Seasonal Infertility

Gilts and sows are suceptible to seasonal infertility during late Summer and early Autumn it is due to the environment, mismanagement and malnutrition over the summer months and leading into the beginning of Autumn. This inturn will delay puberty, post weaning anoestrus (sexual inactivity), infertility and irregular hogging (seasons).


Seasonal infertility occurs mainly in summer and results from a combination of the effects of day length and high temperature. The ideal day length should be a steady 12-16 hours and this should be maintained year round. Seasonal infertility is most serious where sows are housed with access to natural light (e.g. outdoors) and where light exposure cannot be controlled. Effects are most obvious in the female, but high temperature may also have an effect on semen quality and libido in the boar, which we discussed in a post under the heading “So what do we know about boars”. In addition, there may be reduced conception during the summer, caused partly by the seasonal effect on the sow and partly as a result of reduced semen quality and libido in the boar. A rise in infertility resulting from leptospiral infection may be present in some farms in the early autumn.

Clinical signs

Sows become anoestrous (sexual inactive) for a period of 19 weeks (range 11-30) in late summer and early autumn, but may cycle throughout this period without demonstrating oestrus behaviour. When service occurs, animals may return at 3 weeks or irregularly thereafter. Abortions may also be more common at this time. The combination of all these factors may reduce fertility during the late summer and early autumn. Breeding stock affected by the heat may remain lethargic during the day, to become active again in the cooler part of the day ie: late afternoon early evening. Fertility may be reduced by around 20-25%.

Diagnosis is based on the failure of identified non-pregnant sows to show oestrus at 21 day intervals or within 21-30 days of weaning during the late summer and early autumn. Daily testing using boar exposure can be used to confirm the presence of anoestrus, the vulva should be inspected daily for signs of redness and swelling and sow and gilts can be tested by back pressure. Signs of mounting should be recorded.

Good records are important in identifying summer infertility. Anoestrus can be investigated in an individual by confirming that the animal is not pregnant, examining the ovaries and uterus by ultrasound for evidence of other causes of anoestrus such as inactive ovaries, cysts, retained corpora lutea (a small, transient endocrine gland formed following ovulation) or uterine pus. Blood tests can confirm whether or not cycling is occurring. Boars should be checked for health and semen quality.

Treatment and prevention

The effects of temperature may be overcome in part by boar stimulation and shading of the mating area, cooling of the boar and sow using wallows or sprays and mating early in the morning when temperatures are lowest. The control of light exposure and introduction of a fixed daylight length of 12-16 hours may reduce the effects in housed animals. The provision of additional roughage was useful in one study and there may be a satiety effect. The adverse effects on fertility of boar semen quality can be overcome by the routine supplementation of natural service by artificial insemination, and the effects of summer infertility on production can be overcome by increasing the number of services over the period by 15% in order to maintain farrowings during the period of risk.

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As mentioned in previous topics, the temperature that pigs feel is seldom the same as what we read on a thermometer or that we as humans feel in the same environment. The temperature that the pig feels is called Effective Temperature.

First of all, it is critical that we measure temperature at pig level since that may differ several degrees from a reading made at eye level on the wall several feet away from the pigs. For nursery pigs, this would be at a height of about 8-12 inches inside the animals’ pen. Even if measured properly, the reading on the thermometer is probably not the temperature that the pigs feel because there are several factors in addition to age and size that influence Effective Temperature. Therefore, the animal may not be comfortable and productive even if the temperature on the thermometer is within its Comfort Zone.


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photo: Harry Bowler

Lower Critical Temperature is the temperature below which a pig must expend additional energy to maintain normal body temperature and essential body functions such as eating, drinking, playing and moving about.The Upper Critical Temperature is that which adversely effects pig performance and normal bodily functions including decreased feed intake and rate of gain due to heat stress. The range between the both is called the Thermo- neutral Zone or Comfort Zone.The Comfort Zone varies by the age and size of our pigs with larger pigs generally tolerating extremes in temperature. This is especially true for the Lower Critical Temperature, which is much higher for younger pigs than older ones. Young pigs up to 18-22kgs are very sensitive to low temperatures and become chilled quickly. On the other hand, finishing pigs and lactating sows are much less sensitive to cold but do not tolerate high environmental temperatures, 2019 and Summer this year was testament to that as there was losses due to the hot summer we had due to heat stress.


Subscribe to our quarterly magazine on our main page Here

If you are looking to purchase weaners and breeding stock subscribe to our weekly stocklist on our main page Here and scroll down the page

We do what we do for love not money however, to help us continue to provide free information, tools and continue our plight with programmes and initiatives that benefit our independent producers, breeders, keepers and create a better future for our breed and its breeding potential please would consider a small donation by clicking the “donate” button on our homepage.


