Source: IOWA STATE UNIVERSITY submitted to NRP
HOOP BARNS FOR LIVESTOCK: AN INNOVATIVE HOUSING SYSTEM
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
Reporting Frequency
Annual
Accession No.
0199570
Grant No.
2004-34478-14478
Cumulative Award Amt.
(N/A)
Proposal No.
2004-06094
Multistate No.
(N/A)
Project Start Date
Sep 15, 2004
Project End Date
Sep 14, 2007
Grant Year
2004
Program Code
[TG]- (N/A)
Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
ANIMAL SCIENCE
Non Technical Summary
Livestock farmers are searching for innovative, low-cost solutions for animal housing. Hoop barns are a recent innovation that are low-cost and versatile that utilize bedding. The use of hoop barns for livestock housing needs scientific research and demonstration to document their potential and limitations. Work with swine, beef cattle and dairy cattle is proposed. The project conducts research using bedded hoop barns for finishing swine, gestating swine, and market beef cattle. Dairy cattle hoop barns will be monitored. The project will conduct modeling to determine the energy efficiency of livestock farms that use hoop barns.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
3073310310020%
3073410310010%
3073510310070%
Goals / Objectives
1. To complete analysis of in-depth qualitative interviews completed with 14 Iowa farmers using hoop structures and located across the state's agro-geographic regions; to complete analysis of in-depth qualitative interviews completed with 8 Iowa small-scale meat locker proprietors. 2. To conduct an analysis of the energy efficiency of pork production by type of pork production system: total confinement systems, hoop systems, partial confinement systems, etc., and to conduct a sensitivity analysis which examines impacts of changes in energy prices on the profitability of pork production. The I-FARM simulation model will also be used. 3. To further examine group bedded hoop barn housing compared to individual crate confinement housing for gestating sows. 4. To benchmark growth performance and carcass value of cattle finished in a hoop barn, to compare beef quality and yield grade of carcasses from cattle finished in an open feedlot to carcasses from cattle finished in a hoop barn, and to determine the extent to which finishing environment (open feedlot vs. hoop structure) affects the composition of fresh beef. 5. To document the environment inside hoop barns for dairy cattle. 6. To determine the influence of stocking density within hoop structures on pH decline in the early postmortem period, on fresh pork color and composition, and on carcass composition and value. 7. To investigate nutrient flows and losses in beef cattle hoop structures and associated manure management systems. 8. To develop curriculum materials to teach secondary and undergraduate agricultural students about hoop barns for livestock and to complete a conference on hoop barns.
Project Methods
Interviews covering 1) history and decision-making in production; 2) current production practices; 3) animal welfare perceptions; 4) perceptions of human and community health/environmental impacts; 5) marketing and prospects are being analyzed for common and divergent themes, with particular attention to identifying how farmers perceive the links between economic, management, environmental and social dimensions of their hoop house swine system. For the energyflow/efficiency analysis, energy budgeting will be utilized. This information will be developed to reflect the total energy flow that is embodied in pork production for the alternative pork production systems. Various production systems will be evaluated. Three sow gestation housing systems will be compared at the ISU Bilsland Swine Research Farm, Madrid, IA. The housing systems are 1) individual gestation crates in a mechanically ventilated, slatted floor, confinement building (CRATE); and 2) group pens in deep-bedded, naturally ventilated hoop structures (HOOP); and 3) confinement slatted floor pens (PEN). The study is designed for a 2-3 year duration. Comparisons will be based on reproductive performance in conception rate, culling rate, wean-to-breed interval, litter size at birth, and weaning and sow mortality, as well as sow behavior. Cattle of similar genetics will be finished in an open feedlot for comparison to cattle finished in a hoop structure. Growth rate, feed intake and feed efficiency will be documented during the finishing phase. Upon reaching an endpoint body composition - determined by ultrasound - market cattle will be transported to a commercial processing facility for harvest. Automatic data loggers will be installed in a variety of hoop barns used for housing dairy cattle. Uses will include housing dairy calves, heifer development, and freestall housing for cows. Temperatures, relative humidity, light intensity and duration, and drafts will be recorded Within each hoop building, areas will be constructed and stocked with different densities (8.5, 10, and 13 square feet/pig). Diet, genetics, management will be standardized between the groups. Average daily gain, average daily feed intake, and feed efficiency will be monitored. Nutrient flows and losses will be tracked using a mass balance analysis, incorporating procedures and conversion factors used in animal science, soil science, and agricultural engineering for the different components of the system. Materials will be created that expose agricultural students to hoop barns and their use for housing livestock. The materials will be suitable for vocational agricultural classes and introductory undergraduate courses. Materials will include photos, slides, exercises and instructor materials. A national hoop barn conference will be completed with the implementation of their objective.

