Pig production in Vietnam is an important industry for smallholder farmers, who supply 80 per cent of all pigs. The long-term viability of production is threatened by the high cost of feeds, most of which are imported. These high quality feeds are likely to continue to rise in price. The use of cheaper local feedstuffs is a viable solution, but is limited by a lack of knowledge of their suitability for pigs. This project aims to bridge the gap by assessing locally available protein and energy sources as potential components of commercial pig diets. On-farm assessments and other extension activities will share these results with the commercial and smallholder sectors.
Protein is frequently the main constraint for the improvement of pig performance in South-East Asia. Because of this most Asian pig production countries have a high dependence on importation of various protein meals. The long-term viability of such pig industries is dependent on the ability of these countries in the future to access cheaper local source of non-conventional feeds. Rubber seeds (Hevea brasiliensis) from the Euphorbiaceae family (Njoku et al., 1998) are a substantial by-product of rubber production that currently have little use in animal feeding despite having a reasonable level of protein content. If the anti-nutritive component of rubber seed could be eliminated or have its impact on pig performance ameliorated then rubber seed meal would have a great potential for feeding pigs either by small holder producers or by inclusion in commercial diets. In Vietnam according to the Vietnam Statistical book (2001), Vietnam has 420,000 ha of rubber trees with density of 500 tree/ha. Based on an estimated production of approximately 300 kg rubber seed /ha, it is then possible to collect nearly 130,000 metric tons rubber seed equivalent to 65,000 metric tons of rubber seed meal without hulls (pers com Kinh 2004) every year from this level of rubber production
The first project-planning meeting was held in Australia in late September 2004. A memorandum of agreed project work plan was developed.
Progress thus far for Year 1
Objective 1 Content
Currently, Vietnamese project staff are collecting samples of feedstuffs for batch analyses. An understanding of the initial level of toxins such as cyanide and gossypol present in the rubber seed and the changes that would occur in those levels as a result of time, handling and processing of the rubber seed is needed. This will enable the development of protocols for the elimination of the toxins present or provide data to assess their risks whilst maintaining maximum nutritive value of the feedstuff.
Objective 2 Treatment
A detailed literature review has been completed to provide essential preliminary information on anti-nutrients and their stability. The literature has shown that the source of the rubber seed will impact significantly on the toxins present and on the composition of the rubber seed. This suggests that variety or agronomy are important both for the nutritive animal feeding value of the meal and also for the use of the rubber seed oil in other industrial applications. This would impact on the economics of any industrial rubber seed processing. Particularly as high value oil would better facilitate investment in large-scale plants to process the rubber seed. Thus the chemical results of the samples being collected will provide data on the feeding values of meal produced and the best use option for Vietnamese rubber seed oil.
Objective 3 In vivo digestibility
Experimental protocol and animal ethics approval have been obtained for studies to be conducted in Australia and these will commence soon with supervision and training of Vietnamese project staff in Australia
Objective 4 Inclusion level
Planning phase
Objective 5 Commercial demonstration on farm
Not until Year 3
During 2005 the characteristics of the Vietnam rubber production industry were surveyed, data was collected on rubber seed yields over time and for different varieties and ages of rubber trees. Fresh rubber seed were also harvested from plantations in Vietnam by collection within one day of dropping. These were frozen and bulked together. Sub samples of these underwent a number of treatments using heat, pressure, washing and sun drying following which they were chemically analysed for presence of residual hydrogen cyanide (HCN) and assessed for proximate chemical composition and will undergo further analysis for amino acid content.
