Feeding swine with mycotoxin contaminated feed: expect the worse
Mycotoxins are toxic substances produced by naturally occurring metabolic processes in fungi. Mycotoxins can invade the seeds whilst the crop is still in the field before the harvest. As a result, high numbers of mycotoxins could already be present in the ingredients before they are received in feed mills or farms. Alternatively, mould growth can occur during storage at the feed mill or on the farm. Mould can also grow during the processing of feed especially when the temperature and humidity in the feed is increased during mixing. Finally, mould growth and mycotoxin production can also occur at the farm level from improperly cleaned silos, transportation and feeders. The production of mycotoxins is enhanced by factors such as the moisture of the substrate (10 to 20%), the relative humidity (≥ 70%), the temperature (0 to 50°C, depending on the fungus species) and the availability of oxygen (Kanora and Maes, 2009). Feed mills therefore have an important role of keeping the levels of mycotoxins as low as possible whilst also avoiding multi-mycotoxin contamination. Most of the mycotoxins occur concurrently and a commodity usually contains more than one mycotoxin at the same time. According to the statistics from the United Nations Organization, approximately 40 to 45% of pig feeds worldwide are contaminated with mycotoxins.
Mycotoxins in swine feed, what to expect?
Non-specific symptoms of mycotoxin contamination in fattening pigs and piglets that occur most frequently and concurrently are decreased feed intake, diarrhea and feed refusal - which are typical for deoxynivalenol (DON) contamination. It is known that DON is capable of compromising several intestinal barrier functions, including a decreased surface area available for nutrient absorption and potentiate intestinal inflammation. Both feed refusal and diarrhea might contribute to decreased daily weight gains and low FCR in growing pigs.
In this article, we will focus our attention on zearalenone (ZEN). ZEN is a mycotoxin produced by cereal species of Fusarium fungi (including F.graminearum). These fungi are common, occurring in cereal plants around the world and causing ZEN contamination in harvested grains. This toxin is frequently found in maize and its products. Reports have suggested that grass, hay and straw can also contain ZEN. ZEN is estrogenic and has various effects in different animals. The most striking clinical feature is the swollen red vulva of immature gilts. The other signs depend on the levels present in the feed and the state of pregnancy. The following may be used as guidelines to the symptoms that may be observed:
In pre-puberty gilts (1 - 6 months old): 1 to 5 ppm in feed causes swelling and reddening of the vulva and enlargement of the teats and mammary glands. Rectal and vagina prolapses also occur in the young growing stock.
In mature gilts: 1 to 3 ppm will cause variable lengths of the estrus cycle due to retained corpora lutea and infertility.
Boar: semen can be affected with feed levels above 30 ppm. Poor semen quality causes poor reproductive performance of boars exposed to ZEN. At higher levels, poor libido, edema of the prepuce and loss of hair can occur.
- In sows: levels of 5 to 10 ppm can cause anestrous, which may also be associated with pseudo-pregnancy due to the retention of corpus luteum. However, ZEN does not normally cause abortion. 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. Above this level, complete loss between implantation and thirty days occurs followed by pseudo-pregnancies. Low levels of 3 to 5 ppm 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 5 ppm has no effect on lactation but the weaning to service interval may be extended. The clinical signs are distinctive and include…... Rations that are suspected of contamination should be examined for both the presence of ZEN and also other estrogen-like substances. Removal of the suspect feed will be followed by the regression of symptoms within three to four weeks.
Study of the detrimental effect of ZEN on boar semen quality
The aim of this study was to evaluate the influence of ZEN on the reproductive performance of boars and the protective effect of a complex mycotoxin deactivator TOXY-NIL®PLUS as an effective tool against ZEN in swine.
Thirteen Large White boars, 10-months of age with an average live weight of 150-155 kg were included in the study. The animals were allotted to three groups:
Control: good quality compound feed (3 animals)
Zearalenone: feed contaminated with 570 ppb ZEN (5 animals)
Zearalenone + TOXY-NIL®PLUS: feed contaminated with 570 ppb ZEN with inclusion
of TOXY-NIL®PLUS at 1.0 kg/t (5 animals)
All boars were fed good quality control feed during the pre-experimental period of 2 weeks. Following this, the boars were allocated to one of the three groups and fed with the different treatment diets during the experimental period which lasted 5 weeks. This was followed by a 3-weeks recovery period when boars from the different treatment groups were fed on the same mycotoxin-free feed (good quality control feed) again. Semen was collected once a week from each boar during the pre-experimental, experimental and recovery periods. The parameters measured were: volume of ejaculation (microscopic evaluation using 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 of the experimental period onwards, the volume of ejaculation in the boars fed on the ZEN-containing feed decreased by 40.8 % compared to the control group and amounted to 141.0 ±12.6 ml (Fig. 1). In contrast, the volume of ejaculation in the contaminated group with inclusion of TOXY-NIL®PLUS remained similar to that of the control group.
The spermatozoa count per ejaculation in the group with ZEN was reduced within two weeks of the experimental period (Fig. 2). The difference between the control group and the group fed with ZEN-contaminated feed with 1 kg/t of TOXY-NIL®PLUS included was negligible. The lowest spermatozoa motility was determined in boars fed ZEN-contaminated feed (Fig. 3). During the experimental period, the sperm motility of boars fed TOXY-NIL®PLUS treated feed was not significantly different from the sperm motility of the control group.
Fig.1. Volume of ejaculate, ml
Fig. 2. Spermatozoa count per ejaculation, billion
Spermatozoa motility score
The results from this study showed that estrogen-like mycotoxin ZEN had a significant influence on the reproduction performance of boars (volume of ejaculate, spermatozoa count and motility of spermatozoa). There was no effect of ZEN observed on the reproductive performance of boars following the inclusion of TOXY-NIL®PLUS at 1 kg/t in the feed.
The efficacy of the mycotoxin deactivator TOXY-NIL®PLUS was confirmed in an in vivo trial. TOXY-NIL®PLUS provides a layered defense that functions on a cellular, organ and system level to protect the animal from toxic metabolites of moulds and a variety of mycotoxins including the ones which are more difficult to control such as zearalenone.
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Article made possible through the contribution of Radka Borutova and Nutriad International