Progress 09/15/04 to 09/14/07

Outputs
The primary focus of the project has been to expand the understanding of deep-bedded hoop barns as a housing system for livestock. Outputs have included: 1) Generation of a body of knowledge to support alternative bedded swine production systems. The information has formed the foundation of the growing pork niche market in the U.S. that produces an estimated 750,000 pigs annually and continues to expand. The information includes managing market pigs, manure utilization, stocking densities, hoop barn layouts, bedding type comparisons, reduction of sub-therapeutic antibiotics, and pig growth in hoop barns. A comprehensive niche pork production handbook is used to train new producers that enable the market to continue to grow. 2) Successful housing of gestating sows was documented showing more live pigs born per litter from hoop-housed sows compared with sows gestated in crates. This information is critical as the U.S. swine industry searches for alternatives to the gestation crate. Detailed comparative budgets showed that cost per pig was 3 to 11% less from sows housed in hoop barns compared with sows housed in confinement gestation crates, although more feed was required. 3) Pork from pigs reared in hoop barns and conventional confinement had no major differences in meat quality or eating characteristics. This information will be useful in niche pork marketing. 4) Our work clearly established hoop barns as an environmentally sound option for beef cattle feeding, where the cattle perform well and runoff potential is virtually eliminated or greatly reduced.

Impacts
Overall, hoop barns have been firmly established as a new viable alternative housing system for livestock in the U.S. Hoop barns have a lower construction cost and require less energy and repairs than many conventional forms of livestock housing. Feasibility of feeding beef cattle in bedded hoop barns was shown. Cattle growth, carcass quality, behavior, and feed intake were documented. No major differences were noted at this time. Hoop barns for cattle feeding now qualify for NRCS EQUIP funds. Due to expanded ethanol production, the number of cattle on feed in Iowa has increased 11% in 2007 compared with 2006. A portion of this increase is housed in bedded hoop barns, partly as a result of this demonstration. Major development of curriculum for teaching about alternative livestock production in hoop barns has occurred. Collectively these efforts are reaching young, developing agriculturists. Detailed plans have been completed to model energy flows in U.S. swine production. Energy use in all aspects of pig production from the manufacture of materials used in building construction to the cultivation and processing of feedstuffs and the utilization of manure will be modeled. Comprehensive, accurate information is the basis of informed decision making by policy makers, farmers, and community members. Young farmers, beginning farmers, risk-averse farmers, niche producers, and acreage owners are considering hoop barns as a low cost, versatile housing for their livestock. Livestock in hoop barns require bedding. Use of bedding reconnects livestock production to the land. Properly managed, the solid manure has a low risk of spills or leaks. Bedded hoop barns are viewed as an economically competitive housing alternative to confinement gestation crates for sows where pigs can be produced at a lower cost and sows can be managed effectively as a group. Feeding stalls are a key component that allows sows housed in groups to be managed as individuals. Dairy cattle, horses, sheep, and ratites are also being successfully housed in hoop barns. Numerous niche pork markets recognize and accept pigs reared in bedded hoop barns. Niche pork markets have become established and continue to expand. Our work on alternative, bedded pig production systems forms the foundation of these markets. Producers of niche pork receive premiums of $17 to $50 per pig. Also, our work shows that housing system is not a major factor in subsequent pork quality even though many niche marketers claim housing or rearing environment as a marketing attribute. Manure management plans now include values for solid manure from hoop barns. Efforts are underway to train young agriculturists about hoop barns via land-grant universities and high school vocational agriculture classes.

