Cassava and Flemingia foliage and hay as protein supplements for growing goats fed a basal diet of guinea grass and dried cassava root

Ngo Tien Dung^*, Dinh Van Binh^*, Nguyen Thi Mui^**, T R Preston^*** Inger Ledin^****

*Goat and Rabbit Research Center, Sontay, Hatay, Vietnam

**National Institute of Animal Husbandry, Hanoi, Vietnam

***University of Tropical Agriculture Foundation, TOSOLY, Socorro, Santander, Colombia

****SwedishUniversityof Agricultural Sciences, Dept. of Animal Nutrition and Management

Abstract

Forty weaned goats (F1 between Bachthao and Barbary or Jamnapary) with initial weight of 12.6±0.13 kg and 3.5 to 4 months age were used in a study to evaluate cassava and Flemingia foliage and hay as a protein source compared to a commercial concentrate in diets based on guinea grass and dried cassava root. Eight goats were allocated to each of 5 treatments in a completely randomised design. The experimental period was 90 days. The treatments were concentrate (CC), and concentrates replaced by cassava foliage (CF), or cassava hay (CH), or Flemingia foliage (FF) or Flemingia hay (FH). The growth rates of the CC, CF, CH, FF, FH treatments were 84, 67, 75, 51 and 52 g/day; feed conversion ratios (FCR) were 7.20, 8.60, 7.65, 9.50 and 9.14 kg DM/kg live weight gain (LWG).

Replacement of concentrate with cassava hay and Flemingia foliage and hay led to lower DM intakes, the reduction being greater for Flemingia than for cassava. Numbers of eggs in faeces of nematodes and Cestoda and coccidia oocysts were low on all diets. Numbers increased with time on experiment for the control "concentrate" but remained low on the cassava foliage and hay diets.

1. Introduction

Cassava is a highly productive tropical crop that is traditionally cultivated to produce roots for human consumption or industrial extraction of starch. The leaves are a by-product from this operation and can be sun-dried prior to using them as a source of protein and vitamins in pig and poultry diets (Ravindran 1991). Cassava can also be cultivated in combined forage/root systems with two or more harvests of the foliage prior to letting the root develop to maturity (Wanapat et al 1997). More recently, efforts have been concentrated on managing cassava as a perennial forage crop with repeated harvesting at 2 to 3 month intervals (Preston et al 2000; San Thy and Preston 2001). In this system, the roots are not harvested, but serve as a nutrient reserve to support the forage re-growth. Cassva foliage is increasingly being shown to have high nutritive value for ruminants as a protein supplement (Wanapat et al 1997; Seng Sokerya and Rodriguez 2001; Seng Mom et al 2001). However, cassava is an exploitive crop when grown in monoculture and repeated planting in the same soil leads to loss of soil fertility and erosion (Dinh Van Binh et al 1998).

In view of the potential of cassava as a source of energy (the roots) and protein (the leaves) for livestock, and the fact that it is the preferred crop by poor farmers in hilly-mountainous land, there is a need to develop cropping systems which are more sustainable. Recent research has therefore been focused on ways to maintain yield and soil fertility by recycling of manure and biodigester effluent (Preston 2001) or the association with shrub legumes such as Flemingia macrophylla. Results with Flemingia macrophylla are encouraging with increased total biomass yield and improved soil fertility and reduced soil erosion for the association cassava-Flemingia, compared with cassava in monoculture (Ngo Tien Dung et al 2003a, Nguyen Phuc Tien et al 2003).

Flemingia macrophylla is a leguminous shrub with high biomass yields that grows well on acid soil. It is reasonably tolerant to drought and has given good results when mixed with foliage of Trichanthera gigantea as the protein source for lactating goats (Bien et al. 1998). However, levels of Flemingia in the diet higher than 15% have a negative effect on growth and milk production of goats (Nguyen Thi Mui et al 2001).

