The study was carried out from March 2002 to December 2002 at the Experimental Farm of Cantho University, in the South of Vietnam, and consisted of on-station trials with growing local breed (Tau Vang) chicks and hens, and an on-farm trial with growing chickens, to compare the effect of duckweed on growth and economic performance of scavenging chickens.
The objectives of the research were to evaluate the effects of level of dietary protein and duckweed supply on daily feed intakes and growth rate of chicks and to determine the optimum level of soybean meal in diets for growing local chickens and laying hens when duckweed is available ad-libitum. In the 28-day growth trial, 402 day-old Tau Vang chicks were used in a completely randomized design with 3 levels of protein (CP18, CP20 and CP22) with or without duckweed supplement. Then growing chickens of 4 weeks of age were used in a second growth trial with a completely randomized design with 5 dietary treatments and 3 replicates. The control diet was a mixture of broken rice and soybean meal (SB100). For the other four diets, the level of soybean meal was reduced to 75, 50, 25 and 0% of the control diet, and duckweed was available ad-libitum, giving 5 diets (SB0DW, SB25DW, SB50DW, SB75DW and SB100 respectively) fed to growing chickens from 5 - 15 weeks of age. In the final experiment hens were selected on the basis of growth rate and appearance from the remaining chickens used in the previous growth trial, and continued on the same treatment as in the growth trial.
The parameters recorded were feed intake, weight gain, mortality, feed conversion, feathering rate, carcass value, carcass proportion and economic benefits for the growing chickens, and egg number and weight, quality of eggs and yolk pigment, proportion of fertile eggs and hatchability of eggs for the layer hens.
The results from the experiment with day-old chicks to 4 weeks of age showed that total daily dry matter feed intakes were slightly higher on the CP20 and CP22 diets compared with the CP18 diet (P>0.05) and also higher when duckweed was supplied compared to the treatments without duckweed. CP from duckweed decreased with increasing levels of protein in the diets. Chicks fed DW had slightly higher weight gains compared with chicks fed the diets without DW (P>0.05).
The findings from the experiment with growing chickens from 5 - 15 weeks of age indicated that feed intakes and daily gains were highest on the SB50 diet for female chickens and on the SB0 diet for the male chickens, with the lowest daily weight gains were on the SB100 diet (P<0.05). The proportion of CP of the total intake that came from duckweed increased significantly from the SB75DW to the SB0DW diet (P<0.05). Carcass yields were significantly higher for chicks fed the SB0, SB25 and SB50 diets, and lowest for chicks fed the SB100 diet (P<0.05). The meat from chickens feed duckweed was of a more intense yellow color than that of birds on the soybean meal only diet. Feeding fresh duckweed to local growing chickens resulted in decreased feed cost compared to the diet with 100% of soybean, especially when 100% and 75% of the soybean meal was replaced by broken rice, and fresh duckweed was offered ad-libitum.
The findings from the layer experiment showed that total feed consumption and concentrate intake were not significantly different among treatments (P>0.05). Duckweed intake on the SB0DW diet was significantly higher than for the SB25DW, SB75DW and SB50DW treatments. In consequence, the proportion of the total crude protein intake from duckweed was highest on the SB0DW diet and decreased on the SB25DW, SB50DW diets, which were higher than on the SB75DW diet (P<0.05). There were no significant differences in daily CP and ME intakes and feed conversion ratio (P>0.05) among treatments. Age at first egg was not significantly different among treatments, although was somewhat higher on the SB100 diet compared to the other treatments (P>0.05). There were no significant differences among treatments for egg production, egg weight, fertility, hatchability or egg quality parameters (P>0.05). However, yolk pigmentation was significantly better (P<0.05) for all treatments with duckweed compared to the control diet.
The on-farm trial was a completely randomized design with 3 treatments and 4 replications (farms). The SB25 diet from the on-station trial was provided ad-libitum to all treatment groups. On each farm 60 chickens from 5 weeks of age were divided into 3 groups. Two groups were allowed to scavenge in the gardens with or without duckweed supplement (SCDW and SC) and one group was confined (CFDW) and given duckweed ad-libitum. The results showed that the weight gain was slightly higher on the SCDW diet than on the SC and CFDW diets (P>0.05). The highest economic benefits were on the SCDW diet compared with the SC and CFDW diets.
Key words: Duckweed, Tau Vang chicks, growing chickens, layer hens, weight gain, feed intake, egg yolk color, scavenging, economic benefits.
Go to top