations in corn grains fed to pigs as corn grains are the main energy source in swine diets (Stein et al. 2004; Baker & Stein 2009; Kim et al. 2009). Thus, accurate information on the energy values of corn grains is critical in formulating swine diets, particularly when corn grains are imported from overseas. The comparative energy values of different varieties of corn (Adeola & Bajjalieh 1997; Pedersen et al. 2007; Linneen et al. 2008; Oliveira et al. 2011) or of the same corn varieties harvested in different regions of the country (Opapeju et al. 2007) are available. However, to our knowledge © 2014 Japanese Society of Animal Science
comparative data for the energy values of corn grains from different countries of origin as swine feed ingredients are not available. We hypothesized that corn grains produced in different countries would have different energy values when fed to pigs. The objectives were to determine the DE and ME concentrations in nine sources of corn grains from different origins and to compare the energy values among their countries of origin.
MATERIALS AND METHODS Ingredients and diets Nine sources of corn grains, including five sources of yellow corn from the United States (USY), two sources of yellow corn from South Africa (SAY) and two sources of white corn from South Africa (SAW) were used (Tables 1,2). Experimental diets were formulated to contain 97.5% of each corn source as the sole source of energy (Tables 3,4). Limestone, dicalcium phosphate, salt and vitamin-mineral premix were included in diets to meet or exceed the nutrient requirement estimates (National Research Council 1998).
Correspondence: Beob G. Kim, Department of Animal Science and Technology, Konkuk University, Seoul 143-701, Republic of Korea. (Email: [email protected]) Received 14 April 2014; accepted for publication 17 July 2014.
416 C. S. PARK et al.
Table 1 Analyzed nutrient composition of nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Composition
Dry matter GE, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
86.5 3759 7.18 2.27 1.70 1.66 0.10 0.26 7.54 1.94
87.0 3865 7.02 2.62 1.76 1.36 0.05 0.24 7.52 2.05
86.6 3955 7.94 2.74 2.55 1.82 0.11 0.30 8.26 2.35
86.4 3898 7.41 2.73 1.74 1.68 0.17 0.28 7.91 1.93
86.7 3977 7.67 3.64 2.56 1.78 0.13 0.29 8.39 2.81
88.0 3914 7.29 3.06 2.18 1.55 0.10 0.23 8.35 2.28
87.0 3887 9.16 3.30 2.44 1.78 0.12 0.27 9.97 2.94
88.2 3892 7.21 3.15 2.36 1.76 0.21 0.21 7.62 2.31
87.1 3908 7.10 3.17 2.54 1.09 0.04 0.20 8.74 2.51
ADF, acid detergent fiber; GE, gross energy; NDF, neutral detergent fiber; SAW, white corn from South Africa; SAY, yellow corn from South Africa; USY, yellow corn from the United States.
Table 2 Nutrient variability among nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Item
Dry matter Gross energy, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
Mean
87.1 3895 7.55 2.96 2.20 1.61 0.11 0.25 8.25 2.35
SD
0.6 62 0.67 0.41 0.37 0.24 0.05 0.04 0.77 0.36
Maximum
88.2 3977 9.16 3.64 2.56 1.82 0.21 0.30 9.97 2.94
Minimum
86.4 3759 7.02 2.27 1.70 1.09 0.04 0.20 7.52 1.93
CV, %
0.73 1.58 8.85 13.9 16.9 15.0 48.6 14.2 9.36 15.4
Means for sources USY
SAY
SAW
86.7 3897 7.44 2.80 2.06 1.66 0.11 0.27 7.92 2.22
87.5 3900 8.23 3.18 2.31 1.66 0.11 0.25 9.16 2.61
87.6 3900 7.16 3.16 2.45 1.43 0.13 0.20 8.18 2.41
ADF, acid detergent fiber; CV, coefficient of variation; NDF, neutral detergent fiber; SAW, white corn from the South Africa; SAY, yellow corn from the South Africa; SD, standard deviation; USY, yellow corn from the United States.
