Pigs on pasture: An assessment of pasture health, pork quality, and ecosystem rebound after rotational grazing

Final report for FNE16-859

Project Type: Farmer
Funds awarded in 2016: $14,752.00
Projected End Date: 04/15/2018
Grant Recipient: Hampshire College
Region: Northeast
State: Massachusetts
Project Leader:
Pete Solis
Hampshire College
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Project Information

Summary:

Our research project aims to assist farmers in obtaining information about whether the increased labor costs associated with rotational grazing of hogs is offset by decreased grain costs and increased pasture and soil quality.

In our first year, we successfully raised a total of 24 pigs in two management styles: rotationally grazed, and continually grazed. The experimental layout was designed by Professor Brian Schultz. The carcasses were evaluated in partnership with the Arion Thiboumery and his staff at Vermont Packinghouse. A preliminary look at the data indicate that the management style has little perceptible effect on the carcass quality of the pigs.

Throughout the season, two student interns handled most of the daily pig chores, including feeding, watering, rotating the pigs to new pastures if applicable, and maintaining the fences. They also assisted in soil sampling and loading the pigs onto trailers for transport to the slaughterhouse.

In conversation with other local pig farmers, we discovered that there is significant interest in the results of this experiment. Some farmers were keenly interested in the value of rotational grazing versus continuous grazing.

While we were unable to accurately measure grain consumption, we did find that our data indicated no measurable difference in carcass quality between rotationally grazed and continuously grazed pigs. Our data also showed that pigs provide an increase in soil fertility, but they also negatively impacted pasture quality, with paddocks with rotationally grazed pigs having the most diverse plant populations. However, as we mention in the report, the unusually dry season in 2016 probably had some major effects on our data.

Pete gave several workshops and tours detailing the process and results of the research. These workshops, both at The Livestock Institute’s annual conference and at the NOFA Summer Conference, were well attended by farmers and producers. Pete submitted articles to OnPasture.com and Cornell Small Farms Quarterly detailing our research, results, and lines of further questioning.

Introduction:

S. A. Edwards (2003) suggests that a growing pig can expect to obtain about 5% of its nutritional needs from pasture. Edwards states in the conclusion that “the potential to increase nutrient intakes from pasture exists.” It is worth noting that the pigs in many of the studies mentioned by Edwards were fed concentrates (i.e., grain) via free choice. Through experience, we have found that pasture intake increases when grain consumption is constrained by hand feeding grain twice daily. Honeyman (2005) found that in Texas, outdoor finished pigs had a higher average daily gain (ADG) than their indoor raised counterparts. However, the year-round climate in Texas is quite different than that of New England and it is unclear how that conclusion would hold up farther north. Honeyman suggests that “[a]n enriched environment may improve growth rate and increase backfat…[but]… the relationship was not well defined.”

The Perdue University Pork Industry Handbook (2010) indicates that the proper stocking density for growing pigs on pasture is between 10 and 20 per acre. Further, it provides some indication of the economic value of a pig on pasture. For a growing pig, good pasture should reduce the feed consumed by “0.75 to 1.0lb. per pig per day. To make the pasture profitable in this situation, the cost of purchasing 0.75 to 1.0lb. of feed should be more than $0.14.” Of course, grain prices are higher now than in 2010—the grain we use is about $0.25 per pound. This has the potential to make pasturing pigs even more economically reasonable.
R. Fortina et al., (2011) have found that “some investigations indicate that growth rates obtained in an outdoor system can be comparable to growth rates of indoor production.” The outdoor system Fortina explored is one of pea, clover, alfalfa, and beet pastures and a 50% reduction in fed grain. Fortina found that the pigs raised in this system took longer to reach market weight, but carcass quality was equivalent to pigs raised indoors solely on grain.
There is a need for more information on the effects of pigs on pasture. ATTRA’s Hog Production Alternatives, SARE’s Profitable Pork, GrassWorks’ Small Scale Pastured Hog Production offer good overviews of pasture based systems, but do not offer insight into pasture regrowth and rejuvenation. We will include sampling of plant species, plant biomass, and soil in pastures before and after pigs are present, including how pig grazing action affects the success of reseeding pastures. Our work will allow us to augment the findings of others in different regions. In addition, our examination of attendant pasture and soil health resulting from pasturing pigs is vital to knowing the longer-term effects, both positive and negative, of keeping pigs in a pasture-based management system.

