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Tropical Animal Health and Production

, Volume 51, Issue 2, pp 443–448 | Cite as

Effects of corn particle size on nutrient utilization in pigs evaluated under optimal and heat stress conditions

  • Won Yun
  • Min Ho Song
  • Ji Hwan Lee
  • Chang Hee Lee
  • Seo Young Oh
  • Woo Gi Kwak
  • Doo Wan Kim
  • Hyeun Bum KimEmail author
  • Jin Ho ChoEmail author
Open Access
Regular Articles
  • 248 Downloads

Abstract

The effects of corn particle size on nutrient digestibility and energy utilization in pigs were determined under optimal (experiment 1, 25 ± 1 °C) or heat stress (experiment 2, 37 ± 1 °C) conditions. In Exp. 1 and 2, five experimental diets were tested using a 5 × 5 Latin square design involving five barrows (Landrace × Yorkshire × Duroc, average initial body weight of 30 ± 1 kg and 45.0 ± 1.8 kg, respectively, in individual metabolic cages). Dietary treatments were as follows: 200-, 300-, 400-, 600-, 800-μm corn particle sizes obtained by mesh screens. Under optimal thermal conditions, digestibility of dry matter (DM) and crude fiber (CF) from 200-μm diet was higher (P < 0.05) compared to that from the 300-μm and 400-μm diets. The digestibility of crude protein (CP) and ether extract (EE) was the highest (P < 0.05) at the 200-μm particle size. The apparent total tract digestibility of energy was significantly higher (P < 0.05) on the 200-μm diet. Under heat stress, digestibility of CF when corn was ground to 600 μm was higher (P < 0.05) compared to 300 and 400 μm. Digestibility of NDF and ADF was the highest (P < 0.05) at 600-μm corn particle size. In conclusion, grinding corn to 200-μm corn particles had a positive effect on DM, CP, EE, and CF under optimal thermal condition, while the 600-μm corn particle size had positive effects on digestibility of CF, NDF, and ADF than 200-μm corn particle size under heat stress.

Keywords

High temperature Thermal response Nutrient digestibility Growing pig 

Introduction

In modern pig farming, feed accounts for a major part of production costs. Accordingly, it is necessary to improve the processing of feeds in order to maximize nutrient availability. In this regard, reducing the particle size of cereal grains by cracking, crimping, rolling, or grinding via mechanical force can increase the surface area and improve digestibility (Ohh et al. 1983). This improvement in nutrient digestibility and gain/feed ratio is attributed to an increase in the area of contact with digestive enzymes (Kim et al. 2000; Hancock et al. 2000). However, grains that are too finely ground can cause stomach ulcers in growing-finishing pigs (Nielsen and Ingvartsen 2000). Weaning pigs fed with larger particle size, which might allow more time for mastication and digestion in the mouth, show slower growth than pigs fed a finer particle-sized diet (Kim et al. 2005). Similarly, previous research has shown that a reduction in the particle size of grain from coarse to fine can increase gain/feed ratio (Lawrence 1983). Further, reducing the particle size of cereal grains to 600 μm has been shown to result in greater nutrient digestibility, rate of growth, and lactation performance, and decreased fecal excretion of nutrients, when compared with the effects of diets of coarser particle sizes between 900 and 1000 μm (Wondra et al. 1995b). The growth performance of pigs can also be influenced by temperature. In this regard, Quiniou et al. (2000) reported that the average daily feed intake (ADFI) of pigs was reduced by heat stress at high ambient temperature. Consistent with these findings, the growth performance of growing finishing pigs in an optimal environment was shown to be superior to that in a high-temperature environment (Le Bellego et al. 2002). Thus, the objective of the present study was to investigate the effects of reducing the particle size of corn feed on the growth performance and nutrient digestibility of pigs maintained under heat stress and optimal environmental conditions.

Materials and methods

Experiment design and housing

The protocol for the two experiments was approved by the Institutional Animal Care and Use Committee of Chungbuk National University, Cheongju, Republic of Korea.

