Author: John J. McGlone, Texas Tech University
Reviewers: John Deen, University of Minnesota; Steve Moeller, The Ohio State University
Housing systems for farrowing sows have changed very little in the past 30 years. At the mid 20th century, two farrowing environments were common – the outdoor hut in a pasture or lot, and an indoor farrowing pen. The farrowing pens were in low-cost buildings and thus the cost per square foot of building space was relatively low compared to today’s buildings. Farrowing sows indoors has proved to be beneficial for both the producer and the sow and her piglets. However, recent criticism of the traditional farrowing crate has led to increased efforts to find suitable alternatives that still provide maximum production efficiency.
Sows were brought indoors for three primary reasons. First, the indoor environment was more comfort¬able for both people and pigs. Second, the indoor environment allowed for the elimination of parasites in that the floors could be disinfected and the parasite life cycle broken. Third, the indoor system provided uniform, year-round production through-put. The farm could develop a steady cash flow with farrowings at first twice per year and later on a weekly schedule.
One can conclude that the reasons sows moved indoors included to improve the welfare of the sow and piglets and to improve the farm economics. Thirty years ago, this is a case where economics and welfare were associated in a meaningful way. Clearly, sow and piglet welfare was improved by the move from outdoor lots to indoor pens. Clearly, the farm produced more pigs per year that helped pay the mortgage on the farm. When sows moved indoors, the move was associated, almost simultaneously, with a move from pens to farrowing crates. Farrowing crates saved baby pigs from being crushed. Pork producers were willing to restrict the movements of the sow to save baby pigs from being crushed, as the piglets’ welfare was deemed more important that the sow’s temporary inconvenience.
Because the move indoors was closely timed with the move from pens to crates, the industry did not consider how the pens might be designed to reduce piglet crushing. But this work has taken place and some alternatives to the standard farrowing crate are available.
Humane activist and advocate groups have demanded an alternative to the farrowing crate. For example in the USA, both the Niman Ranch (http://www.nimanranch.com/index.htm) and Humane Farm Animal Care (HFAC, http://www.certifiedhumane.com/) discourage or prohibit the use of farrowing crates.
The key to evaluating any system is to find the critical control points – measures that are key to under¬standing and improving a system. In the farrowing area, there are two production, three anatomical, and three behavioral critical control points.
Anatomical CCPs in farrowing
Production CCPs in farrowing
Behavioral CCPs in farrowing
Items marked with an asterisk (*) are requirements of some systems such as the Niman and HFAC sys¬tems. These requirements may be imposed in the future in Europe and the USA, but today, they are a part of only some niche marketing systems.
One of the main ways to tell if a system is performing well in terms of both economics and welfare is to assess each CCP. As the old adage goes, “if you don’t measure it, you can’t manage it”. Each CCP, by defi¬nition, is critical. Data should be collected, analyzed, and the information used in a continuous improve¬ment program.
Not all newer systems have each CCP evaluated. Some new systems we can speculate on certain CCPs and that may be adequate for now. In this summary, we will examine each major farrowing house system for available information on each CCP.
The farrowing crate is by far the most common farrowing barn system in use in the USA today. Estimates are that in the USA, well over 90% of pigs are farrowed in crates. Crates vary in size and construction. Surprisingly few controlled studies have compared different farrowing crate features.
One feature of the farrowing crate is its allowance of the anatomical CCPs. In the National Pork Board PQA+ program, swine producers that earn PQA+ Certification may then choose to have an operation site assessment. A portion of the site assessment includes visual observation of pig space allowance. For swine located in farrowing crates, adequate space is defined as greater then 90% of the observed swine must be able must be able to lie down fully on its side (full lateral recumbency) without the head having to rest on a raised feeder and the rear quarters coming in contact with the back of the stall at the same time. For operations that do not meet this standard, an action plan must be developed and implemented.
