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Chapter 14 Production systems for adult pigs.


The pig was a good choice for domestication largely because of its plasticity and outstanding biological efficiency. For an animal to be relatively plastic, it must bend, rather than break, when faced with environmental challenges. The pig does quite well at bending and adapting in a wide variety of environments. Signs of lack of adaptation in the adult pig focus on lower--but usually not zero--reproductive rates. Thus, during prolonged times of stress in the wild, conception rates and litter size might be reduced in the pig, while reproduction may completely stop in other wild species. When ovulation rate is reduced in a species that has only one offspring/pregnancy, reproduction may be delayed until the stress is relieved.

Around the world, pigs reproduce in cold and warm climates, in dry and humid climates, and at sea level and high altitude. Because of the extraordinary plasticity of the domestic sow, it is a challenge to define her specific environmental needs. Simply knowing the bare, essential needs for the sow leads to low reproductive performance. Instead, pork producers should seek the highest output possible within economic constraints. However, when economics is added to the equation, lower output may be accepted (pigs per sow per year) if input costs are low enough. On the other hand, in a high-investment facility, producers must have high output. The optimal situation is one with low-cost input and sustained, high output.

This chapter addresses the problem of finding the right system by addressing the two extremes: the high- and low-investment facilities. Once producers commit to a confinement building, their objective must be to maximize output from that investment. With a progressively lower investment, producers might be willing to accept progressively lower reproductive output. In all cases, the objective is to maximize output regardless of the investment in the production unit.


The choices discussed here refer mainly to gestation systems. Several other systems are in place in the breeding and farrowing areas, but typically, once a given system is decided upon in gestation, the breeding and farrowing choices are easier to make. On a weekly production schedule and with 3-wk weaning, the sow inventory falls in the following areas, as a percentage of the population:

* 14.3% in farrowing (3/21 sow groups)

* 28.5% in breeding and heat check (6/21 groups)

* 57.2% in gestation (12/21 groups)

Thus, the gestation unit will drive the rest of the system.

What system should be used in gestation and farrowing? The European magazine, Pigs (1994), recently concluded that the options to pork producers are:

* Outdoor production--Use of this system is increasing rapidly in Europe and involves housing sows in intensively managed pastures in a manner similar to how they might be kept indoors. Outdoor stock people have a philosophy that centers on animal care.

* Pens or yards with individual feeders--This system can be used indoors on slotted floors or bedded floors. Sow feed intake can be regulated by use of individual feeders.

* Electronic sow feeders--The electronic sow feeder business seems to rise and fall in the United States, but it has reasonable representation in Europe. Evidence is insufficient in the United States to recommend use of these systems, especially if the equipment is made in Europe and replacement parts and technical service are not readily available.

* Automated floor feeding--In this system, feed is provided on the floor, usually by use of an auger or by hand feeding. Because of the lack of control over individual feed intake, sows must be sorted by stage of gestation and condition. This means there must be fairly small social groups, which adds to the cost. Sow condition tends to be variable in this system.

* Trickle feeding--Also known as "Biofix," this system supplies feed at a very slow rate. Sows learn to be still and wait for feed because if they steal their neighbors' feed, their spot opens. After an acclimation period, sows are very quiet during feeding. This system uses specialized equipment, but is fairly simple. Developed in Sweden, the system really has not gotten started in the United States.

There are more system choices in the United States because legislation does not prevent the use of any system for pork production. The following system choices are available to U.S. producers in addition to the European systems:

* Stalls or crates--The crate is the most common system in the United States based on the number of sows. The overwhelming majority of new U.S. units use gestation crates.

Europeans do not consider some of the fairly common systems in use in the United States. These systems are not typically recommended:

* Tethers

* Group pens (indoor or outdoor) without control of feed intake

* Post-harvest foraging grain and other crops

* "Fend-for-themselves systems" in forests, swamps, or other uncontrolled areas. These are clearly not modern production systems.

Producers must first decide if gestating sows will be kept outdoors or indoors. Climate is a factor, but outdoor breeding in cold, northern climates does occur. Productive outdoor breeding and farrowing units are now found all the way from the tropics to Sweden, Denmark, and England. Confinement units are found in an equally wide range of climates.

The British seem to have revived outdoor production. Although encouraged earlier, a 1991 UK law forced producers to phase out and eventually abandon tethers and crates. Thus, they began to re-invent the outdoor system. As UK pork producers considered new facilities, they discovered that some producers were very efficient in using intensive outdoor units. Field data and some controlled studies showed outdoor productivity to be quite good.