In experiment 1, a total of five crossbred (Duroc × Landrace × Yorkshire) barrows were randomly allotted five diets over five periods in a 5 × 5 Latin square design. The pigs (average initial body weight of 30.0 ± 1.1 kg) were individually housed in 1.2 m × 0.7 m × 0.96 m stainless steel metabolism cages in an environmentally controlled room (Fig. 1). The experimental condition was conducted at 24 ± 2 °C temperature with 85 ± 1.3% relative humidity and air speed was 0.25 ± 0.02 m/s.

In experiment 2, a total of five crossbred (Duroc × Landrace × Yorkshire) barrows were allotted five diets over five periods in a 5 × 5 Latin square design. The pigs (average initial body weight of 45.0 ± 1.8 kg) were individually housed in 1.2 m × 0.7 m × 0.96 m stainless steel metabolism cages in an environmentally controlled room (Fig. 1). The experiment was conducted at 37 ± 1 °C temperature with 85 ± 1.3% relative humidity and air speed was 0.25 ± 0.02 m/s. The temperature and relative humidity were based on average temperatures found in piggeries in summer seasons of South Korea.
Fig. 1

Schematic drawing of experimental room

Diets and feeding

Table 1 shows the nutrient contents of the main ingredients used in this experiment. Five diets were formulated using various sizes of corn particles (Table 1). The other ingredients except for corn had mean particle size of 1000 μm. These other ingredients except for corn were the same for all treatments. The daily feed allowance was adjusted to 2.7 times the maintenance requirement for DE (2.7 × 110 kcal of DE/kg BW0.75; NRC 1998). The allowance was divided into two equal parts and fed at 08:00 and 17:00 h. The diets were mixed with water in a ratio of 1:1 (wt/wt) before feeding. Pigs had free access to water during the experiment.
Table 1

Chemical composition of the basal diets (as-fed basis)

Ingredients

Percent

 Corn

54.13

 Soybean meal

30.45

 Wheat

3.00

 Canola meal

2.00

 Soybean oil

4.29

 Molasses

3.00

 Limestone

0.63

 Calcium phosphate

1.47

 Lysine

0.34

 Methionine

0.08

 Threonine

0.03

 Choline Cl

0.03

 Mineral premix

0.10

 Vitamin premix

0.20

 Salt

0.25

 Total

100

Analyzed chemical composition

 Dry matter (%)

98.1

 Crude protein (%)

18.5

 Ether extract (%)

6.7

 Crude ash (%)

5.0

 NDF (%)

8.5

 ADF (%)

3.5

 Gross energy (MJ/kg)

20.4

Sampling and analysis

The pigs were weighed individually at the beginning of each period and the amount of feed supplied for each period was recorded, as well as any residual feed quantity. Each experimental period consisted of a 4-day adaptation period followed by a 3-day collection period to collect feces and urine. The feces and urine were collected by total collection method. Feces were collected immediately when the feces appeared in the metabolism cages, kept in plastic bags, and stored at − 20 °C. Urine was collected once a day into buckets containing 50 mL of 6 mol/L HCl that were placed under the metabolism cages. The collected urine was weighed and stored at − 20 °C. The collection of feces and urine was conducted according to the methods described by Song et al. (2003). Fecal samples were dried in a forced air oven and ground through a 1-mm screen, and thoroughly mixed before a subsample was collected for chemical analysis. Diets and feces were analyzed for dry matter (AOAC, 1990), crude protein (AOAC, 1990), and crude fiber (AOAC, 1990). The gross energy of diets, feces, and urine was analyzed using an adiabatic oxygen bomb calorimeter (Parr Instruments, Moline, IL). The content of nitrogen in the urine was also analyzed (AOAC, 1990).

Statistical analysis

The data for effects of various particle sizes of corn on the apparent total tract digestibility (ATTD) of fiber, dry matter, protein, energy, and available energy of the test diets were subjected to an analysis of variance using PROC GLM of SAS (Statistical Analysis System 9.1, SAS Institute, Cary, NC, USA).

