Field fungi like Fusarium spp., Aspergillus spp. and Claviceps spp., produce mycotoxins that can have a negative impact on animals’ reproductive performance. Any such reproductive failure or drop in reproductive performance is referred to as mycotoxicosis.
Here I summarize the negative impacts of these three mycotoxins on swine fertility:
Sows and gilts are especially sensitive to the effects of mycotoxins. The main mycotoxins that impact pig reproduction are zearalenone (ZEN), ergot alkaloids and the type A trichothecene T-2 toxin, and they in particular can lead to a higher number of pathologies and reproduction problems.
Fertility of gilts and sows exposed to ZEN
ZEN, which is mainly produced by Fusarium graminearum and Fusarium culmorum, can lead to a swelling and thickening of the vulva and an increased uterus mass in gilts. A higher concentration can already lead to a higher return to estrus and in the worst case even result in anestrus.
Exposure of ZEN for 45 to 90 days can lead to premature puberty in gilts, whereby the first heats of these gilts are mostly infertile without ovulation.
Compared to gilts, higher contamination of ZEN must be in the feed to see the symptoms like a welling and thickening of the vulva or an increased uterus mass in sows, as gilts react much more to ZEN than sows do.
Impact of ZEN on embryo and fetus
When pregnant sows get feed contaminated with high levels of ZEN, especially during early gestation, this can lead to smaller litters and mummification. Between days 7 and 10 of pregnancy are the most critical ones with a high rate of embryonic death.
Moreover, if the feed contains high amounts of ZEN during the whole gestation, this will result in smaller fetuses and large variations in the weight of piglets of the same litter.
Furthermore, ZEN can also lead to stillbirth and neonatal mortality and in the worst case it can even lead to the death of the entire litter.
Effect of ZEN on piglets
Further studies have shown that ZEN contamination in the feed at very low levels can already influence the sexual development of young pigs, as Bauer et al. (1987) and Döll et al. (2003) have observed that ZEN in the feed increased the number of ovarian follicles and decreased the serum concentration of the gonadotropic hormone FSH which regulates normal growth, sexual development and reproductive function in female piglets.
Effect of ZEN on boars
Boars, which are fed with ZEN contaminated diet, come up with a significantly lower testicular weight (up to 30 %), smaller epididymis and vesicular glands. Even a temporary inhibition of spermatogenesis was observed, but this problem was gone once the feed was not contaminated anymore. Another observation, especially in young boars, was a reduced libido due to a decreased testosterone concentration in the plasma.
Effect of ZEN on boar sperm
Sambuu et al. (2013) came up with the result that direct exposure of boar spermatozoa to ZEN or α-ZOL (=α-zearalenol) under reduced metabolic conditions (5 °C) did not affect sperm quality.
Further studies in this field were made by Tsakmakidis et al. in the years 2006, 2007 and 2008. On the one hand Tsakmakidis et al. (2006, 2007) reported on motility, viability and acrosome reaction using ZEN and α-ZOL and a 4-h exposure time. On the other hand they observed the sperm-zona pellucida of ZEN and α-ZOL with a 1-h exposure time.
These two studies confirmed the time- and dose-dependent direct toxic effects of ZEN and α-ZOL on boar spermatozoa as well as on the binding ability of boar sperm to the zona pellucida. Tsakmakidis et al. (2006) came up with the result that ZEN and α-ZOL affected the motility of boar spermatozoa. In the study of Tsakmakidis et al. (2008) data showed that susceptibility of the sperm to denaturize DNA increased significantly in all ZEN or α-ZEN over incubation time, although after incubation time of 4 hours sperm motility was not affected.
Overall results have shown that the direct toxic effect of ZEN depends on how long the spermatozoa are exposed to ZEN and the dosage. The longer the exposure to ZEN and α-ZOL has been, the higher was the reduction of motility and viability of spermatozoa.
Ergot alkaloids are produced by Claviceps purpurea, Claviceps paspalli and Claviceps fusiformis and can cause fertility problems, especially in sows and gilts with symptoms like agalactia, small litters, premature farrowing, mummification and repeat estrus. Osweiler et al. (1990) observed that already a very low amount of sclerotia in the lactation feed is sufficient to cause agalactia in sows.
T-2 toxin, mainly produced by Fusarium sporotrichioides, can also negatively influence the reproduction performance of sows. Already low levels of T-2 toxin in feed of sows during the last third of gestation can degenerate and atrophy ovaries.
Further results showed that T-2 toxin in feed of gestating sows led to recurrence of estrus and small litters together with small piglets. Vanyi et al. (1991) observed that the piglets of sows which were exposed to T-2 toxin during late gestation showed diarrhea, wasting and died soon after birth.
For swine, the most hazardous mycotoxins are ZEN, ergot alkaloids and T-2 toxins, which can lead to huge reproduction problems in sows, gilts as well as in boars and hence can decrease the performance of the animals and as a consequence the economic results of the farm.