REPRODUCTION
PIH-64
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Artificial Insemination in Swine
Authors
John R. Diehl, Clemson University
Billy N. Day, University of Missouri
Emmett J. Stevermer, Iowa State University
Reviewers
Harold H. Hodson, Jr., Cambridge, Iowa
James W. Knight, Virginia Polytechnic Institute and State University
Don Levis, University of Nebraska
Pam Miller, Chokio, Minnesota
Vernon Pursel, USDA-ARS, Beltsville, Maryland
The techniques and equipment necessary for artificial insemination (AI) in swine are readily available. When considering whether or not to use AI, the following advantages are noteworthy.

AI allows more extensive use of older boars on lighter weight females, and decreases the number of boars and time required for breeding when heat is synchronized. It promotes development of a closed herd where no animals are brought into an existing herd. This makes it possible for any size operation to maintain a more effective disease control program and to bring new genetic material into the herd with minimum risk of introducing new disease organisms.

When sows are placed in gestation crates after first service, AI removes the necessity of taking the sow out of the crate for a second insemination 12-13 hr. later. Experienced herdsmen may not have to remove her for the first breeding or heat checking, depending on their system.

One drawback with the use of AI is that a higher level of management is required. However, several benefits result from the greater input of managerial skills. For instance, with better records, a greater awareness of the true reproductive status of the breeding herd will result in more effective selection of breeding stock.

Only healthy disease-free boars should be used as semen donors. Minimum standards of health and sanitation for those interested in merchandising semen have been published by the Livestock Conservation Institute, 239 Livestock Exchange Building, South St. Paul, MN 55075. Anyone using AI should be thoroughly familiar with these guidelines in order to evaluate the health status of semen donors regardless of source, i.e„ farm or boar stud.
Heat Detection
The most critical factor in achieving maximum conception rates with AI is to inseminate females at exactly the right time. To accomplish this, the breeder must practice proper heat detection. The normal estrous or heat cycle of the pig is 20-22 days in length, but it can range from 18-25 days. The estrous cycle can be divided into segments—the period of receptivity to the male (standing heat or estrus), lasting from a few hours to several days, and the nonreceptive period. The average length of estrus is 1 -2 days for gilts and 2-3 days for sows. If the length of estrus is longer or shorter, the chances of picking the right time to inseminate a female are lower.

Estrus detection is a simple technique. The difficulty is in being sure that detection is carried out correctly. When the female is in heat, she often will try to find the boar herself. There may or may not be evidence of swelling of the vulva. In the presence of a male, the female will assume the mating stance, that is, she stands solidly when pressure is applied on her back. The final sign of standing heat is the “ear popping response," where the female’s ears will repeatedly move toward an erect position as she assumes the mating stance. Determining the correct time to breed is based on the time the female first shows heat. Therefore, the more frequently heat detection is done, the more likely it is that insemination will be carried out at the appropriate time.

The best method of heat detection is to check each female in the presence of a boar by applying pressure to her back (try to sit on her back) to see if she will assume the mating stance as described (Fig. 1). Unless these criteria are met, the time of ovulation cannot be estimated accurately. Using a boar in combination with
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.