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Variation in coefficient of total tract apparent digestibility of dry matter, nitrogen, and phosphorus and coefficient of total tract standardized digestibility of phosphorus in different corns fed to growing-finishing pigs
Animal Feed Science and Technology 201 (2015) 66–71
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Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci
Variation in coefficient of total tract apparent digestibility of dry matter, nitrogen, and phosphorus and coefficient of total tract standardized digestibility of phosphorus in different corns fed to growing-finishing pigs Y.D. Jeong a , S.H. Lee a , C.S. Park b , S.B. Cho a , S.K. Park c,∗ a b c
National Institute of Animal Science, R.D.A., Suwon 441-706, Republic of Korea Department of Animal Science and Technology, Konkuk University, Seoul 143-701, Republic of Korea Department of Food Science and Technology, Sejong University, Seoul 143-747, Republic of Korea
a r t i c l e
i n f o
Article history: Received 6 August 2014 Received in revised form 31 December 2014 Accepted 2 January 2015 Abbreviations: CTTAD, coefficient of total tract apparent digestibility CTTSD, coefficient of total tract standardized digestibility P, phosphorus USY, yellow corns from United States SAY, yellow corns from South Africa SAW, white corns from South Africa DM, dry matter N, nitrogen ATTD, apparent total tract digestibility EPL, endogenous P losses NRC, national research council BW, body weight ME, maintenance energy GE, gross energy CP, crude protein NDF, neutral detergent fiber ADF, acid detergent fiber Ca, calcium SEM, standard error of the means
a b s t r a c t This study was conducted to determine the coefficient of total tract apparent digestibility (CTTAD) and coefficient of total tract standardized digestibility (CTTSD) of phosphorus (P) in nine corn sources fed to growing-finishing pigs. Ten barrows (initial of BW, 55.8 ± 3.0 kg) were individually housed in metabolism cages. Experimental diets consisted of nine different corns and one P-free diet for measurement of basal endogenous loss of P. Corn sources included 5 yellow-corns from the United States (USY-1 to 5), 2 yellow-corns from South Africa (SAY-1 and 2), and 2 white-corns from South Africa (SAW-1 and 2). Pigs were arranged in a 10 × 8 incomplete Latin square design with 10 diets and 8 periods. The CTTAD of dry matter (DM) in SAW-1 was greater (P < 0.01) than that of USY-3, USY-5 or SAY-2. Pigs fed SAW-1 showed greater (P < 0.01) CTTAD of nitrogen (N) than those fed USY-3, USY5 or SAY-2. The CTTAD and CTTSD of P across the nine corns averaged 0.43 and 0.49, respectively, but the values were not significantly different among the corn grains. In conclusion, the digestibility of DM and N varies in corn and needs to be determined to improve the efficiency with which the grain and corn based diets are utilized by growing pigs. © 2015 Published by Elsevier B.V.
Keywords: Corn Total tract standardized digestibility Phosphorus Pigs
∗ Corresponding author. Tel.: +82 31 290 1657; fax: +82 31 290 1660. E-mail address: [email protected] (S.K. Park). http://dx.doi.org/10.1016/j.anifeedsci.2015.01.002 0377-8401/© 2015 Published by Elsevier B.V.
Y.D. Jeong et al. / Animal Feed Science and Technology 201 (2015) 66–71
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1. Introduction Phosphorus (P) is an essential nutrient which plays crucial roles in various biological processes including bone formation and energy metabolism (Nafikov and Beitz, 2007; Kerr et al., 2010). Phosphorus is combined with phytate, called ‘phytate phosphorus’ and is not bioavailable to pigs which lack the digestive enzyme phytase required to remove phosphate from the inositol in the phytate molecule (Baidoo et al., 2003; Knowlton et al., 2004). This is why more than 50% of P in corn and soybean meal passes through the intestines unused, and is excreted in the manure which causes environmental pollution and waste of nutrients (Pallauf and Rimbach, 1997). Therefore, efforts have been made to improve the digestibility of P and to reduce the excretion of P. To meet the nutritional requirements of pigs, diets need to be precisely formulated on the basis of the availability of P from feed ingredients. To this end, the relative bio-availability of P from feed ingredients has been calculated using the slope-ratio technique (Cromwell, 1992). Digestibility of P has also been expressed as the apparent total tract digestibility (ATTD) or coefficient of total tract apparent digestibility (CTTAD) based on the intake and excretion of P (Almeida and Stein, 2010). These values, however, are not always additive in mixed diets because they do not account for basal endogenous P losses (EPL). The EPL is defined as the amount of P voided in feces that does not originate from the diet. EPL can be measured directly by feeding a P-free diet and measuring the amount of P excreted in feces (Petersen and Stein, 2006). Thus, when CTTAD is corrected for basal EPL, the coefficient of total tract standardized digestibility (CTTSD) of P can be obtained (Almeida and Stein, 2010). The reason for reduced excretion of P in diets formulated based on CTTSD, instead of CTTAD, is most likely that values for CTTSD of P are additive in mixed diets. The CTTSD of P was recently adapted in NRC (2012). However, values of CTTSD of P for various types of corns are still limited. Corn, as a major ingredient for pig feed, is grown widely in many countries. Nutrient contents in corn are influenced by region and year produced and by cultivars and this fluctuation may result in considerable variation in digestibility (Cromwell et al., 1999; Spencer et al., 2000; Bohlke et al., 