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Hoop Structures -
Research on Performance and Operation

by

Jay D. Harmon, Ph.D., P.E. Mark S. Honeyman, Ph.D.
Asst. Prof. and Extension Ag Engineer Associate Professor of Animal Science
Iowa State University
Ames, IA

Introduction

Swine producers often look for low cost structures in which to raise swine. Producers use pasture systems, cargill units, modified open front buildings, and curtain-sided finishing buildings to feed swine to market weight. Another technology, low-cost structures known as "hoops", is now being used as well. Hoop structures use treated wood posts and tongue-in-groove sidewalls for siding up to approximately 6 feet. Steel tubes or trusses are fastened to the top of the sidewalls to form an arch. The arch is covered with a UV-resistant polypropylene tarp. An earthen floor is used in the majority of the structure which is heavily bedded. The remaining floor area is designated as the feeding area and is covered with concrete.

Many aspects such as pig performance, labor requirements, building life, bedding costs, and the environmental effects on carcass quality need to be examined. Knowledge of these items will enable farmers to strategically evaluate hoop buildings in comparisons to other options.

Description of Facility and Management

The hoop structure used for the Iowa State University study was erected in 1993 at the ISU Rhodes Research and Demonstration Farm. The structure is 30 ft by 60 ft and was donated by AmCan Inc2., Bloomington, Illinois. Finishing pigs are placed in this structure at approximately 60 pounds at a stocking density of 12 square feet per pig.

The hoop is oriented southeast/northwest, although the recommended orientation is north/south in order to catch the predominate winds. The structure has 6 ft. sidewalls. The southern end has 18 ft. of concrete on which feeders are placed. Nipple waterers are also in this area with a slight slope to the outside in case of a waterline break.

During the winter the north end remains closed during most of the winter while the south end remains open. Ventilation air enters the facility through spaces between the sidewall and the tarp. This air mixes in the structure. Warm, moist air moves up toward the top of the arching hoop and is carried by natural air currents through the south end.

Bedding in most hoop structures in Iowa is done with cornstalks. However, wheat straw, bean stalks, wood shavings and paper have been used with some degree of success. Hoops are not a warm environment and therefore need to be heavily bedded to absorb wetness and provide a way for pigs to modify their effective environment.

Performance

Three different trials were performed at the ISU Rhodes Farm. The first, which will be referred to as "winter 1", began on November 16, 1995 with 151 pigs which were then marketed during February and March 1996. The second trial, called "summer", began on April 15, 1996 with 150 pigs which were marketed during August and September, 1996. The final trial began on November 18, 1996 with 163 pigs which were then marketed during February and March, 1997. Data was gathered on pig performance, environmental performance, bedding, and labor requirements.

Pig Performance

The pig performance appears in Table 1 for the three trials. In general, the pigs performed relatively well with some loss of feed efficiency during colder climates. The average daily gain (ADG) appeared to be relatively consistent between the three groups. PigCHAMP (1995) gives the average ADG on 3600 groups using the PigCHAMP record system as 1.61 lbs with a 90th percentile of 1.80. This would indicate that the summer trial tended to perform better than the 90th percentile while the winter trials were between the average and the 90th percentile. This is consistent with reports from Connor (1993) which concluded that ADG was not significantly different than pigs reared in a system that they referred to as a conventional system.

The two winter trials both exhibited a poorer feed efficiency (FE) than did the summer trial. For a Midwestern climate, a 10 percent poorer feed efficiency should be expected during winter conditions. On-farm results will vary depending on the month in which pigs are started in the hoop structure. Pigs started earlier than November would probably exhibit less of a seasonal effect than pigs started further into the winter, such as January. PigChamp (1995) stated that farms on record achieved a FE of 3.18 and the 90th percentile was 2.80. These numbers indicate that all three trials had a poorer than average feed efficiency. While these are good for comparisons, it should be noted that PigChamp records are compiled for many types of pigs, facilities and management styles and averaged together.

