Mimosine Toxicity Research Articles

Effect of subabul (Leucaena leucocephala) based complete rations on carcass characteristics and serum thyroxine profile of kids

A study was conducted to evaluate the effect of feeding complete rations containing untreated Leucaena leucocepahala leaf meal (ULLLM) (Subabul) and treated (moist heat) L. leucocepahala leaf meal (TLLLM) at 30 and 40 parts on plane of nutrition and nitrogen balance in kids. Mimosine content of LLLM after moist heat treatment for single-treated and double-treated material was 1.91 and 1.17%, respectively. A feeding trial was conducted with 30 non-descript kids (8.42±0.15 kg, 3 to 4 month-old) by allocating to five complete rations as CR1 (control), CR2 (30% ULLLM), CR3 (30% TLLLM), CR4 (40% ULLLM) and CR5 (40% TLLLM). Average daily gain was significantly (p<0.05) higher in CR1 (55.90±2.25 g/d) and CR3 (56.30±0.92 g/d) followed by CR2 (37.90±3.95 g/d) and CR5 (38.70±5.60 g/d) and lowest in CR4 (23.90±3.65 g/d) group. Dressing yield (39.53 to 44.99%) did not indicate significant changes among the groups. The edible, non-edible, organ weights and wholesale cuts did not indicate significant difference among the groups. Serum T3 (|jg/ml) and T4 (ng/ml) hormone profile showed significant reduction (p<0.05) at 90 days in CR2 (1.80±0.10 and 49.43±2.50) and CR4 (1.10±0.10 and 40.11±2.10) as compared to other groups CR1 (3.61±0.70 and 87.14±8.20), CR3 (2.42±0.20 and 83.14±7.20) and CR5 (2.81±0.30 and 78.11±5.10). Histopathological examination of thyroid gland showed hyperplasia of epithelial cells and follicular vacuolation with cuboidal epithelium in CR2 and CR4 groups. However, normal pattern was observed in CR1 and very mild changes in CR3 and CR5 groups. It was concluded that hot water treatment of L. leucocepahala leaf meal is partially effective in ameliorating mimosine toxicity and can be included at 30% level in complete rations of kids.

PERFORMANCE OF RABBITS FED LEUCAENA LEUCOCEPHALA AND AND CONCENTRATR BETWEEN 9TH AND 25TH WEEKS OF AGE.

Fourteen fryer male rabbit (New Zealand white and chinchilla breeds) were used for the experiment. Equal numbers of rabbits from the two breeds were used for each treatment. The rabbits were randomly Leucaena leucocephala respectively. The rabbit in the two groups were given the same amount of pelleted concentrates from a commercial feed miller and were fed to determine the effect of level of leucaena offered/intake on the growth rate of rabbits. Four fryers which were fed the same % of concentrates and Aspilia africana served as the control. Growth rate decreased at the beginning of the study followed by satisfactory growth thereafter. The control animals had a higher growth rate compared to the other two groups (P&lt;0.05. Alopecia and decreased appetite were the initial symptoms of mimosine toxicity observed, but they were soon overcome with time. Rabbits can tolerate up to 100g leucaena in their diet in addition to pelleted concentrate.

Generation of reactive oxygen species by hydroxypyridone compound/iron complexes

ABSTRACT Objectives: Prooxidant properties of iron-binding hydroxypyridone compounds including deferiprone and mimosine were analyzed. Methods: Hydroxypyridone/iron-dependent production of reactive oxygen species was evidenced by the inactivation of aconitase, the most sensitive enzyme to oxidative stress in permeabilized yeast cells. Results and Discussion: Deferiprone and mimosine produced reactive oxygen species in the presence of ferrous sulfate. The inactivation required sodium azide the inhibitor of catalase, and addition of TEMPOL, a scavenger of superoxide radical, protected aconitase from the inactivation, suggesting that the superoxide radical produced from the hydroxypyridone/iron complex is responsible for the inactivation of aconitase. A principal role of superoxide radical was further supported by the finding that the hydroxypyridone/iron complex can inactivate aconitase in the presence of cyanide the inhibitor of superoxide dismutase. Deferiprone and mimosine stimulated the Fe2+ oxidation, resulting in the one-electron reduction of oxygen to form superoxide anion, which can inactivate aconitase by oxidizing the prosthetic iron-sulfur cluster. Mimosine further stimulated the ascorbate/iron-dependent formation of 8-hydroxy-2′-deoxyguanosine in DNA. Conclusion: Biological toxicity of mimosine and deferiprone reported previously can be accounted for by the prooxidant properties of hydroxypyridone compounds: coordination complex with iron generates reactive oxygen species resulting in the disturbance of mitochondrial energy metabolism and DNA damage.

