Volume 11, Number 1, 1999
A total of 15 weaned kids (4 months of age and initial liveweight from 8.4 to 9.8 kg), were allotted in a completely randomised design to five treatments which were offer levels of sugar cane and Guinea grass (Panicum maximum Jacq.) in proportions of 100:0, 75:25, 50:50, 25:75 and 0:100 (fresh basis). The other components of the diet were jack fruit leaves (Artocarpus heterophyllus), a molasses-urea block (10% urea), dried cassava root and rice bran. Over a 120 day period, the daily liveweight gain ranged from 52 to 63 g/day but did not differ among diet treatments (SEħ8.5; P=0.95).
It is concluded that sugar cane can replace Guinea grass as the basal forage for growing goats without affecting performance. Sugar cane produces the most biomass when harvested in the winter season which is the period when Guinea grass is least productive. Thus the two forages complement each other for providing a sustainable year-round supply of forage for goats.
Vietnam is a tropical country with a monsoonal climate. The total area of the country is 332,000 km² and the mountainous - hilly regions make up two thirds of the total. In these regions the agriculture is based mainly on rice production supported by other crops such as maize, cassava and sugar cane. Livestock production forms 25% of the agricultural output value and deals mainly with pigs, cattle, buffaloes and poultry.
Goat production in Vietnam is traditionally practised under an extensive system. The national goat population is estimated to be 0.41 million of which some 70% are in the North, concentrated in the mountainous-hilly areas. Most goats are of the local meat type (the "Co" breed). The balance of the population is derived from the improved dual purpose "Bach Thao" breed, which is having an increasing impact at farmer level on milk and meat production (Dinh Van Binh et al 1995). The Bach Thao breed was developed in Vietnam over the last 50 years by importing exotic breeds from Europe. It is found most widely in the southern provinces with the highest concentration in Ninh Thuan province. According to the study by Dinh Van Binh et al (1995) its productivity can be as high as that of exotic breeds imported from India. Research involving the management of the Bach Thao breed for dual purpose milk and meat production is a recent development (Dinh Van Binh and Preston 1995).
Sugar cane is widely grown throughout Vietnam for chewing, for juice extraction by roadside drink sellers, for artisan production of raw sugar and for industrial centrifugal sugar production. The annual sugar cane production reached 6.34 million tonnes in 1993 resulting in sugar production of some 500,000 tonnes (Anon 1994), of which slightly less than one third (about 150,000 tonnes) was produced in 6 factories where the sugar cane crushing capacity is from 700 to 1800 tonnes per day during a 4-5 month milling season which coincides with the dry season of the year.
The results of recent research show that sugar cane, which is probably the most productive crop in the tropics, can be used as the basis of intensive animal production systems (Preston 1995). The three possibilities for using this crop are: in the form of by-products after extraction of the sugar, as integral whole sugar cane and by fractionation into different end products without extraction of sugar. In this latter case, the juice is fed to pigs and the bagasse and tops to ruminants, giving a potential production capacity of over 5,000 kg animal liveweight/ha (Preston 1995). In North Vietnam, Dinh Van Binh and Preston (1995) showed that feeding lactating goats with sugar cane tops supplemented with rice bran, a molasses-urea block and foliage from the Acacia mangium tree, supported slightly higher milk production and growth in the kids than the conventional diet of Guinea grass (Panicum maximum) and concentrates. Nguyen Thi Mui et al (1996, 1997) studied the effect of planting season on biomass yield and on the nutritive value of the tops and juice for goats and pigs, respectively. Biomass yields were higher for sugar cane harvested in the cold winter season than in the summer season. There appeared to be no effect of season of harvesting on nutritive value of the tops for goats.
Many studies on the utilization of whole sugar cane as animal feed, especially for cattle, have been done in many countries (see reviews by Preston and Leng 1976, 1987; Preston 1995) but there appear to be no reports on its use as the basal diet of goats. The feeding method used at the Goat and Rabbit Research Centre is based on ad libitum offer of Guinea grass (Panicum maximum) and a fixed allowance of a concentrate mixture containing mainly maize, soya bean meal, rice bran and minerals. The yield of Guinea grass is sensitive to season and decreases markedly in the cold winter season. By contrast, the biomass yield of sugar cane is at its peak in the winter (Nguyen Thi Mui et al 1997).
The aim of this experiment was therefore to investigate the relative value of sugar cane compared with Guinea grass as the basal forage in the diet of growing goats. The long term objective was the development of a system for winter season feeding based on the use of sugar cane.
This study was located at the Goat and Rabbit Research Centre in Bavi district of Ha Tay province. The average annual temperature is 20 oC and annual rainfall 1800 mm.
Fifteen weaned kids (10 Bach Thao and 5 F1 of Bach Thao X local meat goat) that were 4 - 4.5 months of age were used in feeding trial which lasted 120 days. The kids were randomly assigned within breed group to five treatments which were proportions of sugar cane (Saccharum officinarum) and Guinea grass (Panicum maximum) of 100:0, 75:25, 50:50, 25:75 and 0:100 (fresh basis) as the basal forage. The kids were housed in pairs or singly (on each treatment there was one cage with two kids and one cage with one kid) in cages with raised slatted floors fitted with feed troughs. The feed trough was enclosed by plastic netting to avoid the goats eating from feed troughs attached to adjacent pens. The different proportions of sugar cane and Guinea grass were offered in amounts slightly in excess of what was consumed. These amounts were adjusted weekly according to observed intakes.
