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Russian comfrey (Symphytum × uplandicum)

Datasheet

Description
Click on the "Nutritional aspects" tab for recommendations for ruminants, pigs, poultry, rabbits, horses, fish and crustaceans
Common names 

Russian comfrey, blue comfrey, Quaker comfrey [English]; consoude d'Upland, consoude panachée, consoude voyageuse [French]

Synonyms 

Symphytum peregrinum auct.

Related feed(s) 
Description 

The Russian comfrey (Symphytum × uplandicum Nyman) is a cultivated perennial herb reaching about 1 m high with large, lance-shaped hairy leaves, hairy stems and magenta-pink flowers (Bareeba et al., 1992; Göhl, 1982; Boonman, 1993; Teynor et al., 1997). The root system of a well-established comfrey plant is fleshy and extensive. The plant can be harvested for both leaves and tubers (Bareeba et al., 1992; Boonman, 1993).

Comfreys have been used as traditional medicinal plants in Europe for centuries, and have been presented in the 19th century as "wonder plants" for food and forage. Russian comfrey has been a staple of organic gardening and commercial herbal medicine since the 1950s due to its allantoin content, which is used by herbalists for treating digestive disorders (Teynor et al., 1997; Bareeba et al., 1992). However, in the 1980s, the use of comfrey leaves was recognized as a substantial health hazard causing hepatic toxicity in humans and with carcinogenic potential in rodents due to the presence of toxic pyrrolizidine alkaloids (see Potential constraints on the "Nutritional aspects" tab). This led to the ban of certain comfrey-based herbal products in several countries (Culvenor et al., 1980; Stickel et al., 2000).

As a fodder, Russian comfrey is valuable for its quick regeneration from the large food reserves in the roots, an ability that once earned the plant the nickname of "world's fastest protein builder" (Bareeba et al., 1992). It used to be promoted as a high-yielding protein-rich forage crop, a promise that was not supported by research data. Because of low yields and digestibility values, high cost of establishment and weed control, and low palatability to some animal species, some authors were not able to recommend Russian comfrey as a forage crop (Hart et al., 1981).

Distribution 

Russian comfrey originated from the natural hybridization of the common comfrey (Symphytum officinale L.) (native from England) with the prickly comfrey (Symphytum asperum Lepech.) (native from Russia). The plant was later exported to North America and Africa. Several trials have taken place in Eastern Africa since the 1950s, notably in Kenya, Egypt and Uganda. Comfrey produces the highest yields in full sunlight and under cooler conditions. Unlike annual crops, the leaves do not readily wilt during extended periods of drought due to its deep root system. This crop is also very frost resistant. Comfrey is adaptable to many soils, but prefers moist and fertile soils. Thin soils over rock will give a poor crop, but on light sands and loams, this crop will be productive if adequate nutrients are present (Teynor et al., 1997).

Processes 

Comfrey must be allowed to wilt for 24 h before ensiling. Additives such as molasses or grain aid fermentation of the ensiled forage. Mixing up to 25% comfrey with small grains or maize forage made high quality silage economically (Teynor et al., 1997).

Forage management 

The plant is semi-sterile and is propagated vegetatively mainly through root cuttings and root offsets. Once comfrey plants are well established, plenty of vegetative material can be harvested by cutting several times during the year. Older plants (over 12 weeks) can become too coarse for harvesting. Dry matter yields of 40 t/ha/year have been reported in Kenya but lower yields have been obtained in Uganda (about 2.5-3.6 t DM/ha/cut harvested in 12 weekly cuts) (Bareeba et al., 1992). In a trial in the United States, the promise of high yields was not fulfilled: Russian comfrey yields were about half those of alfalfa or orchard grass receiving the same amount of N fertilizer (Hart et al., 1981).

Nutritional aspects
Nutritional attributes 

Russian comfrey is moderately rich in protein (about 17% DM but values higher than 20% have been recorded). Owing to the hairiness of the leaves, soil contamination is important and the harvested forage is particularly rich in ash (about 20% DM) (Boonman, 1993). It has been used not only for cattle but also, due to its relatively low fibre content (crude fibre less than 15% DM), for pigs and poultry, to which the fresh leaves are palatable (Göhl, 1982).