Leucaena feeding systems in Paraguay

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Leucaena leucocephala became naturalized in Paraguay long ago. However, due to cases of toxicity in horses and cattle, now identified as mimosine toxicity, leucaena was considered a weed until the beginning of this millennium. At this time the mimosine toxicity problem was overcome by the introduction of ruminal fluid from Australia containing the mimosine-degrading and -detoxifying bacterium Synergistes jonesii. As long as an internationally funded technical assistance project was operating (offering technical advice, provision of seed, seed scarification service and transmission of ruminal fluid containing Synergistes), the area sown to leucaena (either in twin rows into grass pastures or as fodder banks) increased rapidly in Paraguay, particularly in the Chaco area. However, the powdery fluvisols of the drier parts of the Chaco were not well suited to growth of leucaena, as persistence was restricted due to the impact of rodents, termites and also leaf-cutting ants, which prosper particularly well in this part of the Chaco. In more humid areas with usually heavier soils, currently leucaena represents an integral part of the feeding systems in hundreds of Paraguayan farms (large-scale as well as smallholders), mainly for steer fattening and dairy cow supplementation. After taking into account the above-mentioned setbacks, the total area of leucaena is currently estimated at about 10,000 ha.

Leucaena feeding systems in India

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Since its introduction to India in 1976 Leucaena leucocephala ssp. glabrata has spread rapidly, especially in the last couple of decades, mainly due to its use as either firewood or pulpwood. Use of its foliage for feeding livestock has been mainly a by-product of this activity. The foliage is highly nutritious because it has high protein concentration and good palatability, and the tree can withstand repeated defoliation. Research carried out by Indian scientists on leucaena has focused on mainly agronomic management, agroforestry studies of mixed cropping systems, mimosine toxicity, germplasm testing and economic evaluation. Feeding leucaena has had a positive impact on the dairy industry in particular. It is rarely purchased for fodder and is usually poached by smallholders from existing plantations, most of which are established by animal rearers for their own purposes. More widespread use of leucaena for fodder could be achieved in India by introducing varieties with either reduced seed production or sterile ones, which can be easily propagated vegetatively. In addition, psyllid resistance, suitable mechanized harvesting methods and training livestock owners in proper management of leucaena trees should help in making this high quality fodder more popular in India.

Leucaena feeding systems in Argentina. II. Current uses and future research priorities

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.This paper presents the current status of Leucaena leucocephala (leucaena) feeding systems and proposes research priorities for leucaena development in Argentina. Although research on leucaena as forage for cattle production began in the late 1960s, it was not widely adopted until 2010 (5 decades later). The recent adoption is related to the incorporation of the ‘Australian technology package’, previously adapted for use by farmers in the neighboring region of the Paraguayan Chaco. In June 2018, we surveyed 8 properties with about 2,400 ha of leucaena in silvopastoral systems for beef cattle production in the Argentinean Chaco region, as well as 10 smallholder farms with about 10 ha of leucaena protein banks for dairy cattle in the northeast of Argentina. In the silvopastoral systems, leucaena condition was excellent on most properties in the 750‒1,350 mm/year rainfall zone and low/poor on only 1 farm due to low rainfall (600 mm/year). In protein banks, leucaena condition was excellent or good on 6 of the properties and low/poor on the remaining 4, attributed to ingress of weeds and/or overgrazing. Grass condition was good in most of the systems but was low/poor in 2 silvopastoral systems due to very high stocking rates imposed to restrict leucaena height. Although there is high potential for leucaena development in Argentina, expansion should take place carefully with leucaena planted only on areas suitable for successful establishment, and using appropriate management practices to reduce establishment failures and costs, restrict leucaena height, enhance grass persistence, improve grazing strategies and manage mimosine toxicity problems.

