Pigs have more olfactory receptors than most mammals. They have a very keen sense of smell. They can detect odors many-fold lower in concentration than humans. And they can perceive some odors that humans cannot smell. Pigs have many pheromones including:
- Sexual pheromones (male, female, gilt development)
- Maternal-neonatal pheromones
- Stress-related pheromones
- Aggressive and submissive pheromones
Pigs sniff when they encounter a new or interesting odor. In the below video (video 1), a potential pheromone is sprayed on the nose of a weaned pig. Note the sniffing behaviors.
Sow and Boar Sexual Behavior
First, let's look at a sow that was weaned 4 days ago and is not in estrus. On the 4th day after weaning, we expect 60-80% of sows to be in heat. But some may not express estrus for up to 10 days...or not all.
Sows, even of the same genetic line, vary in their sexual behaviors. The below video shows a sow with a strong sexual response indicating she is in estrus and ready to breed. Like the video above, this is a sow weaned 4 days earlier.
Some notes about this video:
- This sow is showing, in some ways, an extreme sexual behavioral response.
- This sow was induced to show this behavior with only the Boar Better pheromone and back pressure -- there was no boar present
- She was bred by conventional AI that day.
- The spraying was not good. Only one nostril was sprayed. Even with inadequate or incomplete application of the pheromone, she still showed a strong sexual behavioral response.
Table of sexual behavior terms adapted from McGlone, 2019.
|Measure||Definitions||% of sows showing each response|
Back Pressure Test. A person puts pressure on the sow's back and determines if she stands still
|Standing Still||The sow is nearly motionless, with contracting, rigid limbs during or after BPT. Standing still is also called The Standing Reflex or Locking up||71%|
|Moving/scratching||Sow moves and may scratch. Usually these are signs she in not in heat||30%|
|Pricked ears||Erect or pricked ears during or after BPT||36%|
|Lordosis||Sow arches her back up or down||32%|
|Vocalizations||Grunts during BPT||40%|
Note that not all sows sow all behaviors. They must express Standing Still also called the Standing Reflex to be bred.
Sow and Boar Sexual Behavior in Nature
Int he wild, sows travel in Matriarchal units. This means there is a dominant sow and a few other adult sows. The rest of the traveling herd is made up of sub-adult pigs and piglets. There are no adult males present in this herd. However, adult males visit the sow herd regularly.
At some point, the adult sows make the sub-adult males leave the herd. This happens about the time they reach puberty. At this point, one can observe pairs of young males traveling together, like in this picture.
Adult males often travel alone. The below boar travels alone, but he "checks" adult sows nearly every day. The sows are dominant over the boars and they will chase him away day after day -- unless she is in estrus.
The adult sows let the larger adult males mount them when they are in estrus (heat). When the sow is in proestrus or about to come into full estrus, she will move towards an adult male. Shown in the picture below is part of an experiment we reported in 1988 on sexual behavior of free-range pigs. Note the electric fence separates the red male from the white females. But the white females are coming into estrus and they now begin to move towards the red male -- a boar had avoided or ignored before (boar is on the left).
Collaboration with Animal Biotech LLC.
Animal Biotech is a company that strives to create and develop products that improve animal welfare and help manage their behavior through creative scientific applications.
This laboratory in collaboration with Animal Biotech has developed BoarBetter™, which is a synthetic pheromone that contains lab-derived, synthetic molecules formulated as Boar Saliva Analog (BSA™). BoarBetter™ contains no animal products. BSA™ is the patented triple boar saliva analog pheromone that is a combination of three molecules (Androstenone, Androstenol and Quinoline). It is formulated in a micro-emulsion that is stable for up to a year in the bottle.
Below are videos and pictures that show how to use BoarBetter™ and how it works to stimulate sow and gilt reproduction.
Boar Saliva Analog (BSA): The Boar Pheromone That Stimulates Sow Estrus Behavior and Enhances Reproductive Performance
When we applied BSA (trade name: Boar Better) to sows, it increased reproductive success. Click here for a PDF of this 2019 paper (or it is listed below in references).
Video 2 shows how a sow that should be in estrus responds to a spray of BoarBetter™. Notice she shows firm, clear standing reflex (lordosis) behavior after the BoarBetter™ spray and back pressure.
Videos 3 shows how BoarBetter™ is applied to sows starting on day 4 after weaning.
The BoarBetter™ should be given each day starting on day 4 after weaning until she
is bred. A second spray can be used to induce a clear standing reflex if needed before
insemination. Video 2 is a wide view and Video 3 is above the sows and close to them.
In both videos, there is no boar present. What you hear is an audio recording of boar
This video was taken before we added a blue dye to BB to help the worker see that they have sprayed the sow on the snout.
We recommend spraying sows and then within 10 to 30 seconds checking for signs of estrus by use of the back pressure test. If conventional AI us used, then AI while she is in standing heat. If PCAI is used, then mark sows in estrus, wait an hour or so and then inseminate. In both cases, an additional spray may be given as the AI rod is removed from the sow.
Video 3 -- how to use BB
Video 4 -- BB use with no boar present
Click on the video below or cut and paste this link into a browser: https://youtu.be/UxDBSf8-ZTk
This video shows how a single person can heat check weaned sows without the use of a boar. Sows in heat are marked for later breeding by PCAI.
