In today's production systems, facility utilization during the grower stage often takes a back seat to maintaining all-in, all-out pig flows.

At one time, it was fairly easy to define the stage of production related to the growing pig.

In the mid-'70s, many producers had separate nursery, growing and finishing facilities. These were often managed as continuous-flow production units.

The advantage of this type of facility flow was that it maximized space utilization. Each facility was generally full (or overfilled), with stocking density based on final weight of the pigs.

Space Allocation

In today's high-health production systems, facility utilization during the growing stage often takes a back seat to maintaining all-in, all-out pig flows.

However, in nursery-finisher pig flows, facility utilization remains an issue for the nursery phase.

In a recent review of space allocation trials for nursery pigs, Harold Gonyou from the Prairie Swine Centre in Saskatchewan, Canada, and others determined that the space requirement for the nursery and growing pig that resulted in maximum daily gain and daily feed intake was defined by the following equation:

Area (in sq. ft./pig) = 0.217 × BW.667, where BW or bodyweight is in pounds.

In general, this equation means that for each 3% reduction in space allocation, there is a corresponding 1% reduction in overall daily gain and feed intake in fully slotted-floor facilities (See Table 1, page 22).

While many nursery units “plan” for 3 sq. ft./pig, in reality, the actual space allocation varies considerably, depending on output from the farrowing facility, and the final weight of the pigs prior to being removed and relocated to finishing facilities.

Wean-to-Finish vs. Nursery-Finisher Systems

Are there differences in performance for pigs housed in nurseries and finishers vs. pigs raised in wean-to-finish facilities?

If the pig's needs are provided for in both types of production facilities, there is no reported difference in performance.

However, it was quite common in the mid-1990s, when wean-to-finish technology was being developed, for proponents of wean-to-finish systems to suggest a major improvement in average daily gain for wean-to-finish-housed pigs vs. pigs housed in nursery and finisher facilities.

In research trials where the feeder type, feeder space, drinkers, etc. were the same between nursery and finishing facilities and wean-to-finish facilities, there has been no recorded difference in pig performance.

In actual production systems, differences between these two types of facilities are often cited for the reported differences in performance.

For example, when wean-to-finish facilities are double-stocked (with twice as many pigs per pen as there will be during the finishing stage), it is not uncommon to expect a 0.10 lb./day reduction in average daily gain compared to pigs at standard stocking rates in nursery facilities.

One of the main reasons for this decrease in early wean-to-finish performance appears to be a reduction in feeder and drinker space per pig and the impact of group size, especially in small-pen facilities that house from 25 to 50 pigs/pen.

Deciding What to Build

Should you build a nursery and multiple finishers, or should you consider a wean-to-finish production system?

The answer depends in part on your current production facilities, and how the new facilities would impact pig flow.

However, let's use an example to demonstrate how some producers have thought outside the box to remain competitive.

It costs approximately $140/pig space to build a nursery today, with pig space defined as 3 sq. ft./pig. Wean-to-finish facilities cost an estimated $225-240/pig space, with pig space defined as 7.5 sq. ft./pig.

When double-stocked and used as a nursery facility, wean-to-finish facilities have a capital cost of $112-120/pig space, with pig space defined as 3.75 sq. ft./pig. In contract situations, if the contract has ended, the space can be used as a wean-to-finish or finishing facility. This makes it more acceptable to lenders, since the risk associated with future use is reduced.

The challenge with this situation is the large group sizes that are required to flow a double-stocked, wean-to-finish room and barn site on an all-in, all-out production basis.

Heat Relief

Data suggests that the growing pig of today, compared to its predecessor of 20 years ago, generates higher levels of heat production (Table 2). Scientists have known for a number of years that deposition of lean releases more heat than deposition of fat.

With the pork industry making great strides in increasing the rate of lean growth and decreasing the rate of fat deposition, it is easy to understand why this situation is occurring. This has tremendous implications in our expectations for a ventilation system.

With greater heat output, ventilation systems during the growing stage of the pig are more likely to be operating in the heat relief mode vs. the minimum ventilation mode.

This increase in heat output of the pig also fits quite nicely with the industry's growing adoption of wean-to-finish facilities.

The excellent growth of pigs in many wean-to-finish facilities also suggests that heat relief should become a higher priority for the late nursery phase of production in conventional nursery facilities.

While the industry routinely utilizes drippers and misting systems for evaporative cooling for finishing hogs, it has been slow to recognize that growing pigs also suffer depressions in performance due to hot weather.

It is not uncommon in the Upper Midwest to have swine nursery and grower units experiencing temperatures in the pig zone in the upper '90s for many days during June, July, August and early September. The lower critical temperature for the 50-lb. pig is thought to be in the range of about 70° F.

Research data suggests that when the temperature in the pig zone is above 85° F, the growing pig begins to adapt its behavior to reduce the impact of heat on its well-being. This adaptation includes a reduction in feed intake, fouling of partially slotted pens, increased respiration rates, and modification of eating habits and drinking patterns.

The recommendation for 50-lb. pigs is that ventilation rates be maximized when the temperature reaches 85° F. The Midwest Plan Service recommends that the ventilation rate be set at 35 cfm/pig for pigs from 30 to 75 lb., and at 75 cfm/pig for pigs from 75 to 150 lb. in hot weather. Drafts in the pig zone are encouraged to provide heat relief.

To achieve the benefits of evaporative cooling, the recommendation is to wet the pigs and then allow them to dry. A good starting point for 50-lb. pigs is a set point of 85° F, a 2-3 minute on-time and a 20 minute drying period. A flood-type nozzle vs. a misting nozzle is recommended. The goal is to wet the pigs and allow the water to evaporate, rather than to evaporate the water in the air as is typical when a misting nozzle is used.