When conditions are too cold, our pigs will attempt to adapt by increasing heat production within its body and by minimising heat loss. Shivering increases metabolic heat production, and increasing feed intake increases heat production from digestion of feedstuffs which helps make the pig feel warmer, yes it is common sense but sometimes there is always one that will slip us by. It is also true to say, when pigs are stressed, they eat less rather than more so their heat production actually decreases. This is especially true at weaning time and when weaners are bought/sold and taken to their new homes in the winter or spring.Common sense prevails and it may not surprise you that great care must be taken to keep them warm during transport and for at least 1-2 weeks after they arrive.Signs to look out forParticular mannerisms to look out for when our pigs are trying to minimise heat loss include:

  • huddling together
  • tucking their legs beneath their bodies to limit contact with the floor
  • seeking shelter or the warmest, least drafty area in their pen.

You may also observe that the younger pigs may even alter their dunging and sleeping habits and lie down in their excrement because faeces and urine provide a temporarily warm floor. But, in the long run, this behaviour gets them wet, increases heat loss from their body and just makes them feel even colder.A nice layer of straw will be greatly appreciated at this time and possibly a rubber matting underneath even heat lamps would be greatly appreciated at this time.


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Prompted by a question from one of our supporters on the Oxford Sandy and Black Pig Foundation regarding the loading of pigs before a movement, IE placing a pig/s in a trailer the evening before a move for the next morning or keeping a pig/s in a trailer which may be awaiting collection or pick up. For confirmation on the stipulation of loading and containing our pigs we turned to AHDB Senior Animal Health & Welfare Scientist, Lauren Cordingley. Who kindly responded with the following:

legislation would deem that the journey starts from when the animals are constrained in the trailer: ‘Journey’ means the entire operation of transport from ‘place of departure’ to ‘place of destination’, including loading at the place of departure, any transfer during the journey, any unloading, rest / accommodation and loading occurring at intermediate points in the journey, until all animals are unloaded at the place of destination.

Even with food and water the animals are still restricted, and considered to be journeying, so it counts towards total journey time. There is no issue with shutting the pigs in for a bit on the days leading up to the journey, to help them get used to loading and unloading etc

A piece of information that will help you and the welfare of your pigs.

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Trinity College Library, Cambridge

A 1,000 year old tradition of pannage begins. Dating back to the time of William the Conqueror, the release of domestic pigs into the New Forest to forage the land for acorns, beechnuts and chestnuts will commence today. This process lasts a minimum of 60 days and is known as Pannage. The pannage season will end on Friday18 November 2022 as mentioned by the New Forest National Park Authority.

The pigs serve a great purpose of clearing the ground of acorns, preventing cattle, ponies and horses from being poisoned. As we know, a recent article in Oxford Sandy and Black Pig Foundation Charity Facebook platform called “Abundance of acorns” tells us of a chemical in the pigs saliva that allows them to eat and enjoy the acorns which provides vitamins, minerals, carbohydrates, proteins and fats. Research on the impact of acorns on the digestive system of pigs indicates that a tannic acid-binding protein in the pig’s saliva prevents the acid breaking down into gallic acid and the other toxic metabolites.

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HEAT STRESS – affects growth rate, fertility and the reproductive herd

Sue Bernhardt-Smith

As we know, heat stress in sows leads to a reduction in feed intake, milk production, body weight loss and reduction in the growth rate of the litter.

Like all our seasons, Summer comes with its own challenges. Heat stress conditions also affect the sow’s subsequent reproductive cycle; recognised as longer intervals between weaning and estrous or, at times, fail to return to estrous. Embryo losses are also recognised during heat stress conditions, consequently reducing the farrowing rate and the total number of pigs born. First time in-pig gilts are purportedly most at risk.

To ensure that our in-pig sows/gilts and nursing sows are comfortable we can ensure that farrowing arks have a through breeze (easily managed if there is an opening at the rear of the ark), sprinklers, shallow wallows, shade and if inside, again, sprinklers, fan and copious amount of fresh drinking water. Feeding in the early morning and late evening when cool. During heat stress, our pigs increase respiration rate and redirect blood flow from tissues and organs to the skin to transfer metabolic heat to the environment. The redirection of blood causes a cascade of adverse effects such as dehydration, organ injury, gut permeability and inflammation.

Should you suspect your sow/gilt/boar/weaners being heat stressed, such as, breathing rapidly with 35 breaths per minute or more, dunging in pen/ark and lying in their own urine, DO NOT THROW A COLD BUCKET OF WATER ON TO YOUR PIG, but place a soaked towel onto your pig around the tummy, ears and neck.