An update on leucaena toxicity: Is inoculation with &lt;i&gt;Synergistes jonesii&lt;/i&gt; necessary?

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Concern about mimosine toxicity and its management has contributed to the restricted adoption of leucaena as a forage for ruminants. The toxicity is a function of the antimitotic effects of mimosine, which is rapidly converted to also toxic compounds, isomers of hydroxypyridone (DHP), by plant and microbial enzymes. Work by R.J. Jones and colleagues (1960‒1994) identified a rumen bacterium (Synergistes jonesii) capable of degrading DHP, and rumen fluid containing this bacterium was subsequently made available in Australia as a commercial inoculum for cattle producers.Research by University of Queensland and CSIRO over 15 years, commencing in 2003, found evidence for another pathway of toxin management in Indonesia, where hundreds of Balinese farmers had fed uninoculated Bali bulls (Bos javanicus) up to 100% leucaena without experiencing toxicity symptoms, apart from an initial 1‒2 week period while their cattle became adapted to the new diet. Tests showed that the Indonesian cattle were not degrading all DHP, as it appeared in high concentrations in urine samples, predominantly as 2,3-DHP and almost all (&gt;97%) in a conjugated form. The conjugating compounds (glucuronic acid and sulfate compounds), produced in the liver, appeared to be the major pathway for neutralizing the toxicity of DHP. Other work revealed that S. jonesii was a ubiquitous organism detectable in the rumen fluid of animals in all countries but always as a minor population, often below the level of detection.Since the Indonesian cattle fed leucaena suffered mimosine toxicity symptoms for only a short time before quickly recovering, we hypothesize that conjugation of DHP by the liver was the major detoxification pathway for these animals. This detoxification pathway is also operative in Australia and other countries but further studies are needed to determine its significance.

The effect of Leucaena leucocephala on beef production and its toxicity in the Chaco Region of Argentina

Hedgerows of the fodder tree legume, Leucaena leucocephala ssp. glabrata (leucaena), planted with a companion grass, provide productive, profitable and sustainable tropical pasture (Shelton and Dalzell 2007). Although leucaena can improve beef production, poor grower adoption has limited development of leucaena in the Chaco Region of Argentina. Factors contributing to poor adoption include: (1) unsuccessful establishment; (2) limited understanding of leucaena management as a forage resource; and (3) concerns about mimosine toxicity. While these 3 limitations have been overcome in other regions of the world (e.g. northern Australia and the Chaco Region of Paraguay), in Argentina little is known about leucaena management and the protection of ruminants against mimosine toxicosis. The objective of this study was to evaluate the effects of leucaena on beef production and its toxicity in the west of the Argentine Chaco Region. We hypothesized that the introduction of leucaena into grass pastures would significantly increase beef productivity, if mimosine toxicosis did not appear.

Development of leucaena mimosine-degrading bacteria in the rumen of sheep in Myanmar

Myanmar has an agricultural base, and about 70% of people reside in rural areas. They depend for survival on agriculture and small-scale crop production, with ruminant livestock consuming fibrous agricultural residues. For optimal ruminant production, concentrates are needed as supplements to these residues. As concentrates are expensive, researchers are testing alternative protein sources like legumes, including foliage from leguminous trees such as leucaena (Leucaena leucocephala). Leucaena is the most widely used leguminous tree as a ruminant feed because it is rich in protein (~ 22%) and contains easily digestible fiber (23% neutral detergent fiber, 16.6% acid detergent fiber; Ni Ni Maw 2004). Khin Htay Myint (2005) noted that 25% of leucaena in the ration tended to increase nitrogen retention without decreasing dry matter and organic matter digestibilities. However, leucaena leaves contain a toxic non-protein amino acid, called mimosine. Research workers have endeavored to reduce mimosine toxicity in animals fed leucaena in Myanmar (Aung Aung 2007; Wink Phyo Thu 2010) and one avenue of research was the development of mimosine-degrading bacteria in the rumen of sheep fed leucaena. In this paper we describe an experiment tracing the development of mimosine-degrading bacteria in the rumen of sheep.

