The Effect of Mycotoxins on Swine Fertility
Swine fertility has a significant effect on farm profitability and the number of pigs produced per sow per year is one of the factors that define production costs per pig. It is crucial to sustain high reproductive indices like litter size, number of farrowings per year and productive days.
Various parameters affect herd fertility, including:
- Anti-nutritional factors
Mycotoxins are known anti-nutritional factors that affect reproduction and over 400 different mycotoxins have been identified to date. The most well-known are trichothecenes, zearalenone (ZEN), ochratoxins, aflatoxins, fumonisins and ergot alkaloids. Every raw material can be affected by more than one fungus, and each fungus can produce more than one mycotoxin, so it is highly likely that there will be more than one mycotoxin in any one feed ingredient (Figure 1).
This increases the chances that mycotoxins will interact and produce synergistic effects, which are of great concern for livestock health and productivity.
The Fusarium toxins deoxynivalenol (DON) and ZEN are a good example of co-contamination. These mycotoxins are mainly produced by F. graminearum, F. culmorum, and F. roseum (Tiemann and Dänicke, 2007).
Direct effect on pigs
Pigs are usually considered to be the species that is most susceptible to mycotoxin contamination, with young animals and breeding females the most sensitive groups.
Figure 2 shows some of the direct effects of mycotoxins on reproductive performance.
ZEN is most notorious for its effects on reproduction (Table 1). It blocks normal hormone synthesis due to its resemblance to the estradiol molecule and competes for estradiol (estrogenic) receptors. This estrogenic effect disrupts the hypothalamic-pituitary-ovarian axis and suppresses secretion of the follicle-stimulating hormone (FSH) in the ovaries, disrupting the endocrine system.
If DON is present in feedstuffs, it compromises feed intake and may cause vomiting (Diekman and Green, 1992). It also inhibits protein synthesis, alters the immune system response and causes reproductive problems by targeting oocyte and embryo development (Pestka et al., 2004; Alm et al., 2006). The effect of DON on reproduction in pigs is more indirect (Figure 3) as the lower feed intake reduces nutrient availability and poses a threat to the metabolic pathways in the reproductive system. Any dysfunction of the vital organs that have a key role in metabolism, such as the liver and spleen, also has an adverse effect on health. Once health is compromised, metabolic priorities change and the requirements of the reproductive system move lower on the list of priorities (Kanora and Maes, 2009).
Follicle development, oocyte maturation and embryo development
In vitro studies of porcine oocytes have shown that ZEN, DON or a combination of ZEN and DON disrupt oocyte development (Figure 4), making them unable to mature. This may compromise embryo viability, maintenance of pregnancy, and birth weight. DON had the most potent effect on embryo development after fertilization, resulting in fewer and abnormal blastocysts.
In a recent trial contracted by BIOMIN at the University of Berlin, Institute for Animal Nutrition, Department of Veterinary Medicine, the reproductive performance of sows challenged with DON and ZEN during long-term (three-cycle) exposure to Fusarium toxins was investigated. Sows were allocated to one of three different groups, as per Table 2.
The results in Figure 5 show that the mycotoxins impaired various reproductive parameters. The most common index of reproductive performance is the number of piglets weaned per sow per year. Farrowing rate and wean-to-estrus interval both affect this index. The presence of mycotoxins, especially ZEN, increased returns to heat in inseminated sows and reduced the farrowing rate.
Feed intake fell, affecting the sows' body condition score at weaning and their milk yield. Underweight sows take longer to come into estrus after weaning, which reduces the number of farrowings per year, so fewer weaned piglets are produced per sow per year. Lower milk yields could also compromise litter growth and weaning weights, resulting in lower weights at slaughter or more days on feed. Mycotoxins also affected piglet quality (Figure 6): the percentage of underweight piglets (<1.2 kg) increased, suggesting that mycotoxins have a detrimental effect on embryo development and maternal nutrition. This negative effect on piglet quality, accompanied by the reduction in milk yield, may increase pre-weaning mortality and reduce weaning weights.
However, animals recovered well when Mycofix® Plus was added to the diet.
Multiple mycotoxins; many consequences
Mycotoxin co-contamination of raw materials is more common than contamination with a single mycotoxin, as routinely reported in the BIOMIN Mycotoxin Survey. Each mycotoxin acts in a specific manner and affects multiple tissues, organs and functions. When combined, these challenges cause a myriad of different clinical or subclinical signs, often not linked to the known effects of direct mycotoxin contamination in animals.
Alm, H., Brüssow, K-P., Torner, H., Vanselow, J., Tomek W., Dänicke, S. and Tiemann, U. (2006). Influence of Fusarium-toxin contaminated feed on initial quality and meiotic competence of gilt oocytes. Reproductive Toxicology. 22, 44–50.
Diekman, M.A. and Green, M.L. (1992). Mycotoxins and reproduction in domestic livestock. Journal of Animal Science. 70(5), 1615–1627.
Tiemann, U. and Dänicke, S. (2007). In vivo and in vitro effects of the mycotoxins zearalenone and deoxynivalenol on different non-reproductive and reproductive organs in female pigs: a review. Food Additives and Contaminants. 24(3), 306–314.
Kanora, A. and Maes, D. (2009). The role of mycotoxins in pig reproduction: a review. Veterinarni Medicina. 54(12), 565–576.
Malekinejad, H., Schoevers, E., Daemen, A., Zijlstra, C., Fink-Gremmels, J., Colenbrander, B. and Roelen, B. (2007). Exposure of oocytes to the Fusarium toxins zearalenone and deoxynivalenol causes aneuploidy and abnormal embryo development in pigs. Biology of Reproduction. 77(5).
Pestka, J., Zhou, H., Moon, Y. and Chung, Y. (2004). Cellular and molecular mechanisms for immune modulation by deoxynivalenol and other trichothecenes: unravelling a paradox. Toxicology Letters. 153(1), 61–73.