The remainder of the diet consisted (fresh matter per goat/day) of 50 g of a molasses-urea block (MUB) containing 10% urea, 100 g rice bran, 200 g dried cassava root and foliage of the jackfruit tree (Artocarpus heterophyllus) at the rate of 50 g/kg liveweight. It was estimated that all the diets would fulfill the minimum crude protein requirements of 50-55 g/day (Devendra and Burns 1983).The timetable of feeding was as follows:
7.00am: Sugar cane
8.30am: Cassava root + MUB
9.30am: sugar cane + Guinea grass
11.00am: Rice bran + Guinea grass
2.00pm: sugar cane + Guinea grass
4.00pm: sugar cane + cassava root + rice bran
5.30pm: sugar cane + MUB
8.00pm: Jackfruit foliage
The whole sugar cane was chopped with a knife into pieces about 1-2 cm before feeding. The Jackfruit foliage was hung on a wire on the top of the feed trough as it was observed that the goats preferred to consume the leaves when they were still attached to the branches. Water was always available in the pen. Every day the kids were allowed into an area of waste ground with sparse vegetation for one hour for exercise.
The liveweight of kids was recorded every 15 days. Feeds offered and refused were weighed daily to measure feed intake. Samples of feed (offered and refusals) were taken at weekly intervals for analysis of dry matter. The dried samples were combined for subsequent analysis of nitrogen which was done by the standard Kjeldahl method (AOAC 1988).
The variance of treatment means of daily intake were not homogeneous and therefore were not analysed for differences on a daily basis but only over the whole experimental period. Weight gains of individual goats were calculated by linear regression of liveweight on time. Treatment means were analysed by the General Linear Model of the Minitab (release 10.2 ) software.
The intakes of the different ingredients of the diet are shown in Table 1.
|Table 1: Feed intakes by growing goats fed different proportions of sugar cane and Guinea grass|
|Sugar cane:Guinea grass||100:0||75:25||50:50||25:75||0:100||SEmean|
There was no consistent effect of the proportions of sugar cane and Guinea grass in the diet on the overall intakes of dry matter and protein. Of the other ingredients, only the intake of the rice bran varied with lower values for treatments of 75% and 100% Guinea grass compared with the zero and 50% levels.
Mean values for initial and final weights and for daily liveweight gain and feed conversion are in Table 2. There were no significant effects of the dietary proportions of sugar cane and Guinea grass on the growth performance or on feed conversion.
|Table 2: Liveweight gain and feed conversion of kids fed different proportions of sugar cane and Guinea grass|
|sugar cane:Guinea Grass||100:0||75:25||50:50||25:75||0:100||SE/Prob|
|Daily gain, g||56.3||52.4||62.5||59.8||57.3||8.5/0.95|
|Conversion, kg/kg LW gain|
The results from the experiment indicate that growth performance of weaned goat kids is not affected when the goats were fed varying proportions of Guinea grass and sugar cane with the given supplement. This finding must, however, be related to the other components of the diet, namely provision of foliage of jackfruit, a molasses-urea block, rice bran and cassava root. The findings might be different if other supplements were used. There was no apparent explanation of the lower intake of rice bran on the diets with highest proportions of Guinea grass, although this could be interpreted as a response to the higher protein content of Guinea grass compared with sugar cane.
There appear to be no data in the literature comparing Guinea grass and sugar cane for goats in confinement. Experiments with sugar cane feeding have mostly been done with cattle In Mexico, supplementary feeding with whole chopped sugar cane, with or without urea plus ammonium sulphate, did not significantly increase liveweight gains of Zebu steers on Guinea grass pasture in an exceptionally good year, but stocking density could be increased by about 30% (Medellin and Alvarez 1978). In Brazil, Holstein x Zebu heifers grazed during the dry season on Guinea grass with a mineral mixture gained liveweight at 164 g/day which increased to 261 g/day when chopped sugar cane was also given (Lima et al 1973). Ferreiro and Preston (1976) compared diets with different ratios of sugar cane stalk and sugar cane tops for fattening zebu cattle, using a supplement of rice polishings (In Vietnam the method of processing rice results in the rice polishings being partly diluted with rice husk and the product is called rice bran. It is thus slightly inferior to "rice polishings" because of the higher fibre content). They found no effects of diet on growth rate although feed conversion was better when only the stalk was fed.
As indicated in the introduction, the growth patterns of sugar cane and Guinea grass in North Vietnam are different, the former being most productive in the cold winter season and the latter in the warmer summer season. The results of this experiment can therefore be interpreted as indicating that one way to develop a sustainable feeding system for goats is to grow sugar cane for use in winter and Guinea grass for summer.
It is concluded that there were no major differences in the nutritive value of chopped whole sugar cane and Guinea grass when fed as components of mixed diets containing jackfruit leaves, a molasses-urea block, rice bran and dried cassava roots. The actual growth rates achieved (52 to 63 g/day) are normal for recently weaned goats of the Bach Thao breed (Dinh Van Binh, personal communication).
Considering that sugar cane production is much greater during the cool and dry winter season and Guinea grass production is greater during the hot wet season, it is recommended to grow both plants in these seasons so that the biomass on offer for feeding to goats will be similar throughout the year.
The Danish Embassy in Hanoi and the UTA foundation is acknowledged for the financial support which made it possible for me to carry out this research as partial fulfillment of the requirements for the Master of Science degree in Sustainable Use of Local Resources in Livestock-based Farming Systems.
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