Comparison of different forages as supplements to a basal diet of chopped cassava stems for growing goats

Trinh Xuan Thanh¹, Khuc Thi Hue¹, Nguyen Ngoc Anh¹ and T R Preston²

¹Goat and Rabbit Research Center, Hanoi, Vietnam

 ² UTA-TOSOLY- finca Ecologica Morario – Guapota- Santander del Sur Colombia

AbstractThirty two Bach Thao goats with an initial weight of 15.3 kg at 4 months of age were used to study the nutritive value of cassava stems and effect of using cassava stems as the fiber feed for goats on intake and live weight gain. The experiment was lasted for 84 days. The treatments were four diets containing cassava stems as the basal feed and supplemented with fresh cassava foliage (CS-CF), guinea grass (CS-GG), cassava hay (CS-CH) or jackfruit foliage (CS-JF). Dry matter intake was 516, 611, 469 and 535 g/day in the diets of supplementing with cassava hay, cassava foliage, guinea grass and jackfruit foliage, respectively, and it ranged from 28 to 3.5 g/kg body weight (BW), which was significantly different. There was a significant difference between treatments was observed in live weight gain (LWG), which was 56.6, 49.5 and 31.6 and 28.5 g for CS-CF, CS-JF, CS-CH and CS-GG, respectively.

Key words: Bach Thao goat, cassava stem, cassava leaf, cassava hay, jackfruit leaf, ghine grass, live weight gain

Introduction

Cassava (Manihot esculenta Crantz) is one of four most important crops in Vietnam, but it has always been a secondary crop after rice. In last decades, especially since the late 1970s, cassava has played an important role in national food security. Recently, cassava has become an important source of cash income for farmers, who use it for animal feed and/ or for sale as substrate to starch factories (Kim et al., 2008). Originally introduced from South America and has expanded widely to Asia and Africa, cassava is now cultivated over 105 countries, mainly for root production as a source of energy and for foliage as the roughage for animals.

The researches indicated that cassava foliage is recognised as a locally available feed resource with a high edible biomass yield  GSO, 2011). By estimated the amount of cassava foliage produced at root harvest was about 2.8 million tons yearly and there is a potential to increase this amount by harvesting more than once (Hue et al., 2010).

Cassava stems are considered as agricultural by-product after root harvesting. Only a small amount of stems is used for planting in the next cultivation. The large quantity of cassava stems are thrown away or used for fuel. According to Akinfala et al. (2002) cassava tender stems contained 10.7% crude protein (CP) and 27.9% crude fiber and were included as part of the whole plant, which was used as the feed for poultry. In practice production, the farmers in Bavi area have been using cassava stems as the fibrous feed for goats, sheep and cattle, even dairy cattle in the dry season when the roughages are shortage.

The objective of this study was to determine the nutritive value of cassava stems and to use it as the fibrous feed for goats.

Materials and Method

Location

The experiment was carried out at the Goat and Rabbit Research Center, Sontay, Hanoi, Vietnam, longitude E 105^o25 and latitude N 21^o06. The altitude is about 220 m above sea level. The climate in this area is tropical monsoon, with a wet season between April and November and a dry season from December to March. Average annual rainfall is 1850 mm. The trial was conducted during August to November, 2011.

Experimental feeds and animals

The feeds used in the experiments were cassava stems, cassava foliage and cassava hay (Manihot esculenta Crantz), guinea grass (Panicum maximum), jackfruit foliage (Artocarpus heterophyllus) and rumen supplement. All foliages and guinea grass were harvested in the fields 1 to 2 hours before feeding. During rainy days, the forages were harvested the day before feeding to limit the effects of low DM content. The guinea grass and cassava stems were chopped into pieces of 7-10 cm and 1-2 cm in length, respectively, before feeding for goats by giving in the feed troughs. Cassava and jackfruit foliages were harvested at the length of the stems was 50 to 60 cm, to be able for goats can consume as much as foliages offered and were offered for goats by hanging in bunches in front of the feed troughs. The cassava variety used was K98-7 (medium bitter).

The goats used in the experiment were Bach Thao, with an average mature body weight (BW) of about 55 kg for the bucks and 45 kg for the does. The initial body weight range of the experimental goats was from 15-16 kg at 4 months of age. Before starting the experiment, the goats were treated against parasites with injections of Ivermectin solution (1 ml per 4 kg BW) and vaccinated against pasteurellosis, enterotoxaemia, foot and mouth disease and goat pox.

Experimental design

Thirty two growing goats were randomly allocated to four treatments with eight animals (equal on sex) per treatment in a completely randomized design. The length of the trial was 12 weeks. The lay out of the experiment was:

CS-CH:     Cassava stems + cassava hay + rumen supplement

CS-CF:     Cassava stems + cassava foliage + rumen supplement

CS-JF:      Cassava stems + jackfruit  foliage + rumen supplement

CS-GG:    Cassava stems + guinea grass + rumen supplement

At the start of the experiment the animals were offered diets based on requirements according to NRC (1991). Goats at 20 kg BW and with an average daily gain of 100 g/day require 755 g dry matter (DM) intake, 60 g crude protein (CP) and 7.26 MJ metabolism energy (ME). The diets were changed after every two weeks according changes in mean BW of the goats in each treatment group.