An outdoor, low-intensity system is probably a bad idea. The word probably is used because if the inputs are low enough (say the pigs live in a forest or in a recently harvested field), it may still be cost effective. However, if sows are outside and not managed closely, herd productivity is low. Modern-day pork production-- the business--does not reward units with poor records, poor health management, and poor facilities. Some people assume that outdoor, intensive breeding/gestation/ farrowing means providing a few fences and letting the pigs fend for themselves in dirt lots. This is clearly not the intent of intensive, outdoor production.

If producers decide to bring the breeding herd inside, they must first decide if the hogs will be kept in groups or in individual pens. If they are in groups indoors, they could either be on slotted floors or on solid floors, or on solid floors with bedding. If they are housed individually, they are most likely to be on slotted floors. With these generalizations understood, the field data become a bit more difficult to interpret. When field data compare group pens versus individual stalls, the group-housed sows typically have bedding and solid floors while the individually housed sows have slotted floors. The comparison of the performance of indoor, crated sow herds on slats with that of sows in group-housed, outdoor herds with natural vegetation and bedded huts is clearly confounded--it is difficult to know which of the individual elements (floor type, social housing, space) might be responsible for production differences. In addition, units with sows in stalls typically have more complete records and they individually hand-mate or use artificial insemination, while many units that group-house sows may pen-mate and have less precise records.

The bottom line is that field data are always suspected of being inaccurate or unreliable, but they often have very large sample sizes. However, when field data support controlled studies, producers can begin to make important generalizations.

To make sense out of field and controlled studies, producers need an understanding of pig behavioral biology. With such an understanding, labor and facility decisions become more clear. Although producers may not fully understand everything about boar and sow sexual behavior, they can improve the process of designing facilities by making use of the present base of knowledge.


Among the many types of breeding areas, the "Lubbock" system is in common use. This system was first widely used by the original Lubbock Swine Breeders (then called DeKalb Swine Breeders, now a subsidiary of Monsanto). In the Lubbock system, recently weaned sows are placed in stalls and a boar is in a pen behind them (Figure 14-1).

The major disadvantage of the Lubbock breeding system is that the boars constantly stimulate the estrous sows and, as a result, sows may get tired or refractory to mating when put with a boar. One solution to the problem is to have a completely separate mating area where boars and sows meet for breeding. Another common alternative is to breed sows in the boar's pen or in the aisle. Diagrams of well-thought-out breeding designs for pen-mating, hand-mating, and AI facilities are available from Dr. Don Levis (1995), long-time faculty member at the Department of Animal Science University of Nebraska, Lincoln (now at Ohio State University).



At first thought, producers might expect pregnancy to be easy to maintain. However, the average farrowing rate in surveys of herds is often less than 80%--even the best farms have trouble keeping the farrowing rate above 90%. The typical 10% to 30% of pregnancies lost on commercial farms represents a huge economic loss. It is not clearly understood why farrowing rates are not near-perfect, but there are some clues.

It is known that in most species, including the pig, reproduction is very sensitive to stress. Stress can have profound negative effects on reproductive rates of pigs (stimulating puberty in gilts is the exception). Poor handling, heat stress, and social stress have significant effects on reproduction (the effects of social stress on reproduction are discussed later).


Sows seek isolation when they prepare for farrowing. Among outdoor sows, the behavior to seek isolation is quite strong. The only problem with isolation-seeking is that prefarrowing sows will "bother" the peri-parturient sows. For these reasons, individual housing is a reasonable biological choice during the peri-parturient and lactating phases. The important question becomes how to reduce piglet mortality, which was 15% in a recent national survey (Tubbs et al., 1993). On the best farms with the best-trained people and equipment, pre-weaning mortality can be less than 10%.

Reduced mortality can be achieved in two ways: (1) give the sow less room (with a farrowing crate) or (2) give her a great amount of room (in certain pen configurations). These options are discussed in the section on controlled studies.



The use of the outdoor system seems to be increasing in parts of Europe and North America but, in fact, is not a recent development. Some producers have been producing higher numbers of pigs per sow per year for many years in low-investment, high-output units. In most years in the UK record system, the indoor and outdoor units have similar productivity.

