The use of mycotoxin binders to prevent intestinal absorption of mycotoxins has become a routine practice, which has led to the introduction of many different products on the market. However, not all mycotoxin binders are equally effective and the efficacy of many have been inadequately proven or not at all.
By Technical Team, Kemin Industries, Des Moines, IA, USA
The contamination of animal feed from mycotoxins represents a worldwide and persistent problem. Zearalenone (ZEA) is the number one mycotoxin as it can be detrimental to the sow's reproductive performance. This mycotoxin is found worldwide, especially in temperate and warm regions. It is produced by Fusarium species, mainly by F. graminearum and F. culmorum, and can be found on a variety of cereals and grains, including wheat, maize and soybeans. It is worthwhile to mention that ZEA might occur in its conjugated form, resulting in an underestimation of the degree of contamination.
Following ingestion, ZEA is known to bind to estrogen receptors, causing functional and morphologic changes in the responsive reproductive organs. This condition, often referred to as apparent hyperestrogenism, reduces fertility. Female pigs of all age groups are considered the most sensitive animals, but the hormonal effects vary in intensity according to age and reproductive cycle. Breeding sows and particularly gilts are extremely sensitive to the estrogenic effect of ZEA. Hyperestrogenism in female swines may manifest as swelling and reddening of the vulva and enlargement and reddening of the mammary glands. In severe cases, this syndrome may progress to rectal and vaginal prolapse. Other reported adverse effects include ovarian atrophy, prolonged estrus, persistent corpora lutea, pseudopregnancy, decreased fertility and implantation failure. Embryonic death, smaller litter sizes, birth of weak and splay-legged piglets and neonatal estrogen syndrome are common for sows ingesting ZEA during gestation. In boars, ZEA causes feminisation and reduced libido.
In many regions of the world, the risk of mycotoxins entering the feed chain is almost unavoidable. Besides preventative measures, the use of feed additives – so called mycotoxin binders - is a must for responsible and effective management of feed and food chain safety.
Feed additives: Mycotoxin binder
For a mycotoxin binder to be effective, it has to bind mycotoxins inside the gastrointestinal tract without dissociating. In this way, the toxin-binder complex passes through the animal and is eliminated via the faeces. The net effect is a reduced bioavailability of mycotoxins and reduction in the associated negative effects. As this approach is rather inexpensive and products can be easily incorporated in the animal's diet, the use of nonnutritive mycotoxin adsorbents for the control of mycotoxins has become common practice. This has resulted in many different products on the market. However, not all products are equally effective.
Most studies on the use of mycotoxin binders have been directed towards naturally occurring silicates (clays) and their ability to bind aflatoxins. While these products are offered at a low price, it is now scientifically accepted and generally recognised that the efficacy of natural minerals is limited to aflatoxins, with bentonites being more effective compared to other minerals. Furthermore, it must be noted that clays can adsorb micronutrients thereby negatively affecting the bioavailability of minerals and trace elements. Also, the risk of natural clays that are contaminated with dioxins has to be considered.
A supposed alternative for inorganic adsorbing agents are yeast cell walls derived from Saccharomyces cerevisiae. The claim is that the polysaccharide fraction of the yeast cell walls has mycotoxin-binding properties for multiple mycotoxins, including Fusarium mycotoxins such as ZEA. However, the number of independent, scientific studies on the chemistry of binding and the stability of the yeast cell-wall-mycotoxin complex under gastrointestinal conditions is limited. In addition, a critical evaluation of the existing in vivo studies reveals that some of the studies used incomplete designs and were limited to a recording of performance responses, which are rather non-specific.
Discovery of a new ingredient
Recent developments have been made in the fight against ZEA. During a multi-year research project at Kemin, numerous binding agents were screened for their ability to bind different mycotoxins. At the conclusion of the comprehensive selection process - considering features such as the ability to bind different mycotoxins at different pH levels, absence of undesirable sideeffects and safety - a new ingredient consisting of plant-derived organic polymers showed an extraordinary ability to bind ZEA. The material has a high number of active binding sites and high specificity to allow effective mycotoxin binding even at a low level of inclusion. This innovation is being marketed as Toxfin Supreme, a combination of different binding agents offering true broad-spectrum protection against all relevant mycotoxins.
In vivo efficacy tested
To evaluate the ability of Toxfin Supreme in binding ZEA under gastrointestinal conditions, an animal trial with female weaned piglets was conducted during a 42-day feeding period. Sixty female weaned piglets with an average weight of 9 kg were randomly distributed among five different treatment groups with three replicates for each group and four piglets per replicate. Dietary treatments included:
- Negative Control (NC)
- Negative Control + 1 ppm ZEA (Positive Control, PC)
- Negative Control + 1 ppm ZEA + 0.1% Toxfin Supreme (TS1)
- Negative Control + 1 ppm ZEA + 0.2% Toxfin Supreme (TS2)
- Negative Control + 1 ppm ZEA + 0.3% Toxfin Supreme (TS3).
Body weights and feed consumption recorded at day 1 and 42 were used to calculate average daily feed intake (ADFI), average daily gain (ADG), and feed conversion ratio (FCR). To determine the ability of Toxfin Supreme to bind ZEA, a mass balance study was conducted. Total faeces was collected and weighed during three consecutive days starting at 21 and 40 days of age. During the same period feed consumption of each group was recorded to accurately calculate the amount of ZEA consumed. At day 1, 21, and 42, three blood samples from each group were collected via the external tail vein and analysed for 17 -estradiol. The vulva length and width of each piglet was measured using a vernier caliper at the start of the trial, at day 21, and day 42. The vulva area was calculated according to the formula: area = (length x width / 2).
Exceptional binding efficacy
The study showed that zootechnical performance was largely unaffected by the diet, with the exception of ADG. The feeding of the contaminated diet caused a significant reduction in ADG but this effect was overcome by the addition of Toxfin Supreme.
The results of the mass balance study, shown in Figure 1, are expressed as a percentage and calculated as the ratio of total ZEA content in faeces over total ZEA intake. Only about 35% of ZEA was excreted in the positive control group, probably as a result of non- specific binding to feed particles. The addition of Toxfin Supreme resulted in a significant increase in the level of excretion in a dose-dependent matter at each time point. These results indicate a very high binding efficacy for ZEA in the gastrointestinal tract.
The vulva size measurements (Figure 2) are expressed as a percentage, and calculated as the ratio of change during the respective period over vulva area at the start of the trial. Consumption of the contaminated diet without Toxfin Supreme resulted in a significant increase of vulva area at day 21 (+ 413%) and 42 (+ 478%). There was no statistical difference between the negative control group and the group receiving the contaminated diet with 0.3% Toxfin Supreme, indicating a full recovery of the vulva size at both time points.
At day 21 and 42, 17 –estradiol concentration in serum in the group receiving the contaminated diet without adsorbent was significantly lower (52% and 41%, respectively) compared to the negative control group (Figure 3). At day 42, all groups receiving Toxfin Supreme showed a significantly higher level compared to the positive control group. Addition of 0.2% and 0.3% Toxfin Supreme to the diet restored the 17 -estradiol concentration to the same level as the negative control group. A blend of carefully selected binding agents, is exceptionally effective in binding ZEA under gastrointestinal conditions.
[Source: Mycotoxin Special]