Mortality for the three trials averaged 2.6%. PigChamp (1995) records show an overall average of 2.32 percent for farms on record and a 90th percentile of 0.00%. The hoop structure had mortality which was slightly worse than the average of the PigChamp record participants. This may be, in part, due to the fact that pigs may be more difficult to check in a large group than they are in small groups of 20-30 per pen.

Table 1. Pig Performance data from the ISU Rhodes study.

Trait

Winter 1

Summe r

Winter 2

Starting Weight (lbs)

55

51

60

ADG (lb/day)

1.78

1.87

1.75

FE (feed/gain)

3.53

3.27

3.62

Mortality (%)

2.6

2.7

2.5

FFLI (% lean)

46.7

47.6

48.1

Backfat (in.)

1.01

0.99

0.89

Market Weight (lbs)

246

265

250

Environmental Performance

The environment within any building is defined by several factors which affect the comfort level of the animals. Such factors would include temperature, relative humidity, air speeds, and temperatures of surrounding surfaces. Hoop structures are not intended to be warm structures. The are merely intended to temper the environment and give pigs the opportunity to modify their own environment by the utilization of bedding.

 Figure 2 shows the average temperatures that were measured inside and outside the hoop structure during the first winter trial. On average, the air temperature in this structure was only 5 to 8 degrees warmer than the outside temperature. Results from the second winter trial were very similar. While this temperature is certainly cooler than is desired to raise pigs, the actual effective temperature that the pigs experience is somewhat different. This can be attributed to the fact the pigs can modify their environment by burying themselves in the bedding and also because some heat comes off the bedding. This will be discussed in more detail in the Bedding section.
Figure 2


Figure 3 illustrates the summer environmental performance. During the summer, both ends of the building were open and a temperature controlled sprinkler system was in place. Average temperatures were usually only slightly higher than the outside temperature. This is also common in conventional confinement facilities. The sprinkler system actually operated very little during the summer of 1996 because of relatively cool temperatures. 
Figure 3

Bedding & Labor

During these experimental trials the goal was to bed heavy enough to absorb all the liquid during the winter trials. For winter trials generally 5 large cornstalk bales (approximately 1100 lbs each) would be placed in the hoop at the beginning. Once per week two more bales were added. Bedding data is shown in Table 2. Considerably less bedding was used during the summer. During the winter 2, less bedding was used than in the winter 1. This was due to two reasons. First of all, the winter 2 was not as cold as winter 1. Secondly, a shortage of bedding prompted the farm crew to bed more conservatively. The winter 2 pigs had a poorer feed efficiency which may be partly due to a shorter bedding supply.

 Table 2. Bedding & Labor for the hoop structure trials.

Trait

Winter 1

Summer

Winter 2

Bedding

cornstalks, large

cornstalks, large

2/3 cornstalks,
1/3 oat straw

Total Bedding (lbs)

39,600

18,600

31,500

Bedding/pig

262

124

193

Manure Removed (tons)

100

36

74

Total labor (hrs)

90

62

51

Labor/pig

0.61

0.42

0.32

The amount of labor is greatly related to the amount of bedding. Most labor is used for bedding, checking animals, hauling manure and sorting/loading animals. The decline in winter 2 is due probably to the farm crew learning how to manage the system more efficiently and also due to less bedding being utilized. Labor is a hotly debated issue with some producers saying less labor is spent using hoop production while other state the opposite.

Because this system uses a deep litter bed, some composting will occur during a production cycle. This helps to break down the bedding and provides some heat for the pigs. While this is certainly a source of some heat, it varies greatly with location. Figure 4 illustrates the measurement sites of the bedding and Table 3 gives the temperatures at different depths. Table 4 gives nutrient content at these same locations. Manure from hoop structures is generally highly variable depending on the dunging locations.

Figure 4

Figure 4. Measurement sites of bedding traits. The right end is the concrete feeding area.

