AS-446
In the competitive swine business, the future will belong to the efficient. The seedstock that pork producers can depend on will be tested, productive, and predictable.
The pork industry has undergone some dramatic changes in the past few years. Poultry, pork's major competitor at the marketplace, has made rapid genetic improvements-ones that have resulted in lower production costs, which in turn resulted in an expanded demand for poultry meat. So to remain in business, pork producers have had to become aware of their production costs and measures of production efficiency, including feed conversion, litter size, pigs weaned per sow per year, and days to market. Emphasis on carcass quality has increased as packers initiated purchase programs based on estimated carcass value.
To properly serve the total pork industry, swine seedstock producers must become concerned about measures of production efficiency. Genetic improvement of purebred swine herds can lead the way to more efficient pork production and improve pork's competitiveness with other protein sources. At first glance, successful animal breeding programs within each class of livestock may seem quite different; however, closer examination shows four common features of genetically successful poultry, dairy, beef, or swine programs.
They are:
It is apparent that successful swine breeding programs will result from the development and implementation of these four features. The development of a Swine Testing and Genetic Evaluation System (STAGES) has been initiated as a joint project between Purdue University, U.S.D.A. Agricultural Research Service, U.S.D.A. Extension Service, National Association of Swine Records, the purebred associations, and the National Pork Producers Council. STAGES computer programs will be implemented on national breed association computers to serve their members.
The development of STAGES programs will involve six steps.
STAGE 1: Within-herd genetic evaluation for post-weaning growth (average daily gain or days to 230 pounds) and backfat thickness will be developed for a single contemporary group. A contemporary group is defined as all individuals having an equal opportunity to express their genetic potential. For example, a contemporary group might consist of boars or gilts found to be within a month of age, fed the same diet, and housed in the same facility. Sires, dams, young boars, and young gilts (five to six months of age) will be evaluated simultaneously within each contemporary group.
STAGE 2: Genetic evaluation of post-weaning traits will be extended for multiple contemporary groups. This procedure will bring forward information from past progeny of the sires and dams. By doing this, STAGE 2 becomes a more in-depth analysis of the data collected in STAGE 1. Sire evaluations will be adjusted for the predicted genetic differences of their mates.
STAGE 3: Revision will then be made in the current sow productivity program to include additional within-herd information taken from relatives to further evaluate gilts and boars and their sires and dams. STAGE 3 will increase the accuracy of selection for the reproduction traits of low heritability such as litter size and litter weight.
STAGE 4: Analysis of post-weaning traits found in (STAGES 1 and 2) will be extended to include the options for individual or full-sibling pen feed conversion and/or carcass data. The options would allow inclusion of data from central test stations and intensive on-farm performance tests.
STAGE 5: The reproductive and post-weaning traits for multiple within-herd contemporary groups will be combined into comprehensive indexes. Three alternative indexes: maternal, general, and terminal sire will be calculated. The maternal index will place greater emphasis on reproductive performance than on the other indexes, and the terminal sire index will emphasize post-weaning performance.
STAGE 6: Across-herd sire evaluation for reproduction and post-weaning traits will be developed. This will allow for the identification of top sires within each breed for each trait or index value. The across-herd evaluation will require performance records collected over a period of two or more years.
After the completion of these six steps, the program will analyze the records and evaluate all tests including on-farm central test station and barrow tests. The program will then analyze all tested swine within each breed.
Several concepts are important to understanding selection procedures. The first concept is that genetic variability exists within the swine population and is transmitted to progeny and descendants. Thus, for seedstock herds to improve, genetically superior individuals must be selected; however, it is important to realize that the true genetic merit (breeding value) of each individual is not known. So selection must be based upon estimates of the animal's genetic merit from available performance data.
The concept of breeding value is based on the fact that genes occur in pairs. The true genetic merit (breeding value) of the animal is the effect of all of its genes upon relevant traits. Selected individuals transmit a sample of one-half of their genes, or breeding value, to each offspring. For this reason, one-half of the breeding value is the expected progeny difference.