The output in terms of pigs per sow per year is similar in the indoor and outdoor units in the United Kingdom, even in 1988 (see Table 14-1). In many data sets, the outdoor system is slightly less productive on average. There is also similar productivity between indoor and outdoor herds in France. However, there is a trend that is quite annoying to the supporters of intensive, outdoor production for the outdoor system to have a greater pre-weaning mortality and, therefore, fewer pigs weaned. In the UK data presented, the outdoor unit had 0.2 fewer pigs weaned and in the French report, the outdoor units showed 1.4 fewer pigs weaned than the indoor unit. The increase in piglet mortality is thought to be due to a greater rate of crushing outdoors than indoors, on average. Once again, some producers can make the outdoor system a highly productive system. Note the excellent records for the one-third better producers using the outdoor system in France (Table 14-2).

There are very few intensive, outdoor units in the United States. The intensive, outdoor herd comprises less than 2% of all sows, even if the percentage of low-investment sows is a much greater percentage. The U.S. data represent a mixture of low-investment systems that includes only a few European-style, intensive outdoor herds.

Two sources of information with very large databases were examined for effects of indoor versus outdoor productivity: (1) The PigChamp database, which includes herds of a variety of genotypes and housing systems (see Table 14-3); and (2) the PigTales (1994) database from the Pig Improvement Company (PIC). The PIC[R] database is a much more narrow genetic base, but it includes a variety of housing systems.

The PigChamp[R] database was surveyed by Polson (1994) and includes a sample of closely scrutinized herds. Among the PigChamp database of over 143,000 sows, outdoor herds weaned about 1.7 fewer pigs per sow per year than did indoor herds.

Companies are sensitive to providing actual means for housing systems. They report odds ratios (odds of being among the 20% of poor herds). Indoor herds in the PIC database are eight times less likely to be in the bottom 20% of herds than are herds that have any sows outdoors.

The observations from both the PigChamp and PIC databases fit conventional, U.S. wisdom that indoor systems are better, on average, in terms of reproductive performance. However, it is important to remember that the conventional U.S. outdoor system is not typically the European-style intensive, outdoor system.

One outdoor hog enterprise was developed on the Southern High Plains as a 2,400-sow breeding and farrowing complex with off-site nurseries and growing-finishing buildings. Several 2,400-sow-intensive, outdoor herds were also established. While company records are confidential, it was revealed that output (pigs weaned per sow per year) was actually equal or better in the outdoor unit than in the indoor units for its first 3 yr of operation. The successful Plains unit had a few key features: Europeanstyle layout, European-style equipment, and a British herdsman. Two key features are clear--good equipment and highly qualified people.


Field data are available in both Europe and the United States to compare certain systems for indoor sows. The indoor systems discussed in this section are systems other than intensive, outdoor systems. Some field data on group pens might use a system that has sows indoors some of the time and outdoors some of the time.

Table 14-4 presents data from the United Kingdom on sow performance when pigs are housed with electronic feeders, group pens, and stalls and tethers. One problem for this type of summary is although both stalls and tethers house sows individually, they are not similar in the sows response to the system.

The British data in Table 14-4 clearly show that the three systems have similar reproductive performance--all systems produce within 0.7 pigs per sow per year. The only system with a hint of lower productivity is the group pen system. Experiences in the United States indicate that stalls and tethers should not be combined because they can result in strikingly different reproductive rates.

Field data from the United States do not entirely agree with UK data presented in Table 14-4 (but they may agree if stalls and tethers are separated). The PigChamp and PIC databases show trends in performance of sows in different systems.

Polson (1994), in a survey of PigChamp participants in the United States, found much better reproductive performance for sows in crates and tethers than for sow herds in pens or on pasture/dirt. The data clearly show that reproductive performance was better by 2.0 to 3.0 pigs per sow per year for sows kept in individual systems than for sows kept in social groups. Combining crates and tethers in the data set may not be such a good idea if the sow's reproductive performance was different in the two systems. However, in Polson's data set, which contained only a few herds with tethers, the pigs per sow per year were similar for the crate system (20.4 pigs weaned per sow per year from 112 herds) and for the tether system (20.7 pigs weaned per sow per year from six herds).

In the PigTales records, data comparing indoor and outdoor systems agree in general with the Polson (1994) data (see Table 14-5). PigTales estimates that herds with any degree of pasture/dirt outdoor production were eight times more likely to be among the bottom 20% of herds in its database compared with indoor herds. Herds with indoor (confinement) pens were five times more likely to be among the worst 20% of herds than were herds with gestation crates. PigTale's March 1994 report stated that herds with tethers had similar performance as herds with crates.



