Effects of tree foliages compared with grasses on growth and intestinal nematode infestation in confined goats

Nguyen Kim Lin, T R Preston*, Dinh Van Binh and Nguyen Duy Ly

Goat and Rabbit Research Center,
Bavi, North Vietnam
binhbavi@netnam.vn
* University of Tropical Agriculture Foundation
regpreston@utafoundation.org

 

Abstract

Two experiments were carried out to study effects of tree foliages versus grasses on intestinal nematode infestation and growth of confined goats.

In experiment 1, 20 males and 10 females of Bachthao and cross-bred (Bachthao x Barbari) goats (initial live-weight from 9 to 14 kg) were allocated to 5 sources of forage which were offered as supplements to rice bran (RB) and a  Molasses Urea Block (MUB). The forages were: fresh foliage of cassava (Manihot esculenta), Jack Fruit (Artocarpus heterophyllus) and Leucaena (Leucaena leucocephala) and fresh grasses of Guinea (Panicum liconi) and Ruzi (Brachiaria ruziensi). The goats were confined in pairs in wooden pens of 1.2 x 1.4m area on a raised slatted floor. They were fed the experimental diets for 10 days and de-wormed before starting the experiment. The feed offered was adjusted at 14 day intervals according to live weights. The experiment began on 11 December 2001 and continued until 11 April, 2002.The forages were harvested daily from the fields in the Goat and Rabbit Research Center (GRRC). The foliage from cassava (C) and Leucaena (L) were harvested after approximately 2 months re-growth by cutting at 30 cm (C) and 70 cm (L) above soil level. The foliage from Jack fruit (trees were older than 5 years) was harvested after 3 months re-growth by cutting at 150 cm and higher above soil level. The Guinea and Ruzi grasses were harvested after 4 weeks and 7 weeks re-growth by cutting at 3 to 5 cm above soil level. All the foliages were fed at ad libitum. Rice bran was given at 10 g/kg live weight and a molasses-urea-block at 5 g/kg live weight.

In experiment 2, 24 male goats recently weaned, with initial live-weight from 9 to 12 kg, were allocated to 4 treatments in a 2*2 factorial arrangement: Guinea versus Ruzi grass and two cutting heights of each grass (3 to 5 cm and 10 to 12 cm above soil level). The Guinea and Ruzi grasses were cut after 4 weeks and 7 weeks re-growth at between 9 am and 5 pm. The grasses were fed ad libitum. Rice bran was given at 15 g (DM)/kg live weight.

In both experiments, records were kept of feed intake (daily) and live weight (15 day intervals). Faeces samples were taken at the beginning and monthly to determine eggs of Strongyle and coccidian oocyts.

The goats  grew faster and had lower levels of infestation with nematode parasites when fed: tree foliages rather than  grasses (Experiment 1); or grass cut at 10 to 12cm rather than 3 to 5cm, above soil level (Experiment 2).

It is concluded that  there are two mechanisms which favour the use of tree and shrub foliages in diets for goats: the presence of condensed tannins in the leaves and the physical attributes of such plant species which do not facilitate the migratory habits of infective nematode larvae.

Key words: cassava, coccidia, endo-parasites, goats,  growth, Jack-fruit, leucaena,, strongyle eggs

 

 

A principal characteristic of the goat is its dietary selectivity, which enables it to survive in apparently harsh environments. Some researchers have pointed out that the goat is more susceptible to parasites than sheep and that their resistance to the humid tropical climate is not as good as is the case for cattle or sheep (Baxendell 1984; Dunn 1978; Restrepo and Preston 1989). In India, parasites were considered to be a major health hazard for goats particularly in hilly and swampy regions (Battacharya 1989). In Kenya, endoparasites were also considered to be a major constraint to goat improvement (Shavulimo 1989). Thus a first priority in any production program for goats in the humid tropic is parasite control. In this respect, avoidance of re-infestation is more cost effective and biologically sustainable than use of anthelmintics. The features of this strategy are: complete confinement; uncontaminated forages; dry bedding and use of locally available feed resources according to the principles of balanced nutrients both for the rumen and for the animal (Restrepo and Preston 1989).

 

Cassava is a tropical crop with a high biomass production, that popularly and traditionally cultivated to produce roots. The leaves are by product that can be sun- dried and used as a source of protein and vitamins in pig and poultry diets (Ravindran 1991). Cassava can also be cultivated in a combined forage / root system with two or more harvests of foliage prior to letting the roots develop to maturity (Wanapat et al 1997). More recently, cassava has been used as a perennial forage crop with repeated harvesting at 2 to 3 month intervals. In this system, the roots are not harvested, but serve as a nutrient reserve to support the forage re-growth (Preston et al 2000; San Thy and Preston 2001). Cassava foliage has been made into “hay” in Thailand and used successfully as a source of protein for dairy cattle (Wanapat et al 1997). Seng Sokerya and Lylian Rodriguez (2001) showed that growth rate of confined goats was higher, and nematode infestation lower, when the forage supplement was cassava foliage as opposed to cut grass. 