Publications

  • Lammers, P.J., M.S. Honeyman, J.W. Mabry, and J.D. Harmon, 2007. Performance of gestating sows in bedded hoop barns and confinement stalls. Journal of Animal Science 85:1311-1317.
  • Sullivan, Z.M., M.S. Honeyman, L.R. Gibson, and K.J. Prusa, 2007. Effects of triticale-based diets on finishing pig performance and pork quality in deep-bedded hoop barns. Meat Science 76: 428-437.
  • Lammers, P.J., M.S. Honeyman, J.B. Kliebenstein, and J.D. Harmon, 2008. Impact of gestation housing system on weaned pig production cost. Applied Engineering in Agriculture. In press.
  • Honeyman, M.S., J.D.Harmon, S.C. Shouse, W.D. Busby, and D.L. Maxwell, 2008. Feasibility of bedded hoop barns for market beef cattle in Iowa: Cattle performance, bedding use, and environment. Applied Engineering in Agriculture. In press.
  • Morrical, J.R., M.S. Honeyman, J.D. Harmon, T.J. Baas, and C.R. Schwab, 2008. Evaluating finishing pig growth during summer and winter in bedded hoop and confinement buildings. Applied Engineering in Agriculture. In press.
  • Patton, B.S., E Huff-Lonergan, M.S. Honeyman, J.D. Crouse, B.J. Kerr, and S.M. Lonergan, 2008. Effects of deep bedded finishing system on market swine performance, composition and pork quality. Animal. In press
  • Patton, B.S., E Huff-Lonergan, M.S. Honeyman, B.J. Kerr, and S.M. Lonergan, 2008. Effects of space allocation within a deep bedded finishing system on swine growth performance, fatty acid composition and pork quality. Animal. In press
  • Lammers, P.J. and M.S. Honeyman, 2006. Impact of gestation housing system on weaned pig production costs. Journal of Animal Science 84(Suppl. 1):269. (Abstr.)
  • Lammers, P.J. and M.S. Honeyman, 2006. Sow and litter performance in individual crate and group bedded hoop barn gestation systems. Journal of Animal Science 84(Suppl. 2):84. (Abstr.)
  • Goldsmith, C., L. Sadler, K. Stalder, L. Karriker, M. Honeyman, and A. K. Johnson, 2007. Removal of sub-therapeutic antibiotics from nursery pigs diets: influence on behavior, performance and physiology. J. Anim. Sci. 85(Suppl. 1):127 (Abstr.)
  • Busby, D., S. Shouse, M. Honeyman, D. Loy, J. Harmon, and D. Maxwell, 2008. Beef cattle feeding in a deep-bedded hoop barn: year two. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Honeyman, M.S., R. Breach, and L. Rossiter, 2008. A comparison of alternative winter farrowing systems. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Honeyman, M., D. Stender, W. Roush, and D. Hummel, 2008. Feeding DDGS to finishing pigs in deep-bedded hoop barns. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Jackson, C., A.K. Johnson, K. Stalder, M. Honeyman, and L. Karriker, 2008. Removal of sub-therapeutic antibiotics from nursery pigs diets: influence on behavior, performance and physiology. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Lammers, P.J., and M.S. Honeyman, 2008. Energy Balance in pig production systems: A progress report. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Lammers, P.J., M.S. Honeyman, and D.R. Stender, 2008. The niche pork production handbook. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Stender, D.R., J. Kliebenstein, G. Huber, J. Mabry, and M. Honeyman, 2008. Returns and costs of niche pork production in 2006. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Stender, D.R., J. Kliebenstein, G. Huber, J. Mabry, and M. Honeyman, 2008. Production Efficiency of niche pork production in 2006. In press. Animal Industry Report AS-654, ISU Ext. Serv., Ames, IA.
  • Busby, D., S. Shouse, M. Honeyman, D. Loy, J. Harmon, and D. Maxwell, 2007. Beef cattle feeding in a deep-bedded hoop barn: year one. ASL-R2189. Animal Industry Report AS-653, ISU Ext. Serv., Ames, IA.
  • Lammers, P., M. Honeyman, J. Mabry, and J. Harmon, 2007. Sow and litter performance for individual crate and group hoop barn gestation housing systems: project summary. ASL-R2236. Animal Industry Report AS-653, ISU Ext. Serv., Ames, IA.
  • Lammers, P., M. Honeyman, J. Kliebenstein, and J. Harmon, 2007. Impact of gestation housing system on weaned pig cost. ASL-R2235. Animal Industry Report AS-653, ISU Ext. Serv., Ames, IA.
  • IPIC Niche Pork Production Handbook, 2007. IPIC NPP2007. http://www.ipic.iastate.edu/publications.html.
  • Hoop Structures for Livestock. A website, 2006. http://www3.abe.iastate.edu/hoop_structures/.


