Swine Management Systems Intensive

William L. Flowers

Department of Animal Science, North Carolina State University, Raleigh, North Carolina, U.S.A.


Swine grow rapidly and produce large numbers of offspring. Intensive management systems are designed to allow swine to reach their full biological potential in terms of fecundity and growth. The primary management strategy upon which these systems are based is for humans to provide for the specialized needs of pigs during each stage of their reproductive and growth cycles. For most systems, there is a reproductive component that involves management of sows during breeding, gestation, and lactation and a growth component for market animals that usually is divided into nursery and finishing phases based on the physiological maturity of the pig (Fig. 1).


Many intensively managed sow farms operate on a weekly production schedule. In this type of system, a new group of sows is bred each week. As a result, there usually are 20 different groups of sows on farms at any given time one group that is being bred; 16 groups in gestation; and three groups in lactation. Sows are bred via artificial insemination and boars that produce semen are housed at physically separate locations called boar studs.[1]

Semen Production

Boars enter studs when they are 6 9 months old and remain in production for about 1 yr. Prior to their entry, boars are placed in isolation for 60 90 days. During isolation, serological testing is conducted at least three times to ensure boars are free of diseases before they enter production. Boar studs consist of a boar area and a semen laboratory. The boar area is mechanically ventilated with adaptations such as cool cells and misters to keep the boars cool during the summer. Boars are housed in pens or stalls. Studs that use stalls have at least two different sizes to accommodate size differences between young and old boars. Employee access between the laboratory and boar area is either restricted or workers are required to shower and change clothes when they move between the two areas.

At the studs, semen is collected, evaluated, and extended. Ejaculates that contain less than 70% normal spermatozoa are discarded. The production process is automated and machines are programmed to dilute, extend, and package semen. Most boars are collected every 4 5 days and produce between 1700 and 3000 insemination doses per year. Semen is shipped to sow farms on a regular schedule based on the number of animals scheduled for weaning at the farm (Fig. 1). One insemination dose from each batch is retained by the stud and used to monitor changes in motility. This test sample is evaluated daily and if its motility drops below 70%, the sow farms are contacted and instructed not to use any remaining samples.

Breeding and Gestation Management

Sows in breeding and gestation are housed in environmentally controlled buildings that contain special adaptations for cooling during the summer. Tunnel ventilation in which air is pulled lengthwise through the barn at high speeds is common (Fig. 2). Cool cells are modified air inlets that cool the air as it enters the barn. Buildings without cool cells rely on drippers or misters that spray sows with water at regular intervals.

Biosecurity and serological testing are critical for sow farms. Replacement gilts are isolated and tested in a similar manner as boars. Many farms are called "closed herds'' because they raise their own replacement gilts. Workers and visitors are required to shower and change clothes before they are granted access to sow farms. Types of vaccinations used vary, but sows usually are vaccinated at weaning and gilts prior to breeding.

Detection of estrus and the insemination of receptive females are usually performed separately. Weaned sows are placed in breeding stalls or pens in one location of the barn and checked for estrus via boar exposure. Sows that exhibit estrus are moved to a separate location, where they are inseminated. On some farms, two different groups of workers perform

Fig. 1 Schematic diagram of movement of semen and pigs for intensively managed swine operations.

detection of estrus and breeding. On other farms, the same personnel perform both functions, but detection of estrus is conducted first and breeding does not begin until all the sows in estrus have been identified.

On many operations, once sows are bred, they remain in that location until they are ready to be moved into farrowing rooms. On other farms, pregnant sows are moved to a new location between 30 and 40 days after breeding. The first month after breeding coincides with implantation, so minimizing handling of animals and other types of activities that might disrupt this process is important. It is also during this period that pregnancy diagnoses are conducted. Real-time ultrasonography can be used effectively as early as 24 days after breeding to determine if sows are pregnant. Nonpregnant sows are identified, removed, and rebred.

Sows are typically fed individually during gestation and receive different amounts of feed based on their body condition. During the first 30 days post-breeding, all sows are fed the same amount regardless of body condition, because high levels of feed intake during this period have been associated with an increased occurrence of embryonic mortality in some herds. After day 30, the body condition is assessed visually by examining areas around the sow's shoulders, hips, and tail and via palpation of her backbone. During the next 60 days, sows in good body condition remain on the same level of feed as received previously and those in poor body condition are offered additional feed. Feeding levels are increased gradually with the goal of replenishing the sow's body condition by day 90 of gestation. Finally, all sows usually receive additional feed between days 90 and 114, regardless of body condition, to accommodate the period of rapid fetal growth that occurs during this time.

