Use of rubber seed meal in diets for colored feather chickens

Duong Duy Dong

Nong Lam University, Thu Duc, Ho Chi Minh City
ddd@hcm.fpt.vn

 
Abstract

 

The study includes a survey and two growth trials concerned with the production and usage of rubber seed meal (RSM) in diets for growing colored feather chickens. The survey was carried out in three rubber producing districts of SE Vietnam, and showed that the production of RSM is increasing rapidly, although farmers only include small amounts (up to 7% of the diet) in rations for chickens because of concerns over possible toxic effects. In the first growth trial, diets containing 0 (RS0), 10 (RS10), 20 (RS20), 30 (RS30), 40 (RS40) or 50% (RS50) rubber seed meal were given to scavenging native chickens from 1 to 128 days of age. 

 

Average daily weight gains were 10.8, 10.6, 9.69, 11.9, 11.6 and 9.25g/day, and survival rates 86.4, 94.4, 90.1, 65.5 and 39.0 % for the  RS0, RS10, RS20, RS30, RS40 and RS50 diets, respectively. In the second trial, levels of 0, 5 or 10% RSM were included in diets for confined Tam hoang chickens from 1 to 70 days of age. There were no treatment effects (P>0.05) on average daily gain, feed conversion or survival rates.  It was concluded that up to 30% RSM can be included in diets for scavenging native chickens, and  up to 10% RSM in diets for confined Tam hoang chickens.

 

Key words: Rubber seed meal, colored feather chickens, growth rate, mortality

 

 

Introduction

 

In recent years poultry production has developed rapidly in Vietnam and today provides large amounts of meat and eggs for human consumption. From 77.8 million chickens in 1990, the population reached 196.2 million head in  2000, which implies a mean annual growth rate of 9.2% (FAO 2001). The populations of both white-feathered broilers and colored-feathered hens have both increased steadily. The term “colored feather chicken”, abbreviated to “colored chicken”, includes “pure” native chickens and other medium performance strains such as Tam hoang and Luong phuong that are now raised in Vietnam and are more suitable for small scale farmers compared to white broilers. These colored chickens are better adapted to harsh conditions, with good resistance to infectious diseases, and produce excellent quality meat in terms of flavor and texture. They are also easier to sell and transport from remote areas to urban markets due to their lower sensitivity to stress factors. In addition, colored chickens are always sold at premium prices per unit of live body weight. However, the colored chicken has also disadvantages. Although its nutrient requirements are lower, it grows more slowly, which results in high feed consumption per unit weight gained. To get good profits from colored chicken production farmers should utilize less expensive feeds with medium nutritional quality. To formulate diets based on these kinds of feed, local feed resources are more suitable than feed ingredients that have to be imported.

 

In South-Eastern Vietnam, there are large amounts of rubber seed meal (RSM) available. This is a by-product of oil extraction from rubber seed. It has a medium protein level but is high in fiber and prussic acid (HCN) which is toxic to animals. RSM has been used for a long time to feed livestock at various levels in  diets for monogastrics, but little of this work has been published. Results of studies on RSM are inconsistent, depending on the kind of diet (for example, for pigs or chickens), season of the year, kind of RSM (with hull or dehulled), and sometimes concerning the perception of the farmers.

 

For RSM to be used as an ingredient in diets for chickens, studies need to be done to review the production, processing and chemical composition of  the rubber seed meal, as well as to determine its effect on the growth, feed efficiency and economics of chicken production under practical conditions.

 

The study had the following objectives:

• To assess the production of rubber seed meal in South Eastern Vietnam, especially in Dong Nai and Tay Ninh provinces, areas with a high concentration of rubber tree plantations.

• To determine the most suitable level of rubber seed meal inclusion in diets for colored chickens, and whether rubber seed meal is toxic to colored chickens at high inclusion rates (up to 40%) in the diet.

• To evaluate the economical efficiency of using rubber seed meal in colored chicken diets.

