Effect of cassava (Manihot esculenta Crantz) and Erythrina (E. subumbrans) foliage on growth of goats fed basal diets of banana (Musa spp) leaves or Elephant grass (Pennisetum pupureum)

Souksakhone Vivasane and T R Preston¹

Champasack University, Lao PDR
skvivasane@yahoo.com
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

Abstract

The objective of this study was to measure the relative nutritive value of two protein-rich shrubs (Cassava and Erythrina subumbrans) fed as supplements to locally available forages (Elephant grass and banana leaves). Sixteen male local goats aged between 4 and 6 months and with a mean live weight of 10.2±2.3 kg were housed in individual cages according to a 2*2 factorial arrangement of 4 treatments: cassava or Erythrina as supplements; and banana leaves or Elephant grass as basal diet. There were 4 replications of each treatment. The protein-rich foliage was fed at 1% of live weight as DM; the basal diets were given ad libitum.

Growth rate and DM feed conversion were improved when Elephant grass replaced banana leaves as the basal diet and tended to be better for cassava compared with Erythrina. There was a significant interaction between the basal diet and the source of the supplement. The advantage of the cassava over the Erythrina was much greater when the basal diet was Elephant grass than when it was banana leaf.

Key words: feed conversion, nutritive value, protein, shrubs, trees

Introduction

Agriculture is the mainstay of the economy in Lao PDR employing more than 80% of the population. For the rural smallholders, livestock keeping is often a vital source of cash income. Ruminants, pigs and poultry are the most important livestock species in the country (MAF and FAO 2007). Most farmers raise animals by traditional methods and output per animal is not high (Daovy et al 2008a). Ruminants are grazed freely on communal grazing areas (eg: on forest land, on the roadsides or they scavenge around the village). During the cropping season they are confined or tethered. The main feed resources are native grasses, tree leaves, shrubs, legumes and crop residues which are available according to the seasons (Bounthavone et al 2010).

Goat production in Laos is widespread but limited to small numbers of animals per household. In 2014 there were approximately 470 thousand goats with 41 % in the north or mountainous area, 40% in the central part and 19% in the southern part of the country (LSB 2014). Local breeds which have a small size are adapted to the local environment. The litter size is normally two kids per litter after first kidding. The mature live weight is 26.8 kg for the females and 31.8 kg for the male goats in the free range system (Xaypha 2005).

The goats often graze freely in fallow crop land and forest. They are held in small groups which are herded by their owner and the animals eat from fodder trees, bushes, shrubs and grass (Allard 2010). According to Acharya (1986), goats spend 90 % of their total eating time browsing and only 10 % on grazing . This means that leaves and other parts of shrubs and trees may account for the greater part of their feed intake. Fodder trees and shrubs are the only naturally occurring feeds available in the dry season and have been utilized for a long time (Allard 2010). The leaves of leguminous fodder trees may contain from 12 to 30% crude protein in the DM, compared to 3-10 % in grasses (Gutteridge and Shelton 1998).

Fodder trees have the advantage of being more tolerant to drought than grasses because of their deep root systems which can reach water sources deep below the ground surface (Helena 2010). Trees and shrubs tend to be green a long time into the dry season, at which time the grasses have become like standing hay (Lukhele and Vn Ryssen 2003). Even in drought years, most fodder trees will grow leaves (Simbaya 1998).

The leguminous tree Erythrina subumbrans is commonly found in the southern part of Lao PDR, where it is cultivated and used mainly as a shade tree and as a fertilizer for Arabica coffee plants (Kongmanila et al 2012). In a study by Daovy et al (2008b) on selective behavior of local goats offered different tree foliage, it was found that the mean time spent eating, number of selective changes and feed intake were higher for Erythrina foliage.

The feeding of cassava foliage to goats is a recent development (Preston and Rodríguez 2004). The foliage can be harvested continuously at 2 to 3 month intervals over 1 to 2 years without the need for replanting (Preston 2005). Growth rates of goats were increased and fecal worm egg counts reduced when fresh cassava foliage replaced Guinea grass (Panicum maximum) as a supplement to cassava stems (Thanh et al 2013).

