Pigs are generally the most sensitive farm animals to mycotoxins. Among the different families of mycotoxins, zearalenone is the one that is responsible the most for reproductive disorders in swine. Zearalenone is produced by Fusarium fungi, which frequently contaminate maize, wheat, oats, and barley, mainly when they are growing at the crop stage. Zearalenone and its derivatives are estrogenic toxins, which means they can compete effectively for the specific binding sites of the oestrogen receptors. The oestrogenic syndrome in swine primarily affects the reproductive tract and mammary gland, and it induces infertility, vaginal and rectal prolapses, swollen vulvas and other breeding problems.
Zearalenone can also cause pseudopregnancy in sows and gilts. It can cause a female to exhibit a normal standing heat but does not allow the animal to conceive or experience repeated oestrus every21 days. This leads to the producer assuming that the sow has settled. Mycotoxin can also induce early puberty in gilts, although the affected gilts will continue to have heats but they will be infertile and without ovulation. Zearalenone has also been known to cause the oestrus period to last up to 80 days in some cases, when the sows have been fed low levels of the mycotoxin. Zearalenone intoxication in boars can lead to enlarged mammae, and atrophied testes, and their semen quality and quantity may also be affected.
ZEA is rapidly and well absorbed after oral administration (80-85%), and there is an important entero-hepatic cycle effect on the fate of ZEA. The particularly high sensitivity of swine to ZEA is partly related to the fact that swine convert ZEA into α-zearalenol, which is a more estrogenically active molecule than its parent compound.
Thirty 6-month-old Large White gilts were allotted to three different treatments (10 animals per group):
The experimental lasted 2 months and the gilts were given a feed based on 86% barley and 14% protein, as well as vitamin and mineral supplements. The gilts were weighed once a month. Signs of oestrus were visually observed twice a day (behavioral changes and genital redness) and the standing reflex was measured three times a day. After the trial, that is, at 8 months of age, five gilts from each group were slaughtered to evaluate the reproduction system. The measured parameters included the length of the uterus, the size of the vagina vestibule, the length of the vagina, the length of the cervix, as well as the ovarian size and volume.
The gilts fed the zearalenone contaminated diet had significantly prolonged oestrus times, compared to the control group and to the contaminated group with the included mycotoxin deactivator (Fig.1). The mycotoxin group also resulted in an extended standing heat, although this effect was fully moderated by the supplementation of the mycotoxin deactivator (Fig.2). An inspection of the reproductive tract of the gilts after slaughtering indicated a significant influence of 660 ppb zearalenone on the uterus length, the size of the vagina vestibule, and on the volume and weight of the ovaries (Table 1). These observations confirmed a suboptimal development of the reproductive system of the gilts, which showed clear signs of oestrus and prolonged standing heat. However, when the gilts consumed the contaminated feed with the simultaneous inclusion of the mycotoxin deactivator, the length of the uterus and volume of the ovaries were similar to the control gilts.
Figure 2. Standing heat, h
a,b Means with different superscripts differ (0.05 ≤ p ≤ 1.10)
| Control | Zearalenone | Zearalenone + Mycotoxin deactivator | |
|---|---|---|---|
| Length of the uterus (m) | |||
| left side | 1.2a | 1.02b | 1.2a |
| right side | 1.2a | 0.9b | 1.1b |
| Weight of the genital organs and the urinary bladder (g) | 506.0a | 496.6a | 505.6a |
| Size of the vagina vestibule (cm) | 7.3a | 6.9b | 6.1c |
| Length of the cervix (cm) | 9.8a | 10.3ab | 11.4b |
| Volume of the ovaries (cm3) | 16.2a | 9.71b | 14.2a |
Table 1. Status and functionnality of the reproductive system
Thirteen 10-month-old Large White boars with an average live weight of 150-155 kg were included in the study. The animals were allotted to three different groups:
All the boars were fed a good quality control feed during a pre-experimental period of 2 weeks. The boars were then fed the different treatment diets over the rest of the experimental period (5 weeks). Boars from all the treatment groups were fed the same mycotoxin-free feed (control feed) during a 3-week recovery period. Semen was collected once a week from each boar during the pre-experimental, experimental, and recover periods. The following parameters were measured: volume of ejaculation (microscopic evaluation, Goryaev’s chamber), spermatozoa count per ejaculation (eosin coloring), and spermatozoa motility (on fresh semen evaluated on a 10-point scale).
From the first week onward, the ejaculation volume in the boars fed the zearalenone-containing feed decreased by 40.8 %, compared to the control group, and amounted to 141.0±12.6 ml (Fig. 1). On the other hand, the ejaculation volume in the contaminated group with the inclusion of the mycotoxin deactivator remained similar to that of the control group. The spermatozoa count per ejaculation in the group with zearalenone was reduced within two weeks (Fig. 2). There was a negligible difference between the control and the group fed the zearalenone-contaminated feed with the included 1 kg/t of mycotoxin deactivator . The lowest spermatozoa motility was determined in the boars fed the zearalenone-contaminated feed (Fig. 3). During the experimental period, the sperm motility of the boars fed the mycotoxin deactivator treated feed was not significantly different from the sperm motility of the control group.
Figure 3. Volume of ejaculate, ml
Figure 4. Spermatozoa count per ejaculation, billion
Figure 5. Spermatozoa mobility score
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