Table 3 Ingredient composition of experimental diets containing nine sources of corn grains (%, as-fed basis)
Ingredient
Diet
Ground corn Limestone Dicalcium phosphate Salt Vitamin-mineral premix†
97.5 0.6 1.0 0.4 0.5
†Provided the following quantities per kg of complete diet: vitamin A, 25 000 IU; vitamin D3, 4000 IU; vitamin E, 50 IU; vitamin K, 5.0 mg; thiamin, 4.9 mg; riboflavin, 10.0 mg; pyridoxine, 4.9 mg; vitamin B12, 0.06 mg; pantothenic acid, 37.5 mg; folic acid, 1.10 mg; niacin, 62 mg; biotin, 0.06 mg; Cu, 25 mg as copper sulfate; Fe, 268 mg as iron sulfate; I, 5.0 mg as potassium iodate; Mn, 125 mg as manganese sulfate; Se, 0.38 mg as sodium selenite; Zn, 313 mg as zinc oxide; butylatedhydroxytoluene, 50 mg.
Animal care and experimental design The protocols for the present experiment were reviewed and approved by the Institutional Animal Care and Use Committee at the Konkuk University. Nine crossbred barrows (Landrace × Yorkshire × Duroc) with an initial body weight (BW) of 37.1 ± 8.6 kg were used. All pigs were individually housed in the metabolism cage (0.48 m × 1.49 m). Pigs were randomly allotted to a 9 × 9 © 2014 Japanese Society of Animal Science
Latin square design with nine diets and nine periods using a spreadsheet program (Kim & Kim 2010). To prevent the metabolic disorder caused by deficient amino acids in diets, a commercial diet was provided for 7 days after the periods 3 and 6.
Feeding and sample collection Daily feed allowance was calculated as 2.5 times the estimated maintenance requirement for energy (i.e. 106 kcal ME/kg BW0.75; National Research Council 1998) based on BW of pigs measured at the end of the each period. Daily feed allowance was divided into two equal meals and was fed to pigs at 08.00 and 16.00 hours. Water was freely available to the pigs. Each period lasted 7 days. The initial 3 days were considered as an adaptation period. Feces were collected following the marker-to-marker method as described by Adeola (2001). Chromic oxide was added in the morning meal at 0.5% as an indigestible marker and provided on days 4 and 8 of each period. The collection of fecal samples was initiated and terminated when chromic oxide visually appeared in the feces. The collection of urine was initiated on day 4 at 14.00 hours and terminated on day 8 at 14.00 hours. At the end of the each period, a subsample of urine was filtered by cotton sheet and collected in a 200 mL bottle. Fecal and urine samples were immediately stored at −20°C for further analyses. Animal Science Journal (2015) 86, 415–421
ENERGY VALUES IN CORN GRAINS
417
Table 4 Analyzed nutrient composition of experimental diets containing nine sources of corn grains (%, as-fed basis unless otherwise indicated)
Composition
Dry matter GE, kcal/kg Crude protein Ether extract Crude fiber Ash Calcium Phosphorus NDF ADF
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
86.5 3689 7.22 1.88 2.14 3.18 0.45 0.32 7.92 2.28
87.0 3798 6.81 2.43 1.94 3.33 0.56 0.38 7.05 2.59
86.7 3731 7.69 2.36 2.03 3.49 0.55 0.40 7.24 2.48
86.3 3690 7.06 2.30 1.62 3.29 0.60 0.41 6.28 2.21
86.5 3746 7.39 2.66 1.97 3.18 0.48 0.35 7.34 2.50
87.4 3838 7.16 3.26 2.06 3.07 0.50 0.37 7.87 3.02
87.2 3824 9.41 3.07 3.12 3.76 0.50 0.35 7.12 3.08
87.7 3835 7.17 3.27 2.39 3.26 0.53 0.34 7.51 2.21
87.8 3838 7.25 3.05 2.22 3.06 0.45 0.39 6.85 2.81
ADF, acid detergent fiber; GE, gross energy; NDF, neutral detergent fiber; SAW, white corn from South Africa; SAY, yellow corn from South Africa; USY, yellow corn from the United States.
Chemical analysis Nine sources of corn grains and experimental diets were analyzed for dry matter (DM; Association of Official Analytical Chemists 2005; method 930.15), crude protein (CP; Association of Official Analytical Chemists 2005; method 990.03), ether extract (EE; Association of Official Analytical Chemists 2005; method 920.39), crude fiber (Association of Official Analytical Chemists 2005; method 978.10), ash (Association of Official Analytical Chemists 2005; method 942.05), neutral detergent fiber (NDF; Goering & van Soest 1970), acid detergent fiber (Association of Official Analytical Chemists 2005; method 973.18), calcium (Association of Official Analytical Chemists 2005; method 978.02) and phosphorus (Association of Official Analytical Chemists 2005; method 946.06). Frozen fecal samples were dried at 55°C in a forced-air drying oven until constant weight. Frozen urinary samples were thawed and 3 mL of subsample was added in the cotton ball and lyophilized for further analysis as reported by Kim et al. (2009). Experimental ingredients, diets, fecal samples and lyophilized urinary samples were analyzed for gross energy (GE) using an adiabatic bomb calorimeter (C2000; IKA, Staufen, Germany).