 

 Jack fruit is a popular fruit tree, distributed widely in North Vietnam, with features of: rapid growth and the facility of  harvesting the branches as sources of forage. The leaves have a high dry matter and protein content, and are readily consumed by goats  (Tran Quoc Viet 1997; Keir et al 1997).

 

Leucaena is a leguminous tree with high biomass yield and leaves rich in protein and vitamins. It is used popularly in mixed plantations with grasses such as Guinea or Ruzi (Nguyen Thi Mui 2000). The foliage is very palatable to goats (Ngo Van Man et al 1993). Recently, some new varieties and crosse have been introduced in the GRRC,. such as  Leucaena leucocephalla (K636), Leucaena pallida (K748) and a cross between K636 (mother tree) with K748 (father tree), named KX2. The KX2 and K636 lines have grown well in hilly and mountainous areas in North Vietnam. The KX2 breed has given biomass yields as high as 45 to 60 tonnes/ha/year (Le Van Khoa et al  2000).

 

Guinea and Ruzi are popular grasses, with high fresh matter yield, and are the major forage sources for traditional goat feeding systems in Vietnam. However, with this feeding system, the rate of nematode worm infestation is high with mortalities as high as 35% on some farms, despite frequent use of anthelmintics (Dinh Van Binh, personal communication). 

 

The following study aimed to provide further information on the relative benefits of tree foliages compared with grasses as the forage supplement for confined goats.

 

Materials and methods

Experiment 1:

Treatments and design

The treatments were 5 sources of forage fed ad libitum to confined goats, together with hay, rice bran and a molasses-urea block (MUB):

CF: Fresh foliage of cassava

JF:  Fresh foliage of Jack fruit.

LF: Fresh foliage of leucaena (KX2)

GG: Guinea grass (Panicum liconi).

RG: Ruzi grass (Brachia ruziensi)

The basal diet included rice bran at 10 g DM/kg live weight, MUB (5% urea; 15% crude protein) at 5 g DM/kg live weight, hay (dried mixed grasses of Ruzi and Guinea) and water, which was freely available.

Animals

Twenty males and 10 females of Bachthao and cross-bred (Bachthao x Barbari) weaned goats with initial live-weight from 9 to 14 kg were chosen for the experiment. The goats were blocked according to sex and breed and then allocated at random to the 5 treatments. The experiment began on November 12, 2001 and continued until 11 April, 2002. The goats were confined in pairs in wooden pens of 1.2 x 1.4m area on a raised slatted floor, which was cleaned daily. The goats were fed the experimental diet for a preliminary period of 10 days and de-wormed (Ivermectin at 1.5 ml/10 kg live weight) before starting the experiment. The amounts of supplements offered (Rice bran and MUB) were adjusted  at 14 day intervals according to live weight.

Measurements and statistical analysis

Feeds offered and refused were recorded daily. Live weights were taken at 15 day intervals. About 4 g of faeces were taken from each goat at monthly intervals directly from the rectum for determination of nematode eggs and coccidia oocysts. Each faecal sample was ground and mixed with 56 ml of flotation fluid (either 1250 g sugar and 1 litre water or 450 g salt and 1 litre water). After filtering through a “tea strainer”, a sub-sample was transferred to both side of a McMaster counting chamber and allowed to stand for 5 minutes. All eggs were counted under a microscope at 10x10 magnification.

The growth and feed intake data and faecal egg counts were analysed by the One-way option of the ANOVA software from Minitab (version 12.1). Variables were treatments and error.

Experiment 2

Treatments and design

The treatments were 2 sources of fresh grass cut at two heights above soil level arranged as a 2*2 factorial.

GL: Fresh Guinea grass cut at low level (3to 5 cm above soil level).

RL: Fresh Ruzi grass cut at low level (3 to 5 cm above soil level).

GH: Fresh Guinea grass cut at high level (10 to 12 cm above soil level).

RH: Fresh Ruzi grass cut at high level (10 to 12 cm above soil level).

Animals

Twenty-four crossbred (Bachthao x Barbari) weaned male goats with initial live weight from 9 to 12 kg were allocated at random to the 4 treatments. The experiment began on 16 July and continued until 15 December 2002.

Diets and management

The fresh grasses were offered ad libitum. Rice bran was given at 15 g (DM)/kg. The goats were housed and managed as in experiment 1.

Measurements and statistical analysis

These were the same as in Experiment 1, except that the variables in the ANOVA analysis were: grasses, height of cutting, interaction grass*height, and error

Results

Experiment 1

Intake and growth

Total DM intake was highest for goats fed Jackfruit and lowest for goats fed Guinea or Ruzi grass (Table 1). Growth rates were higher for the foliage treatments than for the grasses, the Guinea grass being better than the Ruzi grass (Figure 1).