Results

Exp. 1. Under optimal thermal conditions

Table 2 presents effects of various corn particle sizes on the apparent total tract digestibility of nutrients. Intakes of DM, CP, EE, CF, CA, NDF, and ADF were different among treatments (P < 0.05). Pigs fed the 300- and 400-μm diets excreted higher concentrations of DM and CP than pigs fed the 200-μm corn diet (P < 0.05). The EE excreted from the 200-μm treatment was significantly lower than that from other treatments (P < 0.05). Content of CA in excretion from 200-μm treatment was significantly higher than that from the 800-μm treatment. Apparent total tract digestibility of DM and CF from 200-μm diet was higher than that from 300- and 400-μm diets, and apparent total tract digestibility of CP and EE from 200-μm diet was higher than that of other treatments. Apparent total tract digestibility of CA for 400-, 600-, and 800-μm treatments was higher than that of 200- and 300-μm treatments (P < 0.05).
Table 2

Effect of various corn particle sizes on the apparent total tract digestibility (ATTD) of nutrients in pigs under optimal thermal condition

Items

Particle size of corn (μm)

SE1

200

300

400

600

800

Intake

 Dry matter (g)

1058

1064

1063

1053

1018

56

 Crude protein (g)

222

223

223

221

214

17

 Ether extract (g)

77

78

78

77

74

4

 Crude fiber (g)

35

35

35

35

34

3

 Crude ash (g)

62

63

63

62

60

2

 NDF (g)

94

95

95

94

91

3

 ADF (g)

42.3

42

42

42

40

3

 Energy (MJ/day)

22.4

22.6

22.5

22.3

21.6

0.7

Excretion (g)

 Dry matter

201b

233a

230a

224ab

213ab

10

 Crude protein

38b

46a

46a

44ab

43ab

2

 Ether extract

24b

30a

30a

30a

29a

1

 Crude fiber

19

21

21

20

19

3

 Crude ash

49a

47ab

46ab

46ab

44b

2

 NDF

47

52

50

52

46

4

 ADF

20

21

22

21

20

3

ATTD (%)

 Dry matter

81.00a

78.12b

78.30b

78.73ab

79.00ab

0.86

 Crude protein

82.50a

79.02b

79.11b

79.81b

79.48b

1.01

 Ether extract

68.12a

60.84b

60.93b

60.80b

61.00b

3.01

 Crude fiber

44.50a

40.96b

40.27b

42.02ab

42.74ab

2.10

 Crude ash

21.30b

23.73b

25.82a

25.82a

25.80a

1.98

 NDF

48.86

44.29

46.50

44.01

48.70

3.56

 ADF

50.38

50.25

48.20

49.88

49.33

2.65

 DE2

82.61a

79.47b

79.25b

79.58b

79.39b

2.17

 EUDE3

78.14a

74.07b

73.75b

74.32b

73.83b

2.30

1Standard error

2Digestible energy

3Excluding urinary energy loss in DE

abMeans in the same row with different superscripts differ (P < 0.05)

Exp. 2. Under heat stress

Table 3 presents effects of various corn particle sizes on the apparent total tract digestibility of nutrients in heat stress conditions. Intakes of DM, CP, EE, CF, CA, NDF, ADF, and dietary energy from the 400-, 600-, and 800-μm diets were higher than those from the 200-μm diet (P < 0.05). Pigs fed the 800-μm diet had higher excretion of DM compared with those with the 200-μm diet (P < 0.05), and excretion of EE in 400-, 600-, and 800-μm diets was significantly higher than that of the 200-μm diet (P < 0.05). Apparent total tract digestibility of EE from 200- and 300-μm diets was higher than that of other treatments (P < 0.05). Contents of dietary energy in excretion from 400- and 800-μm diets were higher than those from 200- and 300-μm treatments (P < 0.05). The apparent total tract digestibility of energy was not significantly different among treatments (P > 0.05).
Table 3