Progress 01/01/06 to 12/31/06

Outputs
The primary focus of the project is to expand understanding of deep-bedded hoop barns as a housing system for livestock. Progress was made on all of the objectives. A major paper was published and another was accepted for publication in the Journal of Animal Science. Detailed financial analysis of gestating sows in hoop barns was presented at the national meeting of the American Society of Animal Science. The long term data set on the reproductive performance of gestating sows in bedded hoop barns was analyzed and showed that sows gestated in hoop barns furrowed 0.7 more live pigs per litter as sows housed in individual gestation crates. This work was presented at the Midwest Section of the American Society of Animal Science and was part of a thesis during 2006. It was the work that has been accepted by the Journal of Animal Science. Work supporting niche markets related to oregano as an alternative to sub-therapeutic antibiotics was completed. Adding oregano to nursery pig diets resulted in no improvement in pig performance. The U.S. pork niche market phenomenon was documented and shown to be significant. Bedding sources were evaluated for absorbency. Cornstalks and oat straw absorb about three times their weight in water, shredded paper and triticale straw about twice and shredded lumber about equal weights. Our work on the effects of season and housing type on finishing pig growth was completed and will be submitted for publication. The hoop-reared pigs' growth lags early in the feeding period but then compensates later. Data on pig production in Iowa was collected from U.S. Census of Agriculture and was summarized by county to show pig density shifts. Pig inventories have shifted within the state and are much less evenly distributed. The cost of producing weaned pigs in a natural pork system was determined to be $34 to $39 per head. A comparison of feeding beef cattle in a hoop barn to a conventional confinement showed no major differences in summer or winter.

Impacts
For years, beef producers and environmental specialists have looked for economical ways to curb intensive runoff from feedlots. In addition, environmental regulations in high-rainfall areas, such as Iowa, are creating increased interest in new livestock production systems. As a result, this research attempts to quantify the environment in a bedded hoop barn used for finishing cattle, and to compare beef cattle performance in hoops to conventional open feedlots. Recent innovations have expanded hoop production use to include providing shelter to dairy and beef cattle, sows and piglets and other livestock systems. A unique advantage of hoop buildings for finishing cattle is the containment of waste runoff, which can address concentrated animal feeding operation regulations for larger beef operations. The work has provided the production framework for the expanding pork niche market. In 2003, there were about 40 active niche pork markets in Iowa. It is estimate that 500,000 to 750,000 pigs are in the U.S. niche pork market annually. The market demand continues to grow faster than the supply. Also, the bedded hoop barn is proving to be a viable alternative for beef cattle feeding that would greatly reduce feedlot runoff. In order to be viable, today's finishing facilities must be profitable as well as environmentally responsible, with particular attention to an operation's effects on water quality. Hope buildings proof to provide those benefits.