To get a sense of how long the farrowing crate must be, we evaluated the length of hundreds of sows in a commercial setting . In the sample, 95% of sows were shorter than 78.7 inches (200 cm) or 6.6 feet – and some genetic lines of sows were longer by 2-6 inches on average. Thus, the crate must be at least 6 feet 7 inches long, not counting the raised feeder for these sows to lie fully on their side without touch¬ing the front or rear of the crate. If the feeder extends 12 inches inside the farrowing crate, then the crate is not long enough for sows to lie in full recumbency without the head having to rest on the feeder. If the sow has a length of 7 feet (213 cm) to lay down, then most sows will fit comfortably. Because the sow width can typically reach under the bottom bar or fingers, farrowing crate width is usually not an issue. In addition, if the crate has sharp edges in the pen materials, feeder or flooring, then it could cause in¬jury and would not be positive for sow welfare. As with all lactation environments, sows should be fed to maintain body condition. In the NPB PQA+ program, sows with a body condition score 1 (backbone clearly visible due to insufficient backfat) are not desirable. This happens often due to a lack of sow feed intake relative to milk production and piglet milk intake. Farrowing crate feeder and water devices must be designed to allow easy access to available fresh feed and water resources.
In terms of production CCPs, an extensive evaluation of crate features was conducted by Curtis et al., . In this work, they evaluated, among many other measures, the rates of stillborn pigs and pre-wean¬ing mortality. They examined 16 farrowing crate design features including crate width (narrow or wide; 56 vs. 61 cm or 22 vs. 24”), crate length (short vs. long; 183 vs. 198 cm or 72 vs. 78”) and lower side type (fingered, bowed or straight rails at 20 vs. 25 cm off the floor; 8 vs. 10”). They found that the stillbirth rate was increased by 0.2 pigs per litter (0.3 Narrow vs. 0.5 Wide) and the pre-weaning mortality was greater by 2 % ( 4% Narrow vs. 6% Wide) due to crushing for wide crates compared with narrow crates. Use of low-height lower rails (8 vs. 10”) increased the number of pigs per litter with knee abrasions. None of the crate lengths were considered long by today’s standards – sows had access to 6’ or 6.5’ of length. Something over 5% of sows would be longer than the space they provided in their long crate (6.5’) and 30% of the sows would be too long for the short crate (6’). To meet the anatomical CCP of sow length, today’s sows, depending on genetic line, require a crate length of either 6.5 or 7 feet in length.
Fraser et al.,  examined features of the farrowing crate including sloped side rails (called the Ottawa crate), flared rails, straight and finger rails. Generally, there were few production differences among crate design features. Straight-rail crates tended to have larger within-litter variation in piglet body weight gain. These studies support the idea that farrowing crates should not have straight-rails penning materials. Fin¬gers or bowed rails may have a slight advantage in terms of litter productivity.
Sows are motivated to turn around. The standard farrowing crate does not allow sows to turn around. To evaluate sow motivation to turn around, McFarlane et al.,  gave gilts modified gestation crates that made it difficult to turn around. If the feed and water were located on the same end of a modified crate, gilts still turned around over 100 times per day. When the modified crate was made more narrow turning rates were reduced to 8 to 11 turns per day. The authors concluded that turning is a behavioral need, but not a very strong one (they gave no reason for this conclusion as relative motivations were not assessed).
To accommodate turning in as little space as is possible, the turn-around crate was developed by several producers around the USA. One turn-around farrowing system was evaluated and reported by McGlone and Blecha . The pen was triangular-shaped and its outside dimensions were 5 X 8.5’. The turn-around farrowing pen was a modified crate in that the side walls were flared outwards, but were fixed in place on either side of the feeder. The stillbirth rate was a little lower and the pre-weaning mortality was signifi-cantly lower for sows in the turn-around crate compared with the standard crate (Table 2).
The sloped pen was found on commercial farms decades ago. The logic of this indoor farrowing pen was that when sows farrowed in rolling hill country, they often had no problem with nursing on a slope – some producers even thought they did better when nursing on a hill. The sloped has been called the Hillside or Sloped pen. It was popular on commercial farms 30 to 50 years ago.