Genetic evaluation programs express the genetic merit estimates as expected progeny deviations (EPD's) which are indicators of the animal's breeding value or true genetic merit. The predicted progeny deviation is an estimate based upon performance and sibling or progeny data. The EPD is equal to one-half the breeding value (EPD = 1/2 EBV) of either sires, dams, or progeny. Thus, EPD measures the effects of the particular genes an animal is expected to transmit to his/her offspring. It is an estimate of how future progeny of the sire (or dam) are expected to perform relative to the average performance of the contemporary group when mated to individuals of average performance and when the resulting progeny are treated alike. The EPD for the mating of a specific male to a specific female is the sum of the EPD's of the two parents.
The most important aspect of progeny deviations is the reliability in predicting future progeny performance from the sample of performance records currently available. Therefore, the EPD's are regressed toward the average predicted progeny deviation, which is zero, depending on the number and distribution of individual performance, sibling performance, ancestral and/or progeny performance, plus records. EPD's will deviate more from the average as additional records are included. EPD's take into account the heritability of the particular trait (or the heritabilities and associations of the traits within an index). These are in the same units of measure as the trait. Deviations can be either a plus deviation or a minus deviation; for example, a boar with a EPD of -3.0 for days from weaning to market would be expected to sire offspring that reach market three days faster than the average boar.
Because the EPD's are regressed toward the average, depending on the number and distribution of records, EPD's are directly comparable even though the numbers of records and the resulting possible change values are different. This allows the seedstock producer to compare young performance tested boars with older progeny tested sires and young replacement gilts with older sows. These comparisons facilitate replacement decisions.
A contemporary group is a group of animals of similar age and of the same breed or cross, who receive similar treatment, and who have equal opportunity to perform and express their true genetic potential. Accurate genetic evaluation is possible when individuals are compared to others in the same contemporary group. Participants who collect performance information are the only ones who know how animals in their respective herds should be grouped. It is paramount that within a contemporary group the animals be treated as uniformly as possible including similar pen space and diet.
Contemporary groups should exist during a short enough duration in time that the environment is kept as uniform as possible; however, contemporary groups should include enough animals to form a reliable basis of comparison. The producer must compromise between small, short-duration contemporary groups and larger, long-duration contemporary groups. The optimal strategy is to include as many animals as can be fairly compared. For example, a contemporary group might include those sows farrowing within a one month period in the same facility, or a group of young boars within one month of age that have been raised together.
Different genetic groups should be treated as if they are different contemporary groups, i.e., if some females are mated to purebred and others are mated to produce F1 progeny, they must be submitted as two different contemporary groups. The program also allows participants to identify sub-contemporary groups, which is a group option to be used when animals of similar age have been subdivided into different facilities, fed different diets, or managed differently. Examples might include 1) sows farrowing together but fed different lactation diets, or 2) boars within one month of age fed different diets or tested in different facilities. Even though the animals were evaluated at the same time, the environments are different and animals should therefore be divided into two sub-contemporary groups.
The complete objectives of STAGES can be met only if the whole herd is tested. Complete herd testing allows each individual to be evaluated more accurately through the accumulation of additional information on relatives (parents, progeny, and siblings) and larger contemporary groups. As the percentage of animals tested declines, the accuracy of each individual's genetic evaluation decreases. Testing a limited sample of the herd yields limited and possibly biased information. Testing a small percentage of the animals can distort the EPD's and the index values.
Growth and backfat records should be obtained on all animals including intact boars, gilts, and barrows. Weight and backfat of castrated barrows should be recorded and included in the analysis even though their evaluation as breeding stock is not of concern. Measurements on these animals contribute to a more accurate evaluation of their parents and siblings.