Prevalence of mimosine and DHP toxicity in cattle grazing Leucaena leucocephala pastures in Queensland, Australia

A postal survey of the level of awareness of leucaena toxicity and an on-farm study of the toxicity status of Queensland cattle herds grazing leucaena were conducted to investigate the prevalence of mimosine and dihydroxypyridine (DHP) toxicity in Queensland. In total, 195 of 356 graziers surveyed responded to the postal survey. Sixty-three percent had inoculated their cattle with in vitro Synergistes jonesii inoculum (produced in an anaerobic fermenter) and 30% of these had inoculated more than once. The remainder used inappropriate procedures. Many graziers (43%) had occasionally observed toxicity symptoms of hair loss and poor animal growth rates. In the on-farm study, the toxicity status of 385 animals in 44 individually managed herds on 36 properties was determined by urine analysis of mimosine and DHP concentrations. No animals were experiencing mimosine toxicity, based on low concentrations of this compound found in the urine. Using the criterion that average herd urine concentrations of DHP &gt;100 μg/mL was indicative of subclinical toxicity, 48% of herds were exposed to subclinical toxicity due to dominant 3,4-DHP (21%) or dominant 2,3-DHP (27%) toxicity; many of these herds had been inoculated with S. jonesii and were thought to be protected. The finding that 27% of herds were excreting high concentrations of 2,3-DHP was unexpected. Statistical analysis of herd-management data revealed that the method used by graziers to inoculate their herds was significantly (P &lt; 0.05) but weakly linked to herd protection status. It was concluded that subclinical 3,4-DHP and 2,3-DHP toxicity remains a problem in Queensland and is likely to be limiting animal production in a significant number of cattle grazing leucaena-grass pastures.

Mimosine in Leucaena as a potent bio-herbicide

Mimosine [a-amino-β-(3-hydroxy-4-oxo-l,4-dihydropyridin-1-yl)-propanoic acid] is a major constituent of Leucaena (Leucaena leucocephala de Wit) and responsible for the strong allelopathic potential of the legume tree. Mimosine showed strong herbicidal activities on six plants in a bioassay. All plant parts of Leucaena contain mimosine. The quantity of mimosine in the young leaves and mature seeds was the greatest, 2.66 and 2.38% of dry weight, respectively, while the quantity in the root xylems and xylems was the lowest: 0.18 and 0.11% of dry weight, respectively. Younger plant parts of Leucaena contained greater amounts of mimosine than the mature parts. Mimosine released from young parts and the seeds of Leucaena was proportional to the quantity of soaking water. Compared with the mature seeds, other mature parts of the plant did not give any mimosine through exuding. In soil to which mimosine was added, about 60% of the mimosine was adsorbed in 1-5 days, and only a minor volume of mimosine was decomposed: 5.30 and 0.16% after 1 and 5 days, respectively. Using a mixture of FeCl 3 and mimosine in a 4:6 ratio may be the most effective and economical method of lowering the toxicity of mimosine in Leucaena leaves, giving a safer cattle feed and decreasing the soil toxicity caused by mimosine in areas where Leucaena is grown. On the other hand, the incorporation of mimosine leaves into cultivated soils may be helpful for the biological control of weeds. The findings of this research reveal that mimosine may be useful for the development of bio-herbicides.

Effect of Transinoculation of Goat Rumen Liquor on Degradation and Metabolism of Mimosine in Sheep Fed with Leucaena leucocephala Leaves

The effect of transinoculation of goat rumen liquor into sheep rumen on mimosine toxicity was studied. One adult Kutchi male goat having higher mimosine degradation capacity than sheep was gradually adapted to Leucaena leucocephala (Leucaena) leaves by feeding increasing level of eucaena leaves supplementation for 1 month. Six Bharat Merino rams (12-18 months of age) were divided into two equal groups with (group I) or without (group II) infusion of 200 ml of goat rumen liquor per animal. The mimosine degradation in groups I and II were 3.04 and 2.31; 3.90 and 3.73 mg per day per 10 ml rumen liquor respectively after 1 and 2 weeks of leucaena feeding leaves. Total rumen bacterial population in RGCA medium and in a selective medium containing iron showed an increasing trend in both groups, while the bacterial population growing in the presence of cellulose showed a decreasing trend. Animal performance data did not show any adverse effect. Results revealed that transinoculation of rumen liquor from leucaena leaves adapted goat to sheep rumen did not help to improve mimosine degradation in the sheep. The sheep transinoculated with goat rumen liquor displayed no in vivo improvements in nutrient utilization vis-a-vis mimosine metabolism.

