Infertility (seasonal: late summer/autumn) occurs worldwide in gilt and sows. The delayed effects are puberty, post-weaning anoestrus, infertility, irregular returns
- Causes of Infertility >
- Effects of Infertility >
- Diagnosis of Infertility >
- Treatment & Control of Infertility >
Causes of Infertility
Seasonal infertility occurs mainly in summer and results from a combination of the effects of day length (a Putative residual effects remaining from the ancestral wild boar) 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 (eg outdoors) and where light exposure can not 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.
In addition, there may be reduced conception during the summer, partly caused 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 that result from that leptospiral infection may be present in some farms in the early autumn.
Effects of Infertility
Sows become Anu strous for a period of 19 weeks (range 11-30) in late summer and early autumn, but may cycle throughout this period without demonstrating estrus behavior.
When service occurs, animals may return at 3 weeks or irregularly thereafter. Abortion 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, only becoming active again to catch any breeze and attempt to remain in the shade. Fertility may be reduced by around 20-25%.
Diagnosis of Infertility
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 suing 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 gilt 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 confirm that the animal is not pregnant, examine the Ovaries and uterus by ultrasound for evidence of other causes such as inactive or anoestrus Ovaries, cysts, retained corpora lutea or uterine pus. Blood tests can confirm Whether or not cycling is occurring.
Where there is a herd problem, the reproductive tracts of sows can be culled Examined by the veterinary surgeon to confirm that summer infertility is occurring. Boars should be checked for health and semen quality.
Treatment & Control of Infertility
- The effects of temperature may be overcome in part by boar stimulation and shading of the mating area, cooling of the boar and sow wallows or using sprays and mating early in the morning when temperatures are lowest.
- The control of light exposure and introduction of a fixed length of 12-16 daylight hours may reduce the effects Housed in animals.
- Melatonin has been evaluated as a means of overcoming the effect of sows, but was not completely effective.
- The provision of additional roughage was useful in one study and there may be a satiety effect.
- Weaned sows should be injected with hormones 24 hours after weaning to reduce the effects of seasonal anoestrus.
- The addition of 4 units of oxytocin to semen doses improved farrowing to first service in summer to levels found at other times of the year.
- 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 on production of summer infertility can be overcome by increasing the number of services over the period by 15% in order to maintain Farrow during the period of risk.