Modern publications comparing herd performance indoors with intensive, outdoor systems are rare. An investigation with nearly 300 gilts was recently completed at Texas Tech University, in which the confinement herd was restocked simultaneously with the establishment of an intensive outdoor unit. Fifty gilts of each of three genotypes started either indoor or outdoors. Genotypes were PIC Camborough-15 (C-15) or PIC Cam borough-Blue (C-Blue) or a cross of Yorkshire by Landrace (YL). The C-15 is a typical confinement line and the C-Blue was a line developed for outdoor production; it contained a portion of the British outdoor breed the Wessex Saddleback.

The outdoor herd was on pasture or dirt, depending on rainfall and season. Sows were kept in groups, fed on the ground, and contained by electric fence. The American-style porta-hut, bedded with wheat straw, was used to farrow the gilts and sows. Sows always had shade and during warm weather had a man-made mud wallow.

The indoor unit was on slotted floors in a mechanically ventilated building. Buildings were heated by gas furnace and cooled by water spray or drip in the summer. The farrowing rooms also were evaporatively cooled.

The interaction between environment and genotype was not significant. Each genotype responded about the same both indoors and outdoors. Other work has shown that genotypes by environmental interactions are found but, in this case, for example, the C-Blue did not do much better outdoors than the confinement line (the C-15).

Reproductive performance was much better indoors than outdoors during this first phase (Table 14-6). Indoor sows over the first two parities weaned 8.6 pigs/litter while outdoor sows weaned only 7.5/litter. Assuming equal litters per sow per year, indoor sows approached 20 pigs per sow per year, while outdoor sows weaned just over 17 pigs per sow per year.

The results from this controlled study fit nicely with the field data in the United States, suggesting indoor herds have higher reproductive rates than outdoor herds. But, the experiences on local farms and in Europe seem to be different than the U.S. field data and the results from the first phase of the Texas Tech University investigation. In examining the difference, the focus is on one key element--good equipment.

A major difference between a local farm and the Texas Tech University unit was that the local farm used an English-arc type of farrowing hut. The data in Table 14-7 show that litters farrowing in the English-style hut with 31% more floor area (9 ft wide and 5 ft deep, or 2.8 x 1.5 m or 4.2 [m.sup.2]) had lower mortality and weaned more pigs than did sows in the American-style hut (5 ft wide and 7 ft deep, or 1.5 _ 2.15 m or 3.2 [m.sup.2]). In the American-style hut, sows weaned 8.3 pigs/litter, while in the Englishstyle arc, sows weaned 10.3 pigs/litter. This is an amazing difference of over 4.5 more pigs per sow per year in the English-style arc than in the American-style hut. This finding may help explain the phenomenal productivity of the local outdoor unit. The results also give encouragement to pork producers who prefer the outdoor system and have the land and climate suitable for such a system.


Sows housed in groups often, but not always, have lower reproductive rates than sows housed in crates (see previous field data). Texas Tech University initiated a study in 1994 to compare reproductive performance and other measures for sows in groups of three or housed in crates. Group-housed sows were placed in a pen and videotaped. Initial fights and a competitive feed test determined socially dominant, intermediate, and submissive sows. The results were striking (see Table 14-8).

In comparing the average fertility of group-housed sows and sows in individual crates, the means are quite similar. However, not all group-housed sows have similar reproductive performance. Socially subdominant sows had clearly suppressed reproductive rates. Socially intermediate sows had lower farrowing rates, fewer pigs born, and fewer pigs weaned/litter. Socially dominant sows had about as good a reproductive rate as sows kept in gestation crates.


Many reports of field data and summaries of controlled studies group individual housing systems. However, not all individual systems produce similar sow behavior, physiology, and performance. Results from the study described previously clearly showed that one type of outdoor hut (that provided more room) produced many more weaned piglets than did other systems. The same might be true for indoor gestation and farrowing systems.

The two most common indoor systems for gestating and farrowing sows are the crate and tether. In some cases, countries have legislated these systems as being similar and in others as possibly being different. As of 1991, UK pork producers cannot install either crates or tethers in new facilities. In the European Union, tethers are now banned--crates will be banned on all farms by 2013.

Table 14-9 presents data from McGlone et al. (1994) in which behavior, physiology, and reproductive performance for gilts and sows in crates or girth tethers during gestation and lactation were compared. Sows (but not gilts) in gestation/lactation crates had more pigs born and weaned than the sows in the girth tether. The suppressed reproduction among tethered sows was an effect during gestation because the stillbirth and pre-weaning mortality data were statistically similar for the two systems. The girth tether either suppressed ovulation rate or caused more early embryonic mortality. The gestation crate would be clearly favored in terms of pork producer economics, based on this study.