An early evaluation of the Hillside crate was made by Collins et al.,  and a more complete evaluation was performed by McGlone and Morrow-Tesch, . While the sloped floor improved pre-weaning survival of litters in pens, piglet survival was reduced when the crate was sloped. Sloping the floor of a farrowing pen causes the sow to stand and lie more carefully and it encourages piglets to rest at the bottom of the slope. Sows often lay with their teats parallel to the creep area which facilitates suckling.
The family pen concept includes an area where the sow can be with her piglets and an area that allows the sow to get away from her piglets. The idea is that sows are motivated to be close to their piglets the first few days of their life and then they gradually spend more and more time away from their piglets. After about one week of age, the piglets are highly motivated to explore with the rate of exploration increasing with age. The family pen attempts to accommodate ever changing piglet and sow motivations. The family pen concept evolved out of work done by Stolb and Wood-Gush  on the behavior of sows and piglets in what was described as a ‘semi-natural habitat’. The sows can be isolated in their own pen during the peri-farrowing period and then she can socialize with other sows after a few days (when she is motivated to do so).
While some reports show very poor production with this system, further refinements lead to good sow and litter performance. Arey and Sancha  reported stillbirth rates and pre-weaning mortality rates in the family pen as comparable to those from the farrowing crate. If this system includes bedding, it would be considered the most enriched environment among the indoor farrowing systems. Some commercial models are also available that include electronic sow feeders and gates.
Werribee farrowing pen
The Werribee farrowing pen was developed by Cronin in Australia as an alternative to the farrowing crate based primarily on welfare concerns . The Werribee pen includes a sow and piglet area (called a nest) and a dunging area (or non-nest area). The Werribee farrowing pen occupies about twice the floor space as a standard farrowing crate. Attempts to reduce the floor space area in the Werribee farrowing pen caused a sharp increase in piglet pre-weaning mortality . In its standard format, the Werribee farrow-ing pen occupies 147% more floor space than the standard farrowing crate, but with statistically similar rates of stillbirths and pre-weaning mortality as the standard farrowing crate.
Ellipsoid farrowing crate
The ellipsoid farrowing crate was developed to give the lactating sow the ability to turn around while still protecting piglets. The side walls are concave with the top and bottom of side rails closer to the sow at the top and bottom of the rail. The ellipsoid crate gives sows improved access to piglets in terms of both visual and tactile interactions with only a minimal increase in space when compared with standard farrow¬ing crates.
Lou and Hurnik  reported that the ellipsoid farrowing crate was 9% larger in floor area than the stan¬dard farrowing crate. Sows turned 3600 an average of 40 times per day in the ellipsoid farrowing crate. The ellipsoid crate significantly reduced the rate of stillbirths compared to the standard farrowing crate. Pre-weaning mortality and number of pigs weaned per sow were similar in the ellipsoid and standard far¬rowing crates.
Outdoor English-style farrowing hut
All of the previously mentioned systems consider indoor alternatives to the farrowing crate. Among outdoor systems, significant differences were reported in pre-weaning mortality among farrowing huts. McGlone and Hicks  reported that the Quonset-style (American) farrowing hut had 19.7% pre-weaning mortality while the English-arc style farrowing hut had 11.2% pre-weaning mortality (a significant reduc¬tion).
Johnson et al.,  compared sow and piglet behavior and performance for sows farrowing in the English-style arc outdoor hut with sows and piglets in a standard indoor farrowing crate system. They observed no difference in stillbirth rates or pre-weaning mortality in the two diverse systems. Therefore, although the diverse environments caused significant behavioral differences (sows were much more active outdoor compared with indoors, for example), the outdoor English-style arc hut and the indoor farrowing crate resulted in similar sow and piglet performance.
Other alternative systems
Other proposed alternatives to the farrowing crate have been published. In some cases, higher pre-wean¬ing mortality was reported  in the alternative system compared with the standard farrowing crate. Reduced sow or piglet performance would not make an alternative a viable alternative since others suc¬cessful alternatives are published (Table 2). New systems will continue to be developed and they may be viable if sow and piglet productivity are similar among litters in the alternative and standard farrowing crate.