Effect of various corn particle sizes on the apparent total tract digestibility (ATTD) of nutrients in pigs under heat stress

Items

Particle size of corn (μm)

SE1

200

300

400

600

800

Intake

 Dry matter (g)

896b

921ab

971a

991a

982a

41

 Crude protein (g)

188b

194ab

204a

208a

206a

8

 Ether extract (g)

66b

68ab

71a

73a

72a

1

 Crude fiber (g)

30b

31ab

32a

33a

33a

1

 Crude ash (g)

40b

41ab

44a

45a

44a

2

 NDF (g)

68b

70ab

74a

75a

75a

2

 ADF (g)

36b

37ab

39a

40a

39a

1

 Energy (MJ/day)

19.0b

19.5ab

20.6a

21.0a

20.8a

0.5

Excretion (g)

 Dry matter

136b

145ab

150ab

149ab

153a

9

 Crude protein

27

29

30

28

27

5

 Ether extract

9b

11b

15a

17a

19a

3

 Crude fiber

12

14

14

11

12

3

 Crude ash

36

40

43

40

41

5

 NDF

43ab

45ab

50a

39b

41b

4

 ADF

18b

20ab

24a

18b

19b

1

ATTD (%)

 Dry matter

84.82

84.26

84.54

84.96

84.43

5.65

 Crude protein

85.77

85.17

85.15

86.76

86.89

6.21

 Ether extract

85.77a

83.53a

78.58b

76.70b

73.55b

3.02

 Crude fiber

60.49ab

55.26b

55.61b

66.25a

64.61ab

4.01

 Crude ash

11.62a

3.79b

2.12b

10.41a

7.94a

3.11

 NDF

37.08b

35.16b

31.87c

47.55a

44.67ab

2.01

 ADF

49.50ab

46.04b

38.52c

55.59a

51.35a

2.56

 DE2

86.93

86.54

85.69

86.33

85.39

4.78

 EUDE3

76.46

75.55

77.30

78.00

76.76

3.83

1Standard error

2Digestible energy

3Excluding urinary energy loss in DE

abcMeans in the same row with different superscripts differ (P < 0.05)

Discussion

Exp. 1. Under optimal thermal conditions

In our study, pigs fed a diet of smaller particle size had greater nutrient digestibility under optimal thermal conditions. This result is consistent with the findings of Kim et al. (2002), who showed that pigs fed a diet of 500-μm particle size had significantly higher nutrient digestibility than those fed a diet of 1000-μm particle size. Paulk et al. (2011) reported a greater ADG for finishing pigs fed diets containing finely ground corn than for those fed on coarsely ground corn. Similarly, Wondra et al. (1995b) demonstrated that reducing the particle size of cereal grains to a minimum of 600 μm resulted in greater nutrient digestibility, rate of growth, and lactation performance, and decreased fecal excretion of nutrients, than was observed for grains of coarser particle size (from 900 to 1000 μm). Thus, the results of both the present and previous studies indicate that a smaller particle size of corn is beneficial for pig performance. Additionally, Kim et al. (2000) showed that corn of a smaller particle size had the most beneficial effect on apparent total tract digestibility of energy, which is again consistent with the results of the present study. Reduced particle size of grains has been reported to improve nutrient digestibility, growth rate, feed intake, feed conversion ratio, and gut health (Choct et al. 2004). As such, the results we obtained under optimal thermal conditions, showing that corn of smaller particle size has positive effects, are generally consistent with the findings of previous studies.

