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Volume 7, Number 3 - March 2001

This Month in Ag Connection

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Effect of Sorting and Mixing Strategy on Pig Growth Performance


An often misunderstood swine management practice affecting swine performance is the social environment or interaction of pigs within and between pens. Social environment in a building is difficult to change because pig flow was determined by the facility's original design. Typically, pigs have been sorted in an attempt to optimize growth rate, make efficient use of available space, ensure pig health, and reduce pen weight variation.

Sorting By Weight

A Canadian study evaluated weight variation at market of weaning pigs which were sorted into either a high weight variation (20 lbs.) or a low weight variation (10 lbs.) treatment. The results indicate that the low weight variation in a pen was not maintained through finishing. The social strife in a pen appears to be the greatest between pigs of similar weight because the hierarchy structure of the pen is possibly pushed to increase variation until social order is established.

Sorting By Sex

Producers have begun sorting pigs by sex to reduce feed costs and better match nutrient supply with requirements. Barrows grow faster, eat more and have higher nutrient requirements than gilts. While research has shown split sex feeding does not impact market weight variation in a pen, it does decrease cost of gain.

Sorting By Litter

It is known that mixing pigs results in more aggression, which ultimately affects the productivity for at least the following 2 weeks. One way to maintain familiarity is to keep litters of pigs together at weaning. However, studies have shown no differences in performance due to the number of pigs coming from the same litter within the same pen.

The data suggests that the wean-to-finish response is a nursery phase response with no difference in growth performance between the housing (wean-to-finish) and mixing during the growing-finishing phase. Those pigs housed in a wean-to-finish building did have a lower coefficient of variation at market weight or when the first pig was removed from the pen, which could result in better market premiums or less sort loss applied by the packer.

Wean-to-Finish Technology

The objective behind the development of wean-to-finish facilities was to minimize the moving and resorting of the growing pigs between the nursery and finishing phase. Earlier wean–to–finish research has only looked at the impact during the nursery period on growth performance. The research concluded that pigs housed in wean-to-finish housing systems were slightly heavier in body weight at the end of the 8 week nursery period compared to pigs weaned into a conventional nursery. However additional research has shown little improvement in subsequent grow-finish performance.

An experiment was conducted evaluating the following four housing treatments:

  1. Wean–to-Finish (WF) into 2.4 x 4.3 m pens (15 pigs/pen)
  2. Double stock wean-to-finish (Same pen)
  3. Double stock wean-to-finish (Move to new pen)
  4. Nursery (N)
Table 1
Effect of Wean-to-Finish
Housing Systems on Growth Performance
Item Wean-to-Finish DS – Same DS – Move Nursery
Initial wt. (lb.) 63.14 59.18 59.18 60.94
ADG (lb/d) 1.87 1.89 1.84 1.85
ADFI (lb/d) 5.07 5.04 5.00 5.04
FE .812 .823 .812 .810
% Lean 51.5 51.6 51.3 51.6
CV within pen 9.3 10.4 11.3 10.5


The research referenced indicates the best method to sort or mix a group of pigs at weaning is whatever minimizes labor requirements and maximizes the pig flow through facilities. There appears to be no lasting impact of mixing or sorting on nursery or grower pig performance. Sorting by sex can improve feed efficiency and reduce feed costs. Regrouping pigs for the finishing phase should be avoided.

(Author: Marcia S. Carlson, State Swine Nutrition Specialist, University of Missouri Columbia)

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Taxation Tidbits: Financing Retirement for Farmers and Other Small Business Owners

Cash and coins

Everyone knows it is best to begin funding retirement accounts early in life, however, financial planning for retirement is one of those topics that gets more lip service than action. Too frequently, the funds for investments into retirement accounts just aren’t available. School loans must be paid off, investments to be made in the business, the family needs to replace a car or house, and the expenses of helping the children with their college education. Suddenly, at about 50 years of age with retirement looming in the future, people begin to seriously invest for retirement. The obvious limitation is the short investment time frame. The IRS Code contains two investment vehicles that farmers and other small business owners should consider: 1) SEP “Simplified Employee Pension” and 2) SIMPLE “Savings Incentive Match Plans for Employers”. Both of these retirement investment vehicles provide for greater tax-deductible contributions than traditional IRAs (Individual Retirement Arrangements).

