Feed quality can be important to improving feed intake, but having moldy feed could cost you more than poor performance. If your feed develops high levels of mycotoxins you could be playing with fire.
In general, changes in palatability and nutrient content of grain infected with mold before harvest is slight, and there may even be some improvement in nutritive value as a result of starch hydrolysis similar to that seen in early germination, says Josa Ferrer, president of Agranco. But if mycotoxins develop, that’s a different story.
“Mycotoxins are secondary meta-bolites produced by molds growing in feedstuffs,” says Ferrer. “Several key points should be considered when faced with options of purchasing fungus-infected grain or using feed that has become moldy in storage.”
Here are some points you should consider:
Whether fungal toxins are present in concentrations sufficient to affect pig health and performance;
Whether the palatability and nutrient content has been altered for better or worse;
Whether the lower price of the grain or other feed component compensates for the risks involved.
There are many different kinds of mycotoxins. Ferrer names a few of the more common varieties, including:
Aflatoxins. The fungi that produce aflatoxins most commonly grow during storage of summer crops, but wheat and barley also can be affected. Aflatoxins usually occur on farms that mix their feeds from grains they produce. These molds grow best at 30°F to 40°F. Aflatoxins can be produced within two to six weeks and signs of mycotoicosis of pigs may be noticed within a week of it being introduced in the diet.
Clinical signs of aflatoxin poisoning are not characteristic. Pigs go off their feed, some may die, some are pale and jaundiced. It damages the liver, which can be detected during post-mortem exams. There is no specific treatment for affected pigs.
“Replace or dilute moldy feed with clean feed that contain adequate protein, as the effects of aflatoxin poisoning are made worse by low dietary protein,” says Ferrer. “Pigs may take several weeks to recover and never reach their growth potential.”
Ochratoxins. Ochratoxin A is produced by a number of aspergillus and penicillum fungi. Ochratoxin A may occur in combination with citrinin and both of these cause kidney damage. Depressed appetite and reduced growth rate may result. Ochratoxin A is a common contaminant of barley grown in cool to wet conditions, such as in northern Europe and Canada.
Zearalenone. Zearalenone is the most detrimental mycotoxin to pigs, with some properties of the female sex hormone oestrogen. Several fusarium molds produce zearalenone in grains grown in cool, wet climates. The fungus actually grows on the grain before harvest when rainfall is high and insect damage is prevalent, but damp, cool post-harvest storage increases the hazard.
“When fed to female grower pigs, zearalenone causes swelling and reddening of the vulva similar to that seen at natural heat,” says Ferrer. “This can progress to straining and prolapse of the rectum and vagina. It can cause slight development of the teats of gilts and occasionally swelling of the prepuce of boars.”
A dark purple discoloration of maize or pink tips on bleached wheat may be an indication of infection with zealanone-producing mold, but it also can be present in weather-damaged sorghum. Diagnosis is confirmed by feed analysis.
Trichothecenes. This group of mycotoxins includes deoxynivalenol, which is occasionally detected in corn and wheat. If the pigs are hungry when the feed is first offered they may eat and then vomit. A purple-red mold infecting wheat, corn and soybeans before harvest produces these mycotoxins, often in conjunction with zearalenone.
Fumonisins. Fumonisins are common in corn infected with fusarium moiliforme in most temperate regions of the world. Fumonisins can be produced before harvest. They have been associated with pulmonary oedeman, or fluid in the lungs, of pigs, says Ferrer.
When you make feed purchasing decisions it’s important to recognize feed that is at risk of developing mycotoxins.
“Deteriorated grain will be lighter in weight, be discolored and darkened if mold invasion is extensive,” says Ferrer. “The endosperm is likely to have a chalky appearance due to the partial hydrolysis of the nutrient stores.”
Gross energy on a weight basis may be unaffected, but fiber and non-protein nitrogen may increase. Minor nutritional deficiencies of weather-damaged grains can generally be ignored in dietary formulation, but increasing digestible energy with fat can easily compensate.
Many molds can grow in stored feed when hygiene is poor, says Ferrer. Mold spores are always present, but the main factor stopping mold growth is lack of moisture. However, that can cause reduced palatability and negatively affect feed conversion. In material with extensive mold during storage, the relative amount of fiber in the grain will increase proportionately to the decline in starch, protein and fats, resulting in lower energy content. Vitamins and other essential nutrients also can be affected. Cleaning silos and feed-handling equipment regularly, as well as rapid feed turnover is important to maintain feed quality.
In times of high humidity, feed may become slightly moldy despite good hygiene. Damaged feed that has undergone fungal growth during storage may have “off” aromas and flavors and be unpalatable when first offered to pigs. Usually, this lasts only a few days before pigs become accustomed to the taste and smell. If it persists longer, it might indicate infectious disease or dietary imbalance, although mycotoxins are always a possibility.
Finishing pigs are a better proposition for unpalatable feed. You can minimize the risks by checking for zearealenone-contaminated feed for sows in the gestation/lactation phase.
Mycotoxins aren’t a new issue, but the threat can be overlooked. You may want to evaluate your feed occasionally, to avoid mycotoxin-related risks.