Leucaena feeding systems in Myanmar

Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.Agriculture and livestock provide the main source of income for farmers in Myanmar. As feeds with low nutritive value and digestibility are traditionally used for animal feed, alternative feed sources of better quality are needed to improve production levels. While concentrates can be used to improve the quality of diets, this leads to high feed costs. To solve this problem, researchers in Myanmar conducted trials to replace some concentrates with leucaena. The nutritive value of leucaena in Myanmar is relatively the same as found in other countries. Control of leucaena toxicity was also studied in Myanmar by isolating mimosine-degrading bacteria and managing the feeding of leucaena. While farmers in Myanmar are aware that leucaena can be fed to livestock and can be toxic to animals, they have limited knowledge of the real benefits of leucaena as a feed for animals. Research to demonstrate the potential of leucaena feeding to animals in Myanmar and efforts to promote establishment of leucaena stands are urgently needed.

Effectiveness of inoculation with rumen fluid containing Synergistes jonesii to control DHP toxicity in ruminants in eastern Indonesia

The feasibility and efficacy of inoculating with rumen fluid as a method to control hydroxypyridone (DHP) toxicity in ruminants on high leucaena diets in eastern Indonesia were investigated. Rumen fluid collected from 2 buffalo identified as ‘protected’, due to low levels of DHP excretion in urine, was orally administered to animals identified as ‘unprotected’ and concentrations of urinary DHP monitored. Control animals were dosed with water only. Treatments were randomly allocated to 10 recipient animals: 3 goats and 7 cattle. All animals were fed a diet containing fresh-cut 100% leucaena during the 18-day study period. Measurement of urinary DHP via colorimetric analysis commenced 8 days prior to animals being drenched with rumen fluid or water and continued for 10 days afterwards. Urinary DHP levels in animals that received the inoculum did not differ from those in the control group 10 days post-inoculation (mean 425 mg DHP/L; P = 0.50). Unexpectedly, DHP levels in all animals (rumen fluid and water) declined with time, although the difference did not reach statistical significance (P = 0.12), and remained above considered safe threshold levels. These results suggest that transfer of rumen fluid to overcome leucaena toxicity in animals in eastern Indonesia may not be effective despite great care having been taken to ensure the viability of the anaerobic organisms during the inoculation process; this methodology is also not a practical solution to replicate on a commercial scale. The findings suggest that inoculation may not be necessary if animals previously naïve to leucaena are able to adapt to DHP toxicity by other means.

Incidence of subclinical toxicity in goats and dairy cows consuming leucaena (Leucaena leucocephala) in Thailand

A survey of the leucaena toxicity status in four major goat-producing provinces of Thailand where leucaena is fed as the principal dietary component was conducted. Three adjacent dairy farms in one province where leucaena silage was being fed were also sampled. Urine samples were collected from 63 animals on six goat farms and from 32 cows on three dairy farms. Samples were acidified, cleaned and analysed by high performance liquid chromatography for 3,4-DHP and 2,3-DHP concentrations, using a modified procedure developed at the University of Queensland. Total DHP concentrations varied from 375 to 3357 μg/mL on goat farms, and from 142 to 182 μg/mL on dairy farms. These concentrations are indicative of subclinical toxicity that might cause reduced feed intake and productivity. The impact of high DHP on productivity needs to be further studied because leucaena is a readily available source of high-protein forage for ruminant industries in Thailand.

Survival of the rumen bacterium Synergistes jonesii in a herd of Droughtmaster cattle in north Queensland

Droughtmaster steers from the CSIRO Research Station at Lansdown, 50 km south of Townsville, Queensland, were assessed at slaughter for indications of leucaena toxicity and the presence of the 3,4 dihydroxypyridine (DHP)-degrading bacterium Synergistes jonesii. This bacterium had been introduced to the herd 25 years earlier. Absence of clinical signs of ulceration of the oesophagus, absence of DHP in the urine, the presence of normal thyroid glands and the ability of rumen fluid to degrade high levels of mimosine from leucaena shoot tips in vitro all confirmed that these steers had an active bacterial culture capable of degrading mimosine and its degradation products 3,4 and 2,3 DHP. Steers had been away from the Research Station and away from leucaena pastures for long periods but had clearly not lost the bacteria or if they had, they had regained them on return to leucaena pastures on Lansdown. It is postulated that the bacteria may spread via the faeces in cattle yards and remain in the rumen for long periods, even at low levels, in the absence of leucaena in the diet. Reasons other than the effectiveness of the bacterium should be explored to explain the failure of cattle in some Queensland herds to fully degrade 3,4 and 2,3 DHP.