September, 2000 . Volume 23, Number 8 
NCSU Extension Swine Husbandry
September, 2000 . Volume 23, Number 8
Accurate estrus detection in swine operations is essential to keeping herd reproductive efficiency high. Estrus, the period when sows are sexually receptive, can be identified through physiological and behavioral aspects. Once estrus is detected, insemination can occur—placing viable semen in the sows' reproductive tracts 12 to 24 hours before ovulation.
Failure to accurately detect estrus is one of the major causes of suboptimal reproductive performance of a herd. Poor heat detection of weaned and gestating sows can lead to mistimed or completely missed matings. Both will increase nonproductive sow days and reduce herd reproductive efficiency.
The period from the beginning of one heat to the beginning of the next heat is called the estrus cycle. Females first go through a period known as proestrus, a one- to four-day period when they show signs of approaching estrus. During this time, the female seems more excited and increasingly aware of her environment. Gilts, however, have a much longer and more pronounced proestrus than sows. Also, the vulva of a gilt becomes more swollen and redder in color than it does in a sow.
Signs of estrus
The physiological and behavioral aspects of estrus are caused by increased estrogen. Physiological signs include swelling of the vulva and clitoris and a mucous discharge. Behavioral signs are increased activity, increased vocalization, mounting, and the standing reflex. Sows typically come into estrus five to seven days postweaning. Before a sow or gilt is mated, check for as many signs of heat as can be determined by the following:
Remember that each female is an individual and will show slightly different signs of estrus. Systematic and consistent heat checks enable you to become familiar with the normal situation of all females and when it changes to estrus. When in doubt, take the sow or gilt to the boar. Most of the time, the two together will let you know if the female is in heat.
Boar exposure
Boars should be used to check for estrus in small groups. If the boar is placed in the alley in front of the sow, then estrus detection is a two-person job: one handles the boar; the other checks the sow. One person is responsible for keeping the boar focused on the sow as the other gives her a backpressure test and examines her response for signs of estrus.
The person checking the sows should set the rate of movement down the row of gestation crates, not the person handling the boar. Movement should be deliberate, not rushed. Workers also should take time to look back on sows that have already been checked so as not to miss tardy signals. It takes some sows a bit longer than others to decide to show standing heat, and occasionally a "locked-up" sow will be seen that wouldn't show a standing heat when she was checked initially.
Every known or suspected open sow or available gilt should be heat-checked with a boar every day because some sows may not show visual signs of standing heat without the presence of a boar. Using different boars rather than the same one every time may be wise, too. This can be effective with a sow that is suspected of cycling, but for some reason just does not like the particular boar she was exposed to.
The standing reflex in females, which is caused by isometric contractions of skeletal muscles that require a large expenditure of energy, is enhanced by intense periods of boar exposure. Specific behavioral centers in the brain may also be involved. However, prolonged boar exposure may result in habituation, fatigue, and a "refractory" state in which the female may become unresponsive to stimulus. As a result, she will not be able to elicit a standing reflex for several hours. This can be prevented by the boar exposure pattern and detection and/or insemination in small groups.
Repeated exposure to a boar will promote the onset of puberty in gilts and the return to estrus of weaned sows. The level of libido the boar exhibits also may be important to these effects since it has been shown that boars with "high" libido will stimulate an earlier onset of puberty in gilts than boars with "low" libido. The same may apply to weaned sows. Thus, a mature, active boar with a good level of libido is a good choice for checking heat.
Todd See
| Representative Period or Eligibility Period |
One year. Producer must have sold 1 or more pigs at any time from August 18, 1999, to August 17, 2000. |
| Voter Eligibility | An entity who has owned and marketed 1 or more swine during the representative period. |
| Who Can Vote (Group Representation) |
A corporation, partnership, estate, or other legal business entity that owned and sold 1 or more pigs or hogs during the representative period is entitled to 1 vote. |
| Importers | Anyone who has imported pigs, hogs, pork, or pork products during August 18, 1999, to August 17, 2000 is eligible to vote. |
| In-Person Voting | In-person voting will last 3 days. September 19-21, 2000. Producers will certify by completing a form. |
| Absentee Voting | Absentee voting period is August 18-September 21, 2000 (32 days). Absentee ballots must be delivered in person or postmarked by September 21, 2000, and received by mail in the county FSA office by September 28, 2000. |
| Absentee Ballot Request | Individual absentee ballots may be requested beginning August 1, 2000, and will be available August 18-September 18, 2000, at county FSA offices. An absentee ballot may be requested by mail, telephone, fax, or in person. The absentee ballot must be requested from and returned to the same county office. |
| Voting Location | Producers will vote in-person at: 1. The county FSA office where the producer normally does business. 2. If the producer does not participate in FSA programs, voting is at the FSA office in the county where the producer raises hogs or pigs. 3. If the producer owns hogs or pigs in more than one county, voting is in the county where the producer does most of his or her business. |
| Referendum Question | "Do you favor continuing the Pork Checkoff Program?" Voters will be asked to mark "yes" or "no." |
| Challenge Process | Each challenge of a voter's ballot must be made on a separate sheet of paper and signed. Challenger's name will remain confidential, except when required by law or by the Secretary of Agriculture. |
| Challenge Period | Challenge period extends 7 business days after the last day of in-person voting. Challenge of Absentee Voter Request List "will be facilitated." (See Absentee Ballot List Availability) |
| Challenge Documentation | Challenged voters will be requested to provide documentation and will be allowed five days to do so. The county FSA office must notify all voters of a challenge no later than 12 days after the last in-person voting day. |
| Challenge Determination | Determination will be made on the eligibility of challenged ballot no later than 22 business days after the last in-person voting date by FSA county committees. Appeals of the county FSA committee decision go to the Administrator of AMS. |
| Importer Challenges | No challenges will be allowed on importer votes. |
| Voter Registration | Voter registration list will be updated and posted daily at the county FSA office. |
| List Availability | This begins with the first day of voting, September 19, 2000. |
| Absentee Ballot Request List Availability |
Absentee ballot request list will be updated and posted daily. This begins with the first day of voting, September 19, 2000. |
| Counting Votes | Votes will be counted November 29, 2000, on the county level. Results then will be sent to the state FSA office and ultimately to the Secretary of Agriculture. Results will be posted in the county offices for 30 days after the announcement by the Secretary of Agriculture. |
For additional information or the location of your Farm Service Administration (FSA) office, contact the N.C. Pork Council or your local Cooperative Extension Office.
Adapted by
Todd See
| Breeder | Address | Breeds |
| Bob Ivey* | 314 N.C. 111 S, Goldsboro 27530 | L, D, H, Y, CW, X |
| Wesley Looper* | 4695 Petra Mill Rd., Granite Falls 28630 | L, D, H, Y, X |
| Thad Sharp, Jr., & Sons | 5171 N.C. 581 Hwy., Sims 2788030 | D, Y, X |
| Tommy Spruill | Rt. 1, Box 149, Columbia 27925 | L, X |
| Swan Acre Farm | 1060 Main Street, Swan Quarter 27885 | X |
| Thomas Farms | 8251 Oxford Rd., Timberlake 27583 | X |
| UCPRS (Swine Dev. Center) | Rt. 2, Box 400, Rocky Mount 27801 | X |
| *Real-Time Ultrasound | ||
Frank Hollowell
David Lee