Analyses showed that HCN in rubber seed slowly declined at ambient temperature to less than 50% of the initial level after 150 days of room temperature storage. It was also observed that the there was a substantial loss of water from the seed over time. The presence of the rubber seed hull limited the reducing effect of sun drying on the cyanide content, with only the decorticated seed showing any decline in cyanide with sun drying, to about 16% of initial HCN level. Heat processing studies have shown that a number of high temperature processing methods, which utilised both wet or dry heat for period between 10-35minutes, on both decorticated seed and un-decorticated rubber seed failed to significantly reduce the cyanide content of the rubber seed, although the boiling treatment suggested a lowering of the residual cyanide in the decorticated rubber seed. Preliminary results using combinations of treatments in lab scale studies showed that if seeds were first either homogenised with water or crushed to extract the oil and moisture followed by sun drying then the cyanide content declined significantly with increased time in the sun. It was observed that after the water wash and 1d sun drying there was a significant reduction in HCN in chopped seeds, whereas after 1d sun drying there was only a lesser reduction in crushed seeds without the wash step. The removal of the hull prior to these processes enhancing the cyanide reduction response. The greatest rubber seed cyanide reduction was achieved in seeds that were initially decorticated, then crushed to remove oil and water followed by a homogenisation (wash) in water with a period of 2-5d of sun-drying to yield a dry meal product with almost complete elimination of the HCN content. Further studies will continue to replicate this result on a larger scale with processing of bulk quantities of rubber seed which will be used to provide raw material for later pig digestibility and dietary inclusion feeding studies.
Survey work on cassava starch processing plants and the production of cassava residue were also completed. Sub-samples from both same and larger scale mills were collected and evaluated for residue HCN. Analyses has shown that the processing and sun drying results in a product with relatively consistent low HCN level. Samples are undergoing further chemical analysis and nutritive assessment. Pig digestibility studies and dietary inclusion feeding studies have commenced and these will provide valuable information on the nutritional value of this by-product and the levels at which it can be effectively and safety used.
Planning has commenced on further research into two other local Vietnamese feeds with identified newer priorities, these being groundnut meal and sesame meal.
Research has examined the digestible energy content of a number of sunflower meal types available in Australia and identified major differences in their energy value based on processing, additionally, amino acid analysis has shown a significantly lower lysine content than previous reported. Further work will further examine these apparent changes in more detail and assess the impact of such nutritive changes on the value of this feed in pig diet formulations.
During the reporting period a project-planning review meeting was held in Vietnam in June 2005 with another project meeting and review in April 2006.
Following the detailed cyanide processing studies in Australia Vietnamese project staff repeated the identified successful protocols in Vietnam. During 2006 additional fresh rubber seed were harvested from plantations in Vietnam. These were frozen and bulked together. Sub samples of these underwent a number of treatments using press oil extraction, washing and sun drying. These were then chemically analysed for presence of residual hydrogen cyanide (HCN). This was an up-scaled replication of the protocols initially carried out successfully in Australia on smaller samples. Also this protocol was carried out on much fresher rubber seed material which it is believed generally have a higher cyanide contents initially.
Research results indicated that the processing protocols identified were successful in substantially reducing the cyanide level in rubber seed. However the particularly good results in Australia, achieved previously on smaller rubber seed quantities, may have raised Vietnamese expectations of total elimination of cyanide.
Information from the literature and our own chemical studies have indicated that the age of the rubber seed and its storage conditions post-drop will affect the relative proportion of oil, moisture and the level of HCN detected in the seed. Consequently these parameters will also influence the protocol used and the relative success of selected processing protocols implemented to reduce HCN and the degree to which the HCN is reduced.
Further to the primary role of the processing protocol to reduce cyanide, it is important to note that whichever protocol is selected it will also significantly affect the cost of the final product derived and could also influence the proximate chemical composition, amino acid content and ultimately the nutritive value of the processed feed ingredient.
Our processing revealed that following the protocol recommended, that the cyanide level could be consistently reduced to <20mg/kg. Additionally as rubber seed meal inclusion will never be 100% then this would mean the residual level of cyanide in pig diets containing rubber seed would be substantially less than this. Currently some further studies are being carried out to examine the ratio of water to seed, time and temperature on cyanide reduction. As the actual age of the seeds was unknown there is a possibility that the endogenous cyanide releasing enzymes are themselves been affected by the age of the seed and hence the apparent higher residual cyanide level following processing.
During project meeting in Vietnam a number of cassava processing plants were visited, fortunately whilst they were operating (cassava is a seasonal crop). This enabled an understanding of the processing to obtain cassava residue and how the material was on-processed into a feed ingredient material. Based on these observations it appears that there may be an opportunity to utilise the spare capacity of these cassava processing plant via additions and modification to possibly develop a commercial rubber seed processing industry.
