The effects of water spinach on growing crossbred pigs
 

Prak Kea, T R Preston*, Chhum Phith Loan** and Kong Rada***

RoyalUniversity of Agriculture,
Faculty of Animal Science and Veterinary Medicine
prakkea@yahoo.com / prakkea@hotmail.com
* University of Tropical Agriculture Foundation
regpreston@utafoundation.org
** Royal University of Agriculture,
Faculty of Animal Science and Veterinary Medicine
loan@hotmail.com
*** Royal University of Agriculture,
Faculty of Animal Science and Veterinary Medicine

Introduction

Feed is the key factor for improving pig productivity. When there is a lack of feed resources for feeding pigs this will cause them to grow slowly and the result is a decrease of the income. Thus many researchers in developing countries try to find the way to improve the pig performance by making better use of the available feed resources.

As Cambodia is an agrarian country, there are large amounts of rice by-products, such as rice bran, broken rice, and also vegetables are traditionally used for pig raising throughout the country.

The large water surface areas have brought potential advantages to farmers by allowing the cultivation of water spinach all year round for human food and for feeding to animals. According to Le Thi Men et al (1999), annual yields can be as high as 455 tonnes fresh biomass (about 40 tonnes DM) per ha from 17 three-week vegetative cycles a yield of 24 tonnes/ha in only 30 days after sowing the seed was reported by Kean Sophea et al (2001). The fresh leaves and stems of water spinach have a high crude protein content in the range of 18 to 31% in dry matter (Le Thi Men et al 2000; Bui Huy Nhu Phuc 2000; Prak Kea et al 2003). The plant is also rich in minerals with an ash content of 12% in dry matter (Göhl 1998; Bui Huy Nhu Phuc 2000; Prak Kea et al 2003). It has been used successfully to replace part of the protein in sugar cane juice diets for breeding sows (Le Thi Men and Bui Hong Van 1993) and as the main protein source for growing pigs fed broken rice (Ly 2001; Prak Kea 2003). On an annual basis protein yields of between 4 and 6 tonnes/ha appear to be possible. This high yield potential enables farmers to get a regular high income from harvesting water spinach and selling it to local markets.

Although water spinach has a high protein content its digestibility is rather low. According to Ly et al (2002), the in vitro digestibility of the nitrogen is only 56% compared with 75% in duckweed. The low energy density in water spinach is another limitation and could be corrected by supplementation with energy-rich feeds such as cassava root meal. The protein in water spinach, as in other plant proteins, is deficient in sulphur amino acids, thus dried fresh water fish, available locally in Cambodia, would be a logical supplement to complement the protein in water spinach.

The aims of the research

This research aims to determine the effect on feed intake, apparent digestibility, N retention and growth rate by crossbred pigs, of different ratios of fish meal and water spinach as protein sources in basal diets of cassava root meal and rice bran.
 

Materials and methods

Location and duration

The research is conducting at the animal farm of the Faculty of Animal Science and Veterinary Medicine located in the campus of the Royal University of Agriculture, about 12 km from Phnom Penh city. This research is starting from 08 March 2004, it still continuing and will last until August 2004.

Experimental design

This experiment is using cassava root meal (CRM) and rice bran (RB) as the basal diet with the protein supplied by mixtures of water spinach (WS) and dried fish meal (fish meal levels of 0, 3, 6 and 9%), arranged according to a randomized complete block (RCBD) to measure performance traits in growing pigs. The feed composition and levels of supplementation is revealed in table below.

The composition of the diets is in Table 1.

Feeding and Management

The water spinach is purchased daily in the local market and chopped into small pieces (3-5 cm) prior to offering it in one of two feed troughs; the other feed trough was used for the dry components (supplements) of the diet which was mixed before feeding. The daily allowances of the supplements was weighed and put in small polyethylene bags (2-3 kg capacity) in sufficient numbers for each two weeks of experimental period. The pigs are fed triple daily, first at 7 am, second time is at 12 am and then in the afternoon at 4 pm based amount of basal diets. The water spinach was offered after the pigs have consumed the supplements. Water was offered ad libitum through the automatic drinking nipples. The total daily feed allowance is set at 4% of live weight (DM basis).

The pigs were weighed once every two weeks in the morning before feeding and will stop the experiment at a mean liveweight of 70 kg. Daily gains were calculated from the linear regression of liveweight on days on trial.

Data on feed offered and refusals will be collected and recorded every day to estimate the intake. Faeces are collected during one day every two weeks and kept in the plastic bucket stored in the freezer at -20 ºC. At the end of the experiment, the samples will be analyzed for DM, crude protein, neutral detergent fibre, crude fiber and ash in feed offered and refused and in faeces. The chemical analysis will be done following standard procedures according to AOAC (1988) except for DM which was determined by micro-wave radiation (Undersander et al 1993). Neutral detergent fibre (NDF) is determined according to Van Soest et al (1991).

Statistical analyses

The data was analyzed using the General Linear Model (GLM) of the ANOVA programme in the MINITAB software version 13.31 (Minitab 2000). Sources of variation are treatments, sex, blocks, the interaction treatments*sex and error.

Results

Growth performance

During the first two months, live weight gains were higher for castrate males than for females and increased in accordance with the level of fish meal  (Figure 1).

 

Figure 1: The daily weight gain of the pigs during the first 2 months of the experiment