Comparing Sow Sexual Behavior with a Boar vs BB
This video is the same sow who was videoed after boar exposure. She would then be refractory towards stimuli for at least 30 minutes. Then, after an hour, the same sow was sprayed with BB and the back pressure test applied. Note the behaviors are similar, but not identical. Note her sniffing and the Standing Reflex.
This is the same sow, an hour later, that was sprayed with BB. Note the sniffing and her mouth opening and closing as she applies the liquid to her vomeronasal organ (VNO). She is simultaneously stimulating the main olfactory epithelium and the VNO.
BoarBetter (BB) Improves reproduction during seasonal infertility (click below)
Click above to see the story from Pig Progress.
Gilts and BB
The pictures below shows how BoarBetter™ was applied in gilt pens to ropes starting at 5 months of age. With no boar contact (only BoarBetter™), 100% of the gilts had large follicles and/or corpra lutea by 6 months of age. Ropes can be strayed by hand or via an automated system.
GILT HEAT DEVELOPMENT AND GILT HEAT DETECTION (ropes have blue BB)
Adding Boar Grunting Audio to the Heat Check Procedure
We recommend that when using BoarBetter™ with gilts or sows with the boar grunting audio playing at the same time. You can download a boar grunt audio file below.
The player and speaker are water resistant. One can use a phone's Bluetooth capability to transmit the boar grunting to the speaker instead of a simple MP3 player. These items are available from Amazon (Scandisk MP3 player with Bluetooth and Ecogear speaker with Bluetooth). Any player or speaker can work as long as they are loud and water resistant.
Research Presentations of our Lab
- McGlone J. 25th IPVS Congress. International Pig Veterinary Society, Chingqing, China; 2018. A large-scale field study finds a novel boar pheromone stimulates reproductive performance in sows. [Abstract]
References from our Lab
- McGlone, J. J. 1985. Olfactory cues and pig agonistic behavior: evidence for a submissive pheromone. Physiology and Behavior. 34:195-198. Doi:10.1016/0031-9384(85)90105-2
- McGlone, J. J., L. F. Tribble and W. S. Stansbury. 1986. Aerosolized 5 alpha-androst-16-en-3-one reduced agonistic behavior and temporarily improved performance of growing pigs. J. Animal Science. 63:679-684. Doi:10.1016/0168-1591(87)90010-4
- McGlone, J. J., S. E. Curtis and E. M. Banks. 1987. Evidence for aggression-modulating pheromones in prepuberal pigs. Behav. Neural. Biol. 47:27-39. Doi:10.1016/S0163-1047(87)90134-8
- McGlone, J. J. and J. L. Morrow. 1988. Reduction of pig agonistic behavior by androstenone. J. Animal Science. 66:880-884.
- Hurst, R. J. and J. J. McGlone. 1989. Androstenone aerosol and azaperone injection influence on pig aggressive and submissive behaviors. Texas J. Agriculture and Natural Resources. 3:52-53.
- Morrow-Tesch, J. L. and J. J. McGlone. 1990. Sensory systems and nipple attachment behavior in neonatal pigs. Physiology & Behavior. 47:1-4. Doi:10.1016/0031-9384(90)90034-2
- Morrow-Tesch, J. and J. J. McGlone. 1990. Sources of maternal odors and the development of odor preferences in baby pigs. J. Animal Science. 68:3563-3571. https://www.ncbi.nlm.nih.gov/pubmed/2262409
- McGlone, J. J. and D. L. Anderson. 2002. Synthetic maternal pheromone stimulates feeding behavior and weight gain in weaned pigs. J. Animal Science. 80:3179-3183. https://www.ncbi.nlm.nih.gov/pubmed/12542158
- Krebs, N. and J. J. McGlone. 2009. Effects of exposing pigs to moving and odors in a simulated chute. Appl. Anim. Behav. Sci. 116:179-185. Doi: https://doi.org/10.1016/j.applanim.2008.10.007
- Lewis, C.R.G, N. Krebs, L.E. Hulbert, and J. J. McGlone. 2010. The use of a putative maternal pheromone during transport and the effect of trailer temperature on pig losses and welfare. Animal Production Science. 50:1-9. Doi:10.1071/AN09147
- McGlone, J. J., W. G. Thompson, and K. A. Guay. 2014. Case study: The pig pheromone, acting as an interomone, stops dogs from barking. Prof. Anim. Sci. 30:105-108. Doi: 10.15232/S1080-7446(15)30091-7
- M. D. May , K. Surowiec , and J. J. McGlone. 2015. Vapor release of 2-methyl-2-butenal from dog collars and spray containing pheromone or interomone measured by solidphase microextraction and gas chromatography-mass spectrometry. The Professional Animal Scientist. 31:302-307. DOI: 10.15232/pas.2014-01372
- Pirner, G. and J. McGlone. Impact of androstenone on leash pulling and jumping up in dogs. Animals. 6: 34-43. doi:10.3390/ani6050034
- McGlone, J. J., G. Thompson, and S. Devaraj. 2016/2017. A natural interomone 2-methyl-2-butenal
stimulates feed intake and weight gain in weaned pigs. Animal. Published online 13
July 2016. In print February 2017 issue. 11:306-308
- McGlone, J.J.; Garcia, A.; Rakhshandeh, A. Multi-Farm Analyses Indicate a Novel Boar Pheromone Improves Sow Reproductive Performance. Animals 2019, 9, 37. https://doi.org/10.3390/ani9020037
- John J. McGlone, Sankarganesh Devaraj and Arlene Garcia, Applied Animal Behaviour