The McGlone et al. (1994) data show that outdoor huts can strongly influence sow and litter productivity. In addition, by providing more room in an outdoor hut, producers can save baby pigs and wean more pigs/sow. What if more room is provided for sows indoors?

Many older pork producers remember that a greater piglet mortality was sustained when sows were farrowed in pens. Many farrowing pen designs have come and gone, but in today's high-sanitation confinement units where there is great control over waste, producers cannot easily use straw or bedding of any kind. Therefore, one important question is, can producers improve the quantity and quality of space without compromising piglet mortality?

A 1990 Texas Tech University study examined sows that were farrowed in level or sloped crates or pens (McGlone and Morrow-Tesch, 1990). The crates were standard 5 x 7 ft crates (1.5 x 2.15 m, with a 0.6 x 2.15 m sow area). The pens had an area of 7 x 7 ft (2.15 x 2.15 m) with a creep area of 7 x 2 ft (2.15 x .55 m).

Sows in the level pen crushed more piglets than did sows in the level crate, confirming why the industry moved to the farrowing crate (Table 14-10). However, when the sow was provided the increased area and when the pen was sloped 8%, the crushing rate was reduced in the pen. The sloped pen gave the same high weaning rate as the level crate. Interestingly, there was a classic interaction in that the sloped crate actually increased crushing of piglets. The crushing of piglets in the sloped crate occurred primarily during farrowing (as pigs were born, they were pressed against the back of the farrowing crate). The crushing in the level crate was throughout the 28-d lactation period.

The sloped pen provided more room, but it also changed the quality of space. Sows had to stand and lie down much more carefully in the sloped pen. They rested either with their udder pointed downhill or with their head uphill most of the time. Thus, producers can provide more room, without bedding, and obtain the low mortality rates without use of the crate--but with a cost. The sloped farrowing pen requires 40% more room; this added room would add to construction costs.


Producers must have an understanding of pig behavior and physiology to understand pig welfare. While other physiological systems are changed in stressful environments, reproductive performance is considered primarily as a sensor of physiology. The premise includes two main points: (1) If an environment is stressful to the sow, she will have reduced fertility (or reduced pigs per sow per year); and (2) if an environment supports a high rate of reproduction, the environment cannot be said to be stressful. Data from field studies and controlled studies provide some generalizations about how sows perceive their environments (in terms of reproductive responses). Taken with behavioral measures, producers should be able to design facilities that are comfortable for the breeding herd, promote sound well-being, provide relatively high economic returns, and are acceptable to consumers.

Human perception can be the only measure taken into consideration in legislating appropriate systems. Even if decisions are not based on science, producers may still be able to have high productivity in alternative systems. This is possible because the sow is highly plastic and because tools are available to design highly productive systems both indoors and outdoors.

The two most important elements to successful pork production are to have good pig people (Hemsworth and Barnett, 1990; Hemsworth et al., 1994) and good equipment. Good people understand, through intuition or training, that sows, boars, and growing pigs have behavioral needs. Good equipment is designed to accommodate the behavioral biology of the pig. Field data and controlled studies show trends in reproductive rates under common systems. The pig is amazingly plastic and can perform well in an plethora of systems. When pig behavioral needs are met and when the environment accommodates the appropriate physiology, producers find a high level of productivity that rewards workers and owners.


In spite of the large number of countries around the world and an apparent wide variation in views about pig biology and management, a few common building layouts are found around the world. Figures 14-2 through 14-6 show some examples.


This chapter addresses the choices of production systems for sows in response to major shifts in the structure of the swine industry. The discussion focuses on the selection of appropriate housing and husbandry conditions during gestation and lactation. Information is presented from research data and actual production data, primarily from Europe and the United Kingdom, on reproductive performance in conventional indoor confinement systems at one extreme versus outdoor intensive production systems at the other extreme. Behavior and physiology are affected by the level of stress associated with the environment in which sows are kept, which in turn affect reproduction performance. Based on the information obtained from comparing different production systems for gestating and lactating sows, facilities may be designed that provide comfort and well-being to the animal and relatively high economic returns to the producer. The appropriate facility design depends on many factors, including geographic location, climate, market infrastructure and population density, and environmental concerns.







