How to Achieve Less Than 3% Wean to Finish Mortality


By Kelly Greiner, DVM,
Carthage Veterinary Service, Ltd.

Most organizations have a laundry list of how to achieve wean to finish mortality of less than 3%; but only in the last few years have I drilled down further to look at other factors that can be controlled to achieve that benchmark in wean to finish. The key to achieving less than three percent mortality in wean to finish is focused on three things:

  1. Excellent health
  2. Correct environment
  3. Monitoring growth

Besides excellent health of the weaned pig, which is the most important criteria to achieving 3% or less mortality, correct ventilation is also a key component. Understanding the relationship between a temperature probe’s location, the controller, and minimum ventilation is the key to optimizing the environment in the pig barn.

One thing I have started doing with my clients is benchmarking LP usage against other producers in our system. Based on their geographical location, I have a benchmark number for that producer. In our area, I target no more than 1.5 gallons of LP use, per space, per year wean to finish, and no more than 0.5 gallons per finishing space per year. We track heater run times, and, based on that, we adjust minimum ventilation while balancing relative humidity in the barn.

My target for temperature difference between high and low is less than 3 degrees in a 24-hour period during mild and cold months of
the year. In many cases, I have been able to drive that number lower, but it takes diligence and continual monitoring and adjusting minimum ventilation.

One practical exercise I do when measuring temperature is measuring hour to hour changes. My goal for temperature change is no more than a three degree fluctuation per hour. A data logger is placed in the room, and temperature measurements are taken every 10 minutes. This allows me to see when heaters are turning on and off, and how quickly minimum ventilation is reacting to increases in room temperature. More often than not, I see barns where the minimum fans ramp up too soon after the heater turns off. My rule of thumb is that the heater offset temperature should be set so that the probe temperature gets to within half of a degree to one degree under set-point and no higher. Once temperature reaches set-point, and pigs are not producing enough heat to maintain set-point temperature, we are burning excess propane.

Air stratification is the next aspect of ventilation to review. As you may know, there are areas of the barn where air does not mix evenly and we get stratification of air. There are a couple of different ways to eliminate stratification. The first is to reduce the air temperature of heated air coming from the heater. This concept of modulating down heat output from the heater relies on the blower fan to circulate air longer, which should reduce stratification. Another method is to use circulating fans along the ceiling to circulate the air. The key concept here is to make sure fans are not tilted down for summer ventilation, but are blowing air parallel with the ceiling in the winter.

Once the environment is fine-tuned, we need to focus on starting pigs. I believe there are a couple of key drivers needed to benchmark a group is on its way to a strong finish.

The first is feed intake during the first four days. A healthy group of pigs should be able to start on the first grind and mix ration by four days placed. As with most parameters, there is a range of days, with the largest pigs starting the grind and mix ration after 1 day, to the smallest pigs that may take a week. The key is to understand the distribution of weights in the new group of pigs and manage those groups accordingly.

An average weight is important to know in order to budget feed, and set ventilation. It is just as important to know the distribution of piglet weights. Because we’re dealing with biological production, we cannot turn out 2,400 widgets of the same size from the sow farm every week. Distribution is important because we now have a larger weight difference between the smallest and largest pigs in a group. Increased lactation lengths in sows have given wean to finish managers the opportunity to use that variation to their advantage by feeding the smaller pigs differently than the larger pigs. In a normal distribution we know that one third of pigs fall between the mean and one standard deviation (SD) above the mean. Another 13 percent of the pigs are between one and two SD above the mean, and the last three percent are three SD above the mean. Using this information, we are able to predict how many pigs should be a certain weight at the end of the growout.

