Can Feed Damage Your Stock?
Mycotoxins affect up to 25 percent of the world's food crops. As well as being a health concern to humans they cause significant economic losses in animals due to reduced productivity, increased disease incidence, chronic damage to vital organs (e.g. kidneys, liver) and decreased reproductive performance. In fact estimated losses incurred by U.S. pig producers in 1980 due to they use of mycotoxin contaminated feed at $100 million.
And as far back as 1952, sow reproductive problems in Ireland associated with the use of barley infected with fusarium mycotoxins were being reported!
Mycotoxins are the toxic metabolites of fungi growing on cereal grains that are produced during growth, harvest, transport or storage. They are produced mainly by three genera or types of moulds - Fusarium, Aspergillus and Penicillium.
The present or absence of toxin-producing fungi is a poor indicator of the presence or absence of mycotoxins. The mycotoxins are believed to be produced in response to stress factors acting on the fungus - they require moisture, oxygen and carbohydrates to multiply and temperatures from 10oC to 250C.
Individual moulds, fungi or mycotoxins rarely occur in isolation and two or more mycotoxins together may have a greater toxic effect than any one alone.
Mycotoxins occur sporadically both seasonally and geographically. Table 1 shows the mycotoxins that may be found in feeds that come from different locations.
Aflatoxinsare produced by some strains of Aspergillus flavus and Aspergillusparasiticus.As temperatures of 25oC to 30oC are required for optimum production of aflatoxins, they generally occur in cereals/feedstuffs coming from warmer climates.
Fusariummycotoxins require lower temperatures for growth than the Aspergillus species, hence they are associated with cereals in temperate countries. The most common fusarium mycotoxins are zearalenone, vomitoxin, the fumonisins, T-2 toxin and fusaric acid.
Causes of Fusarium poisoning include:
1) purchase of mouldy, damp or badly stored grains
2) mixing of contaminated and uncontaminated grains
3) holding cereals in moist, damp conditions
4) allowing grains to heat
5) prolonged usage of feed bins, feed bridging across the bin and development of moulds
6) placing moist warm compounded feeds into bins
7) poorly maintained bins that allow water to leak in the bridging of feed in bins over long periods of time and their sudden descent
8) prolonged use of automatic feeders and retention of mouldy feed.
Zearalenone is the most important fusarium mycotoxin produced. It is an oestrogenic toxin - it mimics the effects of the female hormone, oestrogen. At high concentrations (1-30 ppm) it can interfere with ovulation, conception, implantation and foetal development. In pregnant sows it can increase the incidence of abortions and still births, reduce litter size and piglet viability. It may increase the weaning to service interval.
Young gilts are most sensitive, with concentrations as low as 0.5 to 1 ppm causing pseudo-oestrus and vaginal or rectal prolapse. The most striking clinical feature is the swollen red vulva of immature gilts. Young boars may have reduced libido and decreased testicular size but mature boars are rarely affected.
Vomitoxinis a potent inhibitor of feed intake and growth - 13 to 20 percent reductions in finisher pigs at a concentration of 4 ppm in the feed. …