REPRODUCTON
PIH-96
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Troubleshooting Swine Reproductive Failure
Authors:
Lawrence Evans, Iowa State University
Jack Britt, North Carolina State University
Clyde Kirkbride, South Dakota State University
Don Levis, University of Nebraska
Reviewers:
Larry Beck, Cochise, Arizona
John P. Hurigen, New Freedom, Pennsylvania
Wayne L. Singleton, Purdue University
Gerald R, Swartley, Waterloo, New York
Some reproductive failure occurs in all swine breeding operations, but for practical purposes reproductive failure is regarded significant only when production levels fall below the expected norm. These norms vary from operation to operation and are based on such things as percentage of animals cycling, conception and farrowing rates, average litter size, and number of pigs produced per sow per year (Table 1). The detection of moderate rates of subfertility depends upon the observation ability of the caretaker, regular recording of reproductive events, and analysis of reproductive records.

There is a tendency to equate reproductive failure with infectious disease, but in fact most problems are not infectious. This tendency probably springs from the need to assign the problem to a tangible factor such as an infectious agent and to public awareness of infectious diseases. Most reproductive problems have causes that may involve management practices, nutrition, environmental effects, toxicoses, genetics, and disease conditions. Solving reproductive problems requires a thorough knowledge of the breeding herd management and the collection and analysis of pertinent objective data (Table 2). This may be followed by submission of appropriate samples to a diagnostic laboratory. Many problems defy an exact laboratory diagnosis because the causative agent may no longer be present or the problem may have been related to management or environmental factors.

It is often practical to categorize the reproductive problem into one or more areas so that specific investigations or tests can be applied. Table 3 shows the more common reproductive signs or complaints concerning swine reproduction. Bars indicate the relative importance of the female or the male to each of these reproductive problems. Each category will be discussed in this fact
sheet with reference to some known causes and diagnostic procedures.
Anestrus
Gilts
Common complaints with gilts are delayed puberty, silent estrus, and anestrus after a few heats. These problems are often related to confinement housing and are influenced by breed and age of the gilts, the season, whether a boar is present, and to some extent the duration of daylight or artificial lighting.

Landrace and Large White breeds tend to cycle better in enclosed facilities and at an earlier age than most other breeds in enclosed facilities. It is best to purchase breeding stock that has been shown to reproduce well under management conditions similar to those intended for the animals purchased. About 80-85% of gilts should be showing regular cycles by 7-8 months of age, but this percentage may be much lower in the summer and fall months. This percentage will not increase significantly for gilts kept beyond 9 months of age. Thus, it is not genetically or economically sound to keep noncyclic gilts beyond 9 months of age.

Gilts that are kept in an enclosed facility, isolated, or tethered are slower in reaching puberty than are gilts kept outside. With gilts in enclosed facilities, smaller numbers per pen (8-12) are better than larger numbers. It is best to provide at least 12 hours of daylight or artificial light per day and a minimum of 15 sq. ft. floorspace per animal. Movement of gilts to new pens or to outside housing and increased exposure to adult boars will often stimulate heat in a number of anestrous gilts.
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.