Calculation and statistical analysis The DE concentrations of experimental diets were calculated by the difference between the total GE intake and fecal GE output. The ME concentrations of experimental diets were calculated by the difference between the total DE intake and urinary GE output (Kil et al. 2013). The DE and ME concentrations in corn grains were calculated by dividing the proportion of each corn grain (97.5%) in the experimental diets. Data were analyzed by the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC, USA). The corn source was used as the fixed variable and the animal and period were used as random variables. The CONTRAST statement was also used to determine significant differences in energy values of corn among different countries of origin. Least squares of means for each dependent variable were calculated and separated by the PDIFF option with Tukey’s adjustment. With this option, letters indicating significant differences were generated using a macro program (Saxton 1998). The experimental unit was the pig and the significance was declared at an α level of 0.05. Animal Science Journal (2015) 86, 415–421
RESULTS Chemical composition Mean, standard deviation (SD), and coefficient of variation (CV) for nutrient compositions of nine sources of corn grains were calculated, and mean values for nutrient compositions of three countries of origin were also calculated (Table 2). Mean values for the GE concentrations in USY, SAY and SAW were fairly comparable. The concentrations of CP ranged from 7.02% to 9.16%. The concentrations of EE in USY were slightly less than those in SAY and SAW (2.80% vs. 3.18% and 3.16%). Variation of the GE concentrations in nine sources of corn grains (CV = 1.58%) was relatively less compared with other nutritional compositions.
Energy utilization of diets containing various corn grain sources Energy digestibility of diets containing USY sources 1 and 2, and SAW sources were greater (P < 0.05) than all other diets except diets containing USY source 4 and SAY source 1, which were not different from diets containing SAW source 2 (Table 5). Energy digestibility of diets containing SAY source 1 was greater (P < 0.05) than diets containing USY source 3 and SAY source 2. Energy digestibility of the diets containing SAW was greater than the diets containing USY (P < 0.001) and SAY (P < 0.001). Values for the DE concentration of diets containing SAY source 1 and SAW sources were greater (P < 0.05) than other diets except diets containing USY source 2, which was not different from diets containing SAY source 1 and SAW source 2. The DE concentration of diets containing SAY was greater (P < 0.001) than diets containing USY, but was less (P < 0.001) than diets containing SAW. Values for the energy retention rate of pigs fed diets containing USY source 1 and SAW sources were greater (P < 0.05) than those of pigs fed diets © 2014 Japanese Society of Animal Science
© 2014 Japanese Society of Animal Science
Values are expressed as least squares mean. Means within a row without a common superscript letter differ (a < b < c < d < e < f, P < 0.05). †Each least squares mean represents nine observations. DE, digestible energy; GE, gross energy; ME, metabolizable energy; SAW, white corn from South Africa; SAY, yellow corn from South Africa; SEM, standard error of means; USY, yellow corn from the United States.