SEP “Simplified Employee Pension”

This is a plan under which the employer makes contributions directly to IRA accounts for employees and themselves. However, the contribution limits are significantly greater than with a traditional IRA.

Employees who must be covered by the plan:


Other important considerations:

SIMPLE “Savings Incentive Match Plans for Employers”

This retirement vehicle provides for substantial salary reduction of employees. SIMPLEs may be established by employers with 100 or fewer employees who earned compensation of $5,000 or more in the prior year.

Employees who must be covered by the plan:


Other important considerations:

(Author: Parman R. Green, UO&E Farm Business Mgmt. Specialist)

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Variation in Feed Nutrient Levels

All feedstuffs can have considerable variation in actual nutrient levels versus book values. The chart below illustrates this variation for by-product feeds. You should have a nutrient analysis of your feed if significant amounts of by-product feeds are going to be included in a diet.

The cause for concern is that there is no one particular feedstuff, traditional or by-product, that is balanced in all nutrients. For example, corn gluten feed is known for being low in calcium and high in sulfur. This imbalance can cause a condition referred to as induced polio. In the chart below, the local sample was considerably higher in sulfur than was listed in book value (local sample Ca =0.03; S = 0.45 vs. NRC Ca = 0.36; S = 0.23 percent). In this case you would need to feed more calcium or feed less of the corn gluten feed.

  Ca % P ppm Mg % K Na Fe Zn Cu Mn S Cl Ash
Brewers grains, dry
Sample 0.23 0.63 0.25 0.36 0.02 123.40 93.90 17.40 48.70 0.24 0.11 4.50
NRC 0.33 0.55 0.16 0.09 0.23 266.00 30.00 23.00 40.00 0.32 0.17 4.80
Corn gluten feed, wet
Sample 0.03 0.84 0.36 1.24 0.05 121.50 56.40 3.60 19.00 0.45 0.19 5.77
NRC 0.36 0.82 0.36 0.64 0.15 471.00 72.00 52.00 26.00 0.23 0.25 7.50
Distillers dried grains
Sample 0.07 0.80 0.35 1.01 0.06 175.80 52.80 2.40 39.00 0.57 0.16 4.70
NRC 0.15 0.71 0.18 0.44 0.44 259.00 ** 58.00 25.00 0.33 0.18 4.80
Soybean hulls
Sample 0.60 0.13 0.25 1.32 0.01 523.00 38.00 6.70 21.90 0.10 0.02 5.33
NRC 0.49 0.21 ** 1.27 0.01 324.00 24.00 18.00 11.00 0.09 ** 5.10
  • Bold values indicate a minerals and feeds with substantial difference between the samples collected and NRC values
  • Sample – collected in California by American Registry of Professional Animal Science members and analyzed by an independent lab in New York
  • NRC – National Research Council book values

Of the feeds reported above, distillers dried grains, and soybean hulls had the most variation in mineral content

Notice that some of the values are very different than that reported by NRC.

Trace mineral, magnesium, potassium, and sulfur values of feeds that are markedly different than NRC values are highlighted.

(Author: Mark Stewart, Livestock Specialist)

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AgriExpo 2001

March 20-21, Capitol Plaza Hotel, Jefferson City, MO


Day One offers fundamentals for starting a value-added business. Day Two provides in-depth look at guiding entrepreneurs to success. Sessions include marketing on the Internet, advertising, using demographics, cross-marketing and networking for success.

One day registration is $20 or two days for $35, including lunch, before March 6. After March 6, the fees are $30 and $45. For more information call 877-ValuADD (825-8233). AgriExpo 2001 is sponsored by University of Missouri Outreach and Extension, Missouri Dept. of Agriculture and USDA Rural Development.

Click here for more information on the Value-Added Agriculture Program.

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Publishing Information

Ag Connection is published monthly for Central Missouri Region producers and is supported by University of Missouri Extension, the Commercial Agriculture program, the Missouri Agricultural Experiment Station and the MU College of Agriculture, Food and Natural Resources. Managing Editor: Kent Shannon.