1. What is meant by "confounding of variables" when farm records are compared? Consider the example of typical indoor versus outdoor systems. How many variables are different when one farm's records are compared with another farm's records?

2. Historically, a low-input production unit, like an outdoor unit, also is low output. Is it possible to have a lower-input farm with a high output?

3. Compare the outdoor system of 50 years ago with a modern, intensive outdoor system.

4. Why do you think the gestation crate was not banned in most of Europe in early legislation, but the tether was (both are a method of individually housing sows)?

5. From an economic point of view, why is the gestation crate favored for indoor pigs compared with group housing? Is economics the only criterion that should guide a producer's decision about a housing system?

6. Ergonomics is the study of human time and motion. In the pig industry, particularly in the breeding area, ergonomic evaluations become important. Do you think it takes longer to pen-breed, hand-breed, or breed by AI? You might find literature by Dr. William (Billy) Flowers from North Carolina State University of value in addressing this question.


Berger, F., J. Dagorn, M. le Denmat, J. P. Quillien, Vaudelet, J. C., and J. P. Signoret 1997. Perinatal losses in outdoor pig breeding. A survey of factors influencing piglet mortality. Annales de Zootechnie. 46:321-329.

Hemsworth, P. H. and J. L. Barnett. 1990. Behavioural responses affecting gilt and sow reproduction. J. Reprod. Fert. Suppl. 40:343-354.

Hemsworth, P. H., G. J. Coleman, and J. L. Barnett. 1994. Improving the attitude and behaviour of stockpersons towards pigs and the consequences on the behaviour and reproductive performance of commercial pigs. Appl. Anim. Behav. Sci. 39:349-362.

Le Denmat, M., J. Dagorn, A. Aumaitre, and J. C. Vaudelet. 1994. Outdoor pig breeding in France. Pig News Info.

Levis, D. G. 1995. "LEVIS" swine breeding facilities. Extension Report. University of Nebraska, Lincoln.

McGlone, J. J. and J. Morrow-Tesch. 1990. Productivity and behavior of sows in level vs sloped farrowing pens and crates. J. Anim. Sci. 68:82-87.

McGlone, J. J. and T. A., Hicks, 2000. Farrowing hut design and sow genotype (Camborough-15 vs 25% Meishan) effects on outdoor sow and litter productivity. Journal of Animal Science. 78:2832-2835.

McGlone, J. J., J. L. Salak-Johnson, R. I. Nicholson, and T. Hicks. 1994. Evaluation of crates and girth tethers for sows: Reproductive performance, immunity, behavior and ergonomic measures. Appl. Anim. Behav. Sci. 39:297-311.

Nicholson, R. I. 1994. Gestating sows: Influence of housing, rearing environment, gut-fill, and pharmacological manipulations on stereotyped behavior. Ph.D. dissertation, Texas Tech University, Lubbock.

Pigs. 1994, October. European housing laws mean simpler systems for pigs. Pig-Misset.

PigTales. 1994, March. Pig topics. Series 11, Number 2. Pig Improvement Company, Inc., Franklin, KY.

Pig Year Book. Various years. Meat and Livestock Commission, Milton Keynes, UK.

Polson, D. 1994. Problem-solving in swine breeding herds: Methods for analyzing production problems, and assessing herd-level risk factors. Ph.D. dissertation, University of Minnesota.

Tubbs, R. C., S. Hurd, D. Dargatz, and G. Hill. 1993. Preweaning morbidity and mortality in the United States swine herd. Swine Health and Production. 1:21-28.


Texas Tech University has a Pork Industry Institute home page at:

Temple Grandin has a home page that provides information on handling pigs and provides some diagrams:

Grandin's design of pig chutes is found at:

The University of Nebraska has a home page that includes information on pork production. One site, designed by Don Levis et al., contains information on a spring-loaded gate latch for swine breeding facilities:

The Midwest Plan Service has many publications available at a reasonable cost:
TABLE 14-1
Comparison of Outdoor and Indoor Herds in the United Kingdom in 1988.


Litters per sow per year            2.2             2.3
Pigs born alive/litter             10.4            10.7
Pigs weaned/litter (a)              9.4             9.6
Mortality, % of born alive         10.2            10.9
Pigs weaned per sow per year       20.9            21.8

(a) This measure was not in the original
paper; it was obtained by calculation.

Source: Adapted from MLC Pig Year Book (1989).

TABLE 14-2
Comparison of Outdoor and Indoor Herds in France in 1993.