2005; Almeida and Stein, 2010, 2012). The objective of the present study was to determine the CTTSD of P and CTTAD of dry matter (DM), nitrogen (N) and P in different corn types fed to growing-finishing pigs. 2. Materials and methods 2.1. Diets, animals, and experimental design The experimental protocols describing the management and care of animals were reviewed and approved by the Animal Care and Use of National Institute of Animal Science. Ten barrows (initial BW, 55.8 ± 3.0 kg) were obtained from a local farm and housed in individual metabolism cages. The experimental design was a 10 × 8 incomplete Latin square design with 10 diets and 8 periods. The 10 diets consisted of five yellow-corns from the United States (USY1 to 5), two yellow-corns from South Africa (SAY1 and 2), two white-corns from South Africa (SAW1 and 2) and a P free diet was also used. All nine corn grains were ground through a 3 mm screen and the diets were fed as a mash. The nutrient compositions of nine corn grains are presented in Table 1. The ingredient and nutrient compositions of the experimental diets are shown in Tables 2 and 3, respectively. 2.2. Feeding and sample collection The daily amount of feed provided to the pigs was calculated as 2.5 times the estimated requirement for maintenance energy (i.e., 444 kJ ME per kg0.75 ; NRC, 1998) and fed in two equal meals at 0900 and 1700 h. Animals had free access to water throughout the experiment. Pigs were adapted to the experimental diets and metabolic cages for 4 d. Chromic oxide was added to the morning meals at 1 g/kg as an indigestible marker on days 5 and 10. Fecal samples were collected according to the marker-to-marker approach (Adeola, 2001) for color assisted sample selection. Urine was collected daily in buckets that Table 1 Analyzed nutrient contents of nine corn grains1 (g/kg, as-fed basis). Composition
Dry matter Gross energy, MJ/kg Crude protein Crude fat Crude fiber Ash Calcium Phosphorus Neutral detergent fiber Acid detergent fiber 1
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
856 17.45 70.5 21.5 10.9 13.7 1.3 2.5 85.5 16.7
856 18.0 66.1 28.0 7.2 9.7 0.7 2.1 79.8 13.4
865 18.67 75.1 28.8 8.3 14.4 1.3 2.4 89.5 18.3
860 18.8 71.2 33.7 10.4 14.3 1.8 2.9 87.2 18.2
862 17.5 69.9 29.8 7.0 12.7 1.3 2.6 87.0 17.7
867 18.2 70.2 34.4 12.1 12.0 1.2 2.2 90.2 20.8
869 18.9 90.3 31.5 13.0 16.3 1.7 2.7 97.3 20.9
870 17.8 70.1 33.0 10.5 14.6 2.2 2.1 85.1 17.7
870 18.45 70.4 38.6 9.5 8.6 0.7 2.0 93.4 18.9
USY, yellow corn from the United States; SAY, yellow corn from South Africa; SAW, white corn from South Africa.
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Table 2 Ingredient composition of experimental diets (g/kg, as-fed basis). Ingredient
Diet
Ground corn Cornstarch Sucrose Soybean oil Gelatin Solka-floc dl-Methionine l-Tryptophan l-Histidine l-Isoleucine Limestone Potassium carbonate Magnesium oxide Salt Vitamin–mineral premix1
Corn
P-free
969.0 – – 15.0 – – – – – – 7.0 – – 4.0 5.0
– 460.6 200.0 30.0 240.0 40.0 2.2 1.2 0.6 0.4 11.0 4.0 1.0 4.0 5.0
1 The vitamin–mineral premix provided the following quantities of vitamins and minerals per kilogram of diets: vitamin A, 10,000 IU; vitamin D3 , 2000 IU; vitamin E, 250 IU; vitamin K3 , 0.5 mg; vitamin B1 , 0.49 mg as mononitrate; thiamin, 0.49 mg as thiamin mononitrate; riboflavin, 1.50 mg; pyridoxine, 1 mg as pyridoxine hydrochloride; vitamin B12 , 0.01 mg; niacin, 10 mg as nicotinic acid; pantothenic acid, 5 mg as calcium pantothenate; folic acid, 1 mg; biotin as d-biotin, 0.1 mg; choline, 125 mg as choline chloride; Mn, 60 mg as manganese sulfate; Zn, 75 mg as zinc sulfate; Fe, 20 mg as ferrous sulfate; Cu, 3 mg as cupric sulfate; I, 1.25 mg as calcium iodate; Co, 0.5 mg as cobaltous carbonate; Mg, 10 mg as magnesium oxide.
contained 50 mL of 4N sulfuric acid during the collection periods. All feces and urine were stored at −20 ◦ C before chemical analyses. 2.3. Sample analyses and data processing Fecal samples were dried at 60 ◦ C in a forced-air drying oven and ground. All samples, which are ingredients, diets, feces, and urine, were dried in a forced-air drying oven at 135 ◦ C for 2 h to analyze DM (method 930.15; AOAC, 2005) and N (method 990.03; AOAC, 2005). The ingredient and experimental diets were analyzed for gross energy (Model C2000, IKA, Germany), crude fat (method 920.39; AOAC, 2005), crude fiber (method 978.10; AOAC, 2005), ash (method 942.05; AOAC, 2005), acid detergent fiber (method 973.18; AOAC, 2005), and neutral detergent fiber (Holst, 1973). The Ca concentrations in the ingredients, diets, and feces were analyzed using an atomic absorption spectrophotometer (method 978.02; AOAC, 2005 Perkin Elmer 3300, Perkin Elmer, USA). The P concentrations in the ingredients, diets, and feces were analyzed using a spectrophotometer (method 946.06; AOAC, 2005; Optizen 2120UV, Mecasys, Republic of Korea). The CTTAD and CTTSD of P and the endogenous P loss in each diet were calculated as previously described (Almeida and Stein, 2010). Values for CTTAD of N and DM, expressed as a proportion of their intake, were calculated by subtracting N and DM excreted in the feces from intake, and dividing by intake. All data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC, USA). Homogeneity of the variances among treatments was confirmed by using the UNIVARIATE procedure and this procedure was also used to test for outliers, but no outliers were identified. The model included diet as the fixed variable and animal and period as the random variables. Least squares means were calculated and separated using the PDIFF option with the Tukey’s adjustment. The pig was the experimental unit for all analyses and an alpha level of 0.05 was used to assess significance among means.