References

Anderson, D., M. Honeyman and J. Luna. 2002. How to Conduct Research on Your Farm or Ranch Sustainable Agriculture Network.  On-line version: http://sare.org/publications/research/research.pdf

Edwards, S. A. “Intake of nutrients from pasture by pigs.” Proceedings of the Nutrition Society 62.02 (2003): 257-265

Fortina R. et al. “Pasture-Based Swine Management: Behavior and Performance of growing-Finishing Pigs” Scientific Papers: Animal Science and Biotechnologies, 2011, 44 (1)

Gegner, Lance. 2004. Hog Production Alternatives http://smallfarms.wsu.edu/education/pierce/ssfr2010/Lesson%209_Sustainable%20Livestock%20&%20Poultry/hog.pdf

Gomez K. A. and A. A. Gomez.  1984.  Statistical Procedures for Agricultural Research, 2nd Ed.  Wiley and Sons, New York.

Honeyman, M. S. “Extensive bedded indoor and outdoor pig production systems in USA: current trends and effects on animal care and product quality.” Livestock Production Science 94.1 (2005): 15-24.

Kephart et al., 2010. Extension, PIH-126, Forages for Swine USA (http://articles.extension.org/pages/27447/forages-for-swine#.VkICCa6rSRs)

Little T.H. and F.H. Hills.  1978.  Agricultural Experimentation: Design and Analysis.  Wiley, NY.

O’Meara, Bridget GrassWorks Grazing Guide: Small Scale Pastured Hog Production grassworks.org/?300604/Guidebook.Hog%20Production.pdf

Sustainable Agriculture Research & Education. 2003. Profitable Pork: . http://www.sare.org/content/download/29702/413126/Profitable_Pork.pdf?inlinedownload=1

Sokal, R. R. and F. J Rohlf.  1995.  Biometry: The Principles and Practice of Statistics in Biological Research.  3rd Ed.  W. H. Freeman and Co., New York.

Project Objectives:

Access to pasture is thought to provide many benefits to raising hogs, including reducing feed/grain costs, better quality meat, and higher profitability. Our study will assess growth rates, grain consumption, and carcass quality of rotationally-grazed pigs relative to pigs on pasture, without rotation. We will also examine the impact of hogs on pasture plant growth, re-growth, and soil quality. In addition, we will explore ways to address pasture degradation and regeneration at the end of a grazing season.

Cooperators

Click linked name(s) to expand
  • Brian Schultz

Research

Materials and methods:

Experimental Layout

There were three main experiment treatments: pigs in a rotational grazing system, pigs in a similar-sized continuous grazing system, and a control without pigs for plant and soil comparisons. The control paddocks were mown periodically to prevent brush infiltration and to mimic general pasture care. To prevent massive destruction at feeding, watering, and loafing sites, the pigs were fed at different locations daily and water and shade structures were moved weekly.

24 pigs were successfully raised on pasture. Three groups of fours pigs each were rotated on smaller paddocks weekly, while the remaining three groups of four pigs were given complete access to their pastures. The field where we raised the pigs is classified with the soil type Sudbury fine sandy loam, with slopes of 3-8 percent. In practice, this field is often dries out later in the spring than many other fields. In the past it has been used as a hayfield and occasionally grazed by cattle.

The continuously grazed pigs were in an area of approximately 0.3 acres, with an effective stocking density of 13 pigs/acre. The rotationally grazed pigs were in paddocks of 0.1 ac, or an effective stocking density of 40 pigs/acre. See Figure 1 for the experimental layout.

Figure 1 - Experiment Layout

We observed a great deal of variety in the grazing action of the pigs. Some groups rooted extensively while others rooted very little. This did not appear to have any relation to the management style (rotationally grazed versus continuous).

We randomly assigned groups of pigs to be either rotationally or continuously grazed. The groups that were to be rotationally grazed were moved into a new paddock weekly. In both groups, we moved feeding, watering, and shelter areas weekly to minimize the amount of soil compaction and "moonscaping."

We used portable electric fence, powered off of deep-cycle batteries. Feed was dispensed twice daily during morning and afternoon chores. Water was provided in large barrels with hog nipple drinkers. Rotations were executed during morning chores. We periodically used a string trimmer to cut down vegetation along all the fence lines.

Once the pigs were purchased, we placed them in a "training pen" to ensure they understood electric fence. This was a pen made of hog panels with electric wire strung along the inside of the pen. We have used this method of introducing pigs to electric fence with great success. The pigs spent a week inside the training pen and were sent out to pasture on June 1 and 2 of 2016. 