                                ALL OUTDOOR  BEST ONE-THIRD   NATIONAL
MEASURE                            HERDS     OUTDOOR HERDS   AVERAGE OF
                                                             ALL HERDS

Litters per sow/yr (a)              2.3            2.4           2.4
Pigs born alive/litter             10.8           11.3          10.9
Pigs weaned/litter                  9.1            9.7           9.5
Mortality, % of born alive (a)     10.8            9.3           6.9
Pigs weaned per sow per year       21.3           23.2          22.7

(a) This measure not in the original
paper; it was obtained by calculation.

Source: Adapted from Le Denmat et al.
(1994) and Berger et al. (1997).

TABLE 14-3 Comparison of Outdoor and Indoor Herds in the United
States. From a Survey of 143,695 Sows Participating in the PigChamp
Recordkeeping System. Data Represent Herds that Hand-Mated and Were
on a Weekly Farrowing Schedule.

                                OUTDOOR     INDOOR
MEASURE                        HERDS (a)   HERDS (a)

Litters per sow per year          2.1         2.3
Pigs weaned/litter                8.6         8.7
Pigs weaned per sow per year     18.1        19.8

(a) Rounding causes numbers to not precisely multiply and agree.

Source: Adapted from D. Polson (1994).

TABLE 14-4
Comparison of Indoor Systems in the United Kingdom in 1993.

                                   ELECTRONIC                   AND
MEASURE                            SOW FEEDERS   GROUP PENS   TETHERS

Litters per sow per year               2.3          2.3         2.3
Pigs born alive/litter                10.7         10.9        10.7
Pigs weaned/litter                     9.4          9.5         9.5
Mortality, % of born alive            12.0         12.6        11.3
Pigs weaned per sow per year (a)      21.7         21.0        21.7

(a) Numbers of pigs weaned per sow per year do not agree with other
data in the table, but are presented as published. Rounding errors
probably explain the discrepancy.

Source: Adapted from MLC Pig Year Book (1994) and MLC pigplan data
(adapted from Pigs, October, 1994).

TABLE 14-5
Comparison of Reproductive Performance for Sows
in Three Common Systems in the United States.

                             CRATE OR          PASTURE OR
MEASURE                       TETHER    PEN     DIRT (a)

Farrowing rate, %              83.8     78.2      78.2
Pigs born alive/litter         10.2     10.1       9.9
Pigs weaned/litter (b)          8.98     8.42      8.01
Mortality, % of born alive     12.0     16.6      19.1
Pigs weaned per sow per
  year (c)                     20.6     18.5      17.6

(a) This system is not the intensive, outdoor system.

(b) Calculated from other data. Rounding effects probably
explain the discrepancy.

(c) Calculated assuming 2.3 litters per sow per year for
crates/tethers and 2.2 for others.

Source: Adapted from Polson (1994).

TABLE 14-6
Farrowing Environment and Sow and Litter Performance.
Data in Table Are Least Squares Means-Averaged Over
the First and Second Parities.
MEASURE                           INDOORS   OUTDOORS   SE (a)     (b)

Number of litters                 148        210          --      --
Number born/litter                 11.0       11.0       .27     .97
Number born live/litter             9.9       10.6       .30     .08
Number found dead/litter            1.47       0.38      .15     .0001
Birth weight alive, lb/piglet       4.1        4.2       .06     .17
Number of pigs weaned/litter        8.6        7.5       .28     .007
Pre-weaning mortality, %           12.3       27.5      2.17     .0001
Weaning weight, lb/pig             14.3       15.3       .48     .106
Total weaning weight, lb/litter   120.5      114.6      4.45     .30
Sow farrowing weight, lb          454.8      469        5.44     .11
Sow weaning weight, lb            381.7      400.7      6.59     .079
Sow lactation weight loss, lb      72.0       66.6      3.37     .21
Lactation length, days             28.1       25.7       .59     .007

(a) SE is the standard error of the mean.

(b) P-value (probability) for environment effect.

Source: Adapted from Nicholson (1994) Texas Tech University.

TABLE 14-7
Performance of Outdoor Sows Farrowing in American Style Port,
Huts or English Style Arc Huts. Huts Were Made From Galvanized
Steel by the Porta Hut Company.