Pig digestibility studies and dietary inclusion feeding studies on cassava residue were completed and these will provide valuable information on the nutritional value of this by-product and the levels at which it can be effectively and safely used.
Due to Vietnamese concerns on residual cyanide content in rubber seed the in vivo digestibility and feeding studies planned for this feed ingredient have been put on hold until the matter has been clarified and until when the next uniform fresh batch of rubber seed is available.
In Australia the digestible energy content of a number of sunflower meal types available have shown major differences in their energy value based on processing & additionally, amino acid analysis has shown a significantly lower lysine content than previously reported. Further work to examine these apparent changes has been delayed due to difficulty in sourcing material as a result of the drought
During the reporting period a project-planning review meeting was held in Vietnam in April 2006 and briefly in June 2006 prior to the Forage Legumes in Lao project meeting and review.
A number of in vitro HCN studies on a large consignment of rubber seed have been completed, the material supplied was highly variable, with lower HCN for supposedly freshly dropped seed, detailed examination revealed that these were not harvested fresh and contained older seed (exhibiting mould infection). The greatest reduction of cyanide in rubber seed was achieved in seeds that were initially decorticated then crushed to remove oil and water followed by a homogenisation (wash) in water with a period of 2-5d of sun-drying to yield a dry meal product with almost complete elimination of the HCN content. Following consultation with collaborators In Vietnam, equipment was designed to enable an industrial processing of bulk quantities to achieve similar HCN reduction. This equipment has now been manufactured and used to process an initial large lot of rubber seed to yield sufficient quantity of IAS rubber seed meal for in vivo studies. A digestibility experiment was conducted in Vietnam to evaluate the digestible energy and amino acid value of diets composed of various treated rubber seed meals. The trial lasted for 21 days it was found that the diet with normal commercial rubber seed meal had a lower total digestibility of dry matter, and energy compared with the new IAS rubber seed meal and a soybean diet. The digestibility of dry matter and energy of the basal cassava chips diet and a soybean diet were similar and higher than the two rubber seed meals.
An inclusion level growth trial with sixty four Yorkshire x Landrace castrated male pigs fed ad libitum of corn/rice bran/soybean meal diets with four levels of IAS rubber seed meal and two levels of defatted commercial rubber seed meal has been concluded. Preliminary results have shown that the FCR and ADG of pigs given the diet with the 10% inclusion of IAS-RSM were similar to those of the soybean meal control diet. At higher inclusions of 20 and 30% there were observed small decreases in ADG and feed efficiency with the IAS-RSM, while, with commercial rubber seed meal inclusions at these higher levels there were significant decreases in ADG and feed efficiency. The results indicate that the IAS RSM treatment protocol has successfully improved the feeding value of rubber seed in pig diets when compared to the normal commercially available RSM. Economic assessment of the reductions in dietary costs and improvement in overall profitability will be carried out once all pig digestibility studies and dietary inclusion feeding studies on rubber seed meal have been completed. These results will provide valuable information on the nutritive value of this by-product and the levels at which it can be effectively, safely and profitably used
Experimental studies in Australia examined the digestible energy content of a number of stylo forage legume harvest batches and identified the differences in their energy value based on age/harvest time of the forage legume. Analysis results of various stylo cuts showed that the early cut stylo has a higher starch content and lower fibre fraction content than observed in late and recut stylo which were allowed to grow longer. As a result the faecal digestible energy content was higher for the early cut stylo than for the subsequent cut stylo material which had been allowed to become woody. The results have shown that feeding of stylo meal does provide some nutritive value to the pig with increased energy and nitrogen supply, with a portion of the nitrogen presented which the pig is able to retain.
During the reporting period a project-planning review meeting was held in Vietnam in Sept 2007 and with a brief project update in Nov 2007 with the Vietnam project leader in Brisbane whilst attending the Australasian Pig Science Association conference.
Links:
[1] http://www.aciar.gov.au/country/Vietnam
[2] http://www.aciar.gov.au/programarea/Livestock Production Systems