Table 3 Analyzed nutrient composition of experimental diets1 (g/kg, as-fed basis). Composition
Dry matter Gross energy, MJ/kg Crude protein Crude fat Crude fiber Ash Calcium Phosphorus Neutral detergent fiber Acid detergent fiber 1
USY
SAY
SAW
P-free
1
2
3
4
5
1
2
1
2
861 17.45 68.9 36.0 4.3 18.1 3.1 2.6 82.7 17.7
871 19.0 66.2 35.1 8.6 20.9 4.1 2.1 90.6 20.6
868 18.1 75.3 42.6 2.1 23.0 4.5 3.2 89.0 26.4
866 18.4 68.0 42.4 2.6 22.0 5.0 2.7 94.1 27.9
867 18.4 68.9 47.1 4.9 20.2 4.2 2.6 96.0 22.4
871 18.1 69.2 46.6 10.9 18.1 3.2 2.2 94.1 22.3
871 18.1 85.7 45.4 9.7 20.1 3.7 2.5 109.5 36.0
872 18.2 69.3 45.3 5.9 18.9 4.4 2.0 85.5 18.8
873 17.7 69.3 47.9 6.8 16.3 3.4 2.0 84.9 25.5
USY = yellow corn from the United States; SAY = yellow corn from South Africa; SAW = white corn from South Africa.
908 18.8 26.13 47.7 2.0 16.3 3.1 0.1 23.0 10.3
Table 4 Nutrient balance (g/d -as fed) and the coefficient of apparent total tract digestibility (CTTAD) for dry matter, N and P and the coefficient of standardized total tract digestibility (CTTSD) of P in nine corn based diets fed to growing-finishing pigs.1 , 2 Item
USY 1
a,b,c,d,e
2
3
4
5
1
SEM3
SAW 2
1
P-value
2
P-values for contrast USY vs. SAY
USY vs. SAW
SAY vs. SAW
2.14
2.13
2.13
2.11
2.14
2.14
2.10
2.11
0.11
0.451
0.429
0.052
0.023
1.86
1.85
1.85
1.83
1.87
1.86
1.83
1.84
0.10
0.446
0.110
0.381
0.037
22.5d 4.44d,e
25.6b 6.85a
23.1c,d 5.81b
23.3c,d 5.51b,c
23.7c 4.73d
29.2a 5.33c
23.2c,d 4.25e
23.3c,d 4.29e
1.26 0.28
<0.001 <0.001
<0.001 <0.001
0.053 <0.001
<0.001 <0.001
145b,c,d 138b,c,d 3.50c,d 2.86a,b,c
175a,b 167a,b 4.84a,b 3.53a
135c,d 129c,d 3.36c,d 2.89a,b,c
162a,b,c 155a,b,c 4.03b,c 3.40a,b
144b,c,d 138b,c,d 3.38c,d 2.48c
187a 179a 5.10a 3.23a,b,c
123d 117d 3.03d 2.68a,b,c
148b,c,d 142b,c,d 3.82c,d 2.56b,c
12.92 12.37 0.36 0.39
<0.001 <0.001 <0.001 0.001
0.073 0.086 0.124 0.042
0.006 0.005 0.006 0.001
0.000 <0.001 <0.001 0.214
0.925a,b,c,d
0.909c,d
0.929a,b
0.914b,c,d
0.925a,b,c
0.904d
0.937a
0.922a,b,c,d
0.01
<0.001
0.141
0.007
0.001
0.843a,b,c
0.810c
0.854a,b,c
0.824b,c
0.856a,b
0.824b,c
0.873a
0.833a,b,c
0.01
0.001
0.315
0.010
0.167
0.360
0.491
0.508
0.393
0.473
0.408
0.391
0.413
0.06
0.204
0.858
0.338
0.333
0.429
0.536
0.562
0.448
0.540
0.466
0.464
0.485
0.06
0.339
0.707
0.640
0.472
Means within a row without a common superscript letter differ (P < 0.05). USY, yellow corn from the united states; SAW, white corn from South Africa; SAY, yellow corn from South Africa. 2 Each least squares mean represents 8 observations except USY4 and SAW1 (7 observations), and USY2 (6 observations). Diet intake and fecal output were based on 5 d of collection. 3 SEM = standard error of the means. 4 Coefficients of total tract apparent digestibility (CTTAD), coefficients of total tract standardized digestibility (CTTSD). 5 Values for CTTSD of P were calculated by correcting CTTAD values for the basal endogenous loss of P. The basal endogenous loss of P was determined in pigs fed the P-free diet at 168 ± 140 mg/kg dry matter intake.