An early report from the Dominican Republic showed that fresh cassava foliage supported growth rates of over 800 g/day when fed as the only supplement in a basal diet of molasses-urea (Ffoulkes and Preston 1978). Made into hay, the foliage was used successfully as a source of bypass protein for dairy cattle in Thailand (Wanapat et al 1997; Wanapat 2001). The fresh foliage supported high growth rates in goats in Cambodia and Vietnam, and reduced nematode infections as indicated by very low faecal egg counts (Seng Sokerya and Rodriguez 2001; Seng Sokerya et al 2003; Ngo Tien Dung et al 2003b; Nguyen Kim Lin et al 2003). Supplementing grazing buffaloes with cassava hay also reduced faecal worm egg counts in Thailand (Netpana et al 2001). It is thought the condensed tannins in the cassava foliage may be the agents conferring anthelmintic properties in the cassava leaves (Seng Sokerya et al 2003).

The objective of the present study was to evaluate cassava and Flemingia foliage and hay as a source of protein in diets based on guinea grass and cassava root for growing goats. The hypotheses to be tested were:

• Drying the cassava and Flemingia foliages would not reduce their nutritive value for growing goats.

• The tannins in Cassava and Flemingia foliage and hay could be a means of reducing internal parasites in goats.

2. Materials and methods

2.1 Location and climate of the study area

The experiment was conducted at the Goat and Rabbit Research Centre, Sontay, Hatay province, 60 km North-west of Hanoi. The centre is located in the buffer zone between a mountainous area and the delta at 105^o25E and 21^o06N and 220m above sea level. The climate is tropical monsoon, with a wet season between April and November and a dry season from December to March. The experiment was conducted in the wet season (June to October, 2004).

2.2 Experimental animals

Forty growing goats, F1 between Bachthao and Indian goats (Barbari or Jumnapary), were used as experimental animals. The experiment started when the goats had an initial weight of 12.6±0.13kg and were 3.5 to 4 months old. The animals were vaccinated against pasteurellosis and enterotoxemia and treated against internal and external parasites with Ivermectin (1ml/kg BW injected subcutaneously) and Albendazole (0.1 mg/kg given orally) before the experiment commenced).

2.3 Experimental design

There were 5 treatments:

CC (Control): Guinea grass + Dried cassava root + Concentrate

CF: Guinea grass + Dried cassava root + Cassava foliage

CH: Guinea grass + Dried cassava root + Cassava hay

FF: Guinea grass + Dried cassava root + Flemingia foliage

FH: Guinea grass + Dried cassava root + Flemingia hay

Eight growing goats were allocated to each treatment in a fully randomised design with 8 replications.

2.4 Feeding and management

The diets offered were based on guinea grass (Panicum maximum), dried sliced cassava roots, cassava foliage (CF), cassava hay (CH), Flemingia foliage (FF), Flemingia hay (FH) and concentrate. The guinea grass was cut daily at 35 to 40 days of age in the fields around the Centre and wilted for 1 hour under shade or in a house, before feeding. The cassava hay (CH) and Flemingia hay (FH) were made from cassava and Flemingia foliage which was collected in the Centre in May 2003 at an age of 45 and 60 days respectively. The foliage was chopped into small pieces mechanically (1 to 2 cm) and dried in the sunlight. When the foliages were fed fresh they were not chopped but broken by hand to a size that could be accommodated in the feed trough. The commercial concentrate used in the experiment was produced by the Guyomach-VCN factory in Hanoi, Vietnam and contained 87% DM and 16.1% CP. The feeds were offered in separate feeding troughs.

All animals were fed the same amount of guinea grass and cassava root, with amounts increasing with increasing body weight (BW). The diets were calculated to cover the requirements of a goat weighing 13 to 21 kg and growing 50 to 100 g/day according to Devendra and McLeroy (1982), with calculated refusals of 25% of the guinea grass, cassava and Flemingia foliage and hay fed. When the goats reached 15, 17, 19 and 21 kg BW on an individual basis, the guinea grass, dried cassava root, concentrate, cassava and Flemingia foliage and hay were increased.

The animals were fed guinea grass 3 times per day (at 8:00 h, 13:00 h and 17:00 h). Cassava root were fed at 8.00 h. Concentrate, cassava and Flemingia foliage and hay was fed twice per day at 8.00 and 13.00h. Mineral lick blocks with a composition of 73% minerals (70% limestone meal and 30% bone meal), 17% cement as a binding agent and 10% salt were supplied to each pen. The animals had free access to fresh water. The goats were kept in individual pens in the same house and were exercised once daily in a yard for 1 h in the morning. The experimental period was 90 days.

