| Livestock Research for Rural Development 9 (4) 1997 | Citation of this paper |
Brenda Keir*, Dinh Van Bien, T R Preston and E R Ørskov*
Goat and Rabbit Centre, Hatay, Vietnam
* Rowett Research Institute, Bucksburn, Aberdeen, Scotand (e-mail: blk@rri.sari.ac.uk)
The leaves from two trees - Trichantera gigantea and Artocarpus heterophyllus (Jackfruit) - were used as the basal diet of growing goat kids. The only supplement was a multi-nutrient block containing molasses, urea and minerals. The leaves and the block were fed ad libitum and refusals recorded daily. There were 6 goats in individual cages on each treatment. The design was a single changeover with periods of 21 days on each of the two treatments. The apparent dry matter digestibility was measured during the last 7 days of the second period by total collection of faeces.
Jackfruit leaves had a higher dry matter content (36%) than leaves of T. gigantea (11%).The intake of fresh leaves was 29% higher for the jackfruit diet compared with T. gigantea. On a dry matter basis the intake was 270% higher for jackfruit (50g DM/kg LWt) than for T. gigantea (9.8 g DM/kg LWt). Kids fed T. gigantea lost 70 g/day of liveweight; in contrast, the weight gain on jackfruit leaves was 70 g/day. Apparent dry matter digestibility was higher on the jackfruit diet (66%) than on T. gigantea (48%).
It is concluded that the leaves of the jackfruit tree have a high nutritive value for growing goats.
Tree leaves have been used traditionally by farmers as animal feed but relatively little is known about their potential to replace conventional protein-rich concentrates such as soya bean meal and fish meal. Trees also fulfill a valuable environmental role. In many tropical countries deforestation is a widespread problem. Encouraging farmers to plant trees and shrubs which can be used as animal feed helps to alleviate the problem.
Two approaches are possible for developing feeding systems using tree leaves. One is to use the leaves from trees already established in the traditional farming systems. The other is to introduce trees with known potential as animal feed.
This study examines the value of leaves from two species of trees - Trichantera gigantea and Artocarpus heterophyllus (Jackfruit) - as feed for growing goats. In many parts of Vietnam jackfruit trees are grown for their fruit, but the market for this commodity is now over-supplied and prices are low. Using the leaves to feed animals instead of cutting down the tree for firewood will be a better way to utilise this otherwise under-utilized resource which also has a very important environmental role. Trichantera gigantea was introduced into Vietnam from the coffee growing region of Colombia where it is used as shade for coffee, as a live fence and as feed for animals. The leaves are consumed readily by pigs (Sarria et al 1991; Sarria 1994) and by rabbits (Le Thi Thu Ha 1997). There are no reports of its use to feed goats.
The study was carried out at the Goat and Rabbit Research Centre, Son Tay, Ha Tay in Vietnam.
Voluntary intake of leaves of T. gigantea and of jackfruit (Artocarpus heterophyllus) was studied with 12 growing kids of the Indian Babari breed over a period of 6 weeks with 6 kids in each treatment group and a changeover after 3 weeks. The leaves were fed ad libitum twice daily and the goats had free access to a multi-nutrient block (35% molasses, 25% cassava, 12% minerals, 10% rice bran, 10% urea, 5% salt and 3% bone meal). Liveweight was recorded every 7 days.
The in vivo digestibility of T. gigantea and jackfruit leaves was assessed during week 3 of the intake studies. Faeces were collected by means of a nylon net suspended under the slatted floor of each pen. Faeces were collected daily, pooled after 7 days and 150g taken for analysis. Representative samples of the leaves offered to the animals and of the residues were taken. Faeces and leaf samples were analysed for dry matter and ash content.
The liveweight gain of the kids was predicted using linear regression of liveweight over time. Analysis of variance was used to compare the two treatments (General Linear Model of Minitab, Release 10.2). The data for dry matter digestibility were corrected by covariance for differences in intake of feed dry matter.