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Feed intake 2.13 Total intake (kg/d) Dry matter 1.84 intake (kg/d) Nitrogen intake 23.5c,d Phosphorus 5.58b,c intake Fecal output Total feces 153a,b,c,d Dry matter feces 147a,b,c,d Nitrogen output 4.03b,c,d Phosphorus 3.29a,b,c output Coefficients of digestibility CTTAD4 of dry 0.920a,b,c,d matter CTTAD of 0.829a,b,c nitrogen CTTAD of 0.421 phosphorus 5 0.476 CTTSD of phosphorus
SAY
1
69
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3. Results The result for nutrient balance and digestibility are given in Table 4. No difference was observed in daily intake and DM intake among different corn sources (Table 4). However, SAY group had greater (P < 0.05) daily intake and DM intake than SAW group. N intake was least (P < 0.01) in USY-2 and greatest (P < 0.01) in SAY-2. Pigs fed USY corn group had greater (P < 0.01) P intake than those fed SAY or SAW corn group. Pigs fed USY-3 and SAY-2 showed greater output of total and DM feces than those fed USY-4 and SAW-1. Fecal N excretion was greater (P < 0.01) in USY-3 and SAY-2 than in USY-2, USY-4, SAY-1, SAW-1 or SAW-2. Pigs from USY corn group showed greater (P < 0.01) level of fecal output of P than those from SAY or SAW corn group. The CTTAD of DM was greater (P < 0.01) in SAW-1 than USY-3, USY-5 or SAY-2. Pigs fed SAW corn group had greater (P < 0.01) N digestibility than those fed USY corn group. The CTTAD and CTTSD of P across the nine different corns ranged from 0.36 to 0.51 and from 0.43 to 0.56, respectively. Values for CTTAD and CTTSD of P were highest in USY-4 and lowest in USY-2 among corn groups but the difference across corns were not statistically significant. 4. Discussion Our results showed that the P content of the nine corns ranged from 2.0 to 2.9 g/kg which is similar to previous results (Bohlke et al., 2005; Almeida et al., 2011; Almeida and Stein, 2012; NRC, 2012). Our values of CTTAD and CTTSD of P ranged from 0.36 to 0.51 and from 0.43 to 0.56, respectively, but not statistically different. This range is higher than that reported by Almeida and Stein (2012) and Bohlke et al. (2005). The average values of CTTAD and CTTSD of P in our study (0.43 and 0.49, respectively) are also higher than those given in NRC (2012) (0.26 and 0.34, respectively). This variation may be associated with differences in the phytate content of the corns on which the information is based. Low-phytate corn hybrids are known to have a higher P digestibility (Bohlke et al., 2005) than conventional corns. The addition of phytase to pig diets had similarly been reported to improve P digestibility (Almeida and Stein, 2010; Baidoo et al., 2003; Rojas et al., 2013). Clearly, however, further research is required to determine the phytase levels of different corns. The DM levels of nine corn grains in our study ranged from 856 to 870 g/kg. These values are similar to those reported by Almeida and Stein (867 g/kg, [Almeida and Stein, 2012]2012), Li et al. (882 g/kg, [Li et al., 2014]2014), and NRC (883 g/kg, [NRC, 2012]2012), but higher than those reported by Almeida et al. (841 g/kg, [Almeida et al., 2011]2011). Differences in DM digestibility have been reported between soft, hard and medium-hard corns by Li et al. (2014). In our study, DM digestibility also varied among the nine corns and ranged from 0.90 to 0.94. Variation in energy levels also exists among different corn sources (Fent et al., 2001; Li et al., 2014; Stein et al., 2009). In the present study, GE levels in nine corns varied from 17.5 to 18.9 MJ/kg and the average (18.3 MJ/kg) is higher than those reported by NRC (16.5 MJ/kg, [NRC, 2012]2012), Rojas et al. (16.4 MJ/kg, [Rojas et al., 2013]2013) and Widmer et al. (16.3 MJ/kg, [Widmer et al., 2007]2007). These differences support our contention that the nutrient levels of corns vary and need to be precisely measured. The CP contents of the nine corns in our study ranged from 66.1 to 90.3 g/kg and the average value (73.3 g/kg) is similar to those of Almeida and Stein (72.7 g/kg; [Almeida and Stein, 2012]2012) and Widmer et al. (72.0 g/kg, [Widmer et al., 2007]2007) but lower than that reported by Bohlke et al. (94.6 g/kg, [Bohlke et al., 2005]2005) and NRC (82.4 g/kg, [NRC, 2012]2012). The CTTAD of N varied by 6.3%. The N content and its digestibility is known to affect N excretion and our results clearly demonstrate that to optimize diet formulation and minimize N excretion the digestibility of N in corn and other grains needs to be measured (Canh et al., 1998; Otto et al., 2003). There is large variation in levels of crude fiber, including NDF and ADF, and crude fat in feed ingredients. The average crude fat content of the corns used in our study (10.4 g/kg) is lower than that in NRC (19.8 g/kg, [NRC, 2012]2012). In contrast the average NDF content of our corns (89.6 g/kg) is similar to the NRC (2012) value (91.1 g/kg) and those reported by Almeida et al. (85.3 g/kg, [Almeida et al., 2011]2011) and Widmer et al. (90.0 g/kg, [Widmer et al., 2007]2007) and lower than Li et al.’s result (98.5 g/kg, [Li et al., 2014]2014). Average ADF level in our study (18.7 g/kg) is comparable to Almeida et al. (20.0 g/kg, [Almeida et al., 2011]2011) and Li et al. (21.6 g/kg, [Li et al., 2014]2014), but lower than the values reported by NRC (28.8 g/kg, [NRC, 2012]2012) and Widmer et al. (25.0 g/kg, [Widmer et al., 2007]2007). The crude fat content of our nine corns ranged from 21.5 to 38.6 g/kg. These are similar to the levels reported by Li et al. (2014), NRC (2012) and Widmer et al. (2007). Taken together, results from the current study demonstrate considerable variability in nutrient levels and in the digestibility of nutrients in different corns. Both need to be determined if we are to improve the accuracy and cost effectiveness of diet formulations and minimize nutrient excretion. Conflict of interest The authors declare that they have no conflict of interest. Acknowledgements This work was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project title: Standardized digestibility of phosphorus in various feed ingredients of pigs, Project Nos. PJ907038032014 and PJ009312)” Rural Development Administration, Republic of Korea.