The banana plant (Musa spp.) produces a lot of biomass in the form of leaves and pseudo stems, most of which is wasted after the fruit is harvested. It has a great potential for ruminant feeding according to Olivera (2006). However, Ffoulkes et al (1977) and Kimambo and Muya (1991) observed that the DM degradabi;ity of the leaves was low.

Elephant grass (Pennisetum purpureum) is a major tropical grass. It is a very versatile species that can be grown under a wide range of conditions and systems: dry or wet conditions, smallholder or large scale agriculture. It is widely used as feed for cattle in the tropics due to its high productivity in cut-and-carry systems. The range of protein content of elephant grass varies from 4.4 to 20.4% in DM with the mean around 12% (Rusdy 2016).

The objectives of the research described in this paper were to compare fresh foliage from cassava and from Erythrina as protein supplements in basal diets provided by either Elephant grass or banana leaves.

Materials and methods

Location and duration

The experiment was carried out in Salao village, Phonthong district, which is located approximately 10 km from Pakse district, Champasack province, Lao PDR. The experiment was conducted for 4 months, from March to June 2016.

Treatment and experimental design

The treatments were:

· Protein supplement: Cassava or Erythrina foliage

· Basal diet: Banana leaves or Elephant grass

The experiment was arranged as a 2*2 factorial in a Randomized Complete Block Design (RCBD) with 4 treatments and 4 replications of each treatment.

Individual treatments were:

· BL-CF: Banana leaf ad lib + Cassava foliage offered at 1% of LW (DM basis)

· BL-EN: Banana leaf ad lib + Erythrina foliage offered at 1% of LW (DM basis)

· EG-CF: Elephant grass ad lib + Cassava foliage offered at 1% of LW (DM basis)

· EG-EN: Elephant grass ad lib + Erythrina foliage offered at 1% of LW (DM basis)

Animals and housing

A total of sixteen male local goats aged between 4 and 6 months and with a mean live weight of 10.2±2.3 kg (Photo1) were purchased from a farm located in Phonthong district. The animals were housed with in separate cages made from wood (dimension of 0.8 m width, 0.9 m length and 0.9 m height) (Photo 2). All animals were vaccinated against foot and mouth disease and treated with Ivermectin (1 ml/33 kg LW) to control parasites.

Photo 1. Local goats used in the experiment	Photo 2. The goat kept in individual cages

Feeding and management

The goats were adapted to the diets for 14 days before starting the experiment. The cassava was planted in an area close to the experimental site. The area was into six sub-plots of 133 m²/plot and each sub-plot provided foliage for a period of one week with repeated harvesting at 42 day intervals (Photo 3). Erythrina foliage (E.subumbrans) was collected from the coffee garden of a farmer in Paksong district.

The elephant grass was planted in an area of 800 m² with the same management as for the cassava (Photo 4). Banana leaves were collected from the banana garden of a neighboring farmer. The foliages from cassava, Erythrina and Elephant grass were hung in bunches above the feed trough. The banana leaves were chopped into small pieces of 2 to 4 cm (Photo 6) and put into the feed trough.

Photo 3. Cassava at harvest foliage (42 days of regrowth)	Photo 4. Erythrina foliage
Photo 5. Elephant grass at harvest time (42 days of regrowth)	Photo 6. Chopping of banana leaf

Data collection and measurements

Feeds were weighed before giving them to the goats. Feed refusals were collected each morning and weighed to measure the feed intake. The live weight of the goats was taken at the beginning, every 14 days and at the end of the experiment.

Chemical analysis

Samples of feed offered and refused were collected every 14 days to determine DM, ash and crude protein according to AOAC (1990) methods.

Statistical analysis

The data were analyzed by the General Linear Model option of ANOVA program in the Minitab software (Minitab 2000). In the model, the sources of variation were blocks, source of supplements, source of basal diet, interaction supplements*basal diet and error.