Publications

  • Honeyman, M.S., R.S. Pirog, G.H. Huber, P.J. Lammers, and J.R. Hermann. 2006. The United States pork niche market phenomenon. Journal of Animal Science 84:2269-2275.
  • Lammers, P.J. and M.S. Honeyman. 2006. Impact of gestation housing system on weaned pig production costs. Journal of Animal Science 84(Suppl. 1):269. (Abstr.)
  • Lammers, P.J. and M.S. Honeyman. 2006. Sow and litter performance in individual crate and group bedded hoop barn gestation systems. Journal of Animal Science 84(Suppl. 2):84. (Abstr.)
  • Morrical, J.R., M.S. Honeyman, J.D. Harmon, T.J. Baas, and C.R. Schwab. 2006. Evaluating finishing pig growth, loin muscle area, and backfat accretion during summer and winter for bedded hoop and confinement barns. Journal of Animal Science 84(Suppl. 2):56. (Abstr.)
  • Busby, D., S. Shouse, M. Honeyman, D. Loy, J. Harmon, and D. Maxwell. 2006. Beef cattle feeding in a deep-bedded hoop barn: a preliminary study. ASL-R2006. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Honeyman, M. and M. Duffy. 2006. Iowa s changing swine industry. ASL-R2158. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Kulchaiyawat, C. and M. Honeyman. 2006. Effects of oregano supplemented diets on nursery pig performance. ASL-R2156. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Lammers, P., M. Honeyman, J. Mabry, and J. Harmon. 2006. Sow and litter performance for individual crate and group hoop barn gestation housing systems: progress report III. ASL-R2171. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Morrical, J., M. Honeyman, C. Schwab, J. Harmon, and T. Baas. 2006. Evaluating growth loin muscle area, and backfat accretion during summer and winter for finishing pigs in bedded hoop and confinement buildings. ASL-R2157. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Patton, B., E. Huff-Lonergan, M. Honeyman, and S. Lonergan. 2006. Effects of finishing pigs in hoop structures on swine performance, pork composition, and pork quality. ASL-R2162. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Patton, B., E. Huff-Lonergan, M. Honeyman, and S. Lonergan. 2006. The effect of space allocation in hoop structures on swine performance and pork quality. ASL-R2161. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Voyles, R. and M. Honeyman. 2006. Absorbency of alternative livestock bedding sources. ASL-R2153. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.
  • Reich, D., and J. Kliebenstein. 2006. Economics of breeding, gestating and farrowing hogs in natural pork production; financial comparison. ASL-R2165. Animal Industry Report AS-652, ISU Ext. Serv., Ames, IA.


Progress 01/01/05 to 12/31/05

Outputs
The primary focus of the project is to expand understanding of deep-bedded hoop barns as a housing system for livestock. Progress was made on all of the objectives. Detailed financial analysis of gestating sows in hoop barns is underway for presentation at the national meeting of the American Society of Animal Science. The long term data set on the reproductive performance of gestating sows in bedded hoop barns is complete and showed that sows gestated in hoop barns farrowed 0.7 more live pigs per litter and had equal pre-wean mortality rates as sows housed in individual gestation crates. Work supporting niche markets related to oregano as an alternative to sub-therapeutic antibiotics was started. Two new 30-foot by 90-foot hoop barns were completed at the Iowa State University Bilsland Swine Research Farms and allow our work to continue. Detailed work comparing the pork quality of market pigs fed in bedded hoop barns and conventional confinement facilities found no major differences in pork quality. Pigs in hoops that were crowded had more saturated and less poly-unsaturated lipid in their backfat. The fatty acid differences between hoop and confinement-fed pigs (less total saturated and more mono- and poly-unsaturated fatty acids for hoop pigs) were attributed to environmental temperatures differences in the hoop barns, i.e. colder in winter. A detailed serial analysis of the growth and backfat and loinage accretion of hoops and confinement pigs was completed and showed that the hoop fed pigs had more variation in growth rate. The performance of hoop-fed pigs is dependent on thermal environment and that the hoop-fed pigs (particularly in winter) may compensate for a lag in performance early in the finishing period with greater accretion rates of loin muscle and body weight and lower accretion rates of backfat later in the finishing period.