Plan on covering no more than 50-70% of the pen area with the wetting device. This keeps water out of the feeder and allows pigs to choose whether to be wet or not.

A good tool for determining whether evaporative cooling is needed is to closely examine the pigs when temperatures in the pig zone are 85° F or higher. If a majority of the pigs are lying on their sides with elevated respiration rates, this is an indication of heat stress.

A normal pig's respiration rate is approximately 20-30 breaths/minute. Anything over 40 breaths/minute is an indication that the pig has adopted panting as a means to increase heat transfer from the lungs, and serves as a sign that feed intake will be depressed.

Winter Temperature Management

Consider the use of reduced nocturnal temperatures in nursery and grower facilities. There is an abundance of data that suggests the pig prefers a cooler nighttime temperature.

In experiments where pigs were able to select the temperature of their sleeping area, they generally indicated a preference for a reduced temperature beginning around 4 p.m. to 6 p.m., with a preference for warmer temperatures beginning around 3 a.m. to 5 a.m.

In research conducted at the University of Nebraska in the 1980s, when the nighttime furnace setting was reduced 10° F from the recommended daytime setting beginning one week after weaning (Figure 1), nursery pigs showed a 6% improvement in average daily gain and a 15% savings in propane expense in winter trials.

Note that in the trials depicted in Figure 1, only the furnace setting was altered. The set point for when the ventilation fans would increase was not changed. There were two thermostats installed for the furnaces. Selection of a thermostat to control the furnace (and room temperature) from 7 a.m. to 7 p.m., and from 7 p.m. to 7 a.m., was done using a time clock.

If this research data on reduced nocturnal temperatures has been available for a least 20 years, why hasn't it been widely adopted by the swine industry? The main reasons appear to have been skepticism by producers and use of electronic ventilation controllers.

Today, just about every swine facility in the United States utilizes an electronic controller of some type to control the heating system and ventilation fans. In most controllers, the fans and furnaces are controlled at a temperature set point that is relative to the “set point” of the controller.

Thus, if the set point is reduced so that the furnace comes on at a lower temperature, this also means that the ventilation fans begin operating at lower temperatures.

While it appears that the new generation of ventilation controllers may have the ability to incorporate reduced temperature programming for nighttime conditions into their control logic, this is not the case for the majority of the controllers installed.

For those willing to try reduced nocturnal temperatures as a means to stimulate feed intake, increase average daily gain and reduce propane expenditures, it can be done manually using the controllers.

On most controllers, the furnace is controlled by means of an offset setting and differential setting. For the furnace to run, the temperature must decline an amount equal to both the offset and differential settings. The furnace turns off when the controller detects an increase in temperature equal to the differential. The purpose of the offset is to allow for the continued warming of air in the vicinity of the temperature probe following shutdown of the furnace.

In small rooms with large-capacity furnaces, this overshoot of temperature settings can be by several degrees. Rather than reducing the set point (which influences all of the set points for both fans and furnaces on most controllers), it is recommended that producers reset the furnace offset.

For reduced nocturnal temperatures, only the offset has to be changed, often from a setting of 2 to 12° F. It is recommended that the offset be reduced by 10° F from 5-7 p.m. to 7 a.m.

In addition, to be successful, don't begin reducing temperatures until the pigs are eating aggressively, generally five or more days after weaning. If pigs are sick or otherwise appear to be doing poorly, don't be afraid to return to a constant temperature setting.

However, continue to reduce air temperature in the pig zone 3-4 °F/week (0.5 °F/day) until pigs are 50 lb. or so in weight.

Sick Pens

Pigs are moved to sick pens due to slow growth, injury or illness to receive supportive care and supervision to speed their recovery.

Sick pens should provide an improved environment conducive to reducing drafts and/or frequent temperature fluctuations. The area should include a mat or heat lamp to modify the temperature in the pig zone.

Sick pens should also offer access to feed and water in a non-competitive environment.

All of these modifications highlight the main purpose of a sick pen — to provide a living area that maximizes the sick or injured pig's chance of recovery.

Sick pens also require decision-making skills. If pigs aren't on the road to recovery after a specified time period (generally 3-5 days), the decision should often be made to euthanize them.

The decision to euthanize, while never an easy one, is a humane and welfare-friendly response to a condition that clearly compromises the pig's well-being.

The Swine Welfare Assurance Program (SWAP) of the National Pork Board suggests that a minimum standard of 5% of all deaths in a facility should be recorded as euthanasia, with 20% as the standard.

Summary

The growing pig is often the forgotten stage in critical management decisions. One day it is considered a “nursery” pig and the next day it is a “finisher.”

Rather than adopting a transition management strategy for temperature and space management that acknowledges the needs of the growing pig, all too often the strategy seems to be focused on the extremes, such as the idea that a nursery pig doesn't need heat relief.

As demonstrated in this discussion, there are still plenty of opportunities to improve the performance of the growing pig, while at the same time reducing the net cost to attain that optimum level of performance.

Table 1. Space Allocation Predicted to Have No Impact on Average Daily Gain
Pig Weight, lb. Space, sq. ft./pig
40 2.5
45 2.7
50 2.9
55 3.1
60 3.3
65 3.5
100 4.7
125 5.4
Table 2. Estimated Heat Production by Growing Pigs1
Btu/hour
Pig Weight, lb. Pre-1988 Post-1988
44 294 308
66 369 397
88 434 474
110 492 544
132 544 610
1Data from Brown-Brandl, et al (2004).