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Variation in coefficient of total tract apparent digestibility of dry matter, nitrogen, and phosphorus and coefficient of total tract standardized digestibility of phosphorus in different corns fed to growing-finishing pigs Y.D. Jeong a , S.H. Lee a , C.S. Park b , S.B. Cho a , S.K. Park c,∗ a b c
National Institute of Animal Science, R.D.A., Suwon 441-706, Republic of Korea Department of Animal Science and Technology, Konkuk University, Seoul 143-701, Republic of Korea Department of Food Science and Technology, Sejong University, Seoul 143-747, Republic of Korea
a r t i c l e
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Article history: Received 6 August 2014 Received in revised form 31 December 2014 Accepted 2 January 2015 Abbreviations: CTTAD, coefficient of total tract apparent digestibility CTTSD, coefficient of total tract standardized digestibility P, phosphorus USY, yellow corns from United States SAY, yellow corns from South Africa SAW, white corns from South Africa DM, dry matter N, nitrogen ATTD, apparent total tract digestibility EPL, endogenous P losses NRC, national research council BW, body weight ME, maintenance energy GE, gross energy CP, crude protein NDF, neutral detergent fiber ADF, acid detergent fiber Ca, calcium SEM, standard error of the means
a b s t r a c t This study was conducted to determine the coefficient of total tract apparent digestibility (CTTAD) and coefficient of total tract standardized digestibility (CTTSD) of phosphorus (P) in nine corn sources fed to growing-finishing pigs. Ten barrows (initial of BW, 55.8 ± 3.0 kg) were individually housed in metabolism cages. Experimental diets consisted of nine different corns and one P-free diet for measurement of basal endogenous loss of P. Corn sources included 5 yellow-corns from the United States (USY-1 to 5), 2 yellow-corns from South Africa (SAY-1 and 2), and 2 white-corns from South Africa (SAW-1 and 2). Pigs were arranged in a 10 × 8 incomplete Latin square design with 10 diets and 8 periods. The CTTAD of dry matter (DM) in SAW-1 was greater (P < 0.01) than that of USY-3, USY-5 or SAY-2. Pigs fed SAW-1 showed greater (P < 0.01) CTTAD of nitrogen (N) than those fed USY-3, USY5 or SAY-2. The CTTAD and CTTSD of P across the nine corns averaged 0.43 and 0.49, respectively, but the values were not significantly different among the corn grains. In conclusion, the digestibility of DM and N varies in corn and needs to be determined to improve the efficiency with which the grain and corn based diets are utilized by growing pigs. © 2015 Published by Elsevier B.V.
Keywords: Corn Total tract standardized digestibility Phosphorus Pigs
∗ Corresponding author. Tel.: +82 31 290 1657; fax: +82 31 290 1660. E-mail address: [email protected] (S.K. Park). http://dx.doi.org/10.1016/j.anifeedsci.2015.01.002 0377-8401/© 2015 Published by Elsevier B.V.
Y.D. Jeong et al. / Animal Feed Science and Technology 201 (2015) 66–71
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1. Introduction Phosphorus (P) is an essential nutrient which plays crucial roles in various biological processes including bone formation and energy metabolism (Nafikov and Beitz, 2007; Kerr et al., 2010). Phosphorus is combined with phytate, called ‘phytate phosphorus’ and is not bioavailable to pigs which lack the digestive enzyme phytase required to remove phosphate from the inositol in the phytate molecule (Baidoo et al., 2003; Knowlton et al., 2004). This is why more than 50% of P in corn and soybean meal passes through the intestines unused, and is excreted in the manure which causes environmental pollution and waste of nutrients (Pallauf and Rimbach, 1997). Therefore, efforts have been made to improve the digestibility of P and to reduce the excretion of P. To meet the nutritional requirements of pigs, diets need to be precisely formulated on the basis of the availability of P from feed ingredients. To this end, the relative bio-availability of P from feed ingredients has been calculated using the slope-ratio technique (Cromwell, 1992). Digestibility of P has also been expressed as the apparent total tract digestibility (ATTD) or coefficient of total tract apparent digestibility (CTTAD) based on the intake and excretion of P (Almeida and Stein, 2010). These values, however, are not always additive in mixed diets because they do not account for basal endogenous P losses (EPL). The EPL is defined as the amount of P voided in feces that does not originate from the diet. EPL can be measured directly by feeding a P-free diet and measuring the amount of P excreted in feces (Petersen and Stein, 2006). Thus, when CTTAD is corrected for basal EPL, the coefficient of total tract standardized digestibility (CTTSD) of P can be obtained (Almeida and Stein, 2010). The reason for reduced excretion of P in diets formulated based on CTTSD, instead of CTTAD, is most likely that values for CTTSD of P are additive in mixed diets. The CTTSD of P was recently adapted in NRC (2012). However, values of CTTSD of P for various types of corns are still limited. Corn, as a major ingredient for pig feed, is grown widely in many countries. Nutrient contents in corn are influenced by region and year produced and by cultivars and this fluctuation may result in considerable variation in digestibility (Cromwell et al., 1999; Spencer et al., 2000; Bohlke et al., 2005; Almeida and Stein, 2010, 2012). The objective of the present study was to determine the CTTSD of P and CTTAD of dry matter (DM), nitrogen (N) and P in