2.5 Measurements and analyses

The goats were weighed at the beginning of the experiment and then at ten day intervals. Feeds offered and feed refusals were measured daily. Representative samples of feeds were taken during the experiment. Feed refusals from individual animals were collected and weighed daily. The feed refusals were pooled for 15 days for each treatment group. Feeds offered and feed refusals were analysed for DM, CP, ash, neutral detergent fibre (NDF) and acid detergent fibre (ADF). Ether extract (EE) was analysed in order to be able to make an estimation of energy content. Total tannins were determined in the guinea grass, cassava, Flemingia foliage and hay; HCN was determined in cassava foliage and hay.

Total nitrogen was determined by Kjeldahl technique (AOAC 1990). .Ash (942,05), ADF (973,18) was determined according to AOAC (1990). Ether Extract was determined by method of ISO (6492:1999) and NDF was determined by the method of Van Soest (1991) using sodium sulphite and amylase and was expressed with residual ash. Total tannins were analysed by the Lowenthal method and HCN by the method of Ikediobi et al. (1980).

The experiment started 10 days after drenching against internal and external parasites. Faecal samples were taken directly from the rectum on four occasions, at the beginning of the experiment and after 30 days, 60 days and 90 days. The samples were put in plastic bags to protect from the air, since presence of air may lead to hatching of the eggs of the parasites. The samples were stored in a refrigerator at 4^oC to prevent physical and chemical changes, especially to hatchability, which may cause problems when counting EPG. The faecal samples (4 g) were ground and mixed with 56 ml of flotation fluid (either saturated sugar or salt solution diluted with water). After filtering through a tea strainer, a sub-sample was transferred to both sides of a McMaster counting chamber and allowed to stand for 5 minutes. Nematode and Cestoda eggs and Coccidia oocysts were counted under a microscope at 10x10

2.6 Statistical analyses

The data from the experiment were analysed as a Completely Randomized Design by ANOVA using the General Linear Model option of the MINITAB software (Minitab, 2000). When the "F" test was significant at the 5% level, the treatment means were compared with each other using Tukey's pair-wise comparisons in the Minitab software..

The statistical model used in the analysis was:

Y_ij = µ + T_j + e_ij

Where Y_ij = dependent variable, µ = overall mean, T_j = treatment (j = 1; …5) and e_ij = random error. The initial live weights of the goats were used as a covariate in the model.

2.7. Economical analysis

The variable costs of feeding the goats were the costs of the feeds, as all other costs (labour, capital investment, housing etc) were the same for all treatments. The labour for growing, and harvesting the cassava and Flemingia forage and for making the hay was included in the feed cost for these items.

3. Results and discussion

 

Table 1: The chemical composition of the experimental feeds (means and SEM)
Parameters	Guinea grass	Dried cassava root	Concentrate	Cassava foliage	Cassava hay	Flemingia foliage	Flemingia hay
Number of samples	6	6	6	6	6	6	6
DM (g/kg feed)	212±7.3	878±7.5	885±6.6	208±12	868±8.2	234±3.1	867±9.5
Composition of DM (g/kg)
Crude protein	107±7.5	32±3.1	160±0.9	187±5.1	182±5.6	163±2.2	161±2.3
Ash	85±1.4	23±1.2	35±1.0	65±1.0	67±1.9	43±0.9	47±1.3
NDF	657±19.8	56±1.0	97±2.3	425±7.8	427±5.7	595±8.8	604±7.6
ADF	398±13.2	25±1.3	67±1.2	316±5.8	298±4.6	427±5.6	467±4.3
Ether Extract	189±2.1	24±2.3	132±1.4	123±2.5	121±1.6
Total tannins	9±1.02	-	-	41±0.5	27.6±1.6	28±1.4	17.6±0.7
HCN (mg/kg DM)	-	-	-	328±13	132±5.1	-	-

The guinea grass contained 107g CP/kg DM (Table 1). The cassava root had a very low CP content (32 g/kg DM) and low values of NDF and ADF. The cassava and Flemingia foliage contained 187 and 163g CP/kg DM, respectively. Values for cassava and Flemingia hay were lower (182 and 161g/kg DM, respectively). The cassava foliage and hay had a higher CP content than expected, and was higher than the concentrate, but Flemingia foliage and hay had a similar protein content as the concentrate. The content of tannins in cassava and Flemingia foliage were higher than in the corresponding hays. The HCN in cassava foliage and hay was 328 and 132 mg/kg DM, respectively.