Sow productivity records should include all purebred sows with either purebred (registered and unregistered) or crossbred litters. However, purebred sows with purebred litters and purebred sows with crossbred litters should be submitted as two contemporary groups.
To meet the genetic needs of their commercial producer customers, purebred breeders should select a balanced combination of economically important traits.
STAGES weighs the EPD's to calculate three selection indexes: maternal, general, and terminal sire. The indexes consider the intended use of the seedstock in crossbreeding systems and the relative economic value of each trait. Although feed efficiency was not included in the selection indexes, it was considered in the economic objective.
The general index is intended for seedstock which is used in rotational crossbreeding systems. The general index places equal emphasis on reproductive and postweaning (growth, backfat, feed efficiency) traits.
The maternal index is for seedstock which is used to produce replacement gilts in specific or rotaterminal crossbreeding programs. The maternal index places twice as much emphasis on reproductive traits relative to postweaning traits than the general index.
The terminal sire index is for seedstock which is used as terminal sires in specific or rotaterminal crossbreeding system. The terminal sire index emphasizes the postweaning traits.
Seedstock producers should select their replacement boars and gilts based on the index in which their seedstock is mainly used. For example, if a seedstock producer has breeds that are primarily used in specific crossbreeding systems, the maternal breed should be selected on the maternal index and the terminal sire breed on the terminal sire index. Producers with a majority of their seedstock in a three-breed rotation should select their replacements based on the rotational index.
To rank sows on their reproductive performance and mothering ability, a sow productivity EPD index was calculated which weighs litter size and litter weight according to their economic value. The index differs from previous sow productivity indexes in that EPD's are estimated for the individual traits. These EPD's include data for the sow and her relatives.
Implementation of STAGES by the purebred associations will provide more accurate and more complete genetic evaluation of the nation's purebred swine herds. Careful selection of superior individuals based on STAGES analyses will result in accelerated genetic improvement that will, in turn, result in more efficient commercial swine production.
STAGE 5 is currently available for use by purebred producers, and the importance of early participation in STAGE 1 cannot be over-emphasized. Early participation is necessary for consistently accurate genetic evaluations as STAGE 6 is implemented. Every purebred producer should consider utilizing STAGES in its entirety, as it becomes available, in order to attain maximum genetic improvement.
Commercial swine producers will ultimately determine the success of STAGES--they will do so by making purchase decisions based on highly accurate evaluations. Before purchasing boars or gilts, commercial producers will identify purebred producers who are utilizing STAGES, in its entirety, and they will then select superior individuals from those herds as replacements. Purebred producers should be asked to provide performance pedigrees indicating performance testing and selection history of their herd.
Pork producers should be willing to pay a premium price for genetically improved seedstock, not simply because of its increased value to produce commercial progeny, but to offset performance testing costs incurred by seedstock producers. Commercial pork producer support of seedstock producers who are utilizing STAGES with superior tested boars and gilts is necessary to guarantee their continued existence in the competitive marketplace and lead to a more efficient pork production system.
For further information, contact one of the breed association offices.
American Berkshire Assoc. Poland China Record Assoc. P.O. Box 2436 and, P.O. Box 2537 Lafayette, IN 47906 Chester White Swine Record Assoc. 1803 West Detweiller Drive Peoria, IL 61614 United Duroc Swine Registry 1803 West Detweiller Drive Peoria, IL 61614 Hampshire Swine Registry 6748 N. Frostwood Pkwy Peoria, IL 61615 American Landrace Assoc., Inc. P.O. Box 2340 West Lafayette, IN 47906 American Yorkshire Club, Inc. 1769 U.S. 52 North P.O. Box 2417 West Lafayette, IN 47906
RR 7/89
Cooperative Extension work in Agriculture and Home Economics. state of Indiana. Purdue University and u.s. Department of Agriculture cooperating. H. A. Wadsworth. Director, west Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Cooperative Extension Service of Purdue University is an affirmative action/equal opportunity institution.