0.574 0.688 < 0.001 0.172 < 0.001 < 0.001 < 0.001 0.141 0.695 0.242 < 0.001 < 0.001 0.017 0.198 0.018 < 0.001 0.079 < 0.001 < 0.001 < 0.001 0.700 0.899 0.003 < 0.001 < 0.001 < 0.001 0.12 0.45 12 0.03 56 0.7 0.03 0.50 16.5 13.5 0.6 0.02 0.00
3 2 1
Diet intake, kg/day 1.57 1.54 1.57 1.55 1.55 1.53 1.57 1.53 1.55 5.82ab 5.86ab 5.71a 5.79ab 5.87ab 5.99b 5.87ab 5.95ab GE intake, Mcal/day 5.81ab 158ab 202d 180bcd 189cd 171abc 201d 152a 160ab Fecal output, g/day 163ab 4.71c 4.57ab 4.69bc 4.65bc 4.69bc 4.72c 4.63bc 4.69bc Feces GE, Mcal/kg 4.50a 747ab 924d 846bcd 877cd 801abc 951d 703a 752ab Fecal GE output, kcal/d 735a 87.1d 84.0a 85.0abc 84.6ab 86.4bcd 84.0a 87.7d 86.9cd Energy digestibility, % 87.2d 3.28cd 3.13a 3.14a 3.17ab 3.32de 3.21bc 3.36e 3.34de Diet DE, Mcal/kg 3.22bc Urine output, kg/day 2.15 2.37 2.55 2.22 2.70 2.20 1.81 2.28 2.74 Urine GE, kcal/kg 60.4 70.9 64.3 53.4 33.1 51.0 71.1 61.4 53.5 108.1c 84.5abc 79.8ab 70.6a 102.4bc 87.0abc 72.6a Urinary GE output, kcal/day 95.8abc 104.6bc 85.3bc 82.2a 83.6ab 83.2a 85.2bc 82.3a 86.3c 85.8c Energy retention rate, % 85.6c 3.21cd 3.07a 3.09ab 3.12abc 3.27ef 3.15bcd 3.31f 3.29f Diet ME, Mcal/kg 3.16cd abc ab a abcd bcd cd ab bcd 0.98 0.98 0.98 0.98 0.99 0.98 0.98 0.99d ME : DE 0.98
4
5
1
2
1
2
SEM SAW SAY USY Item
Energy digestibility and retention of pigs fed experimental diets containing nine sources of corn grain (as-fed basis†) Table 5
0.301 0.534 0.035 0.005 < 0.001 0.077 < 0.001 0.001 < 0.001 0.012 < 0.001 0.275 < 0.001 < 0.001 0.644 0.168 0.149 0.552 < 0.001 0.094 < 0.001 0.481 < 0.001 < 0.001 < 0.001 0.091
USY vs. USY vs. SAY vs. SAY SAW SAW
P-value
P-values for contrast
418 C. S. PARK et al.
containing USY sources 3, 4 and 5, and SAY source 2, but were not different from pigs fed diets containing USY source 2 and SAY source 1. The energy retention rate of pigs fed diets containing SAW was greater than pigs fed diets containing USY (P < 0.001) and SAY (P < 0.001). The ME concentrations of diets containing SAY source 1 and SAW sources were greater (P < 0.05) than other diets. The ME concentrations in diets containing USY sources 1 and 2 were greater (P < 0.05) than those in diets containing USY sources 3 and 4, but were not different from diets containing USY source 5 and SAY source 2. The concentrations of ME in diets containing SAW were the greatest (P < 0.001) and those in diets containing USY were the least (P < 0.001). The ME : DE of diets containing SAW was greater than diets containing USY (P < 0.001) and SAY (P = 0.017).
Energy values in corn grains On an as-fed basis, the DE concentrations of SAY source 1 and SAW sources were greater (P < 0.05) than those of USY sources 1, 3, 4 and 5, and those of SAY source 2 (Table 6). The concentration of DE in SAY was greater (P < 0.001) than that in USY, but was less (P < 0.001) than in SAW. Values for the ME concentration in SAY source 1 and SAW sources were also greater (P < 0.05) than those of USY sources 1, 3, 4 and 5, and those of SAY source 2. Similar to the DE concentration, the ME concentration in SAW was the greatest (P < 0.001) and that in USY was the least (P < 0.001) among three different corn origins. Similar results were also observed when DE and ME concentrations of corn were expressed on a DM basis.
DISCUSSION Chemical composition The GE concentrations in corn grains used in this experiment were within the range of previously reported values (Sauvant et al. 2004; National Research Council 2012; Cervantes-Pahm et al. 2013; Liu et al. 2013; Rojas et al. 2013). Although the mean values for the GE concentration were quite similar among their countries of origin, values ranged from 3759 kcal/kg in USY source 1 to 3977 kcal/kg in USY source 5. Cromwell et al. (1999) reported that nutrient compositions in various sources of corn grains were affected by growing environment. In addition, Opapeju et al. (2007) reported that the nutrient composition was different between two genotypes of corn gains grown in the same area. Therefore, differences in the GE concentration of corn grains used in our study may be a consequence of different environmental conditions, genotype or other unknown factors. Animal Science Journal (2015) 86, 415–421
Animal Science Journal (2015) 86, 415–421
Values are expressed as least squares mean. Means within a row without a common superscript letter differ (a < b < c < d < e < f, P < 0.05). †Each least squares mean represents nine observations. DE, digestible energy; GE, gross energy; ME, metabolizable energy; SAW, white corn from South Africa; SAY, yellow corn from South Africa; SEM, standard error of means; USY, yellow corn from the United States.
– < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 – 30 28 4488 3930d 3879e 4412 3937d 3874e 4468 3787ab 3710abc 4588 3749a 3689ab 4441 3868bcd 3789cd 4343 3838bc 3768bcd
4566 3712a 3632a
4510 3724a 3662a
4448 3891cd 3838de
– < 0.001 < 0.001 – < 0.001 < 0.001 – < 0.001 < 0.001 3908 3422de 3378f 3892 3449e 3394f 3887 3294bc 3227bcd 3914 3400de 3354ef 3977 3249ab 3197abc 3898 3219a 3165ab 3865 3366cd 3297de
As-fed basis GE DE ME Dry matter basis GE DE ME
3759 3298bc 3238cd
3955 3215a 3146a
5 1
2
3
4
1
2
1
2
– 26 24
SEM SAW SAY Energy values for nine sources of corn grains (kcal/kg)†
USY Item
Table 6
– < 0.001 < 0.001
SAY vs. SAW USY vs. SAW USY vs. SAY
P-value
P-values for contrast
ENERGY VALUES IN CORN GRAINS
419
Energy utilization of diets containing various corn grain sources The energy digestibility of nine sources of corn grains was within the range of previously reported values (Opapeju et al. 2007; Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). The different energy digestibilities in various sources of corn grains observed in this experiment may be associated with the variability in fiber contents. It has been reported that the concentration of NDF in diets or ingredients was negatively correlated with the energy digestibility (Le Goff & Noblet 2001). Values for the energy retention rate in corn grains agree with previous values (Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). Due to the relatively lower concentration of CP in corn grains, differences between the energy digestibility and retention rate were less than other feed ingredients, such as soybean meal (Rojas & Stein 2013), corn gluten meal and distillers dried grains with solubles (Rojas et al. 2013). Consequently, the ME : DE for corn grains was also greater than other feed ingredients high in CP (National Research Council 2012). Significant differences were not observed among the energy digestibility and retention rates of diets containing USY and SAY. However, the energy digestibility and retention rates of diets containing SAW were greater than those of diets containing USY and SAY. The reason for this observation remains unclear; however, compared with yellow corn, white corn may contain more available starch and lipids that are the major sources of energy in corn. Cowieson (2005) suggested that the digestibility of starch may be negatively affected by the amylase inhibitor, resistant starch, and phytate concentrations in diets fed to chickens. The EE digestibility may also be an important factor. The forms of oil in feed ingredients vary, and thus, digestive capacity to EE in feed ingredients depends on its storage form of oil (Kim et al. 2013).
Energy values in corn grains Mean values for the DE concentrations in USY, SAY and SAW were 3269, 3347 and 3436 kcal/kg on an as-fed basis, respectively, and those for the ME concentrations were 3209, 3291 and 3386 kcal/kg on an as-fed basis, respectively. These values agreed with the values reported previously (Sauvant et al. 2004; Oliveira et al. 2011; Liu et al. 2013; Rojas et al. 2013). However, the DE and ME concentrations in USY sources were slightly less than values suggested by the National Research Council (2012). Although the energy digestibility and retention rate of diets containing USY were not different compared to those of diets containing SAY, the concentrations of DE and ME in USY were less than those in SAY. Yin et al. (2002) also reported significantly different DE © 2014 Japanese Society of Animal Science
420 C. S. PARK et al.
concentrations in two sources of yellow corn grains with no different energy digestibility. The chemical structures of nutrients in yellow corn may be affected by differences in environment and soil conditions between these two countries. And consequently, the energy utilization was different between SAY and USY (Sauber & Owens 2001). Similar to the results of energy digestibility and retention rates, the concentrations of DE and ME in SAW were greater than those in USY and SAY. This may be due to the differences in the energy digestibility and retention rate among the countries of origin.
Conclusion The GE concentrations of nine sources of corn grains were fairly comparable despite their different countries of origin. However, the energy digestibility and retention rate of diets containing SAW were greater than those in diets containing USY and SAY. The energy digestibility and retention rates of USY were not different from those of SAY. The DE and ME concentrations in nine sources of corn grains were different between their countries of origin. The concentrations of DE and ME in USY were less than SAY, and those of SAW were greater than USY and SAY.
ACKNOWLEDGMENTS The authors express appreciation for the support from the Rural Development Administration (Suwon, Republic of Korea; PJ907038). A part of the present work resulted from the Konkuk University research support program.
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