Protein supplementary values of cassava-, leucaena- and gliricidia- leaf meals in goats fed low quality Panicum maximum hay

M B Yousuf, M A Belewu, J O Daramola and N I Ogundun*

Department of Animal Production, University of Ilorin, Ilorin, Nigeria
*Animal Production Technology Department, Federal College of Wild Life Management,New Bussa, Nigeria
mb_yousuf@yahoo.com

Abstract

Fifteen adult male West African Dwarf, WAD goats were used in an 84 -day dry matter and nutrient intake and digestibility, growth and nitrogen retention study to evaluate the leaf meals of Cassava, Leucaena and Gliricidia plants as protein supplements to low quality (7.63 % CP) Panicum maximum hay. The goats were divided into three groups balanced for initial body weights (10.49 ± 0.76 Kg) and assigned randomly to three dietary treatments. Treatment consisted of 130 g Cassava leaf meal, 120 g Leucaena leaf meal or 130 g Gliricidia leaf meal that was used to supplement an ad libitum intake of the grass hay. The three protein-rich supplements as used in the study provided equivalents of 4.87, 4.92 and 4.81 g supplemental nitrogen (about 30 g CP/ head/ day) respectively.

Goats receiving cassava leaf meal supplement consumed dry matter at a level similar (P > 0.05) to those on Gliricidia leaf meal supplemented ration but higher (P < 0.05) than those offered Leucaena leaf meal supplement. Digestibility of crude protein  increased (P < 0.05) in the order: - Cassava leaf meal > Leucaena leaf meal > Gliricidia leaf meal. No significant treatment effect (P < 0.05) was observed on dry matter or NDF digestibility among the three treatment groups. Nitrogen retention (g/head/day) of 2.05 obtained for goats fed Gliricidia leaf meal supplement was lower (P < 0.05) than the values of 2.85 and 3.04 recorded for those on Cassava- and Leucaena leaf meals supplemented rations respectively. Body weight gains (g/day) were 26.4, 27.8 and 18.1 for goats receiving Cassava-, Leucaena- and Gliricidia- leaf meal treatments respectively.

Cassava leaf meal was adjudged superior to Gliricidia leaf meal but comparable to Leucaena leaf meal as forage protein supplement in goats consuming low quality Panicum maximum hay.

Key words: Cassava, goat, gliricidia, leaf meal, Leucaena

Introduction

Leaves of Leucaena leucocephala and Gliricidia sepium plants have been widely reported (Mba et al 1981; Jones and Lowry 1984; Akbar and Gupta 1985; James and Gangadevi 1990; Larbi et al1993; Shelton and Brewbaker 1994) as valuable forage supplements to ruminants consuming low-protein diets. The use of Cassava (Manihot esculenta) as forage plant has not been as popular. Devendra (1997) attributed the apparent lack of interest in the use of Cassava leaves in feeding ruminants to inadequate appreciation of the relatively high crude protein content of the leaves. The crude protein content of 24.7 % in Cassava leaves (Adegbola and Okonkwo 2002) compares favorably with the values of 22.8 (Limcango - Lopez 1997) and 25.8 (Vargas and Elvira 1987) in the leaves of Leucaena and Gliricidia plants respectively.

The objective of the present study was to elucidate the potential of Cassava leaves as dietary source of protein in order to encourage the inclusion of the leaves in diets for ruminant livestock production. Specifically the study compared the protein supplementary value of Cassava leaf meal with that of Leucaena or Gliricidia leaf meal in goats fed Panicum maximum hay of low nitrogen content. Cassava as source of dietary protein for ruminant production has the advantage in Nigeria over Leucaena or Gliricidia, as cassava plant cultivation is suited to a wider range of soil and climatic conditions. In addition, nearly every major parts of the plant including leaves, stalk, stem, roots and root-peelings can be processed into animal feeds while cassava tuber and its by-products have an array of applications in the manufacturing industry. Cassava plant has the potential of being managed as semi-perennial forage that can be harvested at two-month intervals (Preston 2001).

Materials and methods

Location and period of the experiment

The study was conducted under sub-humid tropic environment, at the Animal pavilion, Department of Animal Production University of Ilorin, Ilorin (8.34^o N: 4.34^o S) Nigeria. Feeding trial which lasted 84 days was carried out in the dry season months of April - May 2005.

Preparation of the leaf meals

Cassava leaves were collected during cassava tuber harvest from 6-month old plants on the University Teaching & Research farm. Leucaena and Gliricidia leaves were harvested from fodder banks at the Teaching & Research farm. Leaves were separated from the stalks/twigs, spread on concrete floor in a well ventilated room for 5-6 day and thereafter, stored at room temperature in jute bags.

Animals and treatments

Fifteen weanling male West African Dwarf (WAD) goats of initial live-weight range, 9.78 - 11.32 kg were divided into three equal groups balanced for weights with each group assigned randomly to one of three dietary treatments. Treatments consisted of basal Panicum maximum hay which was fed ad libitum and supplemented daily, with 130 g Cassava leaf meal, 120 g Leucaena leaf meal or 130 g Gliricidia leaf meal. The protein-rich forage supplements were divided into two equal portions and fed at 0800 and 1600 hours daily. Goats were housed individually in concrete-floored pens partitioned with slatted planks to allow visual contacts. The goats were transferred to wooden metabolism cages at the end of the 11^th week for a 5-day dry matter and nutrients intake and digestibility trial that was preceded by 3-day period of adaptation to cage conditions. Clean drinking water and mineralized salt-licks were made available to the individual goats at all times.