Our weaners/fattening/finishing stock will also suffer as their appetite will decrease and as a result you may witness some of your weaners falling back a little. Firstly, dont beat yourself up about it you are doing nothing wrong. To aid a good appetite, again feed in the cooler parts of the day and ensure there is copious amount of shade, please ensure wallows are topped up and there is copious amount of fresh drinking water. Routine and observing your herd is key. This week the country will be on Amber weather warning from Thursday (11 August 2022) through to Sunday (14 August 2022) with temperatures soaring to 35 degrees C which in Farhrenheit is 95 (which is my preferred reading).


May be an image of animal and outdoors
Dawn Horler


May be a close-up of nature
Photo: Moredun

Depending on our geographical area and where we keep our pigs, ticks rarely pose a threat to our pigs. However, we should not get complacent as pigs do and can get ticks depending on the terrain they live. Cases of tick-borne diseases this summer have been reported up and down the country, I know that my veterinary practice has seen quite a few cases and where I live, in the South West, our atmospheric pressure is damp and ticks just love to thrive. Having said this, ticks love all sorts of environments and whilst many of us will be treating our sheep and cattle we must also run over our pigs with a keen eye.

Ticks are becoming more common across large parts of England, especially in woodlands, on heathland and moorland and grassland. Numbers are increasing and it is due to the increasing numbers of deer. There are 20 species of ticks in the UK the majority feed on bats, birds, badgers and foxes. The common tick Ixodes ricinus feeds on all animals, mammals, birds, reptiles, humans and particularly dogs. The tick is active all year, but numbers start to increase from late March, peaking in late spring and summer and will remain active until October.

Do pigs get ticks?

Yes, they can and they do. They are not fussy and will live anywhere and everywhere. Fortunately it is not common to find ticks on our pigs as the skin is difficult to penetrate for them to gorge. Places where ticks can be found is on the soft skin of our pigs, the ears, vulva, under arms, testicles, sheath, tummy and eye lids. If you find them, as with all animals, do not pull off as this will leave the head behind. You can use a tick hook which you slide the tick between a hook, then twist and pull, you can use tweezers using the same method and depending where it is you can use a spray – Barrier Parasite Repel. Please seek veterinary advice.

Ticks cause infection and diseases to pigs it has been reported there are two types of ticks the hard tick and soft ticks. Soft ticks love hot and dry environments and are mostly found in the western parts of USA. Hard ticks, are mostly found in the UK and Ireland and are particularly common in the New Forest, Exmoor, the South Downs, Thetford Forest, the Lake District, North Yorkshire Moors and the Highlands and Islands of Scotland. So, when out with your pigs give them a once over to give you and your pigs peace of mind.

BOARS – Being prepared Part VII

Photo: from source – sperm plug from 7 month boar

What do we know about boars

Boars normally produce 20 – 120 billion sperm.

Spermatozoa that contain the Y chromosome have slightly less DNA than those that contain the X chromosome.

Incidentally, when servicing, boars will produce a semen plug/sperm plug. This “plug” is formed from the ejaculate material and prevents semen from leaking out of the reproductive tract. It can also be noticed from juvenile boars and this gelatinous substance may also be found stuck to the boars stomach. However, it is predominantly noticed at the end of ejaculation. This is used to seal the large volume of ejaculate (150-500 cc) in the female uterus following natural service. The plug will be placed in the cervix where it will remain.

Photo: Leanne Cross – Sperm plug

BOARS – Being prepared Part VI

Photo: Russ Gleeson – 9 month boar uncastrated

What do we know about boars

What of boar taint. Accumulation of the 16 androstenes contributes to what many regards as unpleasant “boar taint” from sexually mature boars. Boars distinguish themselves with their high testicular production of androstenes and estrogens. Commercial breeds are susceptible to this. The rarer and traditional breeds do not need to be castrated as the process is slower.

Generally the amount of fat is less in intact boars. With castrated boars having the most fat. Intact males are raised because they are more efficient (less food per unit gain and leaner) than castrated males; so marketed weights are around 90kg before boar taint appears.

Photo Russ Gleeson – 9 month uncastrated boar

Among individual boars, sperm production is at its maximum after the age of 2 years and relates directly to testicular size, but testicular size is dependent on breed and age.

Factors that influence sperm production include social environment, light, nutrition and temperature. Social isolation along with lack of auditory and olfactory stimuli depresses sexual behaviour, but sperm production generally is not affected. The impact of light and nutrition on sperm production remains controversial, however, as long as extreme conditions are avoided their effects appear minimal.

Elevated temperature adversely affects sperm production and intervention is required to reduce its duration and intensity in order to maintain output of high-quality sperm. It can take 8 weeks for sperm to reproduce after the affects of heat stress.

photo: Russ Gleeson – 9 month boar