Evaluation of Ensiled &lt;i&gt;Leucaena leucocephala&lt;/i&gt; Leaves as Feed Supplement in Broiler Chicks.

To reduce the cost of protein source in poultry feeds, attempt was made to supplement the diet with ensiled leaves of Leucaena leucocephala (leucaena) - a protein rich but toxic forage crop. Four (4) treatment groups consisting of ten (10) chicks each were fed a standard commercial feed (ECWA feeds), 20% ensiled leucaena, leucaena silage inoculated with ruminal fluid, and sun-dried leucaena-supplemented feed ad libitum and growth rate monitored by weight gain and feed efficiency. At 20% supplementation level, the feed efficiency was highest in the group on ECWA standard diet (2.39) and lowest in the group on sun-dried leucaena supplement (1.14). The highest cumulative weight gain (2,260g) and highest feed intake (4,664g) was found in group on ECWA feed while the group on sun-dried leucaena supplement had the lowest cumulative weight gain (1,148g), and the lowest average feed intake (665.8 - 683.8g) was found in groups on “normal” silage and microbe- treated silage-supplemented diets. These results suggest that at 20% supplementation level, leucaena causes reduced growth rate, and that ensiling (with or without ruminal fluid) only has marginal effect on the toxicity of mimosine found in Leucaena leucocephala. Key Words: Leucaena leucocephala, silage, feed supplement, broilers. Trop. Vet. Vol.22: (1) 41-48 (2004)

Field activities and blood profile of pregnant South African indigenous goats after receiving dihydroxy pyridone-degrading rumen bacteria and grazing Leucaena leucocephala-grass or natural pastures

Twenty-four multiparous female South African indigenous goats were used. Once a week during the 2nd (weeks 8, 11 and 14) and 3rd (weeks 18, 19 and 20) trimesters, between 08·00 and 15·00 h, four females per treatment were randomly selected and observed every 1 min for time spent grazing, browsing, ruminating and idling. Blood samples were taken once a week during the 2nd (weeks 8, 11 and 14) and 3rd (weeks 18, 19, 20 and 21) trimesters for measurements of some mineral elements and protein metabolites. Goats on natural pasture (NP) grazed 54·8 min (P&lt;0·001) more and browsed 53 min (P&lt;0·001) less than goats on Leucaena leucocephala-grass pasture (LGP) during the 2nd trimester. During the 3rd trimester, goats on NP treatments grazed and idled more (24·7 min, P = 0·004; 15·8 min, P = 0·044, respectively) but ruminated less (−24·1 min, P&lt;0·001) than LGP goats. Time allotted to each field activity by the goats on both treatments within trimester seemed to be dependent on forage species composition while activity between trimesters was possibly influenced by seasons, plant type, herbage quantity, environment and quality, and changes in stage of gestation of the goats. Blood Mg level on NP was higher (P = 0·051) than on LGP during the 2nd trimester while blood Cu and albumin contents on LGP were significantly higher (P = 0·029 and 0·022, respectively) than on NP during the 3rd trimester. Furthermore, blood concentrations of the haematological parameters (except serum protein) on both treatments were within the normal range for goats in the tropics and subtropics and perhaps explain the absence of mineral and nutrient deficiency symptoms. The absence of visible symptoms of mineral deficiency and mimosine toxicity in LGP goats can be attributed to the transfer of DHP-degrading rumen bacteria. The bacteria effectively detoxified mimosine and its metabolites, thereby overcoming chelating tendency of mimosine and its metabolites. Mimosine-susceptible pregnant SAIG can be safely grazed on LGP once their rumen is completely colonized by the DHP-degrading rumen bacteria (Synergistes jonesii).