 
Materials and methods

To achieve the above objectives a study was conducted from 1998 to 2000 in provinces in Southeast Vietnam, consisting of a survey of the production of rubber seed meal in Dong Nai and Tay Ninh provinces and Ho Ch iMinh City,  and trials on the effect of including rubber seed meal in colored chicken diets. The survey was carried out not only at the sites of production, but also explored the perception of farmers about using rubber seed meal as an ingredient in the diet. The survey was followed by two feeding trials in which different levels of RSM were fed to colored chickens.

Rubber seed meal production in Dong Nai and Tay Ninh provinces

 

The survey was carried out in three areas: Thong Nhat district in Dong Nai province; Trang Bang district in Tay Ninh province and Cu Chi district in Ho Chi Minh City. Data collected included secondary data at the study sites, RRA (Rapid Rural Assesment) methods with the producers of rubber seed meal and chicken farmers in order to get a better understanding of the situation concerning the production of rubber, and rubber seed meal production and usage.

 

During the survey, representative samples of rubber seed meals were also collected, based on processing technique, physical form and location where produced. These samples were taken for proximate analysis and HCN determination at the Department of Animal Nutrition in Nong Lam University (NLU), Ho Chi Minh City, Vietnam.     

 

Trial 1: Determination of the optimum level of RSM in diets for scavenging native chickens

 

Brooding period (1 – 28 days)

Two hundred and fifty day-old native chicks were allocated into five treatments, with five replicates per treatment as a Complete Random Design.  The chicks were kept in cages.

 

Growing period (29 to 128 days)

The birds in treatment RS40 were divided into two groups: one continued on diet RS40 and the other was given a diet with 50% rubber seed meal (RS50). In this phase, the chicks were raised on the floor, with only one replicate per treatment.

 

The rubber seed meal used in the trial was purchased from Dong Nai province and was not processed before being incorporated in the diets. Metabolisable energy (ME), calcium and phosphorus were kept equal among treatments while crude protein and most amino acids increased with increasing level of rubber seed meal in the diets. The composition and nutritive value of diets are presented in Table 1.

 

Measurements of live weight, average daily gain, feed consumption, feed conversion ratio, survival rate and economic efficiency were made every four weeks.

 

Trial 2. Effect of RSM in diets for confined Tam hoang chickens

 

At present, farmers tend to raise Tam hoang chickens in confinement, similar to broiler production. As in Trial 1, 200 Tam hoang chicks were allocated to three dietary treatments with a CRD design:  Control;  5% RSM and 10% RSM.  The RSM used was dehulled and processed by heating.

 

 

 

 

Results and discussion

 

Production of rubber seed meal

 

Rubber trees (Hevea brasiliensis) grow well in bazan soils, and hence they are mainly planted in only four provinces of Vietnam: Dong Nai, Tay Ninh,  Binh Duong and Binh Phuoc, and a part of Ho Chi Minh City. Production of rubber has increased rapidly during the last ten years, from 58,000 metric tons in 1990 to 291,000 tons in 2000 (FAO 2001). The total area of rubber trees has also increased and is projected to reach around 700,000 ha in 2005 (Institute of Rubber Tree Research in Vietnam 1997).

 

The rubber tree begins to produce fruit at 4 years of age. A fruit contains 3 to 4 seeds, which consist of a hard shell, which is brown or black with some white spots, and a soft white kernel. The proportion of the kernel is about 51% of the total weight of the seed. The soft kernel is used to produce oil, and the by-product is rubber seed meal (RSM). A hectare of rubber trees gives 300 to 400 kg of seed per year (Gohl 1981). Average rubber seed meal produced is about 60 to 70% of total seed weight. Therefore, one hectare of mature rubber trees produces 180 to 280 kg of RSM. Rubber oil is the raw material for the production of savon, paint and lubricant.

 

The technique for processing of the rubber seeds to produce rubber oil and RSM was described in detail by Nguyen Quang Thieu (2001). Generally RSM is produced by mechanical processes and is not extracted, and usually contains 5 to 10% of tiny shell particles. These could damage the epithelial cells in digestive tract of swine. Fortunately, the chicken has a gizzard to grind and help to digest hard objects.

