Livestock Research for Rural Development 14 (1) 2002

http://www.cipav.org.co/lrrd/lrrd14/1/ly141.htm

Utilization by pigs of diets containing  Cambodian rubber seed meal

Bun Tean,  Keo Sath, Pok Samkol and J Ly*

 University of Tropical Agriculture Foundation
Royal University of Agriculture
Chamcar Daung, PO Box 2423, Phnom Penh 3, Cambodia
* Visiting researcher at UTA, Present address: Swine Research Institute,
PO Box 1, Punta Brava, La Habana, Cuba
jlyca@yahoo.com

 

Abstract

Sixteen Large White castrated male and female pigs of 11 kg mean initial weight were allocated at random to four diets in which wheat bran was progressively substituted by 0, 10, 20 and 30% ground whole rubber seed meal (N 1.95, NDF 66.0, fat 21.8% and cyanide 23.4 mg/kg DM). The diets  were supplemented with dried whole fresh water fish to contain 19 % crude protein (Nx6.25). Growth and feed conversion were studied over a 6 week period  Digestibility was measured by the acid insoluble ash inert marker method when the average weight of the pigs reached 20 kg. 

There was no effect of the level of rubber seed meal on feed intake, growth rate and feed conversion.  Crude fat digestibility was high and increased linearly with increasing levels of rubber seed meal in the diet. Apparent digestibility of dry matter, organic matter, NDF and crude protein was not influenced by the level of ground rubber seeds in the diet..

Key words: Pigs, growth, conversion, digestibility, rubber seed meal

Introduction

The production of latex from rubber trees (Hevea brasiliensis) has been an important feature of agriculture in many tropical countries, and can be expected to receive increasing attention in the future as fossil fuel – the raw material for synthetic rubber – eventually increases in price in response to declining supply. In the north-eastern provinces of Cambodia there are some 40,000 ha of rubber trees (MAFF 2001), from which could be obtained a substantial amount of rubber seeds, since the annual yield of seeds has been estimated to be from 800 to 1200 kg/ha (Siriwardene  and Nugara 1972).

Perez (1997), after  reviewing earlier research conducted in tropical Asia and Africa (Fetuga et al 1977; Ong and Yeong 1978; Ragajuru and Ravindran 1979), concluded that the results concerning the feeding value of rubber seeds for pigs were conflicting. Ragajuru and Ravindran (1979) reported that the growth response and feed conversion efficiency were depressed progressively as the level of rubber seed meal in the ration was increased. They suggested that the poor performance of pigs fed diets containing 20 or 30% of rubber seed meal could be attributed to deficiencies of lysine and sulphur amino acids. Lu Tong Duc (2001) studied the use of rubber seed meal in pig diets after partially extracting the oil using an artisan method. It was observed that performance was poor when the partially defatted rubber seed meal was introduced in the diet. On the other hand, Babatunde et al (1990) used Nigerian rubber seed meal at levels up to 17% in the diet of young pigs, and did not find a negative influence on pig performance, although a trend was found for lower rate of growth and feed efficiency when the proportion of seeds in the diet was increased. Stosic and Kaykay (1991) studied growth rate of pigs fed diets containing 40% of decorticated unextracted rubber seeds and concluded that the kernels were a good protein source for growing pigs.

Some preliminary data obtained in our laboratory (Nguyen Thi Thuy and Ly 2001) indicated that 27% of whole rubber seed meal could be included in the diet of growing pigs with no impairment of growth. Rubber seeds contain cyanide which could be a factor influencing animal response; nevertheless, it has been shown that after a certain period of storage, the cyanide content decreases to substantially low, possibly harmless levels (Ong and Yeong 1978; Narahari and Kothandaraman 1984).          

The aim of the present communication is to report data from a growth and digestibility study conducted with young pigs fed graded levels of ground whole rubber seed meal.

Materials and methods

Sixteen Large White castrated male and female weaned pigs with an average live weight of 10.7 kg were randomly divided into four treatment groups of four pigs (three castrate males and one female per treatment), assigned to four diets. The animals were penned individually in an open stable. The diets were offered ad libitum as a meal and were formulated by replacing 10, 20 and 30% of the wheat bran from the control diet with whole rubber seeds (Table 1). The rubber seeds were from the Cambodian province of Kampong Cham, and were ground after an unknown period of storage, and then mixed with the other diet components. The ground whole rubber seed meal contained (% in dry matter): N 1.95, NDF 66.0, crude fat 21.8 and cyanide 23.4 mg/kg DM.  

Individual body weight was recorded every two weeks and feed consumption daily for 42 days, following a 15-day period of adaptation to the diets. After a further 30 day period on the experimental diets, when the pigs had a mean live weight of  20.0 kg, samples of faeces were taken directly from the rectum. Samples of the feed and faeces were analysed for DM (Undersander et al 1993), ash and N (AOAC 1990), NDF (Van Soest  et al 1991) and acid insoluble ash (Van Keulen and Young 1977). Neutral and total crude fat were determined in samples of dry faeces by extraction with gasoline before and after hydrolysis with HCl. Faecal pH was determined with a glass electrode.