Impacts
Interest in group sow housing is expanding as a result of our work. We have demonstrated and documented a viable bedded alternative housing system. Niche pork markets continue to grow. Our work provides the production research that the market development relies on. Also, our work shows that housing systems is not a major factor in subsequent pork quality even though many niche markets claim otherwise. A bedded housing system is an attribute that apparently does not impact the intrinsic quality of the pork. Hoop fed pigs accrete muscle and fat differently than confinement fed pigs.

Publications

  • Patton, B. S., E. Huff-Lonergan, M.S. Honeyman, B.J. Kerr, J.D. Crouse, and S.M. Lonergan. 2005. The effect of space allocation on swine performance, pork quality and adipose tissue composition. Proceedings, International Congress of Meat Science and Technology, Baltimore, Maryland. August 6-13
  • Lammers, P., M.S. Honeyman, and J. Harmon. 2005. Alternative winter farrowing demonstration project: two year summary. ASL-R2028. Animal Industry Report AS-651, ISU Ext. Serv., Ames, IA.
  • Lammers, P. and M.S. Honeyman. 2005. Farrow-to-finish in a hoop barn: a demonstration. ASL-R2029. Animal Industry Report AS-651, ISU Ext. Serv., Ames, IA.
  • Morrical, J.R. and M.S. Honeyman. 2005. Serial scanning of pigs in bedded hoop and confinement buildings during summer and winter for growth, loin muscle are, and backfat: a progress report. ASL-R2033. Animal Industry Report AS-651, ISU Ext. Serv., Ames, IA.
  • Hogberg, M.G., S.L. Fales, F.L. Kirschenmann, M.S. Honeyman, J.A. Miranowski, and P. Lasley. 2005. Interrelationships of animal agriculture, the environment, and rural communities. Journal of Animal Science 83(E. Suppl.): E13-E17
  • Patton, B. S., E. Huff-Lonergan, M.S. Honeyman, B.J. Kerr, J.D. Crouse, and S.M. Lonergan. 2005. Deep bedded finishing of pigs: Effects on swine performance, pork quality and adipose tissue composition. Proceedings, International Congress of Meat Science and Technology, Baltimore, Maryland. August 6-13


Progress 09/15/04 to 12/31/04

Outputs
The primary focus of the project was to expand understanding of deep-bedded hoop barns as a housing system for livestock. Progress was made on all of the objectives. The work of the project was presented at the national meeting of the American Society of Animal Science. Detailed financial analysis of finishing hogs in hoop barns was completed. Progress was made on analyzing the data set of sow and bitter performance for individual crate and groups bedded hoop barn gestation housing systems. Preliminary trends were a shorter wean-to-breed interval and 0.50 more pigs weaned/sow/year for hoop sows than crate sows. Work supporting niche markets related to organic okara as a pig protein source and alternative winter farrowing was completed.

Impacts
Discussion of sustainable livestock production was extensive at a national level at the FASS meetings. Winter farrowing is a barrier to expanding niche markets. This project provided the first summary of possible alternative farrowing systems that could work during winter months.

Publications

  • Larson, B., J. Kliebenstein, M. Honeyman, and A. Penner. 2004. The economics of finishing hogs in hoop structures and confinement; financial comparison. ASL-R1960. Animal Industry Report AS-650, ISU Ext. Serv., Ames, IA.
  • Lammers, P., M. Honeyman, J. Mabry, J. Harmon, and D. Hummel. 2004. Sow and litter performance for individual crate and group hoop barn gestation housing systems: a progress report II. ASL-R1962. Animal Industry Report AS-650, ISU Ext. Serv., Ames, IA.
  • Herman, J. and M. Honeyman. 2004. Okara: a possible high protein feedstuff for organic pig diets. ASL-R1965. Animal Industry Report AS-650, ISU Ext. Serv., Ames, IA.
  • Lammers, P. and M. Honeyman. 2004. On-farm examples of alternative winter farrowing systems. ASL-R1967. Animal Industry Report AS-650, ISU Ext. Serv., Ames, IA.
  • Lammers, P. and M. Honeyman. 2004. Alternative winter farrowing demonstration project: A progress report. ASL-R1968. Animal Industry Report AS-650, ISU Ext. Serv., Ames, IA.