different corn types fed to growing-finishing pigs. 2. Materials and methods 2.1. Diets, animals, and experimental design The experimental protocols describing the management and care of animals were reviewed and approved by the Animal Care and Use of National Institute of Animal Science. Ten barrows (initial BW, 55.8 ± 3.0 kg) were obtained from a local farm and housed in individual metabolism cages. The experimental design was a 10 × 8 incomplete Latin square design with 10 diets and 8 periods. The 10 diets consisted of five yellow-corns from the United States (USY1 to 5), two yellow-corns from South Africa (SAY1 and 2), two white-corns from South Africa (SAW1 and 2) and a P free diet was also used. All nine corn grains were ground through a 3 mm screen and the diets were fed as a mash. The nutrient compositions of nine corn grains are presented in Table 1. The ingredient and nutrient compositions of the experimental diets are shown in Tables 2 and 3, respectively. 2.2. Feeding and sample collection The daily amount of feed provided to the pigs was calculated as 2.5 times the estimated requirement for maintenance energy (i.e., 444 kJ ME per kg0.75 ; NRC, 1998) and fed in two equal meals at 0900 and 1700 h. Animals had free access to water throughout the experiment. Pigs were adapted to the experimental diets and metabolic cages for 4 d. Chromic oxide was added to the morning meals at 1 g/kg as an indigestible marker on days 5 and 10. Fecal samples were collected according to the marker-to-marker approach (Adeola, 2001) for color assisted sample selection. Urine was collected daily in buckets that Table 1 Analyzed nutrient contents of nine corn grains1 (g/kg, as-fed basis). Composition
Dry matter Gross energy, MJ/kg Crude protein Crude fat Crude fiber Ash Calcium Phosphorus Neutral detergent fiber Acid detergent fiber 1
USY
SAY
SAW
1
2
3
4
5
1
2
1
2
856 17.45 70.5 21.5 10.9 13.7 1.3 2.5 85.5 16.7
856 18.0 66.1 28.0 7.2 9.7 0.7 2.1 79.8 13.4
865 18.67 75.1 28.8 8.3 14.4 1.3 2.4 89.5 18.3
860 18.8 71.2 33.7 10.4 14.3 1.8 2.9 87.2 18.2
862 17.5 69.9 29.8 7.0 12.7 1.3 2.6 87.0 17.7
867 18.2 70.2 34.4 12.1 12.0 1.2 2.2 90.2 20.8
869 18.9 90.3 31.5 13.0 16.3 1.7 2.7 97.3 20.9
870 17.8 70.1 33.0 10.5 14.6 2.2 2.1 85.1 17.7
870 18.45 70.4 38.6 9.5 8.6 0.7 2.0 93.4 18.9
USY, yellow corn from the United States; SAY, yellow corn from South Africa; SAW, white corn from South Africa.
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Table 2 Ingredient composition of experimental diets (g/kg, as-fed basis). Ingredient
Diet
Ground corn Cornstarch Sucrose Soybean oil Gelatin Solka-floc dl-Methionine l-Tryptophan l-Histidine l-Isoleucine Limestone Potassium carbonate Magnesium oxide Salt Vitamin–mineral premix1
Corn
P-free
969.0 – – 15.0 – – – – – – 7.0 – – 4.0 5.0
– 460.6 200.0 30.0 240.0 40.0 2.2 1.2 0.6 0.4 11.0 4.0 1.0 4.0 5.0
1 The vitamin–mineral premix provided the following quantities of vitamins and minerals per kilogram of diets: vitamin A, 10,000 IU; vitamin D3 , 2000 IU; vitamin E, 250 IU; vitamin K3 , 0.5 mg; vitamin B1 , 0.49 mg as mononitrate; thiamin, 0.49 mg as thiamin mononitrate; riboflavin, 1.50 mg; pyridoxine, 1 mg as pyridoxine hydrochloride; vitamin B12 , 0.01 mg; niacin, 10 mg as nicotinic acid; pantothenic acid, 5 mg as calcium pantothenate; folic acid, 1 mg; biotin as d-biotin, 0.1 mg; choline, 125 mg as choline chloride; Mn, 60 mg as manganese sulfate; Zn, 75 mg as zinc sulfate; Fe, 20 mg as ferrous sulfate; Cu, 3 mg as cupric sulfate; I, 1.25 mg as calcium iodate; Co, 0.5 mg as cobaltous carbonate; Mg, 10 mg as magnesium oxide.
contained 50 mL of 4N sulfuric acid during the collection periods. All feces and urine were stored at −20 ◦ C before chemical analyses. 2.3. Sample analyses and data processing Fecal samples were dried at 60 ◦ C in a forced-air drying oven and ground. All samples, which are ingredients, diets, feces, and urine, were dried in a forced-air drying oven at 135 ◦ C for 2 h to analyze DM (method 930.15; AOAC, 2005) and N (method 990.03; AOAC, 2005). The ingredient and experimental diets were analyzed for gross energy (Model C2000, IKA, Germany), crude fat (method 920.39; AOAC, 2005), crude fiber (method 978.10; AOAC, 2005), ash (method 942.05; AOAC, 2005), acid detergent fiber (method 973.18; AOAC, 2005), and neutral detergent fiber (Holst, 1973). The Ca concentrations in the ingredients, diets, and feces were analyzed using an atomic absorption spectrophotometer (method 978.02; AOAC, 2005 Perkin Elmer 3300, Perkin Elmer, USA). The P concentrations in the ingredients, diets, and feces were analyzed using a spectrophotometer (method 946.06; AOAC, 2005; Optizen 2120UV, Mecasys, Republic of Korea). The CTTAD and CTTSD of P and the endogenous P loss in each diet were calculated as previously described (Almeida and Stein, 2010). Values for CTTAD of N and DM, expressed as a proportion of their intake, were calculated by subtracting N and DM excreted in the feces from intake, and dividing by intake. All data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC, USA). Homogeneity of the variances among treatments was confirmed by using the UNIVARIATE procedure and this procedure was also used to test for outliers, but no outliers were identified. The model included diet as the fixed variable and animal and period as the random variables. Least squares means were calculated and separated using the PDIFF option with the Tukey’s adjustment. The pig was the experimental unit for all analyses and an alpha level of 0.05 was used to assess significance among means.