Results and discussion

Chemical composition of the feeds

The foliage from cassava and Erythrina had similar content of DM and of crude protein, the latter being three times higher than that in banana leaves and Elephant grass. All the values were within the range reported for these forages in the Feedipedia data base (www.feedipedia.org).

Feed intake

The crude protein levels were the same in all diets and adequate for normal growth of goats (Table 2). DM intake was 50% higher when Elephant grass replaced banana leaves as the basal diet; however, there were no differences between the two sources of protein-rich foliage (Figures 1 and 2).

Figure 1. Contrasting effect of supplements of cassava compared with Erythrina foliage on DM intake of goats fed basal diets of banana leaf or Elephant grass	Figure 2. Contrasting effect of  basal diets of banana leaf versus Elephant grass on DM intake of goats supplemented with cassava or Erythrina foliage

Growth and feed conversion

Growth rate and DM feed conversion were improved when Elephant grass replaced banana leaves as the basal diet and tended to be better (p=0.057and 0.07 for growth and conversion) when cassava foliage was the supplement (Tables 2 and 3; Figures 3-6). There was a significant interaction between the basal diet and the source of the supplement. The advantage of the cassava over the Erythrina was much greater when the basal diet was Elephant grass than when it was banana leaf (Figure 5 and 6).

Overall rates of DM feed conversion were relatively poor (range from 9.9 on the best diet of Elephant grass – cassava foliage diet to 14.7 on the poorest diet of banana leaf and Erythrina foliage). This was probably due to the low nutritive value of both Elephant grass (eg: Rusdy 2016; Anta et al 2016) and banana leaves (eg: Ffoulkes et al 1977) which was observed when these forages were fed as the sole diet to cattle.

There is abundant evidence of the high nutritive value for goats of cassava foliage. Growth rates of goats were increased when fresh cassava foliage replaced Para grass (Brachiaria decumbens) (Do et al 2002) or Guinea grass (Panicum maximum) (Thanh et al 2013). Feeding cassava foliage is also reported to reduce strongyle worm infestation in goats as well as improving growth rates (Sokerya and Rodriguez 2001; Seng Sokerya and Preston 2003; Phengvichith and Preston 2011).

There appear to be no comparative data on cassava versus Erythrina foliage as protein supplements for goats. However, the variety Erythrina poeppigiana fed at 30% of the DM replacing King grass (Penissetum purpueum) resulted in doubling of the milk yield (from 326 to 820 ml/day) (Esnaola and Rios 1990). The King grass contained only 8% crude protein in DM while the Erythrina contained 23%.

Figure 3. Contrasting effect of supplements of cassava compared with Erythrina foliage on growth rate of goats fed  basal diets of banana leaf or Elephant grass	Figure 4. Contrasting effect of  basal diets of banana leaves versus Elephant grass on growth rate of goats supplemented with cassava or Erythrina foliage
Figure 5. Contrasting effect of supplements of cassava compared with Erythrina foliage on feed conversion of goats fed basal diets of banana leaf or Elephant grass	Figure 6. Contrasting effect of banana leaf versus Elephant grass as basal diet on feed conversion of goats supplemented with cassava or Erythrina foliage

Conclusions

• Growth rate and DM feed conversion were improved when Elephant grass replaced banana leaves as the basal diet and tended to be better for cassava compared with Erythrina.
  
  
• There was a significant interaction between the basal diet and the source of the supplement. The advantage of the cassava over the Erythrina was much greater when the basal diet was Elephant grass than when it was banana leaf.

Acknowledgements

This research is part the requirement of the senior author for the MSc degree in Animal production “Improving Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change Mitigation” Nong Lam University, Sida-Mekarn II. The authors gratefully acknowledge the MEKARN project financed by Sida for supporting this research. Special thanks to Mr Vanasin who provided valuable help in the laboratory. Greatly thankful to students of the Department of Livestock, Faculty of Agriculture and Forestry, Champasack University for assisting during this experiment.

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Received 1 October 2016; Accepted 16 October 2016; Published 1 December 2016

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