The effect of supplementing different green feeds (water spinach, sweet potato leaves and duckweed) to broken rice based diets on performance, meat and egg yolk colour of Luong Phuong chickens
 

Nguyen Thi Thuy and Brian Ogle*

Collegeof Agriculture, CanTho University, CanTho, Vietnam
^{nthithuycn@ctu.edu.vn
*}Department of Animal Nutrition and Management,
Swedish University of Agricultural Sciences, Uppsala, Sweden

Abstract

A total of 204 female Luong Phuong chickens at 4 weeks of age were allocated at random to 4 treatments and 3 replicates. The control diet was a mixture of broken rice, rice bran, soyabean meal and fishmeal (16.9 % crude protein in DM) with no green feed supplied. For the other 3 diets, duckweed (DW), water spinach (WS), and sweet potato vines (SP) were given ad libitum in separate feeders in addition to the control diet. The birds were weighed each week between 4-16 weeks of age and feed consumption was recorded each day. Because of an outbreak of Avian Influenza in the Mekong Delta, the experiment was stopped when the birds had reached 21 weeks of age.

Total feed DM intake, CP intake and average daily weight gain did not differ among treatments (P>0.05). Intakes of DW (3.3 g/day) and SP (2.8 g/day) were higher than for WS (1.8 g/day) (DM basis) (P<0.01) and CP intake from DW as a proportion of total CP intake (9.6%) was higher than from WS (5.2%) and SP (6.7%) (P>0.01). There were no differences in carcass yield, but liver and gizzard weight on the diet with DW (48.3 and 50.3 g, respectively) were higher than on the control diet (40.0 and 43.3 g, respectively). The control group had highest abdominal fat (81.0 g), more than twice as high than on the experimental diets (P>0.001). The DM, CP and EE contents of the meat were similar among treatments, as were egg weight and egg yolk weight (P>0.05). The egg yolk and skin had a deeper yellow colour in chickens fed DW (59.0 units), followed by those fed WS (53.2 units), SP (41.5 units) and the control diet (30.2 units) (P<0.001).

Keywords: Duckweed, water spinach, sweet potato vines, Luong Phuong, egg yolk colour

Introduction

Chicken production plays an important role in the agriculture of the Mekong Delta, which accounts for 28 % of the total chicken products in the country (Khang 2003). Among many kinds of local breeds, an improved chicken, known as Luong Phuong, that came to Vietnam from China has become popular in the South of Vietnam. They are usually confined and fed concentrates. The breed has good performance, resistance to diseases and parasites, and provides delicious meat. However, the meat colour is rather pale, which makes it not very attractive to the consumers, so the diet that they consume is very important. This is the reason for promoting research into the use of cheap, local protein feeds such as duckweed, water spinach, and sweet potatoes, which have the potential to reduce feed costs and improve meat and egg yolk colour.

Sweet potato (Ipomoea batatas) is a major tropical crop with a short and fast growth cycle. Leaves of sweet potato have high crude protein (CP) content, from 25 to 29% in DM, while the protein content in the stem is from 12 to 14% in DM (Hong 2003). The fresh leaves and stems of water spinach (Ipomoea aquatica) have a CP content of around 28% in DM (Le Thi Men et al 2000). Crude fibre (CF) and ash concentrations are around 12% and 19% of DM, respectively (Göhl 1981). Duckweed is a very good protein source for the chicken (Khang 2003). According to Bui Xuan Men (2001) ducks fed duckweed had an orange - yellow skin and body fat at slaughter, and these natural - yellow coloured carcasses were more attractive for consumers.

Most of these green feeds are of high quality and are high in carotene and xanthophylls, which are important in giving a deep yellow colour to eggs and meat. Therefore, this research was carried out to compare the different types of green leaves as sources of protein and carotenoids and to determine which one can be recommended to the farmers.

Objectives

The aims of the experiment were to:

• Evaluate the effects of three different green feeds (water spinach, sweet potato and duckweed) on feed intake, CP intake, growth rate, carcass quality, and meat and yolk colour of Luong Phuong chickens.

• Determine which of the green feeds would be most suitable for small-scale farmers under village conditions.

Materials and methods

Location

The experiment was carried out in the experimental farm of Cantho University from October 2003 to February 2004.The experiment was conducted during 17 weeks, including 12 weeks of growing and 5 weeks of laying.

Experimental animals, treatments and design

The experimental animals were Luong Phuong chickens from 4 weeks of age. The design was a completely randomized block design (CRD) with 4 treatments and 3 replicates, and 17 chickens per experimental unit.

The treatments were

• Control diet : Mixed diet without any green feed

• DW : Mixed diet + Duckweed (ad libitum)

• WS : Mixed diet + Water spinach (ad libitum)

• SP : Mixed diet + Sweet potato vines (ad libitum)

Duckweed	Water spinach	Sweet potato
Photograph 1. Green plants used

All the green feeds were supplied ad libitum in separate feeders. The mixed diet contained (%): broken rice, 53.8; rice bran, 20; soybean meal 14; fish meal, 12; vitamin premix 0.2. The CP in diet DM was 16.8% and the ME content 12.3 MJ/kg.

Management and data collection

In the preliminary period from day 1 to 21 days after hatching, the chickens were fed a commercial starter diet (ad libitum) which contained 18 % CP and 12 MJ / kg ME. The chickens were transferred to the experimental farm at 21 days of age and given green feed and the mixed feed for 1 week of adaptation. They were confined in pens constructed from trellis and cast nets and bamboo, with concrete floors covered with 20 cm of rice husks for bedding. The average density was 5 birds per m². The temperature inside the house varied between 25.0 and 29.5 ºC and humidity from 80.8 to 56.7 %. During the time of the experiment, the weather between November to January was rather cool. Water was supplied ad libitum in plastic tube drinkers. Feeders were round plastic bowls and both feeders and drinkers were cleaned and refilled each morning.