Lactation Management

Sows are moved from gestation barns around day 110 of gestation and placed in farrowing crates. The farrowing rooms are usually designed such that air used for ventilation enters a hallway in which it can either be warmed or cooled before it is allowed to enter the rooms in which the sows and piglets are housed (Fig. 2). This allows producers to regulate the thermal

Fig. 2 Diagrams of specialized ventilation systems for breeding and gestation barns (tunnel ventilation) and farrow ing barns (end wall ventilation).

environment very precisely and prevent baby pigs from being exposed to drafts. In addition, supplemental heat sources such as heat pads or heat lamps are located in each crate. These allow producers even more control of the thermal environment to which the baby pigs are exposed. Sows are monitored closely prior to farrowing and once farrowing begins, employees check sows visually and remove piglets from the birth canal manually if necessary.

Immediately after farrowing, it is critical that baby pigs receive adequate amounts of colostrum. Colostrum provides protection from diseases via passive immunization and is a rich source of energy and protein. Employees assist small or weak pigs with nursing activities during their first 24 48 hr of life. After pigs have received adequate colostrum, a common strategy is to standardize the number of piglets that each sow in the group nurses. This process is called "cross-fostering'' and helps minimize the metabolic demands of lactation for sows and maximize nursing opportunities for the baby pigs.

Sows typically mobilize body tissues and lose weight during lactation. Excessive loss of body tissues can negatively affect milk production and subsequent reproductive performance. The best way to prevent this from happening is to maximize nutrient intake of sows during lactation. As a result, lactation diets are nutrient dense containing high levels of energy and protein. In addition, it is common for sows to be fed three to four times per day during lactation or have water added to their feed in attempts to increase feed intake. Most farms allow sows to lactate between 18 and 24 days. There tends to be an inverse relationship between lactation length and the subsequent reproductive performance of sows and the growth of the weaned piglets. As a result, most farms have a minimum lactation length of 15 16 days. After weaning, sows are moved to the "heat check'' area of the breeding barn and normally exhibit estrus in 4 7 days.


The growth component of pigs in intensive management systems is divided into nursery and finishing phases. Pigs enter the nursery phase when they are about 3 weeks of age and weigh between 7 and 10 kg. They leave the nursery phase and enter the finishing phase between 9 and 10 weeks of age when they typically weigh between 20 and 30 kg. In most intensive systems, the emphasis for management shifts from weekly to group schedules and pigs from several different locations are co-mingled or housed at a common location (Fig. 1).

Nursery Management

Two of the biggest challenges in the management of nursery pigs are biosecurity and assisting them with the transition from a liquid (sow's milk) to a solid diet. In intensively managed systems, biosecurity primarily is accomplished in all-in, all-out management and early identification, removal, and treatment of sick pigs. Employees typically observe animals daily during the nursery phase and remove, isolate, and treat pigs that show clinical signs of illness. Once removed, these pigs seldom are reintroduced. These two strategies reduce the exposure of pigs to disease and limit the spread of organisms that do manage to enter the system.

The transition of nursery pigs from a liquid diet to a solid diet is accomplished through diet formulation. Piglets are fed three to four different diets in a specific sequence. The first diet contains highly digestible, nutrient-dense ingredients and often includes milk-based products such as whey. These are usually referred to as starter diets and are fed frequently to pigs in small amounts. Milk-based products are gradually replaced by corn, soybean meal, and other plant-based ingredients in the subsequent diets. The final diet nursery pigs are fed usually does not contain any milk-based ingredients. At the same time the formulation of the diet is changing, nursery pigs are fed larger amounts of feed less frequently so that by the end of the nursery phase there is always feed present in the feeder and pigs regulate their own intake.

Finishing Management

The finishing phase of production lasts between 15 and 18 weeks and pigs are usually sold when they are between 110 and 130 kg. Nutrition is the primary focus. When pigs enter the finishing phase of production, they typically are segregated by sex (Fig. 1). Barrows are sent to one farm and gilts to another. The rational behind this is that gilts and barrows have different nutritional requirements and feed intakes. Split-sex feeding allows producers to formulate diets better suited for each sex. In addition, as pigs increase in size, their nutrient requirements and feed intake also increase. Feed intake typically increases at much faster rates than their nutrient requirements, so the nutrient density of finishing diets usually decreases as animals get older. Finally, there is an inverse relationship between ambient temperature and feed intake for swine, so during the warmer months of the year, seasonal adjustments are often made in the formulations of finishing diets. Thus, nutrition management during the finishing phase of production attempts to provide feeds that match the nutrient needs of the animals as closely as possible. Therefore, it is common for there to be as many as eight different diets fed to pigs during the finishing phase.


The distinguishing characteristic of intensive management systems for swine is specialization, not size. Virtually every phase of the production process occurs at separate locations and is managed by employees trained specifically for a given production phase.

Moreover, in the case of reproductive management, further specialization has occurred in that within the same barn, there is a segregation of animals and employees based on routine tasks.


1. Flowers, W.L. Artificial insemination, in animals. In Encyclopedia of Reproduction; Knobil, E., Neill, J.D., Eds.; Academic Press: San Diego, 1999; Vol. 1, 291 302.

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