Figure 1: Relative DM intakes of the dietary ingredients

All the dried cassava root and concentrate were consumed (Table 2). Cassava foliage and hay were more palatable than Flemingia (Figure 1), which resulted in higher feed intake for the former. Feed intakes for diets with cassava foliage were higher than when this forage was given as hay. Feed intake as % of body weight was highest on the concentrate and cassava foliage diets, which were the same, followed by the cassava hay diet and were lowest for the Flemingia diets. Amounts of total tannins were highest on the cassava foliage diet followed by the cassava hay and Flemingia foliage diets, with a lower value for Flemingia hay and with the lowest value on the concentrate diet.

Table 3: Effect of supplementation with Cassava and Flemingia fresh and dried (hay) foliages on the live weight gain of the growing goats and on feed cost
Parameters	Control	CF	CH	FMF	FMH	SEM
Initial weight, kg	12.9	12.8	12.4	12.5	12.6	0.13
Final weight, kg	20.5	18.9	19.1	17.1	17.3	0.52
Live weight gain, g/day	84a	67c	75b	51d	52d	1.6
FCR, kg DM feed/kg of LWG	7.20e	8.60c	7.65d	9.50a	9.14b	0.089
FCR, kg CP feed/kg of LWG	0.86d	1.18b	1.02c	1.24a	1.15b	0.011
Feed cost, VND/goat/day
VND/kg LWG	20970a	14600d	12430e	17970b	16910c	142
Cost reduction over control, %	100	69.6	59.3	85.7	80.6
a, b, c, d, e Means within rows without common superscript differ at P<0.05

Feed cost (fresh basis): Guinea grass: 300 VND/kg; Dried cassava root: 2000 VND/kg; Cassava and Flemingia foliage: 350 VND/kg; Cassava and Flemingia hay: 1,300 VND/kg. VND= Vietnamese dong and 1USD= 15,700 VND

The mean daily live weight gains (LWG) were highest for the goats fed concentrates, followed by those fed the cassava hay, with lowest values for the Flemingia foliage and hay (Table 3). The data for DM conversion showed a similar pattern as for the weight gain.

The feed costs per kg LWG were highest on the control treatment. The lowest feed cost was found in the treatment with cassava hay.

Table 4: Effect of replacing concentrates with cassava and Flemingia fresh and dried (hay) foliages on number of Nematode, Cestoda eggs and Coccidia oocysts in the feaces of goats
Parameters	Control	CF	CH	FMF	FMH	SE
Nematodes, eggs/g faeces
Initial	145	136	137	123	100	11.3
30 days	236a	67b	90b	107b	94b	19.9
60 days	267a	51b	64b	95b	93b	19.0
90 days	462a	35c	40c	125c	81b	12.1
After 90 days compared to initial (%)	318.6	25.7	29.2	102	81
Cestoda, eggs/g faeces
Initial	118a	74b	76ab	85ab	97ab	17.1
30 days	150a	62b	85b	93ab	106ab	20.1
60 days	190a	58c	83bc	122b	113b	21.3
90 days	267a	49c	87b	140b	112b	14.6
After 90 days compared to initial (%)	226.3	66.2	114.5	164.7	115.5
Coccidia oocysts/g faeces
Initial	1146	885	676	976	1030	99.2
30 days	2261a	528c	1048b	490c	482c	153.5
60 days	2640a	115b	229b	362b	418b	122
90 days	4464a	42b	120b	274b	272b	137
After 90 days compared to initial (%)	389.5	4.7	17.7	28.1	26.4
a, b, c, d, e Means within rows with different superscripts differ significantly (P<0.05)

Numbers of nematode and Cestoda eggs and Coccidia oocysts remained low throughout the trial for all treatments with cassava or Flemingia foliage or hay, but increased on the control diet (Table 4 and Figures 2, 3 and 4).

