Effect of taro silage on digestibility of basal diets of palm syrup, rice bran and water spinach for growing pigs

Cheat Sophal

Royal University of Agriculture (RUA)
Phnom Penh, Cambodia
sophalcheat@yahoo.com

Introduction

From the point of view of agriculturalist, livestock play a pivotal role for initiating the improvement of the economy of the country. Pigs are livestock that are involved in the animal production which can improve the family food supply and family income. In commercial pig production as well as household scale, they can use the locally available feed resources such as paddy rice by-products, water spinach, palm syrup and molasses for the production.

Taro (Colocasia esculenta) is known as a food crop which provides high yield roots (or corms), foliage and its leaves are rich in protein and easy to ensile (Buntha P et al 2008). It can be grown under flooded or upland conditions. In Cambodia, taro is known in Khmer as 'Trao' which it can be planted as food supply for both human and animal. Chhay Ty et al (2007) reported that most taro varieties contain an irritating or acrid agent and cannot be eaten fresh. To this point, the leaves can be chopped and ensiled to considerably reduce undesirable substances in taro, which thus becomes more palatable (Malavanh C et al 2008). Taro leaves silage provided 38% of the dietary DM and 75% of the dietary protein and the apparent digestibility of DM and OM tended to be higher for the diets with dried versus ensiled taro leaves (Chhay Ty et al 2007).

After harvesting, rice is milled and its by-products such as rice bran and/or broken rice are used to feed animals. Rice bran is regarded as an energy source which known to supply the energy requirement for animal especially pigs (McDonald et al 2002). Rice bran consumption has shown to be successful in reducing cholesterol level in pigs (Roy H and Lundy S, 2005). Its oil contains a range of fats; with 47% of its fat are mono-unsaturated, 33% poly-unsaturated, and 20% saturated fatty acids. The most common fatty acids in the rice bran oil are oleic (about 42.5%) and linoleic (39.1%) (Anon-1 no date 1). Other studies have shown the content in rice bran with high levels of both tocopherols and tocotrienol, which compromise vitamin E and act as antioxidants in the body (Roy H and Lundy S, 2005).

Water spinach (Ipomoea aquatica) is a water plant. It can be planted or naturally grow for the utilization for both animals and humans. It does not appear to contain anti-nutritional compounds and has been used successfully for growing pigs as the only source of supplementary protein in a diet based on broken rice (Ly, 2002). Prak Kea et al (2003) reported a linear increase in growth rates in pigs fed water spinach, palm oil and broken rice when up to 6% fish meal replaced equivalent amounts of water spinach, which they attributed to an improved amino acid balance, especially in terms of the sulphur-rich amino acids. According to Le Thi Men et al (1999) and Le Thi Men et al (2000), the leaves and stems of water spinach contain more than 20 % crude protein in dry matter basis. Chhay Ty and Preston (2006) reported that water spinach was more palatable and had higher digestibility than cassava leaves.

Palm syrup derived from the sugar palm tree, (Borassus flabellifer) has been shown that it can be used as the sole energy source for growing and finishing pigs (Khieu Borin and Preston 1995). Farmers can get and make the palm syrup by themselves from the palm trees surrounding their village. Feeding systems using the products and/or by-products of sugar cane, the African oil palm, cassava and the sugar palm have been developed for all classes of livestock and are slowly finding acceptance in many tropical countries (Sarria et al 1990; Preston 1995; Ocampo 1994; Khieu Borin and Preston 1995; Perez 1997).

Hypothesis

Giving taro silage as a supplement in a diet of palm syrup, rice bran and water spinach will improve the nitrogen retention in growing pigs.

Objectives

To determine the effect of taro silage in diets based on palm syrup, rice bran and water spinach on nitrogen retention in pigs.

Materials and methods

Location

The experiment will be carried out in the Kampong Cham National School of Agriculture, Kampong Cham province, Cambodia, about 124 Km to the North-East of Phnom Penh capital city of Cambodia, from 11 August to 11 September, 2008.

Experiment design

The experiment will be designed as 3*3 Latin square with the period of 10 days (5 days for adaptation and 5 days for the trial) for each local cross-breed pig. The treatments are levels of taro silage (5, 10 and 15% replacing water spinach (Table 1). The water spinach will be fed at the same amount of 50% of feed intake in DM (about 3 kg DM per 100 live weight).

Three feedstuffs as shown below (Photos 1 to 4) will be used in the experiment.

Sample collection

The rice bran and palm syrup will be bought from the market around the experimental area in Kampong Cham. However, the taro silage will be brought from CelAgrid, which was ensiled. Rice bran, which is bought from the market, will be sieved to remove husk fibre to get fine and coarse rice bran. Only fine rice bran will be used for the experiment.

Water spinach will be collected from the area near by the research location. The moisture content in the water spinach will be determined by the microradiation method (Undersander et al 1993). The amount of feed intake will be recorded during the experiment. The animal will be adapted to the test feed for 5 days before the experiment started and after the adaptation, the data will be recorded for 5 days per period for each animal.

Chemical analysis

The samples (taro silage, water spinach and rice bran) will be analyzed for dry matter (DM) (Undersander et al 1993), crude protein (CP), ether extract (EE), crude fibre (CF) and ash according to AOAC (1990). The sugar content of the palm syrup will be determined as the “Brix” value corresponding to total sugars by using a hand-held refractometer (Atago N1, no date 2, Japan). The feces and urine from the experimental animals will be collected separately (the nylon net for the feces and plastic bucket for urine) for determination of the DM (Undersander et al 1993) and nitrogen (N) content according to the AOAC (1990). In the plastic bucket for urine, it will be put 10 ml of solution of 10% sulphuric acid (H₂SO₄) to keep the nitrogen (NH₃) balance in the urine not to evaporate. The formulae (McDonald et al 2002) for the calculation of the apparent digestibility and N retention are:

Statistical analysis

During and after the experiment, data will be collected and analyzed by Analysis of Variance (ANOVA) of the Minitab software (version 13). Sources of variation are; level of rice bran, periods and animals.

References

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