Another benchmark number to review to determine if a group is started well is weight at three weeks placed. A healthy group of pigs should at least double their weight in three weeks. So, if they average 12 pounds at weaning, they should be at least 24 pounds three weeks placed. Based on a normal distribution of pigs in a barn, we should be able to accurately calculate the average weight in the barn by following the top three percent of pigs in the barn near the end of the turn. A group of pigs averaging 12 pounds at placement should have the top 2.5 % of pigs weighing on average 19 to 20 pounds. So, by 6 weeks placed, they should double their weight again. That same two and a half percent of pigs should weigh 80 pounds at 6 weeks placed.

Following that concept out to marketing time is key to capturing lost opportunity in marketing barns of pigs. There is easily two more dollars per pig of profit on the table that is reasonable to capture. It is quite important that we think of a group of pigs as a population with a uniform distribution to understand how we can influence which pigs are sold at the optimum time.

In the ideal world, we would weight individual pigs at various stages of production to get individual growth curves. Even in research, this is not practical. One thing we can do, however, is to focus on the pigs that fit into the heavy end of the normal distribution. For example, if we have 1,200 normally distributed pigs, we know that there should be 12-15 pigs that will weigh 300 pounds by 115 days placed for example. Using this information, we can back calculate the weight ranges of all pigs in the distribution. In a production system, it may be economical to take half loads of pigs, based on each barn’s distribution of weight. A benchmark number I like to achieve for each barn of pigs is by targeting at least 70% of the group in the optimum weight range determined by each packer.

By getting these heaviest pigs out of the barn sooner, say at 126 days placed, we can start to change the allocation of space in the barn. Using the allometric equation of A=k*body weight 2/3, where “A” equals the area in square feet required to allow optimum growth rate, “k” is a constant 0.215. Previous literature has suggested for every 1% reduction in floor space, we reduce growth rate by 0.33%. For example, if we take a barn to 260 pound average, then the ideal space to allow optimum growth would be 8.9 ft2. If the barn is stocked for an ending space allocation of 7.2 square feet, we reduce those animals’ growth rates potentially by over 6% from 200 pounds on. If the growth rates are 2.2 pounds per day, in the 7.2 sq. foot scenario, then that would mean there’s a potential to increase gain by 0.1 pounds per day for the last 30 days of growout, or sell an additional 3 pounds per pig.

One way to get around this is to go into a barn sooner to determine when the top 80 or 90 pigs will fall into the optimum harvest weight and take those top 90 head out. If the coefficient of variation, or CV in a barn of pigs is 10 percent at marketing, and the average weight of the barn at 18 weeks is 240 pounds, then the top 7 percent of the pigs could be marketed with an average weight of 280 pounds. Freeing up those 2 pigs per pen will increase the space per pig from 7.5 ft2 to 8.2ft2. By twenty one weeks placed in wean to finish, there should be adequate square footage to allow adequate growth rate of the rest of the pigs in the barn.

So in summary, we know the key to achieving less than three percent mortality in wean to finish is focused on three things. First, health is king. We have to have pigs placed that are PRRS negative, and preferably mycoplasmal pneumonia negative to have a chance of attaining our goal. Second, setting up the correct environment on day one, and subsequently make adjustments are necessary to homogenize the room environment and thus reduce morbidity and mortality. And finally, monitoring the growth of the group of pigs at both 3 and 6 weeks placed will indicate if we are driving those pigs to maximize daily feed intake.

In conclusion, understanding that a group of pigs have a distribution of weights, and managing the distribution will allow you to capture more dollars at marketing by getting a higher percentage of pigs in the optimum marketing grid.

Dr. Kelly Greiner is one of eight veterinarians with Carthage Veterinary Service, Ltd., dedicated to the swine veterinary practice located in Carthage, Illinois. Areas of focus for Dr. Greiner include environmental management of swine facilities, on-farm employee training, and implementation of real-time data collection of finishing systems. Dr. Greiner attended Iowa State University, receiving a bachelor’s degree in Animal Science from the College of Agriculture. He went on to graduate from the Iowa State University College of Veterinary Medicine with a Doctor of Veterinary Medicine degree.