Table 1: Feed intake and live-weight of goats fed different forages
		Cassava	Jackfruit		Leucaena	Guinea	Ruzi
Feed intake (fresh basis), g/day
Foliage	1385			1052	1087	1091	1001
Hay	128			132	116	125	117
Rice bran	102			102	109	109	109
MUB	47.7			49.9	50	50	50
Feed intake, g DM/day
Foliage	320c ± 5.1			452a ± 6.5	351b ± 5.4	254d ± 3.6	237d ± 4.1
Hay	112ab ± 1.4			116a ± 1.5	102c ± 1.3	109b ± 1.4	103c ± 1.9
Rice bran + MUB	127b ± 1.2			129b ± 1.6	135a ± 1.1	136a ± 1.1	138a ± 1.2
Total	556b ± 5.5			697a ± 7.1	588b ± 5.9	499c ± 4.1	475c ± 5.3
Live weight, kg
Initial	10.6  ± 0.39			10.5 ± 0.49	10.3 ± 0.15	10.7 ± 0.35	11.4 ± 0.32
Final	17.05 ± 0.54			16.4 ± 0.53	16.6 ± 0.51	15.7 ± 0.45	15.2 ± 0.53
Daily gain, g	42.8a ± 0.87			39.2a ± 1.27	41.7a ± 1.92	33.7  b ± 1.52	25.2c ± 0.83
abc means without letter in common are different at P<0.05

 

Figure 1: Weight gain of  goats fed cassava, jackfruit and leucaena foliages or guinea and ruzi grasses

 

Nematode infestation

The numbers of strongyle eggs in the faeces were almost 4 times higher in the goats fed grasses than in those fed tree foliages (Table 2 and Figure 2). The effects of forage treatments on the numbers of coccidia oocysts were similar to those observed for the strongyle eggs.

Figure 2: Worm egg counts (Strongyle spp.) in growing goats fed different forages
(Number refer to sampling dates which were: 1* = 11 November 01 (before anthelmintic treatment);
1 = 11 December 01; 2 = 11 January 02; 3 = 11 February 02; 4 = 11 March 02; 5 = 11 April 02)

 

Experiment 2:

Feed intake and growth

The goats fed grass cut at the higher level  grew faster  than the goats fed grass cut closer to the soil (Table 3 and Figure 3). Total DM intakes were higher for the treatment with Ruzi grass than with Guinea grass.

 

Figure 3: Growth rates of goats fed Guinea (G) or Ruzi (R) grass cut at low (L) or high (H) levels above the soil

 

Nematode infestation

Counts of nematode worm eggs in the faeces were lower when the goats were offered grass cut at 10 to 12 cm above soil level compared with cutting at 2 to 5 cm (Table 4 and Figure 4). A similar pattern was seen for the counts of coccidia oosysts (Table 4).

 

 

 Figure 4: Worm eggs counts (Strongyle spp.) in faeces of growing goats fed Guinea or Ruzi grasses
cut at high and low levels above the soil.

 

Discussion

The result with the cassava foliage agrees with the reports of Seng Sokerya and Rodríguez (2001) and Seng Sokerya and Preston (2003), in which growth rates of growing goats were higher and faecal egg counts lower, when cassava foliage was the forage source rather than grass. Nematode faecal egg counts were reduced when grazing cattle and buffaloes were supplemented with cassava hay according to Netpana et al (2001).  Seng Sokerya and Preston (2003) attributed the beneficial effects of the cassava to the presence of condensed tannins in the foliage, as there are many reports of anthelmintic effects  associated with the presence of these compounds in plants (Granum et al 2003; Butter et al 2000; Kabasa et al  2000; Molan et al 2002;  Niezen et al 1996; Khan and Diaz-Hernandez 2000; Khan et al 2001). Leucaena leaves are known to contain condensed tannins and it is probable that these compounds are also present in jackfruit leaves, as our observations indicate that the leaves of this tree are rarely attacked by insects, which is an indication of the presence of compounds with toxic properties. 

The other issue, related to the positive effects of tree foliages as a defense against intestinal nematodes, is the anatomical difference between trees and shrubs, compared with grasses. It is known that the infective larvae migrate vertically on plants via the moisture film (Niezen et al 1996). These authors indicated that the number of infective larvae that successfully develop and migrate up the stems of the herbage (to be consumed by host animals) can be influenced by pasture-plant species, and that some plant species might have thicker water films than other plants. In our experiments, this migratory behaviour of the infective larvae could also partially explain why the goats in experiment 1, that consumed the foliages of cassava, jackfruit and leucaena, had much lower levels of parasite infestation,  as it is unlikely that the larvae would climb the stems of the trees. Further support for this explanation is in the results of  Experiment 2,  where the faecal nematode egg counts were reduced when the grass fed to the goats was cut at a high rather than a low level; and in the observations of Coffey et al (2001), who showed that when the grass was tall the infective nematode larvae did not climb up to the top of the plant.

Conclusions

Considering the results of the two experiments, together with the findings of Seng Sokerya and Rodríguez (2001) and Seng Sokerya and Preston (2003), it would appear that there are two mechanisms which favour the use of tree and shrub foliages for goats: the presence of condensed tannins in the leaves and the physical attributes of such plant species which do not facilitate the migratory habits of infective nematode larvae.
 

Acknowledgments

We acknowledge financial support for this research from the SAREC project. The advice and guidance received from Dr Douglas Gray of ILRI is highly appreciated.

 

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