The economics of successful alternative farrowing systems does not relate to sow and piglet productivity because successful alternatives have comparable sow and litter performance as a standard crate. What is different among the published successful farrowing systems is that they require more floor space. In addition to space differences, the cost of construction materials, accessories, and utility expense must be evaluated in the context of determining the full cost of alternative farrowing systems.
Shown in Table 1 are the dimensions of the successful alternative systems that have been reported. Floor space of the alternatives averaged 48% more space when compared with the standard farrowing crate. The range in added space needed is from 9 to 147% more space for the alternatives.
Clearly, building cost is a significant cost of production. With productivity being the same, an alternative system that requires more space will increase the cost of production compared with the less space-occu¬pying standard farrowing crates.
Overall, farrowing facility alternatives are comparable to the farrowing crate in terms of production num¬bers. However, producers must keep in mind that all farrowing alternatives will have a great space re¬quirement than the farrowing crate. The ideal farrowing alternative must be able to sufficiently increase production to compensate for the decrease in number of sows farrowed per building. Furthermore, the ideal alternative must be able to efficiently conform to the dimensions of current farrowing buildings used in the industry. Overall, producers need to be aware that outside pressure from animal humane societies may force the swine industry to find alternatives to the modern farrowing crate.
1. McGlone JJ, Vines B, Rudine AC, DuBois P. The physical size of gestating sows. J Anim Sci 2004;(in press). 2. Curtis SE, Hurst RJ, Widowski T, Shanks RD, Jensen AH, Gonyou HW, Ban DP, Mueling AJ, Kesler RP. Ef¬fects of sow-crate design on health and performance of sows and piglets. J Anim Sci 1989;67:90-93. 3. Fraser D, Phillips PA, Thompson BK. Initial test of a farrowing crate with inward sloping sides. Livestock Production Science 1988;20:249-256. 4. McFarlane JM, Boe KE, Curtis SE. Turning and walking by gilts in modified gestation crates. J Anim Sci 1988;66:326-333. 5. McGlone JJ, Blecha F. An examination of behavioral, immunological and productive traits in four man¬agement systems for sows and piglets. Appl Anim Behav Sci 1987;18:269-286. 6. Collins ER, Kornegay Jr. ET, Bonnette ED. The effects of two confinement systems on the performance of nursing sows and their litters. Appl Anim Behav Sci 1987;17:51-59. 7. McGlone JJ, Morrow-Tesch J. Productivity and behavior of sows in level vs. sloped farrowing pens and crates. J Anim Sci 1990;68:82-87. 8. Stolba A, Wood-Gush DGM. The behaviour of pigs in a semi-natural environment. Anim Prod 1989;48:419-425. 9. Arey DS, Sancha ES. Behaviour and productivity of sows and piglets in a family system and in farrow¬ing crates. Appl Anim Behav Sci 1996;50:135-145. 10. Cronin GM, Lefebure B, McClintock S. A comparison of piglet productivity and survival in the Wer¬ribee farrowing pen and conventional farrowing crates at a commercial farm. Australian J Exp Agric 2000;40:17-23. 11. Cronin GM, Dunsmore B, Leeson E. The effects of farrowing nest size and width on sow and piglet behaviour and piglet survival. Appl Anim Behav Sci 1998;60: 331-345. 12. Lou Z, Hurnik JF. An ellipsoid farrowing crate: its ergonomical design and effects on pig productivity. J Anim Sci 1994;72:2610-2616. 13. McGlone JJ, Hicks TA. Farrowing hut design and sow genotype (Camborough-15 vs. 25% Meishan) ef¬fects on outdoor sow and litter productivity. J Anim Sci 2000;78:2832-2835. 14. Johnson AK, Morrow-Tesch JL, McGlone JJ. Behavior and performance of lactating sows and piglets reared indoors or outdoors. J Anim Sci 2001;79:2571-2579. 15. Bradshaw RH, Broom DM. A comparison of the behaviour and performance of sows and piglets in crates and oval pens. J Anim Sci 1999;69:327-333.
Table 1. Size of successful alternative farrowing systems.
Table 2. Production values for studies that compared crates with successful alternative non-crate farrowing systems.