As we mention in another section of the report, our slaughter schedule for the pigs is somewhat determined by the College dining hall's freezer capacity. As it is limited, we did find it necessary to stagger our slaughter dates, which meant that some pigs were butchered before reaching market weight. Groups 4 and 5 were slaughtered on September 19, 2016; groups 1 and 6 were slaughtered on October 12, 2016; groups 2 and 3 were slaughtered on October 26, 2016.

Sampling and Analysis

We examined three areas of interest:

            1) pasture and soil quality;

            2) carcass quality;

            3) average daily gain

Pasture and soil quality: Soil samples were taken before, during, and after their grazing. Soils were analyzed for the standard suite of agronomic parameters plus organic matter content. We took twelve cores at random locations within each sampling area at a depth of approximately 8 inches for every soil sample. We took care to avoid obvious pig manure when applicable. The soil was dried and an appropriate amount was then sent to the UMass Soil and Plant Nutrient Testing Laboratory for analysis.

We used random square meter quadrat sampling to determine pasture composition before the pigs were given access to the pasture. The quadrant was tossed in a random area of the paddock being measured. Each subsection of the quadrant was marked as being 1) grass; 2) legume; 3) both; 4) mostly bare; or 5) other. Six quadrant samples were taken for each pig group or control area.

Carcass quality: We worked with Arion Thiboumery of Vermont Packinghouse to assess carcass quality of the 24 pigs in the study. We measured hanging weight, backfat depth, meat firmness, and loin eye area.

Data analysis included comparing these measures between the rotationally grazed groups, the continuously grazed groups, and industry norms for confinement-raised pigs.

Average daily gain:

We had proposed to track all the grain fed to the pigs to determine pasture intake. However, we were unable ensure reliable data collection.

Regrowth of pasture and assessment of pasture improvements: Unfortunately, due to the extensive drought in 2016, we were unable to re-seed the pastures as described in our proposal. We accomplished this work in the spring of 2017, with sampling of soils and pasture taking place in spring and summer of 2017.

In 2017, we continued to take soil samples of the control areas and experiment areas. We also used quadrat sampling to determine pasture composition before reseeding and after the seed had germinated.

Our spring 2017 tillage and reseeding was delayed due to abnormally wet spring in a particularly wet field. Although we were late in planting the seed, it did germinate successfully. We seeded with King's Grazing Mix from King's AgriSeeds. After mowing and disking the randomly selected halves of each experiment and control area, we reseeded at a rate of 35 pounds per acre. Our seeding date was May 24th.

Research results and discussion:

A preliminary look at the carcass quality data didn’t appear to show any substantial differences between pigs raised in a rotational grazing system and those raised without one. In 2017, we performed data analysis to compare these measures between the rotationally grazed groups, the continuously grazed groups, and industry norms for confinement-raised pigs.

In 2017, we continued with our soil sampling and performed data analysis to help determine pasture health with regard to reseeding and pig management styles.

In April 2017, we reseeded to pasture and resumed taking soil samples and quadrat samples.

Research conclusions:

Carcass Quality

The results of the carcass quality assessment were interesting. Due to our slaughter schedule, which is based on the limited kitchen space at the College’s dining hall, some of the pigs were slaughtered before they reached full market weight. This skewed the figures towards under-performance when compared to industry standards. We therefore omitted the comparison to confinement raised animals. By comparing the continuously grazed results with the rotationally grazed results, we found no significant difference between the two.

Figure 2 - Carcass Quality Analysis

Soil Analysis

Overall, there did not seem to be much difference between the effects of rotationally grazed and continuously grazed pigs on soil quality The CEC difference between continuous and rotational grazing was only 0.31, which is not significant. There was noticeable difference between control and experimental areas, however. The soil’s CEC increased from 9.7 to 10.8. P increased significantly from 6.4 in the control areas to 11.1 in the continuously grazed paddocks and 16.0 in the rotationally grazed areas, which is not surprising given the amount of manure pigs produce.

Figure 3 - Soil Analysis Graphs

Figure 4 - Soil Analysis Figures and Table

The black bars in the graphs indicate Standard Error.