Figure 2: Changes in FEC of nematodes during the experiment according to dietary treatments	Figure 3: Changes in FEC of Cestoda during the experiment according to dietary treatments

 

Figure 4: Changes in coccidian oocysts in the faeces of the goats during the experiment according to dietary treatments

4. Discussion

The cassava foliage and hay contained green stems as well as leaves and petioles and the relative proportions of these components influence the crude protein content, which probably explains why the values recorded in this experiment were lower than was reported by Nguyen Thi Mui (1994) and by Wanapat et al (1997), of 25.6 and 24.9%, but similar to the value reported by Van and Ledin (2001) (20.1%). The crude protein in the Flemingia foliage was similar to the values of 16.5% of DM reported by Dinh Van Binh et al (1998) 16.0 to 16.4% of DM reported by Nguyen Thi Mui et al (2002). Data from the literature range from lower (14.5% reported by Asare 1985) to higher values (19.0% in DM reported by Dzowela et al 1995 and by Huy et al 2000). According to Ravindran et al (1987a), processing has little influence on the crude protein content of the leaf meal, but in the case of the foliage the process of drying after chopping could result in loss of some leaf relative to the stem material, and hence a reduction in crude protein content.

The HCN content of fresh cassava leaves is normally between 200 and 800 mg/kg DM (Ravindran 1991). According to Chew (1972), 18 cultivars of cassava grown under identical conditions showed a range of 174 to 622 mg HCN/kg DM; while, in a study involving 31 cultivars, Yeoh and Oh (1979) obtained values of 125 to 854 mg HCN/kg DM. The lower content of cyanide in the hay compared with fresh foliage is a finding well established by other researchers (e.g Gomez and Valdivieso 1985, Ravindran et al 1988). This reduction is due to the action of endogenous linamarase on glucosides following loss of cell integrity (wilting) or tissue damage (chopping).

The content of tannins in cassava foliage and hay (4.1 and 2.76% of DM, respectively) was similar to the values of 3.05% of DM reported by Wanapat et al (2000b), of 3.26% of DM reported by Netpana et al (2001) and 3.07% of DM reported by Yuangklang et al (2001). The Flemingia foliage and hay also had a high content of tannins (2.8 and 1.76%, respectively) which is in agreement with the finding of Nguyen Thi Mui et al (2002). The presence of condensed tannins in cassava hay was considered to be a constraint which could reduce the nutritive value of this feed (Reed et al 1982). The condensed tannins normally range from 3% to 5% of DM in fresh cassava leaves (Ravindran, 1992).In high concentrations (above 6% in DM), tannins are reported to reduce the voluntary feed intake and digestibility by ruminants (Barry and Manley 1984; Salunkhe et al 1990; Barry and McNabb 1999). Condensed tannins are known to increase with maturity in cassava leaves (Gomez and Valdivieso 1985; Ravindran and Rajaguru 1988). But levels were lower in cassava hay harvested at a young rather than at a more mature stage and also varied between cultivars (Padmaja 1989). The soluble tannin content of cassava leaves is also reported to be reduced during sun-drying (Padmaja 1989). Similar reductions during drying have been reported for Leucaena leaf meal (D'Mello and Acamovic 1989). It appears that drying irreversibly fixes tannins to other cell polymers (Swain 1979), thus reducing the content determined by the chemical assay. Narjisse (1992) showed that a diet containing 2% of DM as tannins did not affect rumen ammonia or nitrogen balance and digestibility. Miller and Ehlke (1994) showed that condensed tannins from Birdsfoot trefoil in the range 2.7 to 8.5% of DM could reduce rumen protein degradation. In the present study the tannin content in the overall diet was low (0.46% to 2.38% of DM), thus negative effects would not be expected.

The higher DM intake for fresh cassava foliage compared with cassava hay may have been due to the differences in the physical nature of the two feeds. Thus Theng Kouch et al (2003) reported a 30% increase when whole branches of cassava were fed as compared with just the leaves. The physical differences between hand-broken fresh foliage and sun-dried foliage after mechanical chopping could have been the reason for the higher intake of the fresh foliage in the present study. The intakes as a percentage of live weight for the diets with concentrates and cassava foliage and hay were in the range of 3.4 to3.55 which is higher than was stated by Devendra and McLeroy (1982) that meat goats in the tropics seldom have intakes higher than 3% of live weight. However, Nguyen Thi Mui et al (2002) reported DM intakes of 3.45 to 3.65% of live weight for growing dual-purpose goats, while Theng Kouch et al (2003) recorded values of 4.58 and 4.87% of live weight when goats were offered intact branches of mulberry and jackfruit foliages. The values of DM intake expressed as g/kg W^0.75 approached the level (73 g/kg W^0.75)recommended by AFRC (1998) for goats of 13 to 16 weeks of age, and that (68 g/kg W^0.75) reported by Kearl (1982) for goat breeds in developing countries. The values for CP intake were in the range for protein requirements of goats in the tropics (Devendra and McLeroy 1982).

