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Workshop-Seminar on Making Better Use of Local Feed Resources. SAREC-UAF, January 2000

 

By-products (tofu waste and rice bran) and duckweed
for household duck production in North Vietnam

Nguyen Thi Minh, Le Viet Ly and  Pham Van Truong

Duck Centre, National Institute of Animal Husbandry, Hanoi

 

Abstract

A combination of tofu waste, rice bran, duckweed and freshwater snails, ingredients that are readily available and very cheap in North Vietnam, was formulated to give a protein content similar to a basal, traditional feed, and replaced up to 100% of this diet in two experiments with scavenging Co duck layers.

 

In the first experiment, with replacement levels of 0, 20, 30, 40, 50 and 60% of the basal diet by a mixture based on duckweed, tofu waste and rice bran, the ducks produced 5.38, 5.33, 5.39, 4.93, 4.31 and 4.01 eggs/week, respectively.  Mean egg weight (68.6 – 68.9g) did not differ between treatments.  Feed costs were found to be lowest (121 VND per egg lower than for the basal diet) at the 60% level of replacement, and highest on the basal diet.

 

In the second experiment the replacement levels were increased to 0, 40, 60, 80 and 100% of the above mixture, which resulted in a mean weekly production of 3.84, 3.52, 3.46, 3.08 and 2.26 eggs, respectively, over the 13 week laying period. Egg production and mean egg weight on the 80% and 100% replacement levels were significantly lower than for the other treatments. Feed costs were lowest at 60% replacement (102 VND per egg less than for the control diet) of the basal diet with the experimental mixture, and highest for the control diet.

 

Key words: Ducks, by-products, egg production

Introduction

 

The native egg-type duck breed (Co) is very closely associated with household production in Vietnam, and sustainable systems in association with fish and rice production have been developed over a long period. Co ducks can forage in the fields, on detritus, insects, snails, small fish, small shrimps and duckweed during the rice-growing season, and after the harvest also on spilt rice. As a result the farmers feed less rice (» 40 kg/bird/year) than is required under confined feeding (» 60 kg/bird/year). Since each family has on average only around 0.36 ha, the amount of paddy grown is not even sufficient to feed 100 ducks, and paddy has to be bought in the market both for the ducks and for family consumption. There is a need therefore to identify alternative feeds for ducks, and the use of by-products such as rice bran and tofu waste would be very attractive. Available duckweed could be increased by growing it on fertilized ponds. Tofu waste can be an important source of protein, and is much cheaper than other alternatives such as fish meal and soyabean meal.

 

Objectives of the research

 

·        To show that local Co ducks can obtain almost all of their feed from foraging, supplemented with local by-products and still sustain high levels of egg production.

·        To determine the optimum level of replacement of a traditional basal diet by a mixture of locally available by-products in terms of egg production and feed costs.

 

Experiment 1

Materials and methods

A total of 730 laying Co ducks in their second laying year were divided into 6 flocks in 6 villages in Ha Tay and Ha Nam provinces. Flock 1 was given a control diet (ctrl), which was then progressively replaced by 20, 30, 40, 50 and 60% of a mixture of by-products (flocks/diets 20bp, 30bp, 40bp, 50bp and 60bp, respectively). The experiment was carried out between August 1998 and February 1999.

 

The control diet consisted of 65% paddy rice and 35% of a commercial protein concentrate, and had a crude protein content of 16.0% and estimated ME content of 2,710 kcal/kg.  The by-products mixture consisted of  (air dry basis) 40% duckweed, 30% tofu waste and 30% rice bran, and had a crude protein content of 5.47% and an estimated ME content of 971 kcal/kg (as fed).  All ducks were allowed to scavenge in the daytime.

 

Results and discussion

Chemical composition of diets

The ME and crude protein contents of the diets were similar and in line with recommendations for Pekin breeder laying ducks (Table 1).

 

Feed intake and egg production

For the Khaki Campbell layer with a body weight of about 1750g in full egg production a feed consumption of 150g/bird/day of a ration containing 18% crude protein and 2650 kcal ME/kg is recommended.  Daily feed dry matter intakes (Table 2) of the Co ducks were lower than intended intakes and than these recommendations, although it should be remembered that they were out scavenging for most of the day.

 

Table 2. Effect of replacing a traditional concentrate with a mixture of by-products (bp) on egg production
	Ctrl	20bp	30bp	40bp	50bp	60bp
Feed intake, g/bird/d        Egg production    Total/bird /22wks    Eggs/bird/wk                          Rate of lay, %	120   118a 5.38 76.8a	168   117ª 5.33 76.1a	192   118a 5.39 76.9a	200   108ab 4.93 70.4b	197   90.6b 4.30 61.4b	196   88.2b 4.01 57.2b

a,b values in rows with different superscripts differ at P<0.01

         

Egg production was not significantly different between the control and diets with 20 and 30% substitution of by-products, but then progressively declined with increasing levels of substitution of the by-products mixture. Rate of lay decreased from 76.8% for the control diet to 57.3% for the diet with 60% replacement by the by-products mixture (P<0.001). Mean egg weight was in the range of 68.5 to 68.9 g and was not affected by dietary treatment.

 

 

 

 

Despite the fact that egg production was significantly reduced on diets with 50 and 60% replacement by by-products, the feed costs per egg were lower compared with the control diet.

 

Conclusions

 Although egg production declined when more than 40% of the control diet was replaced by the by-products mixture, the cost of feed per egg produced was lowest with the maximum level of by-products substitution (60%).

   

Experiment 2

Materials and methods

A similar mixture of by-products to that used in Experiment 1 was formulated, consisting of  (fresh weight): duckweed 30%; freshwater snails 10%; tofu waste 30%; and rice bran 30%. The mixture contained 5.55% crude protein and 950 kcal/kg estimated ME (fresh weight) and replaced 40, 60, 80 and 100% of a basal diet consisting of paddy rice (65%) and a traditional concentrate (35%) (16.0% crude protein and 2,710 kcal/kg of ME). The diets were given to 5 different flocks over 13 weeks of the laying period.

 

Results and discussion

Mean daily feed intakes over the 13 weeks of the experiment increased from 220g/bird for the control diet to 310 g/bird for the diet with 80% replacement by the by-product mixture, falling slightly to 278 g/bird with 100% replacement. The explanation for this is probably the lower ME content of the by-products mixture due to the inclusion of the snails.

  

Table 4. Effects of replacing a traditional concentrate with a mixture of by-products on egg production and feed costs
	Ctrl	40bp	60bp	80bp	100bp
Eggs in 13 weeks lay	49.9a	45.8ab	45.0ab	40.0 b	29.4 c
Number of eggs/bird/day	0.55	0.50	0.49	0.44	0.32
Mean egg weight, g	66.1a	66.3a	66.5a	64.4b	63.9b
Feed cost/bird/day, VND	406	334	312	284	210
Feed cost/egg, VND	739	669	637	646	657
abc: values within rows with different superscripts differ at P<0.001

Egg production decreased by around 10% (NS) when 60% of the basal diet was replaced by the by-products mixture, and by 20% and 40%, respectively, (P<0.001) with 80% and 100% replacement. Mean egg weight also decreased significantly  (p<0.001) with 80% and 100% replacement of the control diet. Feed costs per egg were lowest on the diet with 60% replacement (102 VND less than for the control diet).

 

Conclusions

The results of the two experiments clearly indicate that the optimum economical level of replacement of the traditional concentrate by the by-products mixture is around 60%.  At higher levels of replacement, egg production and egg weight were reduced, although the cost of feed per bird and per egg were still less than on the control diet.
 

References