MEASURE                                ENGLISH STYLE

Number of litters                           11
Number barn alive/litter             11.0 [+ or -] 0.88
Number found dead/litter             0.18 [+ or -] 0.25
Birth weight, lb/piglet              4.36 [+ or -] 0.24
Piglets weaned/litter               10.32 [+ or -] 0.86
Litter weaning weight, lb/litter   128.19 [+ or -] 12.23
Number of piglets that died          0.73 [+ or -] 0.05
Mortality, %                         6.83 [+ or -] 5.94
Sow Farrowing weight, lb           407.30 [+ or -] 17.24
Sow weaning weight, lb             359.58 [+ or -] 18.37
Days of lactation                   27.92 [+ or -] 1.71

MEASURE                               AMERICAN STYLE      P-VALUE (a)

Number of litters                           64                --
Number barn alive/litter              9.9 [+ or -] 0.38      0.220
Number found dead/litter             0.45 [+ or -] 0.11      0.320
Birth weight, lb/piglet              4.11 [+ or -] 0.11      0.400
Piglets weaned/litter                8.21 [+ or -] 0.38      0.028
Litter weaning weight, lb/litter   110.76 [+ or -] 5.47      0.198
Number of piglets that died          1.68 [+ or -] 0.22      0.087
Mortality, %                        18.97 [+ or -] 2.61      0.065
Sow Farrowing weight, lb           406.19 [+ or -] 7.90      0.950
Sow weaning weight, lb             358.03 [+ or -] 8.28      0.940
Days of lactation                   27.95 [+ or -] 0.77      0.980

(a) Treatment effect.

Source: Adapted from McGlone and Hicks (2000).

TABLE 14-8
Comparison of Crated (individually) Housed Sows and Group-
Housed Sows in Terms of Reproductive Performance.


Farrowing rate, %     100     90.4      100
Pigs born/litter       13     11.1       12.1
Pigs weaned/litter      9.1      9.3    10.2
Pigs weaned per
  sow per year (a)     20.9   20.5      23.4


Farrowing rate, %        85.7          85.7
Pigs born/litter         10.2          10.9
Pigs weaned/litter        7.9           9.7
Pigs weaned per
  sow per year (a)       16.6          20.4

(a) This measure was not in the original paper; it was obtained by
calculation, assuming 2.3 litters per sow per year for crated and
dominant sows and 2.1 litters per sow per year for intermediate and
submissive sows.

Source: Adapted from Nicholson (1994) Texas Tech University.

TABLE 14-9
Reproductive Performance of Sows Kept During Gestation and
Lactation in Either a Crate or a Girth Tether. Data for Gilt
Litters Were not Different among Systems, but for Sows (N = 112
gilts and N = 59 sows), the Number of Pigs Born and Weaned Were
Fewer (P < .05) for the Girth Tether System than for the Crate

MEASURE                    CRATED         GIRTH TETHER

Farrowing rate, %           89.6              83.3
Pigs born/litter      10.6 [+ or -] .5   9.1 [+ or -] .5
Pigs weaned/litter     9.4 [+ or -] .4   8.1 [+ or -] .4
Pigs weaned per sow
  per year (a)              21.6              18.6

(a) Calculations assume 2.3 litters per sow per year for each
system (farrowing rates were not significantly different between

Source: Adapted from McGlone et al. (1994).

TABLE 14-10
Comparison of Sow and Litter Performance for Level and Sloped
Crates and Pens (N = 40 sows and litters).

                                     LEVEL      LEVEL      SLOPED
MEASURE                              CRATE       PEN       CRATE

Pigs born alive/litter                8.3        9.1      '10.4
Crushed piglets/litter (a)            0.51       1.53       1.29
Mortality, % (a)                     10.8       27.1       17.2
Pigs weaned per litter (a)            8.2        6.6        7.6
Pigs weaned per sow per year (b)     18.9       15.2       17.5

                                     SLOPED     POOLED
MEASURE                               PEN         SE

Pigs born alive/litter                9.6        0.71
Crushed piglets/litter (a)            0.27       1.0
Mortality, % (a)                      9.1        4.5
Pigs weaned per litter (a)            8.4        0.51
Pigs weaned per sow per year (b)     19.3        --

(a) Significant interaction, P < .05.

(b) Calculations assume 2.3 litters per sow per year for each
system (farrowing rates were not significantly different between

Source: Adapted from McGlone and Morrow-Tesch (1990).
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Title Annotation:Section IV Housing, Environment, and Nutrient Management
Publication:Pig Production, Biological Principles and Applications
Geographic Code:1USA
Date:Jan 1, 2003
Previous Article:Chapter 13 Creating a comfortable microenvironment for pigs.
Next Article:Chapter 15 Production systems for growing pigs.

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