Characteristics of Rye as a FeedgrainAuthor: T. Allen
Agricultural Economics, University of Saskatchewan
Saskatoon, Saskatchewan, S7N 5A8
The major end use for rye in Canada, and around the world has been as a feed grain. Rye is a cereal grain which can provide a valuable source of energy and protein for animals and poultry (Table 1). However, livestock and poultry feeders have been reluctant to use rye as a dietary ingredient. This reluctance may be attributed to concerns over the presence of ergot alkaloids, over anti-nutritional effects of pentosans in rye or the reduced feed intake of animals consuming rye.
|Poultry ME, kcal/kg||2,508||2,626||3,023|
|Swine DE, kcal/kg||3,108||3,251||3,400|
|Ruminant TDN, (%)||74||73||78|
|NE maint, Mcal/kg||1.76||1.75||1.89|
|NE gain, Mcal/kg||1.19||1.18||1.28|
|NE lact, Mcal/kg||1.71||1.70||1.81|
|Crude Protein, (%)||11.9||12.1||14.2|
|Methionine + Cystine, (%)||0.36||0.36||0.46|
Source: United States - Canadian Tables of Feed Composition, 3rd revision.
Ergot is probably best known as a disease of rye, but it does affect hundreds of plants in virtually every country of the world. The ergot fungus (Claviceps purpurea) can be severely toxic if present in sufficient concentration. Toxicity usually results from the consumption of a cereal which has been infected by the fungus spores. The ergot infestation tends to be particularly severe if ergot ascospores are present from the previous growing season and cool and damp spring weather is followed by dry, windy weather which spreads the ascospores. Ergot is less of a problem today as newer varieties of rye have a greater resistance to ergot. A farmer can further reduce the chance of an ergot infestation by practicing good farm management. Controlling wild grasses around field borders will considerably reduce the chances of an ergot problem.
Ergotism in North America is usually associated with domestic animals. This was not the case around the 10th century as numerous ergotism epidemics occurred in Germany, France, Ireland, Finland, Russia, and Belgium, with millions of people dying over the centuries. Ergotism has generally been a disease of poor people as the rich could afford to clean their grain and also preferred wheat which is less susceptible to ergot. However, rye was the staple food of the poorer class of people in many European countries. The last reported outbreaks of ergotism occurred in Africa in 1979 where 93 cases of ergot were reported and in 1975 in India where 78 cases of gastrointestinal ergotism were reported (Pohland, 1993).
At the present time ergotism is still more commonly thought of as an animal toxicity problem. The poisoning may result from an animal ingesting ergoty grain or from grazing on infected plants. Ergot poisoning takes on two different forms: acute poisoning where the symptoms are muscular trembling, lack of coordination, convulsions, and painful contractions of the muscles and chronic or gangrenous poisoning in which animals become dull and depressed and may develop gangrene of the extremities.
Ergot is widely believed to be especially dangerous for breeding stock, affecting lactation, fertility, or even causing abortion (Evers, 1972). However, evidence from several research studies suggests that the danger of ergot poisoning in animals is greatly overestimated. Dr. B.R. Blakely, of the University of Saskatchewan Western College of Veterinary Medicine, reported that confirmed cases of ergotism are very rare, and in reality the nature of the contractions resulting from the ingestion of ergot are not expulsive in nature and would not likely cause abortion. The fear of ergotism may also be exaggerated because the classic symptoms of ergotism, such as gangrene of the extremities, can easily be confused with those resulting from other problems such as frostbite.
Concern over ergot infestation is also a factor in the production decisions of farmers. Infested crops may suffer from both yield loss and grade loss if the grain is heavily contaminated with ergot. An Alberta study found that from 1972 to 1976 a large percentage of rye fields were infected, ranging from 45 percent in 1973 to 89 percent in 1975. The large number of infected fields, however, did not translate into large economic loss. The yield loss ranged from 0.013 percent to 0.016 percent and a grade loss of 0.08 percent occurred in 1972 but no grade loss occurred in the other years of the study (Harper, 1980).
Heavy infestations of ergot are not common in North America, but the potential for ergotism still exists and most grade standards have maximum allowable tolerance levels. The Canada Grain Act stipulates that rye intended for milling should be free of ergot. The Canadian grading standards have strict requirements for ergot in rye intended for all uses. Any samples containing more then 0.33 percent ergot by weight are graded "ergoty". Table 2 illustrates the maximum levels for other grades.
|Ergot In Rye (% by weight)|
|Canada No. 1 Western||0.05|
|Canada No. 2 Western||0.20|
|Canada No. 3 Western||0.33|
Source: Rye: Production, Chemistry and Technology (1976).
Researchers have recommended that dietary levels of ergot not exceed 0.1 percent by weight even though animals may tolerate higher levels of ergot in some circumstances. Ergot is easily detected in grain samples as the sclerotia are clearly visible to the naked eye and the removal of the ergot bodies is also relatively easy. In addition, if the contamination does exceed 0.1 percent, the contaminated grain can be mixed with uncontaminated grain until an acceptable level is obtained. Detection is not as easy if the rye has been milled into flour or is mixed in a processed feed, although chemical methods are available to detect ergot in milled rye products.
Pentosans are soluble and insoluble carbohydrates found in the plant cell walls of both wheat and rye. The soluble pentosans, which are in much greater concentration in rye (Table 3), can cause feeding problems when high levels of rye are used in domestic bird and animal rations. Rye pentosans have been linked to a depressed weight gain and reduced feed conversion in poultry.
There is a concern that animals do not like the taste of rye and that including rye in a ration may cause reduced feed intake. Thacker (1989) reported that the feed intakes of pigs that are fed a rye-based ration are generally 10 percent lower than the feed intake of those fed a barley-based ration. This reduced feed intake resulted in a slower weight gain, but Thacker also noted that it took significantly less feed to put on a pound of gain when a rye-based ration was used.
Rye does have limitations as a feed but rye is still a valuable feed grain. Its high energy level and protein content combined with a large yield potential make fall rye an excellent choice as a feed crop. The limitations of rye can be largely overcome by limiting the inclusion level of rye in certain diets as outlined by Racz and Campbell.