The green feeds were offered twice per day in the morning and afternoon; the residues were weighed the following morning. The mixed feed was offered once per day and the residue weighed at the end of the week when the live weights of the chickens were recorded. At 14 weeks of age, one representative chicken from each treatment / replicate was slaughtered.

Feed analysis

Samples of mixed feed, duckweed, water spinach and sweet potato vines were analyzed (AOAC 1990) for DM, CP, EE, CF, Ca and P; the residues of green feed were analyzed for DM once every week. Thigh and breast muscles were analyzed for DM, CP and EE in the slaughtered birds.

Statistical analysis

The data were analyzed with the General Linear Model (GLM) option of the ANOVA programme of the Minitab software (version 13.3) (2000). When applicable, pair wise comparisons between treatments means were made using the Tukey test in the same Minitab software.

Results

Chemical composition and nutritive value of the feeds

CP contents in the DM of duckweed and water spinach were similar and higher than in the sweet potato vines (Table 1). Ether extract and ash were highest, and CF lowest, in the duckweed.

Feed and nutrient intakes

Total dry matter intake, including green feed, did not differ among treatments (Table 2). Intakes of green feed were higher for duckweed and sweet potato vines than for water spinach. The duckweed contributed a greater proportion of protein to the diets than water spinach or sweet potato (P<0.001). All the green feeds were rich in ash and phosphorus, with the highest values for duckweed.

Average daily gain and feed conversion ratio

Growth rate and feed conversion ratio did not differ between treatments (Table 2).

Carcass evaluation and chemical composition of meat

The carcass percentage tended (P=0.107) to be lower on the treatments with supplementary green feed (Table 3). Liver and gizzard weights were higher and abdominal fat lower on the diets with green feed compared with the control. The thigh and breast muscle had similar levels of protein and fat on all treatments (Table 4).

Age at first egg and egg yolk colour

There were no differences among treatments in age at first egg, egg weight and egg yolk weight (Table 5). However, egg yolks had the deepest yellow colour (Photo 2) with the duckweed and water spinach supplements; egg yolks from the control treatment had the whitest colour.

Photo 2. Egg yolks from birds fed supplements of duckweed (DW), water spinach WS),
sweet potato leaves (SP) or none (C)

Discussion

The water spinach had a higher content of CP than was reported by Le Thi Men (2000), probably due to the fact that it was grown in a low-lying area which received waste from the university piggery. The DM content of the sweet potato vines was lower compared with the results from Hong (2003), as these plants were also fertilized by pig manure. Vo Lam (2003) reported that sweet potatoes fertilized with goat manure had lower DM in the aerial part than unfertilized plants.

There was a slight tendency (P=0.26) for total DM intake to be higher on the diets with green feed. This could have been due to the increase in fibre content of the green feed diets, which could have caused a faster rate of passage through the digestive tract that stimulated intake. Intake of duckweed was highest but the amount consumed was less than in other studies, possibly because in cool weather fresh duckweed is less attractive than in hot weather, which was the dominant weather at the time of the experiment of Nguyen Thi Kim Khang (2003). The daily protein intake from the control diet was also enough to satisfy requirements so there may have been less incentive to consume the protein-rich green feed. Nguyen Thi Kim Khang (2003) found that when the basal diet was deficient in protein, then the chickens compensated by eating more duckweed.

The lack of difference in growth rate among diets was probably due to the adequate balance of nutrients for growth in the control diet. Haustein et al (1994) reported faster growth rates when dried duckweed was fed to broilers, but in this case the basal diet was low in protein.

The chickens with access to green feed tended (P=0.11) to have a lower carcass yield than the control chickens, probably because of higher contents of digesta in the gastro-intestinal tract, as indicated by greater weights of the gizzard and much lower quantities of abdominal fat. It was also observed that there was less fat under the skin of chickens with access to green feed. The chickens with access to duckweed and water spinach had a yellow skin, which is attractive to customers. This effect on fat colour is in agreement with the results of Bui Xuan Men et al (2001), who found that the meat and skin from ducks fed duckweed had a more intense yellow colour than from ducks fed a diet with soybean meal as the main protein source.

The marked effects of diet on egg yolk color, especially in the case of the duckweed and water spinach, were almost certainly due to differences in intake of carotene. Duckweed is reported to have 1.03 mg/kg of carotene in DM, according to Bui Xuan Men et al (2001) and, in water spinach, beta carotene in the leaves was reported to be 2.4 mg /kg DM (Yang 1979).
 

Conclusions

• It is concluded that the lack of effect of the green feeds on growth rate, feed conversion and meat quality was because the basal diet was already well balanced in major nutrients.

• There was an improved color of the skin and egg yolk when chickens had access to the green feeds, with the most pronounced effects for duckweed and water spinach. This makes the products more attractive to the customers.

• Duckweed has advantages over water spinach and sweet potato leaves as it requires no processing, whereas the water spinach and sweet potato leaves require extra labour for chopping.

 

References

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Hang D T 2003 Effect of level of fresh duckweed (Lemna minor ) in diets of chickens raised in confinement.

Haustein A T Gilman R H Skilicorn P W Hannan H Guevara V Verara V Gastanaduy A and Gilman J B 1994 Performance of broiler chickens fed diets containing duckweed (Lemna gibba). Journal of Agricultural Sciences, Cambridge, 122: 285 -289.

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Yang Y H 1979 Tropical home gardens as nutritional intervention. In: G.E. Inglett and G. Charalambous (eds), Tropical food chemistry and nutrition, Academic Press, New York.

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