Reproductive performance of South African indigenous goats inoculated with DHP-degrading rumen bacteria and maintained on Leucaena leucocephala/grass mixture and natural pasture

This study examined the reproductive performance of dihydroxy pyridone (DHP)-inoculated South African indigenous (SAIG) female goats maintained on two dietary treatments: (i) Leucaena leucocephala/grass mixture and (ii) natural pasture prior to conception, and during gestation. Leucaena leucocephala/grass mixture was nutritionally superior (crude protein and mineral elements) than the natural pasture. The average daily gain, products of pregnancy and foetal development in gravid goats raised on leucaena/grass mixture were significantly ( P<0.03, P<0.009 and P<0.005, respectively) higher than those raised on natural pasture. Conception rate of goats fed natural pasture was higher than the band fed Leucaena leucocephala/grass mixture. Leucaena/grass mixture fed goats had kids that were heavier at birth than their counterparts on natural pasture. Pre-weaning kid mortality over the period of study was significantly ( P<0.01) higher in the Leucaena leucocephala/grass mixture treatment. Colostrum from kidded goats fed leucaena was viscous and difficult to sample. The absence of mimosine toxicity symptoms suggests a possibility of safe use of leucaena as a feed resource to DHP-inoculated SAIG.

Response of goats to pelleted diets containing different proportions of sun-dried Leucaena leucocephala

Adult Jamunapari breed goats ( n=24) were randomly assigned to four iso-nitrogenous and iso-caloric pelleted diets containing 97 (high level; HL), 60 (medium level; ML), 20 (low level; LL) and 0 (control) percent sun-dried Leucaena leucocephala foliage and fed ad libitum for one year. L. leucocephala supplementation increased total DM intake, (g kg −0.75) from 70.4±2.3 in the control group to 94.1±6.9 in HL ( P<0.01). The digestibility of most of the nutrients was depressed ( P<0.05) with increasing dietary levels of Leucaena. All the goats were in positive nitrogen balance, but daily nitrogen retention decreased ( P<0.05) at medium and high Leucaena levels as a result of the poor utilization of the high protein content of the foliage. The nutritive value in terms of digestible crude protein (DCP) and total digestible nutrients (TDN) of Leucaena-supplemented diets was lower ( P<0.05) than the control. However, DCP and TDN intake was comparable among diets. None of the blood biochemical constituents (Haemoglobin, blood urea nitrogen) and activities of serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase at 0, 3, 6, 9 and 12 months of experimental feeding varied significantly due to dietary treatment. Histopathological examination of the thyroid glands of the goats sacrificed at the end of the experiment did not reveal any sign of colloidal goiter associated with mimosine toxicity. However, mild to moderate hyperplasia and degenerative changes in focal area were observed. No significant pathological changes were observed in vital organs (lungs, liver, kidney, heart, testes and intestine) irrespective of dietary treatment. The apparent comparable performance observed in goats fed sun-dried pelleted Leucaena foliage suggests the possibility of its long-term use as a sole feed for the maintenance of stall fed goats without any significant deleterious effect.

Osteopathy in broiler chicks fed toxic mimosine in Leucaena leucocephala.

Further studies of mimosine toxicity in broiler chicks were done to clarify a possibility of osteopathy. The mineral content and density of femur and the strength, ductility, and toughness for the index of mechanical properties significantly decreased in the 1% mimosine group, compared with those in the control and restricted groups. The stiffness had a decreasing tendency in the 1% mimosine group. Consequently, it was concluded that chicks fed ad libitum a 1% mimosine diet for 12 days developed osteopathy. The bone mineral density and the strength of the restricted group were lower than those of the control group, and those of the 1% mimosine group were still lower than those of the restricted group. Contents of pyridinoline and deoxypyridinoline in the excrement were significantly higher in the restricted group than those in the control group, but the contents in the 1% mimosine group were significantly lowest among the groups. Osteopathy in chicks fed mimosine, therefore, seemed to be done by loss of appetite and changing to a low turnover of bone caused by mimosine.

