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*

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

 

Abstract

204 female Luong Phuong chickens at 4 weeks of age were allocated to 4 treatments and 3 replicates. The control diet was a mixture of broken rice, rice bran, soyabean meal and fishmeal (16.9 % of CP in DM) with no green feed supplied. For the other 3 diets, Duckweed (DW), Water spinach (WS), and Sweet potatoe vines (SP) were given ad libitum in separate feeders in addition to the control diet. 

Total of feed intake, CP intake and average daily weight gain did not differ among treatments. Intakes of duckweed and sweet potato vines were higher than for water spinach (DM basis;  CP intake from duckweed was higher compared with that from water spinach and sweet potato vines. There were no differences in carcass yield, but liver and gizzard weight on the diet with duckweed were heavier comparing with the control diet, which had highest abdominal fat. The DM, CP and EE of the meat were  similar among treatments as were egg weight and egg yolk weight. The egg yolk and skin had a deeper yellow colour in chickens fed duckweed, followed by  those fed water spinach.

Key word: Duckweed, Water spinach, Sweet potato vines,  Luong Phuong, egg yolk colour.

Introduction

Chicken production plays an important role in agriculture of the Mekong Delta which accounts for 28 % of total chicken products in the country (Khang  2003). Among many kinds of local breeds, improved chickens known as Luong Phuong that came to Vietnam from China have become popularin 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 quite white, 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 reduce feed costs and improve meat and egg york colour.

Sweet potato (Ipomoea batatas) is a major tropical crop with a short and fast growth cycle. Leaves of sweet potato have high protein content, from 25 to 29% in DM, while the protein content in stem is from 12 to 14% in dry matter (Hong 2003). The fresh leaves and stems of water spinach (Ipomoea aquatica) have a crude protein content of around 28% in DM (Le Thi Men et al 2000). Crude fibre 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 colour carcasses were more attractive for consumers.

Most of these green feeds are of high quality and 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

These were to:

• evaluate the effects of the three different green feeds (water spinach, sweet potato and duckweed) on feed intake, crude protein 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 + Waterspinach (ad libitum)
• SP : Mixed diet + Sweet potato vines (ad libitum)

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

Management and data collection

In the preliminary period from 1 day to 21 days after hatching, the chickens were fed a commercial starter diet (ad libitum) which contained 18 % of CP and 12 MJ 0f ME. The chickens were transferred to the experimental farm at 21 days of age and given greed feed and the mixed feed for 1 week of adaptation. The chickens 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 and  29.5 ºC and from 80.8 to 56.7 % of humidity. During the time of the experiment, the weather was cold from November to January. 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, 1 chicken from each treatment/replicate, which had the average weight of the group,  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 (GML) 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

Crude protein 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 crude fibre lowest in the duckweed.

 

Feed intake and nutrient intake

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. All the green feeds were rich in ash and phosphorus, with 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.  The 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 crude protein 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 piggery. The DM content of the sweet potato vines was lower compared with the results from Hong (2003), as this plant was also fertilized by pig manure. Vo Lam (2003)  reported that sweet potatoes fertilized with goat manure had lower dry matter 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 on the green feed diets which could have caused a faster rate of passage through the digestive tract.  Duckweed was eaten most but the amount was less than reported by , perhaps because in the cold weather, from October to January in this experiment,  the fresh duckweed was less attractive than in hot weather, which was when Nguyen Thi Khang (2003) did her experiment. The protein received from the mixed diet was also enough to satisfy requirements so there may have been less incentive to consume the protein-rich green feed. tNguyen Thi Khang (2003) found that  when 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 control chickens,  probably because of higher contents in the digestive 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 shin 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 ducks fed only on soyabean meal as the protein source.

The marked effects of diets 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 DM according to Bui Xuan Men et al (2001) and, in water spinach, beta carotene in the leaves is reported as 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.

The improved color of the skin and the egg yolk, when chickens had access to the green feeds, with most pronounced effects for duckweed and water spinach, 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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