Collection of samples and measurements

Goats were weighed on the first day and fortnightly thereafter, during the 84-day feeding period. Total feces and urine produced by each goat during the collection period were measured and recorded. Urine was collected into plastic bowls containing 100 ml of 10 % H₂SO₄ (Urine pH< 4)_. Approximately 10 % of the total daily urine production was sampled, bulked over the 5-day collection period and stored separately for each goat in a deep freezer (- 20^o C) for N-determination using the AOAC (1990) procedure. About 10 % of the feces voided daily by the individual goats and the forages offered were sampled during the collection period, bulked and kept frozen (-20^o C) for dry matter and proximate analyses. Dry matter was determined by drying the samples to constant weights at 105^o C. Crude protein and ether extracts were measured by the method of AOAC (1990). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were estimated following the method of Goering and Van Soest (1970). Empirical data were subjected to statistical analysis (Steel and Torrie 1980) with significant difference between means estimated using the Duncan's (1955) multiple-range test.

Results and discussion

Table 1 shows the composition of the rations and Table 2 shows the results of proximate analysis of the ration components used in the present study. The relatively high ADF (47.28 %) and NDF (68.16 %) but low ether extract (1.32 %) and CP (7.63 %) contents of the Panicum maximum hay suggested low nutritional quality for the basal grass hay.

Norton (2003) observed that feeds containing less than 8 % crude protein could not provide the ammonia levels required by rumen microbes for optimum activity. The grass hay could be taken to represent a wide range of low-quality feeds often available for goat production in the developing tropical countries especially during the dry season. Cassava leaves like the forages from Leucaena and Gliricidia plants could be valuable in supplying supplemental nitrogen to goats usually kept on road-side over-grown grasses, cereal straws and stalks or various agro-industrial by-products of low nitrogen contents.

Crude protein contents of the three leaf meal supplements used in the present study were within a narrow range of 24.8 - 30.2% and similar to those reported elsewhere (Adeneye 1993; Ayodeji 2005; Limcango-Lopez 1997); Olatunji 1996). Cassava leaf meal had relatively lower concentrations of crude protein, ether extract, calcium and phosphorous than Leucaena or Gliricidia leaf meal (Table 1). However it also had lower ADF and NDF contents which could impact positively on the digestibility and efficiency of utilization of nutrients by the animals.

Dry matter intake from Panicum maximum hay was similar (P < 0.05) among the three treatment groups (Table 3).

However when intakes of the grass hay and leaf meal supplement were combined, average total dry matter intake (g/KgLW/day) increased (P < 0.05) from 24.08 in Leucaena leaf meal-supplemented group to 25.67 and 26.57 in goats receiving Cassava leaf meal and Gliricidia leaf meal treatments respectively. These DM intakes were lower than reported by Mba et al (1982) for WAD goats fed un-supplemented Gliricidia sepium leaves but higher than obtained  by Ademosun et al (1988) when goats of similar breed received un-supplemented Panicum maximum hay. The potential role of the leaf meals in improving dry matter intake by goats on low quality fibrous feeds such as grass hay and crop residues is emphasized.  Goats on cassava leaf meal supplemented ration digested crude protein at a level similar to those on the leucaena leaf meal treatment but higher than those fed gliricidia leaf meal. A similar trend was observed for the differences in ether extract digestibility. The low digestibility of crude protein in goats on Gliricidia leaf meal treatment could be related to the presence of relatively higher concentration of tannins in Gliricidia leaves. Although quantitative estimation of allellochemical substances in the three leaf meals was not included in the present work, earlier studies had confirmed the occurrence at high concentrations of hydrocyanic acid in assava leaves (Tewe 1992), mimosine in leucaena leaves (Jones 1994) and tannins in Gliricidia leaves (Devendra 1997). Tannins have been established (Barry and Duncan 1984; Kumar and Sing 1984; Makkar et al 1989) as lowering protein digestibility by forming tannin-protein complexes within the digestive tract.

Table 4 shows data on the effects of treatments on body weight gain, feed conversion efficiency and nitrogen balance in the goats.

Differences in body weight gain among the three treatment groups were significant (P < 0.05) with the goats on Leucaena and cassava leaf meals growing faster than those fed Gliricidia leaf-meals. Body weight gains of 17.4-28.7 g/head/day have been reported (ILCA 1988) for WAD goats fed Leucaena and Gliricidia browse as supplements. Results for feed conversion showed the same trend as for live weigh gain.  Urinary nitrogen excretion was significantly higher  for goats on Gliricidia leaf meal treatment than for those offered Cassava or Leucaena leaf meal supplement and resulted in a decrease in nitrogen retention.

Conclusion

• Results from the present study indicated the following ranking for the three leaf meals in terms of their protein supplementary values to WAD goats consuming Panicum maximum hay of low nitrogen content;- Leucaena leaf meal > Cassava leaf meal > Gliricidia leaf meal.

Acknowledgement

The authors gratefully acknowledge the technical assistance of Messrs R M O Kayode and J K Clement in carrying out laboratory analyses.

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Received 7 November 2006; Accepted 5 December 2006; Published 8 February 2007

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