Exp. 2. Under heat stress

In contrast to the optimal thermal conditions, overall in heavier pigs, the nutrient digestibility tended to decrease under heat stress conditions. The availability of amino acid for growth of pigs exposed to comfort-like ambient temperature may differ from that when pigs are exposed to heat stress within the same day (Cervantes et al. 2017). According to Le Bellego et al. (2002), there was lower protein retention at heat stress condition than optimal thermal condition when pigs were fed the same amount of energy. Heat stress changes the organism physiology, metabolism, and behavior to maintain homeostasis. In pigs, HS increases the intestinal temperature (Morales et al. 2015) as well as reduced the proliferation of intestinal cells (Sonna et al. 2002). Furthermore, Yu et al. (2010) found that heat treatment caused marked damage to the tips of the intestinal villi and induced epithelial cell shedding, exposure of the intestinal mucosa lamina propria, and shortening of villus height and crypt depth in the small intestine. These damaged intestinal environments can deteriorate nutrient utilization in pigs. Heat stress creates a bottleneck that slows pyruvate entry into the TCA cycle, which thus increases pyruvate-derived metabolite production. These results negatively contribute to the altered postabsorptive carbohydrate metabolism (Baumgard and Rhoads Jr 2013). For these reasons, it seems that the effects of reduction in particle size were not observed due to reduced nutrient digestibility. Mertens (1997) reported that feeding diets of larger particle size would increase salivary secretion, which would have promoted digestion by salivary amylase. Salivary amylase may well represent a potential compensatory alternative pathway for the digestion of amylose, amylopectin, and glycogen (Emanual 1987). Moreover, saliva is the most important oral fluid, and is critical for the preservation and maintenance of oral health (Edgar 1992). These results indicate that a reduction in particle size to less than 600 μm is not necessary under heat stress conditions. Moreover, finely ground grains have been implicated as a cause of stomach ulcers in growing-finishing pigs (Wondra et al. 1995a). The higher cell wall digestibility for the coarse diet than that for the fine diet could be related to rate of passage. In growing-finishing pigs, the cell wall particles of the coarse diet had a significantly longer retention time (Fioramonti and Bueno 1980; Ehle et al. 1982). Therefore, larger particle size, with a longer retention in the pig than smaller particle size, would be expected to show a greater extent of cell wall digestion. A diet ground too coarsely is potentially inefficiently utilized due to the rapid passage of the large particles through the digestive tract of the animal, resulting in ineffective or incomplete mastication and digestion of the diet (Ivan et al. 1974). In contrast, diets in which the particle size of grains is too fine would become more sticky and unpalatable in the mouth of pigs (Little 1997). Accordingly, on the basis of the various negative effects indicated by previous studies, it would be advantageous not to reduce the particle size of feeds under conditions of heat stress.

Conclusion

In conclusion, for the lighter pigs, grinding corn to 200-μm corn particles reduced energy wastage and improved the positive effect on nutrient digestibility under optimal thermal condition; whereas for the heavier pigs, there was no beneficial effect on energy digestibility among treatments. Furthermore, in heavier pigs, the 600-μm diet had positive effects on digestibility of CF, NDF, and ADF than 200-μm corn particle size under heat stress conditions.

Notes

Funding information

This work was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ01261502)” Rural Development Administration, Republic of Korea.

Compliance with ethical standards

The protocol for the two experiments was approved by the Institutional Animal Care and Use Committee of Chungbuk National University, Cheongju, Republic of Korea.

Conflict of interest

The authors declare that they have no conflict of interest.

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Copyright information

© The Author(s) 2018

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  • Won Yun
    • 1
  • Min Ho Song
    • 2
  • Ji Hwan Lee
    • 1
  • Chang Hee Lee
    • 1
  • Seo Young Oh
    • 1
  • Woo Gi Kwak
    • 1
  • Doo Wan Kim
    • 3
  • Hyeun Bum Kim
    • 4
    Email author
  • Jin Ho Cho
    • 1
    Email author
  1. 1.Department of Animal ScienceChungbuk National UniversityCheongjuRepublic of Korea
  2. 2.Department of Animal Science and BiotechnologyChungnam National UniversityDaejeonRepublic of Korea
  3. 3.Swine Division, National Institute of Animal ScienceRural Development AdministrationCheonanRepublic of Korea
  4. 4.Department of Animal Resource and ScienceDankook UniversityCheonanRepublic of Korea

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