Effects of dietary protein level and a duckweed supplement on the growth rate of local breed chicks

Nguyen Thi Kim Khang and Brian Ogle^*

Department of Animal Husbandry, College of Agriculture, Cantho University
khangntkim@yahoo.com
* Department of Animal Nutrition and Management,
Box 7024 Swedish University of Agricultural Sciences, S-750 07 Uppsala Sweden

Abstract

From a total of 402 local breed chicks (Tau Vang) at 1 day of age, 360  were allocated in a completely randomized design to 6 treatments, with 3 levels of crude protein (% in DM): 18 (CP18), 20 (CP20) and 22 (CP22), with or without fresh duckweed (DW) (Lemna minor) ad libitum.

Total daily dry matter intakes were slightly higher on the CP20 and CP22 diets (12.0 g and 11.7g, respectively) compared with the CP18 diet (11.1g) and when DW was supplied (13.2 g compared to 11.5g), but between treatment differences were not significant. CP from duckweed decreased with increasing levels of protein in the diets and supplied 14.2, 12.0 and 10.3 % of the total CP intake in the CP18, CP20 and CP22 dietary treatments, respectively. Chicks fed DW had somewhat higher weight gains (8.3 g/day) compared with chicks fed the diets without DW (7.8 g/day) but there were no differences between diets with different CP levels. Wing and tail feathers appeared first in chicks on the CP20 and CP22 diets and tended to develop more rapidly on the diets with duckweed.

Key words: growth, duckweed, local chicks, protein

Introduction

Poultry production is an essential element of agricultural production throughout Vietnam, especially chicken production in the Mekong River Delta, which accounts for 16% of the chicken meat and 28% of the total chicken products in the country. Feed supply is a concern because it accounts for 60 to 70% of total production costs. In particular protein is an important cost component in the diets of chicks, and also has a major effect on the performance. Therefore there have been many investigations into the use of cheap, local protein feeds such as water plants, kitchen waste and agro-industrial by products, which reduce feed costs and thus the price of the products and can increase the economic benefits to the farmers. These alternative feeds, especially water plants, should where possible meet the chick's nutrient requirements for normal growth rate.

Duckweed protein has a better array of essential amino acids than most vegetable proteins and more closely resembles animal protein (Hillman and Culley 1978). It is, therefore, a source of high quality protein to be exploited for domestic animal production (Haustein et al 1987), in particular for pigs (Le Thi Men et al 1997; Du Thanh Hang 1998) and chickens (Samnang 1999) and has also been shown to be a good source of vitamins and minerals for growing ducks (Becerra et al 1995; Bui Xuan Men et al 1995). Very little research has been done to determine the protein requirements of local chicken breeds in Vietnam, such as the Tau Vang, Ta and Ri chickens, even though many studies have been carried out to determine the nutrient requirements of hybrid and commercial breed chicks, especially for protein. Therefore, this study was carried out to determine:  the optimum level of dietary protein for starter diets for a local breed of chicks; the effect of providing supplementary duckweed;  and the economic benefit for small scale farmers. The objectives of this study thus were:

• To determine the effect of dietary protein level on the growth rate of local breed chicks
  
  
• To evaluate the effect of duckweed supplied ad libitum on the growth performance of chicks.

Materials and methods

Location

The experiment was carried out in the experimental farm of Can Tho University in South Vietnam.

Experimental design

From a total of 402 local chicks (Tau Vang breed) at 1 day of age, 360 were allocated in a completely randomized design to 6 treatments with 3 replications (pens). The chicks were given complete mixed diets (Table 1) ad libitum from 1day to 4 weeks of age that contained 3 levels of crude protein (18, 20 and 22% CP), with or without fresh duckweed supplied ad libitum. The whole soya beans in the basal diet were roasted prior to grinding to eliminate anti-nutritional factors.