Effects of mimosine administered to a perfused area of skin in Angora goats

The effect of mimosine on a perfused area of skin tissue was studied using an isolated perfusion technique. Four mature Angora wethers (body weight 35 (SE 2.3) kg) were cannulated bilaterally with indwelling silicone catheters in the superficial branches of the deep circumflex iliac artery and vein. Mimosine (40 mg/kg metabolic weight (W)0.75) per d) was infused intra-arterially into one iliac artery of each goat for 3 d and saline was infused in the contralateral (control) iliac artery. Iliac venous blood samples were taken from both sides along with arterial samples from the carotid artery. Mimosine infusion elevated plasma mimosine in the carotid artery (52.6 (SEM 19.21) mumol/l) and iliac vein on the saline-treated side to 54.1 (SEM 16.31) mumol/l and in the iliac vein on the mimosine-treated side to 191.3 (SEM 19.14) mumol/l (P < 0.01). Mimosine decreased feed intake (2.3 v. 0.6 kg/d, SEM 0.29; P < 0.001) and water consumption (5.2 v. 1.3 litres/d, SEM 0.67; P < 0.001). Mimosine did not cause defleecing in the area of infusion and was cleared from the bloodstream within 12 h of cessation of infusion. The following effects were also observed during mimosine infusion: decrease in plasma amino acids to half pre-infusion values (methionine 22.7 v. 13.1 mumol/l, SEM 1.41; lysine 95.9 v. 37.4 mumol/l, SEM 4.28; P < 0.001); decreases in plasma triiodothyronine (1495 v. 695 ng/l, SEM 43.1; P < 0.001), thyroxine (61.5 v. 19.5 micrograms/l, SEM 1.8; P < 0.001) and insulin (28.7 v. 17.3 microIU/ml, SEM 1.89; P < 0.01) concentrations; increase in plasma cortisol (14 v. 62 micrograms/l, SEM 0.35; P < 0.001) concentration; decreases in levels of plasma Zn and Mg (0.97 v. 0.49 mg/l, SEM 0.063; P < 0.001 and 21.4 v. 14.6 mg/l, SEM 1.74; P < 0.001 respectively). All reported variables returned to their normal values 24 h after cessation of mimosine infusion except feed intake which was affected for a longer period. Mohair length and diameter were not affected by mimosine infusion. The toxicity of mimosine may be due to the drastic depletion of Zn and Mg in the blood as mimosine possesses very strong chelating properties and is excreted in the urine as a chelate.

Leucaena Leucocephala a Nutrition Profile

Leucaena leucocephala is one of the fastest-growing leguminous trees. Its foliage is used as animal feed, and its leaves and seeds are used as human food in Central America, Indonesia, and Thailand. Mimosine, the toxic, non-protein amino acid in Leucaena, causes alopecia, growth retardation, cataract, goitre, decreased fertility, and mortality in non-ruminants. The mechanism of this toxicity is complicated. Mimosine probably exerts its toxic action by blocking the metabolic pathways of aromatic amino acids and tryptophan; by chelating metals; by antagonizing the action of vitamin B6; by inhibiting DNA, RNA, and protein synthesis; by exerting adverse effects on collagen biosynthesis; and by interfering in the metabolism of some amino acids, primarily glycine. Besides mimosine, other anti-nutritional and toxic factors in L. leucocephala add to its toxicity. Heat, moisture, chemical treatments, ensiling, rotation feeding, cutting management of the plant, new hybrids, introducing micro-organisms into the rumen of ruminants that are unable to detoxify mimosine, and preparing protein isolate from Leucaena seeds have all been used to overcome mimosine toxicity.

Increasing the amount of leucaena on offer gives faster growth rates of grazing cattle in South East Queensland

We measured the effect of increased supply of leucaena (Leucaena leucocephala cv. Peru) on the growth of steers grazing native pasture in South East Queensland. Steers grazed paddocks of black speargrass (Heteropogon contortus) pasture in which either 0, 25 or 100% of the area was sown to 3 m-wide rows of leucaena. In the 25% leucaena treatment, the leucaena portion was ungrazed in summer. Mimosine toxicity was avoided by dosing cattle with mimosine-detoxifying rumen bacteria. The growth rate of steers increased with the proportion of the paddock covered by leucaena. Steers grazing paddocks with 0, 25, and 100% of the paddock covered by leucaena rows gained 90, 127 and 205 kg/steer.year, respectively. The amount of leucaena foliage on offer appeared to be the major factor increasing steer growth.