Table 3 Analyzed nutrient composition of experimental diets1 (g/kg, as-fed basis). Composition
Dry matter Gross energy, MJ/kg Crude protein Crude fat Crude fiber Ash Calcium Phosphorus Neutral detergent fiber Acid detergent fiber 1
USY
SAY
SAW
P-free
1
2
3
4
5
1
2
1
2
861 17.45 68.9 36.0 4.3 18.1 3.1 2.6 82.7 17.7
871 19.0 66.2 35.1 8.6 20.9 4.1 2.1 90.6 20.6
868 18.1 75.3 42.6 2.1 23.0 4.5 3.2 89.0 26.4
866 18.4 68.0 42.4 2.6 22.0 5.0 2.7 94.1 27.9
867 18.4 68.9 47.1 4.9 20.2 4.2 2.6 96.0 22.4
871 18.1 69.2 46.6 10.9 18.1 3.2 2.2 94.1 22.3
871 18.1 85.7 45.4 9.7 20.1 3.7 2.5 109.5 36.0
872 18.2 69.3 45.3 5.9 18.9 4.4 2.0 85.5 18.8
873 17.7 69.3 47.9 6.8 16.3 3.4 2.0 84.9 25.5
USY = yellow corn from the United States; SAY = yellow corn from South Africa; SAW = white corn from South Africa.
908 18.8 26.13 47.7 2.0 16.3 3.1 0.1 23.0 10.3
Table 4 Nutrient balance (g/d -as fed) and the coefficient of apparent total tract digestibility (CTTAD) for dry matter, N and P and the coefficient of standardized total tract digestibility (CTTSD) of P in nine corn based diets fed to growing-finishing pigs.1 , 2 Item
USY 1
a,b,c,d,e
2
3
4
5
1
SEM3
SAW 2
1
P-value
2
P-values for contrast USY vs. SAY
USY vs. SAW
SAY vs. SAW
2.14
2.13
2.13
2.11
2.14
2.14
2.10
2.11
0.11
0.451
0.429
0.052
0.023
1.86
1.85
1.85
1.83
1.87
1.86
1.83
1.84
0.10
0.446
0.110
0.381
0.037
22.5d 4.44d,e
25.6b 6.85a
23.1c,d 5.81b
23.3c,d 5.51b,c
23.7c 4.73d
29.2a 5.33c
23.2c,d 4.25e
23.3c,d 4.29e
1.26 0.28
<0.001 <0.001
<0.001 <0.001
0.053 <0.001
<0.001 <0.001
145b,c,d 138b,c,d 3.50c,d 2.86a,b,c
175a,b 167a,b 4.84a,b 3.53a
135c,d 129c,d 3.36c,d 2.89a,b,c
162a,b,c 155a,b,c 4.03b,c 3.40a,b
144b,c,d 138b,c,d 3.38c,d 2.48c
187a 179a 5.10a 3.23a,b,c
123d 117d 3.03d 2.68a,b,c
148b,c,d 142b,c,d 3.82c,d 2.56b,c
12.92 12.37 0.36 0.39
<0.001 <0.001 <0.001 0.001
0.073 0.086 0.124 0.042
0.006 0.005 0.006 0.001
0.000 <0.001 <0.001 0.214
0.925a,b,c,d
0.909c,d
0.929a,b
0.914b,c,d
0.925a,b,c
0.904d
0.937a
0.922a,b,c,d
0.01
<0.001
0.141
0.007
0.001
0.843a,b,c
0.810c
0.854a,b,c
0.824b,c
0.856a,b
0.824b,c
0.873a
0.833a,b,c
0.01
0.001
0.315
0.010
0.167
0.360
0.491
0.508
0.393
0.473
0.408
0.391
0.413
0.06
0.204
0.858
0.338
0.333
0.429
0.536
0.562
0.448
0.540
0.466
0.464
0.485
0.06
0.339
0.707
0.640
0.472
Means within a row without a common superscript letter differ (P < 0.05). USY, yellow corn from the united states; SAW, white corn from South Africa; SAY, yellow corn from South Africa. 2 Each least squares mean represents 8 observations except USY4 and SAW1 (7 observations), and USY2 (6 observations). Diet intake and fecal output were based on 5 d of collection. 3 SEM = standard error of the means. 4 Coefficients of total tract apparent digestibility (CTTAD), coefficients of total tract standardized digestibility (CTTSD). 5 Values for CTTSD of P were calculated by correcting CTTAD values for the basal endogenous loss of P. The basal endogenous loss of P was determined in pigs fed the P-free diet at 168 ± 140 mg/kg dry matter intake.