Housing and management

There were 18 pens of 1 m x 1 m built from local materials (bamboo, palm leaves). The chicks were not sexed and were confined in the pens, with 22 birds per pen. Light was used all the time from electric bulbs. At this stage, the birds received the full complement of routine vaccinations against Newcastle, Cholera, Gumboro and Fowl pox diseases. The dry mixed feed and fresh duckweed were offered in separate feeders, and drinking water was freely available.  Duckweed was harvested every morning from ponds fertilized with biodigester effluent, and supplied to the chicks 2 times per day in the morning (08.00h) and in the afternoon (14.00h). The birds' beaks were trimmed at eight days using a hot blade debeaker.

Data collection and analysis

The birds were weighed initially and then every week, with all birds in the pen weighed together in a tared basket. Daily feed intakes were calculated according to the total feed consumption of the group in each pen. Feed and duckweed offered and refused were recorded every morning. Daily live weight gains of chicks were calculated on a weekly basis. Mortality was recorded by counting the initial number of birds and number remaining at the end of each week, and at the end of the trial. Appearance of wing and tail feathers of chicks was recorded as the time when wing or tail feathers had appeared in half of the chicks.

Representative samples of feed and duckweed and residues were collected and stored in a refrigerator for determination of proximate components. The DM content was determined by drying to constant weight at 105^oC. Nitrogen was determined by the Kjeldahl technique and CP as N x 6.25. EE was determined using anhydrous ethyl ether in a Soxhlet apparatus. Calcium and phosphorus were determined by AOAC procedures (AOAC 1994) (CAS-7440-70-2 for calcium and CAS-7723-14-0 for phosphorus).  Amino acids were analyzed using HPLC according to Spackman et al (1958) at CASE (Center of Analysis Service of Experiments) in Ho Chi Minh City (Table 2).

 

Statistical analysis

The data were analyzed by analysis of variance using the General Linear Models procedure of Minitab version 13.31 (Minitab 2000). The temperature and humidity were recorded in the early morning and at midday and were analyzed by descriptive statistics (Minitab 2000).

Results

Feed and nutrient intake

In diets 18DW, 20DW and 22DW, duckweed contributed from 6 to 7% of the diet DM and from 25 to 29% of the protein, with the higher values coinciding with lower levels of protein in the basal concentrate component (Table 3).

 

Growth rate and feed conversion

The factorial analysis (Table 4) showed a tendency (P=0.09) for growth rates to be higher for chicks having access to duckweed but no differences among protein levels.

Rate of feathering and survival

Wing feathers first appeared on day 2 and tail feathers on day 16. There was a tendency for the rate of feathering to be faster on the higher protein diets and on the treatments with duckweed (Table 5)

Survival rates ranged from 88 to 97% and were not related to treatments.

Discussion

The tendency for DM intake to be increased when the chicks had access to duckweed is a similar response to that observed with ducks having free access to concentrate and to duckweed (Bui Xuan Men et al 1995). Duckweed had a generally positive effect on daily gains,  even on the diet with 22%CP.  A possible explanation for this is that even though all diets contained a vitamin-premix, vitamin A is often destroyed quite rapidly in hot and humid conditions, so the treatments without duckweed could have been deficient in vitamin A, which is essential for growth and reproduction and would have been supplied by the duckweed, which is rich in carotenoids (Landolt et al 1987; and Solomons 1996).  The results are in agreement with those reported by Haustein et al (1994) and Samnang (1999), who showed that feed intake and growth rate of birds were improved when offered duckweed. Sulphur-amino acids play an important role for feather development (Duong Thanh Liem et al 2003), and this could explain why the rate of feathering was lowest on the low protein diet (CP18) without duckweed.

Conclusions

From these results, it is concluded that:

• Young chicks offered basal diets with from 18 to 22% crude protein tend to have higher feed intake and growth rate when they also have free access  to fresh duckweed.

Acknowledgements

We are very grateful to the MEKARN project, supported by the Swedish International Development Authority (Sida/SAREC) for the financial support of this study.  This paper is based on research submitted by the Senior Author to the Swedish University of Agricultural Sciences in partial fulfillment of the requirements for the MSc degree in Tropical Livestock Systems.

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Received 19 May 2004: Accepted July 23 2004

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