Mean values for feed intake, liveweight change and dry matter digestibility are in Table 1. Jackfruit leaves had a higher dry matter content (36%) than leaves of T. gigantea (11%). There were marked differences in responses of the goat kids to the two foliages. The intake of fresh leaves was 29% higher for the jackfruit treatment compared with T. gigantea. On a dry matter basis, the intake was 270% higher for jackfruit (50g DM/kg LWt) than for T. gigantea (9.8 g DM/kg LWt). Intake of the multi-nutrient block was similar on both diets but represented 26% of the total dry matter on T. gigantea compared with only 6% for the jackfruit treatment. Kids fed T. gigantea lost 70 g/day of liveweight; in contrast, the kids gained 69 g/day of liveweight on jackfruit leaves. Apparent dry matter digestibility was higher (P=0.02) on the jackfruit diet (66%) than on T. gigantea (48%).
The good growth performance of young goats fed jackfuit leaves has been confirmed by Tran Quoc Viet (1997) who recorded daily gains of 91 g/day compared with 85 g/d for goat kids fed leaves of Gliricidia sepium. Good results for milk production in dual purpose goats fed a diet of jackfruit leaves supplemented with a multi-nutrient block were reported by Nguyen Thi Hong Nhan (1997).
One possible explanation for the unexpectedly high feed intake and growth rate on jackfruit leaves is that the protein in the leaves may be associated with sufficient tannins and lignin to protect it partially from rumen fermentation thus providing a good source of by-pass protein. Analysis of rumen ammonia levels in kids fed leaves of jackfruit and gliricidia plus a molasses-urea block (Tran Quoc Viet 1997) showed that these were lower for the jackfruit treatment (199 mg/litre) than for the gliricidia (239 mg/litre); however, the protein content in the jackfruit leaves was lower (17.2% in DM) than in the gliricidia (23% in DM). Nguyen Thi Hong Nhan (1997) reported rumen ammonia levels of 180 mg/litre in lactating goats fed jackfruit leaves as the basal diet. In both cases the goats had access to a block containing 10% urea thus it is difficult to relate rumen ammonia levels to intake of the leaves.
The poor growth performance of the goats fed leaves of T. gigantea was a direct result of the low intake. But the reason for the low intake is difficult to explain. In a parallel study (Keir et al 1997) it was shown that there were only small differences in crude protein content, in vitro gas production and in sacco rumen degradability between the leaves of the two species.
The lower apparent dry matter digestibility of the T. gigantea measured in this experiment was also a result of low intake since in such a situation the faeces of metabolic origin account for a greater proportion of the total faecal output. According to Galindo et al (1989) and Rosales (1997) the content of anti-nutritional factors in leaves of T. giantea is low. This is supported by the fact that the leaves are readily consumed by pigs (Sarria et al 1991;Sarria 1994) and rabbits (Le Thi Thu Ha 1997) which are sensitive to the presence of such compounds in the feed. Thus the low intake is unlikely to be due to anti-nutritional factors.
Recently, a satisfactory system for ensiling T. giantea leaves has been
developed (Ly J 1997, unpublished data). It is possible that the ensiled product may be
more palatable to goats than the fresh leaves.
The fresh leaves of jackfruit trees are a valuable feed resource for goats when
combined with a multi-nutrient block supplying urea and minerals. By contrast, the fresh
leaves of T. gigantea are not liked by goats even though they appear to have a
reasonably high nutritive value on the basis of chemical, in vitro and in
sacco analyses.
We are grateful to Dr Dinh Van Binh, Director of the Goat and Rabbit Research Centre,
for providing the facilities for doing the experiment, and to staff members of the Centre
who helped with the practical work of feeding and managing the goats.
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Keir Brenda, Nguyen Van Lai, T R Preston and E R Ørskov 1997 Nutritive value of leaves from tropical trees and shrubs; 1. In vitro gas production and in sacco rumen degradability. Livestock Research for Rural Development. Volume 9, Number 3:24-30
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Received 20 June 1997