Management and chemical analysis

Goats were kept in the separate cages, fed individually and were adapted to the experimental feeds for 10 days before starting. Chopped cassava stems were fed ad libitum for goats in all treatments, while cassava hay, cassava foliage or jackfruit foliage were supplemented at the fixed amount of 1.5% of BW. Rumen supplement was mixed by 10% urea, 20% molasses, 2% sulphur, 5% calcium phosphate, 5% salt and 58% rice bran and was supplied directly to all treatments at 2 g per 1 kg live weight of the goats.

Animals were received the feeds with 4 meals per day, cassava stems were fed for goats at 7:30 and 14:30, while the foliages and cassava hay were given at 10:30 and 16:30 daily. Mineral lick blocks (510 stone meal Ca₃(PO₄)₂, 210 g bone meal plus 170 g cement as a binding agent and 100 g salt] were available ad libitum by hanging on the wall of the pens. Water was given free for goats via water nipples. Experimental time was lasted after 84 days. The animals were allowed to exercise once daily for one hour in the afternoon from 14.00 h to 15.00 h. During the exercise time, males and females were separated to avoid mating.

Samples of feed offered and refused were taken weekly for analysing DM, then pooled to monthly samples for further analysis of CP, neutral detergent fiber (NDF), acid detergent fiber (ADF) and ash. Dry matter and ash were analysed according to the standard methods of AOAC   Nitrogen was determined by the Kjeldahl procedure. Neutral detergent fiber and ADF were determined by the methods of van Soest et al.  

Feed offered and refused was recorded daily. The animals were weighed in the morning before feeding at the start and end of the experiments and at two week intervals. Growth rate, feed intake and feed conversion ratio, were calculated.

Statistic analysis

The data was analysed statistically by using the GLM procedure of Minitab Software, version 15   Treatment means which showed significant differences at the probability level of P<0.05 were compared using Tukey’s pairwise comparison procedures. The statistical model used in the analysis of the growth trial was: Y_ijk = m + T_i + e_ijk, where Y_ijk is the dependent variable, m is the overall mean, T_i is the effect of treatment (diets), and e_ijk is the random error, independent and normally distributed.

Results and discussion

The chemical composition of the experimental feeds is shown in Table 1. The CP in cassava stems was very low (55g), while NDF and ADF content were 541 and 388 g/kg DM, respectively. The CP content in the supplements were 176, 165, 148 and 108 g in cassava foliage, cassava hay, jackfruit foliage and guinea grass, respectively.

Table 1: Chemical composition of the experimental feeds

The feed offered, daily feed intake, nutrient intake and feed conversion ratio of the experimental goats are shown in Table 2. The intake of cassava stems as the basal feed was not significantly different in the diets supplemented with cassava hay, cassava foliage, guinea grass and jackfruit foliage, and it ranged from 353-366 g.

The total DM intake recorded for the animals fed the diet CS-CF was significantly highest, and was lowest in the diet CS-GG, while total DM intake from diets of CS-CH and CS-JF were in the between. The total CP intake was higher in the diets of CS-CH and CS-CF, lower in the diets of CS-JF and was lowest in the diet CS-GG.

There was a significant difference on live weight gain (LWG) of the goats according to treatments. Goats in the diets CS-CF gave the highest daily gain with 56.6 g, while it was 49.5 g and 31.6 g in the diet CS-JF and CS-CH, respectively, and was lowest in the diets of CS-GG (28.5 g).

The DM feed conversion ratio was very high in the diets of supplementing with guinea grass and cassava hay (16.3 to 16.5 kg/kg), and was significantly lower in the diet of CS-CF and CS-JF with 10.8 kg/kg.

The conversion ratio of kg CP/kg LWG was also significantly different according to treatments, which was higher in the diet of CS-CH (2.8 kg/kg) and was lower in the diets supplemented with cassava hay, cassava foliage and jackfruit foliage (1.4-1.5 kg/kg).

Table 2 also shows that LWG of the goats was significantly highest in the diet when cassava stems was combined with cassava foliage (56.6 g) and was lowest in the diet CS-GG. The LWG of the goats in the diets of CS-JF and CS-CH were 49.5 and 31.6 g, respectively.

Table 2: Feed offered, feed intake, nutrient intake, feed conversion ratio and live weight gain of the experimental goats

Conclusions

·      Cassava stems can be used as the fiber feed resource for goats with very cheap price and easy to find in the dry season.

·      Feeding cassava stems for goats in the combination with cassava foliage or jackfruit foliage could be a good compromise in order to improve the nutrient value of the diet.

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