Least square means analysis of variance was conducted according to a one-way classification design (Steel and Torrie 1980). Individual animal was the experimental unit. Where significant differences were found, the means were separated by Duncan’s multiple range test. Linear and quadratic effects of increasing proportions of rubber seed substitution in the diet were tested by regression analysis. The Minitab software (Ryan et al 1985) was used in the biometrical analysis of the data.
 

Results and Discussion

Feed composition

The concentration of  crude fat and of NDF in the diet increased as the level of rubber seeds increased (Table 1). This reflected the higher concentrations of NDF and fat in the rubber seeds compared with the rest of the diet.  Narahari and Kothandaraman (1984) also  reported a high crude fibre content (20.7 to 31.7%) in a variety of undecorticated rubber seeds.

Growth data

No toxic effects were observed and the appetite and behaviour of the animals were normal. The diets containing ground rubber seed were readily consumed by the pigs. Dry matter intake was high, especially on the diets containing ground rubber seeds (Table 2).. There was no effect of treatment on growth rate, feed intake or feed conversion (Table 2). Variability among animals was high which may have obscured the results of the analysis of variance.  

A linear, highly significant relationship (R² 0.77; P<0.001) was found between average daily gain of the pigs (y, in g) and daily DM intake (x, in kg), this relationship being established through the equation
y = - 9.3 +328 x (S_yx ± 59.5).

The results from the present experiment tend to support previous findings of Nguyen Thi Thuy and Ly (2001) who claimed that 27% of ground whole rubber seeds in the diets of young female pigs did not adversely affect growth parameters.

Digestibility study

Replacement of up to 30% of the wheat bran with ground whole rubber seeds appeared to increase faecal pH (Table 3), and a significant (P<0.05) linear effect was observed. Similarly, DM concentration in faeces tended be higher (linear effect at P<0.001) as the dietary level of rubber seed meal increased.  

Neutral fat concentration in faeces was very low and very variable, and with no significant treatment effect. In contrast, total faecal fat level increased with level of rubber seed in the diet, thus reflecting the effect of the method of determination of crude fat, as has been shown elsewhere (see for example Eeckhout et al 1983).  

Total tract digestibility of dry matter and organic matter was rather low (Table 4), with a tendency to decrease as the level of rubber seeds in the diet increased, probably reflecting the higher concentration of cell wall material in the diet. It is to be expected that an increase in dietary NDF will result in a decrease in the digestibility of different nutrients in pigs, as reported earlier  by Den Hartog et al (1988) and Close (1993). N digestibility appeared to be constant in the range of 10 to 30% dietary content of  ground rubber seeds. In contrast, the digestibility of crude fat increased linearly with increasing proportions of ground rubber seeds in the diet. 

Gas chromatography analyses have revealed that rubber seed oil has a very high content of unsaturated fatty acids: some 66.5% of total acids from Madras data (Narahari and Kothandaraman 1983), 78.9% of total acids according to Nwokolo (1987) and 81.0% as reported by Orok and Bowland (1974) and Ong and Yeong (1978). Therefore, a high concentration of oleic, linoleic and linolenic acids in the ether extract of the feed could be the cause of high values for apparent digestibility of crude fat with increased levels of dietary rubber seeds. It has been claimed that unsaturated fatty acids have a better digestive utilization in the pig as compared to saturated fatty acids (Doreau and Chilliard 1997). The high nutritive value for pigs of ground whole rubber seeds, reported earlier from our laboratory (Ly et al 2001), could be the consequence of a high rate of utilization of the crude fat component of the seeds, which in turn might neutralize the negative effect of the high cell wall fraction in the husk of rubber seeds.

The low nutritive value of rubber seed meal reported by Kuan et al (1982) was probably because most of the oil had already been extracted. Available data on digestibility of rubber seeds are summarised in Table 5. Undoubtedly, the level of fat in the seeds greatly influences digestibility parameters, taking into account the high digestibility of the crude fat fraction of rubber seeds, as it have been observed in the results derived from the present experiment (see Table 4).   

Table 5. Apparent digestibility values for  South East Asian rubber seed products for pigs
	Crude fat, %	Digestibility, %				References
		DM	OM	Energy	N
Whole seeds	28.4	79.1	85.5	-	83.6	Ly et al 2001
After oil extraction	13.0-24.0	77.3	80.7	-	80.2	Lu Tong Duc 2001#
After oil extraction	8.8	70.1	-	68.6	69.9	Kuan et al 1982
# Values estimated from regression analysis of Lu Tong Duc (2001)

Digestibility coefficients of organic matter, NDF and N were positively correlated to digestibility of dry matter (Table 6). However, digestibility of crude fat was not related to the other digestion indices (Table 6). In other studies, it has been found that several digestibility coefficients are correlated inter se (see Siers 1975; Frank et al 1983). In this connection, the estimation of a simple index such as DM, could approach to some extent to the digestive utilization of other dietary fractions such as N and NDF.  

 

Conclusions

It is suggested that from the point of view of digestibility indices and growth rates that there are no disadvantages in response of growing pigs to levels of up to 30% of ground whole rubber seeds in the diet.

Acknowledgments

The authors are indebted to the Chub Rubber Company, Kampong Cham, for the supply of the rubber seeds. The experiment was carried out as partial requirement for the degree of Master of Science of Bun Tean.

References

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Received 4 October 2001

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