Table 3. Bedding Temperature by Site and Location3

Sit e

Temp at 6" from surface

Temp at 12" from surface

Temp at 18" from surface

W1

30

30

30

W2

44

59

59

W3

58

67

70

C1

80

81

78

C2

113

117

--

C3

102

114

100

E1

75

74

74

E2

86

88

84

E3

78

75

67

Economics

Double curtain swine finishing buildings in Iowa generally cost around $160 to $180 per pig capacity. Hoop structures cost approximately $55 per pig capacity. However, the difference in feed efficiency makes the cost of production of the two systems comparable. The issue of labor and bedding cost is not well known. The best information available on cost of production appears in MWPS (1997) where it is concluded that the cost of production of the two systems are nearly the same.

Table 4. Bedding Nutrients by Site and Location

Sit e

Total Moisture (%)

Total Nitrogen (lbs/Ton)

Phosphorus (lbs/Ton)

Potassium (lbs/Ton)

W1

73.7

20

21

12

W2

75.2

22

22

12

W3

68.5

22

31

16

C1

67.4

14

20

26

C2

22.9

11

21

37

C3

27.6

22

17

26

E1

68.5

29

24

29

E2

30.6

36

40

51

E3

73.5

16

13

15

Summary

Hoop structures are a viable technology for finishing pigs given the right circumstances. There are several conclusions that can be reached based on information in this study. These are broken down into advantages, disadvantages and questions.

Advantages of Hoops

  1. The initial capital outlay is less for hoop structures than for double curtain confinement buildings.
  2. All in/all out may be more easily achieved by smaller operations that are dealing with group sizes of 150 to 240 pigs.
  3. Hoop structures are versatile and may be utilized for other things if production capacity is not needed.
  4. Air quality within the structure is generally good.
  5. Neighbors do not generally object to hoop structures because the odor during the growing period is low since manure is handled as a solid. (It does, however, have an odor during spreading).

Disadvantages of Hoops

  1. Bedding handling and storage. Bedding is the key to this system. Plenty of bedding must be available. Bedding stored for use in spring should be protected from the elements.
  2. Handling and sorting pigs is more of a challenge in a large pen. Outdoor handling and sorting gates are preferred and extra labor may be necessary.
  3. Feed efficiency may be 10 percent or more poorer than warm housing.
  4. Labor may be slightly higher than that need for confinement facilities.
  5. Manure loading and handling may be difficult and specialized equipment may be necessary.

Questions

  1. Will disease and parasites build up in the soil below the hoop?
  2. What is the life of the tarp?
  3. What are the side-by-side cost of production of a good hoop structure versus a good confinement building?

Further Information

Further detailed information, including management tips and cost estimates, may be found in Hoop Structures for Grow-Finish Swine. This is MidWest Plan Service publication AED-41. Copies may be obtained for $5 from MWPS at 1-800-562-3618 or at MWPS@iastate.edu.

 

References

Connor, M.L. 1993. Evaluation of a biotech housing for feeder pigs. Manitoba Swine Update. July 1993. 5(3):1.

Harmon, J.D. and H. Xin. 1997. Thermal Performance of a Hoop Structure for Finishing Swine. ASL-R1391. 1996 Swine Research Reports. P. 104-106. Iowa State University Extension, Ames, IA.

Honeyman, M.S. 1997. Hooped Structures with Deep Bedding for Grow-finish Pigs. ASL-R1392. 1996 Swine Research Reports. P. 107-110. Iowa State University Extension, Ames, IA.

MWPS. 1997. Hoop Structures for Grow-Finish Swine. AED-41. MidWest Plan Service. Ames, IA.

PigChamp. 1995. PigChamp Database Summary. January 1990-May 1995.

_______________

1Information for this paper is from a study done by ISU. Additional faculty members participating were: Tom Richard, Jeff Lorimor and Hongwei Xin, Assistant Professors of Agricultural and Biosystems Engineering.

2Mention of company or product names is for presenation clarity and does not imply endorsement by the authors or Iowa State University, nor exclusion of any other products that also may be suitable for application.

3Temperatures measured by Richard and Lorimor. February 28, 1997. 41 F outside, 38 F inside

 

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