Potential constraints 

Russian comfrey can be considered as a toxic plant, and some comfrey products have been banned for human consumption in some countries (Stickel et al., 2000). It contains at least eight pyrrolizidine alkaloids which cause acute necrosis of liver and lungs in cattle and horses. Administration of comfrey pyrrolizidine alkaloids to rats resulted in liver damage and death (Culvenor et al., 1980). Cases of horse poisoning from Russian comfrey have been reported (Fuller et al., 1986). However, it should be noted that feeding trials with Russian comfrey do not mention toxicity issues.

Ruminants 

Comfrey is not relished by grazing stock because of its hairy leaves and stems (Göhl, 1982). Wilting or ensiling collapses the leaf hairs, making the forage more palatable. Leaf hairs are apparently not a problem when cattle are fed green chop that is harvested daily (Teynor et al., 1997).

Dairy cows

Generally, dairy cows found Russian comfrey less palatable than rape, sunflower and clover, but there was individual variation, with some cows liking it (Yokota, 1974).

Sheep

Freshly cut Russian comfrey was reported to be very palatable to sheep. The digestible nutrient content was similar to that of berseem (Trifolium alexandrinum), and 30% lower than that of maize and sorghum forage. It was suggested that comfrey could be useful for summer feeding (El-Bassousy et al., 1975b).

Pigs 

Russian comfrey was found to be palatable to pigs (gilts) and inclusion rates up to 20% of the diet maintained feed efficiency and growth (Chong Hyung Kwak et al., 1968).

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 13.4 0.9 12.4 15.0 8
Crude protein % DM 18.6 4.1 14.6 29.3 14
Crude fibre % DM 11.4 1.9 9.4 14.0 5
NDF % DM 18.8 1
Ether extract % DM 3.6 1.1 2.5 5.4 5
Ash % DM 24.9 5.3 19.7 33.7 6
Gross energy MJ/kg DM 15.3 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 18.7 4.1 13.5 29.2 12
Phosphorus g/kg DM 4.9 1.7 3.4 10.0 12
Potassium g/kg DM 70.1 5.9 61.1 80.7 8
Magnesium g/kg DM 4.3 0.5 3.8 5.5 8
Copper mg/kg DM 17 3 12 21 8
Iron mg/kg DM 4125 794 2700 5500 8
 
Amino acids Unit Avg SD Min Max Nb
Alanine % protein 7.1 1.2 5.3 8.5 7
Arginine % protein 5.4 1.1 3.6 6.9 7
Aspartic acid % protein 11.6 0.5 10.9 12.0 6
Glutamic acid % protein 13.1 1.3 11.3 14.4 7
Glycine % protein 6.2 1.4 3.2 7.2 7
Histidine % protein 1.7 0.2 1.5 1.9 4
Isoleucine % protein 5.0 1.1 3.8 6.0 3
Leucine % protein 7.0 1.3 5.6 8.4 4
Lysine % protein 3.6 3.4 3.8 2
Phenylalanine % protein 5.0 0.9 4.1 5.8 3
Proline % protein 5.9 0.2 5.6 6.1 7
Serine % protein 4.7 0.5 3.7 5.2 7
Threonine % protein 5.0 0.7 3.6 5.8 7
Tyrosine % protein 3.8 0.5 3.2 4.3 4
Valine % protein 6.8 1.1 5.0 8.2 7
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 84.0 *
Energy digestibility, ruminants % 80.3 *
DE ruminants MJ/kg DM 12.2 *
ME ruminants MJ/kg DM 9.8 *
ME ruminants (FAO, 1982) MJ/kg DM 10.5 1
Nitrogen digestibility, ruminants % 82.2 1
 
Pig nutritive values Unit Avg SD Min Max Nb
Energy digestibility, growing pig % 72.1 *
DE growing pig MJ/kg DM 11.0 *

The asterisk * indicates that the average value was obtained by an equation.

References

Bareeba et al., 1992; El-Bassousy et al., 1975; Nheta et al., 2005; Patel, 1966; Strange, 1959; Van Rensburg, 1956

Last updated on 24/10/2012 00:44:56

References
References 
Datasheet citation 

Tran G., 2015. Russian comfrey (Symphytum × uplandicum). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/92 Last updated on October 5, 2015, 13:16

English correction by Tim Smith (Animal Science consultant) and Hélène Thiollet (AFZ)