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Feed intake 2.13 Total intake (kg/d) Dry matter 1.84 intake (kg/d) Nitrogen intake 23.5c,d Phosphorus 5.58b,c intake Fecal output Total feces 153a,b,c,d Dry matter feces 147a,b,c,d Nitrogen output 4.03b,c,d Phosphorus 3.29a,b,c output Coefficients of digestibility CTTAD4 of dry 0.920a,b,c,d matter CTTAD of 0.829a,b,c nitrogen CTTAD of 0.421 phosphorus 5 0.476 CTTSD of phosphorus
SAY
1
69
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3. Results The result for nutrient balance and digestibility are given in Table 4. No difference was observed in daily intake and DM intake among different corn sources (Table 4). However, SAY group had greater (P < 0.05) daily intake and DM intake than SAW group. N intake was least (P < 0.01) in USY-2 and greatest (P < 0.01) in SAY-2. Pigs fed USY corn group had greater (P < 0.01) P intake than those fed SAY or SAW corn group. Pigs fed USY-3 and SAY-2 showed greater output of total and DM feces than those fed USY-4 and SAW-1. Fecal N excretion was greater (P < 0.01) in USY-3 and SAY-2 than in USY-2, USY-4, SAY-1, SAW-1 or SAW-2. Pigs from USY corn group showed greater (P < 0.01) level of fecal output of P than those from SAY or SAW corn group. The CTTAD of DM was greater (P < 0.01) in SAW-1 than USY-3, USY-5 or SAY-2. Pigs fed SAW corn group had greater (P < 0.01) N digestibility than those fed USY corn group. The CTTAD and CTTSD of P across the nine different corns ranged from 0.36 to 0.51 and from 0.43 to 0.56, respectively. Values for CTTAD and CTTSD of P were highest in USY-4 and lowest in USY-2 among corn groups but the difference across corns were not statistically significant. 4. Discussion Our results showed that the P content of the nine corns ranged from 2.0 to 2.9 g/kg which is similar to previous results (Bohlke et al., 2005; Almeida et al., 2011; Almeida and Stein, 2012; NRC, 2012). Our values of CTTAD and CTTSD of P ranged from 0.36 to 0.51 and from 0.43 to 0.56, respectively, but not statistically different. This range is higher than that reported by Almeida and Stein (2012) and Bohlke et al. (2005). The average values of CTTAD and CTTSD of P in our study (0.43 and 0.49, respectively) are also higher than those given in NRC (2012) (0.26 and 0.34, respectively). This variation may be associated with differences in the phytate content of the corns on which the information is based. Low-phytate corn hybrids are known to have a higher P digestibility (Bohlke et al., 2005) than conventional corns. The addition of phytase to pig diets had similarly been reported to improve P digestibility (Almeida and Stein, 2010; Baidoo et al., 2003; Rojas et al., 2013). Clearly, however, further research is required to determine the phytase levels of different corns. The DM levels of nine corn grains in our study ranged from 856 to 870 g/kg. These values are similar to those reported by Almeida and Stein (867 g/kg, [Almeida and Stein, 2012]2012), Li et al. (882 g/kg, [Li et al., 2014]2014), and NRC (883 g/kg, [NRC, 2012]2012), but higher than those reported by Almeida et al. (841 g/kg, [Almeida et al., 2011]2011). Differences in DM digestibility have been reported between soft, hard and medium-hard corns by Li et al. (2014). In our study, DM digestibility also varied among the nine corns and ranged from 0.90 to 0.94. Variation in energy levels also exists among different corn sources (Fent et al., 2001; Li et al., 2014; Stein et al., 2009). In the present study, GE levels in nine corns varied from 17.5 to 18.9 MJ/kg and the average (18.3 MJ/kg) is higher than those reported by NRC (16.5 MJ/kg, [NRC, 2012]2012), Rojas et al. (16.4 MJ/kg, [Rojas et al., 2013]2013) and Widmer et al. (16.3 MJ/kg, [Widmer et al., 2007]2007). These differences support our contention that the nutrient levels of corns vary and need to be precisely measured. The CP contents of the nine corns in our study ranged from 66.1 to 90.3 g/kg and the average value (73.3 g/kg) is similar to those of Almeida and Stein (72.7 g/kg; [Almeida and Stein, 2012]2012) and Widmer et al. (72.0 g/kg, [Widmer et al., 2007]2007) but lower than that reported by Bohlke et al. (94.6 g/kg, [Bohlke et al., 2005]2005) and NRC (82.4 g/kg, [NRC, 2012]2012). The CTTAD of N varied by 6.3%. The N content and its digestibility is known to affect N excretion and our results clearly demonstrate that to optimize diet formulation and minimize N excretion the digestibility of N in corn and other grains needs to be measured (Canh et al., 1998; Otto et al., 2003). There is large variation in levels of crude fiber, including NDF and ADF, and crude fat in feed ingredients. The average crude fat content of the corns used in our study (10.4 g/kg) is lower than that in NRC (19.8 g/kg, [NRC, 2012]2012). In contrast the average NDF content of our corns (89.6 g/kg) is similar to the NRC (2012) value (91.1 g/kg) and those reported by Almeida et al. (85.3 g/kg, [Almeida et al., 2011]2011) and Widmer et al. (90.0 g/kg, [Widmer et al., 2007]2007) and lower than Li et al.’s result (98.5 g/kg, [Li et al., 2014]2014). Average ADF level in our study (18.7 g/kg) is comparable to Almeida et al. (20.0 g/kg, [Almeida et al., 2011]2011) and Li et al. (21.6 g/kg, [Li et al., 2014]2014), but lower than the values reported by NRC (28.8 g/kg, [NRC, 2012]2012) and Widmer et al. (25.0 g/kg, [Widmer et al., 2007]2007). The crude fat content of our nine corns ranged from 21.5 to 38.6 g/kg. These are similar to the levels reported by Li et al. (2014), NRC (2012) and Widmer et al. (2007). Taken together, results from the current study demonstrate considerable variability in nutrient levels and in the digestibility of nutrients in different corns. Both need to be determined if we are to improve the accuracy and cost effectiveness of diet formulations and minimize nutrient excretion. Conflict of interest The authors declare that they have no conflict of interest. Acknowledgements This work was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project title: Standardized digestibility of phosphorus in various feed ingredients of pigs, Project Nos. PJ907038032014 and PJ009312)” Rural Development Administration, Republic of Korea.
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