The higher growth rate on the control diet could have been a reflection of the superior nutritive value of the energy fraction in concentrates (present mainly as starch) as opposed to forages in which the carbohydrate fraction is mainly cell wall. The higher growth rate with cassava hay as opposed to fresh cassava foliage may have been due a higher content of bypass (or rumen undegradable) protein in the hay due to the partial denaturing of the protein during sun-drying. Thus Promkot and Wanapat (2003) reported that the proportion of the protein not degraded in the rumen was 52% for cassava hay and similar to that for cottonseed meal (50%). According to Wanapat et al (2000a,b), cassava hay fed to cows at levels of 2 kg/day, supported the same milk production as concentrates, with no significant effect on milk composition. The most important finding from use of cassava hay was that it allowed a reduction in concentrate use, which led to reduced feed costs and improved income for farmers.

The growth rates on the Flemingia treatments were lowest probably because of low DM intakes. In research reported by Nguyen Thi Mui et al (2002), growth rates and milk production in goats were reduced when Flemingia foliage exceeded levels of 15% of the diet DM. The levels in the present experiment reached 35% of the diet DM, with resultant negative effects on intake and growth rate.

The goats fed the cassava hay or foliage showed negligible faecal egg counts of nematodes and cestoda whereas in the control goats the counts increased during the experiment. The presence of coccidia oocysts showed a similar pattern. There is increasing evidence that many tropical plants have anthelmintic properties. A review by Hammond et al (1997) listed 23 plants that are routinely used in South East Asian countries as anthelmintics against gastro-intestinal parasites in ruminants, poultry, and pigs. Similarly, Kokwaro (1993) described the use of 50 indigenous plants in Africa for the treatment of nematode and cestode parasites. According to Tuan Bendixsen et al (2004), leaf extracts of Leucaena glauca, Acacia mangium and Caliandra calothyrus inhibited larvae of Nematodes in an in vitro study and reduced faecal egg counts in growing goats. According to Netpana et al (2001), the number of Nematode eggs in the faeces of cattle and buffaloes were significantly lower when feeding cassava hay containing condensed tannins, and were similar to the group that had been drenched. Seng Sokerya and Rodriguez (2001) and Seng Sokerya and Preston (2003b) found the lowest level of EPG of nematodes and the highest growth rate when the animals were supplemented with fresh cassava leaves as compared to natural grasses. Feeding cassava hay containing condensed tannins led to decreased numbers of Nematode eggs and Coccidia oocysts in a trial reported by Ngo Tien Dung et al (2003).

A specific althelmintic effect of condensed tannins has been reported by several researchers. Duncan (1996) evaluated the potential of condensed tannins to inhibit the viability of sheep nematode parasites.According to Kahn and Diaz-Hernandez (2000), the effect may be mediated through ingestion of condensed tannins and their interaction with the external surface of the larvae. Another possible explanation is that the cassava and Flemingia plants are not good hosts for the infective larvae. Condensed tannins may thus have an effect via both direct and indirect mechanisms on internal parasites and larvae migration, but this remains to be elucidated.

5. Conclusions

It can be concluded that:

• Cassava hay is a potential protein supplement for growing goats that can replace concentrates with only a slight reduction (10%) in growth rate

• Cassava hay supported better growth and feed conversion than the fresh foliage, perhaps because the sun-drying may have increased the bypass characteristics of the protein

• Growth performance was poorer on the Flemingia diets probably because of the lower DM intake

• Feeding cassava hay and fresh foliage appeared to have an anthelmintic effect in inhibiting infestation with nematodes and coccidia

• Feeding cassava and Flemingia foliage or hay, as a replacement for concentrates, reduced the feed cost for growing goats

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