Toxicity and nutritional value of some promising pasture legumes to rats and sheep

Maskasame, Chaiyasit (1985). Toxicity and nutritional value of some promising pasture legumes to rats and sheep Master's Thesis, School of Biomedical Sciences, The University of Queensland.

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Author Maskasame, Chaiyasit
Thesis Title Toxicity and nutritional value of some promising pasture legumes to rats and sheep
School, Centre or Institute School of Biomedical Sciences
Institution The University of Queensland
Publication date 1985
Thesis type Master's Thesis
Supervisor D.A. Little
J.H. Aylward
M.A. Pass
Total pages 162
Language eng
Subjects 300500 Veterinary Sciences
Formatted abstract
The work described in this thesis was aimed at testing the potential toxicity of eight species of promising pasture legumes to rats and sheep, and to make preliminary recommendations as to their suitability as animal feeds. The plants tested were Crotalaria christantiflora Commonwealth Plant Introduction (C.P.I.) #60186, C. incana (C.P.I. #CQ1101), C. retusa (C.P.I. #71124), Indigofera schimperi (C.P.I. #65477), I. spicata (C.P.I. #16069), I. spicata (C.P.I. #37686), Tephrosia bracteolata (C.P.I. #40765) and T. purpurea (C.P.I. #69505). 

The first experiments were done in adult sheep and the plants were given via a rumen fistula. The results revealed that only Tephrosia purpurea was likely to be toxic. The other legumes were not toxic when the animals were given 200 g/day of the ground plant for 21 days.

The second experiment investigated the toxicity of the legumes to post-weanling male rats when fed ad lib. as 20% (W/W) of the diet for a period of 29-35 days. It was shown that the diets containing Crotalaria retusa, Indigofera spicata #16069 and I. spicata #37686 were unacceptable as they significantly depressed growth rates and produced some toxic effects in the liver, testes and fat. The diet containing Tephrosia bracteolata was also of doubtful value because it significantly reduced growth rate when componed with animals fed the lucerne control diet. However, no pathological changes were detected in the liver, lungs, kidneys, testes or fat. Rats fed Tephrosia purpurea grew well but there was evidence of mild hepatotoxicity. Rats fed Crotalaria christantiflora or C. incana grew well and these plants appeared to be suitable feeds for rats. Indigofera schimperi was also a good diet but it did suppress spermatogenesis and mild histological changes were observed in the liver.

In the next experiment the plants were fed ad lib. to wethers for a period of 17-45 days. It was apparent that Crotalaria incana was unpalatable to wethers and caused inappetence, drowsiness and weight loss. Indigofera spicata #18069 and Tephrosia purpurea were toxic. I. spicata #16069 caused depression of feed Intake, hepatic necrosis, pulmonary injury and renal damage. Tephrosia purpurea also caused hepatotoxicity. C. retusa was mildly toxic. Crotalaria christantiflora, Indigofera schimperi, I. spicata #37686 and Tephrosia bracteolata were satisfactory when fed to sheep, at least over the time period used in these experiments. 

The plants were also assessed for their nutritive value including their mineral content, crude protein level and fibre component. The apparent digestibility coefficient in vitro and in vivo was determined for each plant, and the nitrogen balance of sheep to which they were fed was also determined. Crotalaria incana and Indigofera spicata #16069 were nutritionally poor. Crotalaria christantiflora, Indigofera schimperi, Indigofera spicata #376863 Tephrosia bracteolata and T. purpurea were nutritionally adequate. Crotalaria retusa was barely satisfactory as a sheep feed.

Based on the results of the rat and sheep feeding trials some of the legumes which appeared not to be toxlc were tested for their teratogenic effects in rats. The plants tested were Crotalaria christantiflora, Indigofera schimperi and Tephrosia bracteolata. Indigofera spicata #16069 was also used in this trial as a positive control since it is known to be teratogenic. Tephrosia purpurea was also tested for teratogenic effects since no such information on it was available. I. spicata #16069 and T. purpurea killed embryos and severely suppressed the litter and placental weights. Birth defects which included cleft palate, exencephaly, ventral hernia and aplasia of the right optic vesicle were observed. C. christantiflora, I. schimperi and T. bracteolata did not impair reproductive performance or cause birth defects. C. christantiflora appeared to be the best food in terms of the growth rate of mothers and offspring.

In summary, Crotalaria incana, Indigofera spicata #16069 and Tephrosia purpurea are unsuitable for feeding to sheep. C. retusa, I. schimperi, I. spicata #37686 and T. bracteolata require further investigation before they could be safely introduced as pasture plants in that C. retusa was toxic to rats and possibly to sheep; I. schimperi reduced sperm production and reduced food growth the rats, and I. spicata #37686 and T. bracteolata decreased growth rate in sheep. C. christantiflora appeared to be nutritionally satisfactory and safe to feed to sheep. Howeverit would be advisable to conduct more extensive feeding trials before it is introduced into general agricultural use.
Keyword Legumes as feed
Legumes -- Toxicology
Additional Notes Spine title: Toxicity and nutritional value of some legumes

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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