BREEDING & GENETICS
PIH-27
pork industry handbook
PURDUE UNIVERSITY • COOPERATIVE EXTENSION SERVICE • WEST LAFAYETTE, INDIANA
Guidelines for Choosing Replacement Females
Authors:
William T. Ahlschwede, University of Nebraska
Daryl Kuhlers, Auburn University
Reviewers:
Maynard Hogberg, Michigan State University
James F. Schneider, Holmen, Wisconsin
The productivity of the sow herd is the foundation of commercial pork production. The sow herd also contributes half of the genetic makeup of growing-finishing pigs. These factors together indicate the importance of careful selection of replacement gilts and wise decisions on their retention in the breeding herd.

The choice of crossbreeding system plays an important role in the development of a gilt selection and sow-culling strategy. With rotational crosses, all gilts are candidates for selection. It is reasonable to be quite selective. With the specialized terminal crosses, the matings producing replacement gilts are less productive than those producing market hogs. Hence, the number of matings to produce replacement gilts and the opportunities to select gilts are minimized.

From among those gilts available for selection, select the fastest growing, leanest gilts that are sound and from large litters; and among sows which have farrowed and will rebreed, cull only those with physical problems, bad dispositions, extremely small litters (more than 3 pigs below herd average) and poor mothering records.

Pork producers with small sow herds will find it difficult to maintain the breeding groups required to produce their own gilts for terminal crosses. For these producers to profit from the increased productivity of terminal crosses, purchasing replacement gilts may be desirable. It is recommended that producers purchasing replacement gilts establish a continuing relationship with a reputable supplier of healthy maternal crossbred gilts.

The Sow’s Job
The success of a commercial pork operation depends upon the sow herd weaning large litters of pigs regularly. This means that a large percentage of the sows and gilts show estrus and breed, farrow large litters of vigorous pigs, keep a high percentage of the pigs alive and get their pigs off to a good start. All of these functions are affected by environmental situations and
management practices. All are affected by genetics. However, the large genetic influences are due to breed differences and heterosis. Differences among gilts and sows in a breed group are much less important. Direct selection from among gilts cannot be made for these sow productivity characteristics.

The size of litter in which a gilt is born and the weaning weight of the litter genetically are traits of the gilt’s mother. Selecting gilts for these traits would be selection on the dam’s record, which dilutes the selection effort. Our understanding of the genetic basis for these traits indicates that economically important genetic changes can be made by selection. The large
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. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age, or handicap.