 

Farmers close to the location of RSM production have included RSM in diets for chickens and also pigs for a ong time. According to these producers pigs can tolerate only about 7% of RSM in the diet due to the toxicity of the RSM. Even though farmers do not know exactly what the toxin is, the symtoms they describe indicate that the cause is probably HCN, as reported in the literature. The farmers reported that scavenging chickens do not show any serious symptoms of toxicity. However, consumers are often afraid of being poisoned through eating chickens which had been fed diets with RSM. This perception results in farmers not revealing the fact that they really feed their chickens diets with RSM. According to some RSM producers, even feed mills purchase RSM to mix into their complete feeds, but they never reveal this to the public.

 

Trial 1. RSM in diets for scavenging native chickens

 

Final live weights and mean daily live weight gains were not affected by including up 40% RSM in the diets,  but the 50% level of RSM inclusion did result in markedly lower weight gains (Table 3). However, the most serious effect of  high levels of RSM was on survival rate, which fell from over 90% for the RS30 diet to 65 and 39% for the RS40 and RS50 diets, respectively (Table 4).

 

Table 3. Effects of RSM on live weight changes and average weight gain of chickens during different growth phases
	RS0	RS10	RS20	RS30	RS40	RS50
Live weight (g)                 Initial weight                 at 45 days                 at 72 days                 at 100 days                 at 128 days	33.8 293 656 1109 1418	34.0 308 582 1055 1396	34.4 308 579 986 1275	34.4 299 682 1238 1557	33.8 270 673 1211 1517	34.1 195 498 944 1218
Average gain  (g/day)                 0-45 days                 0-72 days                 0-100 days                 0-128 days	5.77 8.65 10.75 10.81	6.08 7.61 10.21 10.64	6.08 7.57 9.52 9.69	5.89 9.01 12.03 11.90	5.25 8.88 11.77 11.59	3.58 6.45 9.10 9.25

 

Table 4. Effect of RSM level on culled and mortality rates ( %)
	RS0	RS10	RS20	RS30	RS40	RS50
Period 1 – 72 days
Mortality	6.0	2.00	2.00	4.00	23.6	26.0
Culled	4.0	0.00	0.00	2.00	3.60	4.79
Period 73 – 128 days
Mortality	0.0	0.00	3.57	3.57	3.70	14.0
Culled	3.57	3.57	3.57	0.00	3.57	16.1
Whole period
Mortality	6.0	2.00	5.57	7.57	27.3	40.0
Culled	7.57	3.57	3.57	2.00	7.17	20.9
Survived	86.4	94.4	90.9	90.4	65.5	39.0

 

 

Trial 2. Confined Tam Hoang  growers

 

The chicks remained healthy throughout the trial, and as is clearly indicated there were no effects of inclusion of 5 or 10% RSM on daily gains, feed conversion  or mortality (Table 5).

Table 5. Effects of RSM on live weight changes and average weight gain of confined Tam Hoang chickens during different growth phases
	Control	RS5	RS10
Live weight (g) at 28 days at 70 days	550 1700	570 1829	554 1747
Average daily weight gain  (g/day) 0-28 days 0-70 days	17.9 27.5	18.7 28.2	18.1 27.4
Feed conversion ratio, kg feed/kg gain 0-28 days 0-70 days	2.91 3.55	2.87 3.56	3.00 3.66
Survival rate (%)	92.8	93.9	91.9

 

  

Conclusions

•  Large amounts of rubber seed meal are produced in the provinces surveyed, although poultry farmers only include low levels (around 7%) in the diets because of concerns over possible toxic effects.

• The results of the growth trials show that up to 30% RSM can be included in diets for scavenging native chickens, and up to 10% in diets for confined  improved (Tam hoang) growers.
   

 

Acknowledgements

This research was partially financed by the bilateral SAREC project 2000-2002.

 

References

 

FAO 2001 Selected indicators of food and agriculture development in Asia-Pacific region, 1990-2000. Regional office for Asia and the Pacific, Bangkok.

 

Gohl B 1981 Tropical Feeds. FAO, Rome http://www.fao.org/ag/AGA/AGAP/FRG/afris/default.htm

 

Nguyen Quoc Thieu 2001  Evaluation of rubber seed meal in diets of local chickens. MSc thesis. Swedish University of Agricultural Sciences