These are related to the type of fungus, the toxin produced and the amounts present. The most important one called F2 toxin or zearalenone is produced by a strain of Fusarium graminearum which is found in maize.
It is an oestrogenic toxin and is produced in high moisture environments in maize growing areas well before harvest.
Symptoms
All Pigs
- Rectal and vagina prolapses are common symptoms in the young growing stock.
- The most striking clinical feature is the swollen red vulva of immature gilts.
- Stillbirths
The other signs are dependent up on the levels present in the feed and the state of pregnancy.
These include:
- Returns > 23 days.
- Farrowing early.
The following may be used as guidelines to the symptoms that may be observed.
- Boars – Semen may be affected with feed levels above 30ppm but not fertility. At higher levels poor libido, oedema of the prepuce and loss of hair may occur.
- Gilts (Pre puberty) 1 – 6 months of age – 1 to 5ppm in feed causes swelling and reddening of the vulva and enlargement of the teats and mammary glands. Rectal and vagina prolapses also occur in young growing stock.
- Gilts (mature) – 1 to 3ppm will give rise to variable lengths in the oestrus cycle due to retained corpora lutea and infertility.
- Sows – Levels of 5 to 10ppm can cause anoestrus, which may also be associated with pseudo pregnancy due to the retention of corpus luteum. F2 toxin will not normally cause abortion however, if sows are exposed during the period of implantation litter size may be reduced. In lactation piglets may develop enlarged vulva.
- Effects on pregnancy – Embryo survival to implantation does not appear to be affected at levels less than 30ppm but above this complete loss between implantation and 30 days occurs, followed by pseudo pregnancies. Low levels of 3 to 5ppm do not appear to affect the mid part of pregnancy, but in the latter stages piglet growth in utero is depressed, with weak splay-legged piglets born. Some of these may have enlarged vulvas.
- Effects on lactation – 3 to 5ppm has no effect on lactation but the weaning to service interval may be extended.
Causes / Contributing factors
- Mouldy feeds:
- The purchase of mouldy, damp or badly stored grains.
- The mixing of contaminated and uncontaminated grains.
- Holding cereals in moist, damp conditions.
- Allowing grains to heat.
- Prolonged usage of feed bins, feed bridging across the bin and development of moulds.
- Placing compounded feeds into bins whilst they are moist and warm.
- Poorly maintained bins that allow water to leak in.
- The bridging of feed in bins over long periods of time and their sudden descent.
- Prolonged use of automatic feeders and retention of mouldy feed.
Diagnosis
Based on the clinical signs and demonstrating the toxin in feed.