MOLDY FORAGES AND DEER
This article was originally printed
in the October / November 2001 issue of Tracking The Industry. . .
This
article is copyrighted and may not be reproduced in any form without
permission.
Dry conditions in some parts of Saskatchewan, wet conditions in the other parts and a shortage of forage supplies may result in undesirable effects on forages this year. While most white-tailed deer diets revolve around an alfalfa forage base, producers may not have access to alfalfa and may be contemplating the feeding of cereal forages such as oats, barley or wheat greenfeeds or clover varieties.
Is there a concern in feeding moldy forages to white-tailed deer? Maybe. While deer feeding behavior would suggest that deer will feed around moldy portions and select only the "good" parts, producers should be aware of possible implications associated with moldy feeds.
Molds and funguses are common inhabitants that grow on all feeds and are ever present. However, when conditions permit, their growth becomes more prevalent and affects greater quantities of the feed. While the growth of mold does not indicate mycotoxin production, greater levels of visible mold infection may increase the probability of mycotoxin production, especially under ideal conditions. In forages baled above 16% moisture, conditions are favorable for mold development.
The most common mold produced that has implications for ruminant livestock is Fusarium spp.. Fusarium molds are a result of Fusarium Head Blight (also known as scab or smut) and most commonly associated with cereal crops such as barley and oats. Fusarium molds infect the seed head and seed kernels of cereal crops. When feeding a cereal greenfeed, deer will naturally select the seed head over the stem as it contains the most energy and the least amount of fibre. If the crop has been infected with Fusarium, the deer will be focusing their feeding on the most infected part of the plant.
As mentioned before, the presence of mold growth does not imply mycotoxin production. However, it is possible that Fusarium molds will produce toxins. Fusarium is responsible for the production of mycotoxins such as vomitoxin (DON), T2 toxin, DAS toxin and Zearalenone. Vomitoxin (DON) is the toxin most likely to be produced by Fusarium and is the mycotoxin of greatest concern. If mycotoxins from Fusarium Head Blight are present, DON levels will be highest two to three weeks prior to seed maturity, then decrease. Concurrently, it is recommended that greenfeed and silages be cut when the kernels are in the same development stage. The stage of maturity for cutting occurs at the same time when potential DON production is at its highest. By reasoning, severity of infection of the seed head will determine final DON level with highly infected crops more likely to contain higher DON levels than slightly infected crops. If a feed is infected with mold, tests can be performed to indicate what type of mold species is growing and whether or not that mold has the capability to produce mycotoxins. However, the presence of mold does not indicate a presence of mycotoxins. Tests for mycotoxins, primarily fusarium toxins, should be performed if there is concern.
What are some methods in dealing with mold toxicity in ruminants? Firstly, try and avoid feeding any moldy forages or feed to pregnant does, particularly during the third trimester. It is during the third trimester that the fetus is rapidly growing. Any ingestion of mold or inhalation of dust from moldy forages (contains spores from the mold) may result in abortions, poor calf performance when born or inhibited immune systems of both the fawn and the doe. Also, the inhalation of dust and spores may create respiratory irritations and allergic reactions. The difficulty in feeding moldy forages is that potential toxins may be ingested or inhaled. It is assumed that once toxins infect the animal, any damage done may be irreversible. It is recommended to try and keep moldy forages away from pregnant does and replacement females and if absolutely necessary, fed to mature male deer. On the bright side, given the selective nature of deer they will feed around mold clumps or refuse the feed entirely. However, be ready and expect more feed waste.
Clovers have been a popular feed used by deer producers. However, not all clover varieties are equal and as such have their own drawbacks. Sweet clover makes an excellent feed for deer when in pasture or browsed. However, if baled and allowed to grow moldy, sweet clover can be deadly. Sweet clover contains a substance called coumarin, that in the presence of mold, is converted into dicoumerol. Dicoumerol works much similar to warfarin in that it works to inhibit blood clotting mechanisms, resulting in excessive hemorrhaging or "bleeding disease". It is recommended that long term feeding (several weeks to months) of moldy sweet clover be avoided, and if feeding is necessary, a conservative recommendation would be to feed 2 weeks on sweet clover followed by 2 weeks of a different feed - leaving enough time to let the toxin clear the system. And above all, do not feed moldy sweet clover prior to fawning as the does will continue to bleed once the fawn has been expelled. Other clovers to watch are red clovers that contain phytoestrogens that may negatively affect doe fertility. Lower coumarin sweet clover varieties and lower phytoestrogen red clover varieties are available if clovers are considered.
If feed shortages or moldy feed is a problem, please consult your local nutritionist, Provincial Extension Agrologist or Livestock Agrologist.
Murray Feist, M.Sc.,
P.Ag.
Provincial Feed Industry Development Specialist
Saskatchewan
Agriculture and Food
Phone: 306-933-5570
Fax: 306-933-5605
E-mail:
mfeist@agr.gov.sk.ca
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