Pasture Quality

Observations during and after the experiment indicated that, contrary to our expectations, more bare ground was created in areas with rotationally grazed pigs than with continuously grazed pigs. There could be several reasons for this. Pigs tend to find and worry fence lines, so the fact that in a rotational setup there are simply more fence lines may lead to more severe soil disturbance. The severe weather during 2016 most certainly affected plant regrowth negatively. Combined with the fence line effect, this would also lead to a greater amount of bare ground.

Additionally, the fact that the continuously grazed pigs had three times as much area to live in at any given point would substantially lessen their impact on the land, as their stocking density was dramatically lower (13 pigs/acre versus 40 pigs/acre). It would be interesting to compare rotational versus continuous grazing in the same square footage or with the same effective stocking density.

One aspect of pasture quality that we did not examine in a scientific way was the lay of the land. Pigs, even breeds that are considered grazers, root. Creation of wallows and rooting for underground food alter the topography of the pasture tremendously. To regain a flat, easily mowed pasture will require more dramatic tillage than a disk.

Based on our quadrat sampling before pigs, after pigs but before reseeding, and after reseeding, we can see that the combination of pig grazing and weather favored the regrowth of grasses over legumes. It’s frustrating that we are unable to tease apart how much of this effect was weather-related. However, the effect was substantial.

Looking at the data after the reseeding was done and the seed had germinated, the trend towards grasses continues. Again, we do think the weather played a role in this result, but as to how much, we don’t know. Adjusting to strange weather is part of modern farming.

Figure 5 - Plant Quadrat Graphs

Conclusion

Based on these findings, it seems that reducing stocking density and continuously grazing may be the more labor efficient way to graze pigs. However, how significantly the weather impacted our experimental protocols, we would not be surprised if a replication of this research produced different results.

Participation Summary
1 Farmer participating in research

Education & Outreach Activities and Participation Summary

1 Curricula, factsheets or educational tools
1 On-farm demonstrations
3 Tours
1 Webinars / talks / presentations
2 Workshop field days

Participation Summary:

45 Farmers
Education/outreach description:

We hosted a workshop titled “What Pigs Do to Pasture and What Pasture Does to Pigs” at the 2016 NOFA Summer Conference. Due to bad weather and logistics, no one from the conference traveled to Hampshire Farm for the workshop.

We held another workshop at the 2017 NOFA Summer Conference, which was attended by over 20 farmers and producers. The workshop “Pigs on Pasture: A Look at Management and the Aftermath” consisted of a tour of the pig operation at Hampshire College, a basic explanation of how to manage pigs on pasture. We took a detailed look at the field where the experiment had taken place, examining plant populations and noted some differences in soil disturbance in various experiment areas. There was a good amount of interest in our preliminary results.

NOFA Summer Conference 2017 Handout

In January 2018, Pete presented some findings at The Livestock Institute's annual meeting. The workshop was attended by over 30 farmers and producers. The talk was followed by a very lively question and answer session. Pete submitted articles to OnPasture.com and Cornell Small Farms Quarterly detailing our research, results, and lines of further questioning.

Learning Outcomes

3 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Pete engaged in a few after-workshop discussions with farmers and producers. He shared that one of the biggest things he learned through the experimental process was that it is a good practice to questions one's assumptions about production methods. Pete found it very interesting that the data collected, specifically regarding plant regrowth, seemed to indicate his original assumptions. That is, Pete expected that legumes would show a greater ability to regrow after grazing.

Pete encouraged the workshop participants to use data collection and analysis as a tool to verify or refute ideas they may have about production methods on their farms.

Project Outcomes

1 Farmers changed or adopted a practice
Assessment of Project Approach and Areas of Further Study:

During his talks, Pete had a whole section titled “What Went Wrong and What I’d Change.” Clearly, it would have been beneficial to not have had a drought followed by a very wet spring, but it’s difficult to ensure anything about the weather.

We did have quite a few more escaping pigs than in a normal, non-experimental situation. Partly, this was due to the stock being inadequately trained on electric fence, and that, during a dry year, it is difficult to keep a consistently high voltage in the electric fence. We also think that giving pigs access to woodland for shade would have dramatically cut down on escapes.

We also gave some thought as to how we could improve labor efficiency. Having gravity-fed cup or nipple drinkers that could be easily moved. Moving the fence lines for the rotationally grazed pigs took a surprising amount of time. Since our labor is students with little to no experience farming, it is possible that a labor force with more experience would prove to be significantly more efficient.

Due to the difficulty in returning pig pasture to decently level hay land, we will not place pastured pigs on fields that we also hay. We will continue to rotate our pigs from pasture to pasture.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.