Dried rice straw-chicken litter and urea-treated rice straw as main fodder resources for local cattle in the dry season

 Tran Quoc Viet and Dao Duc Kien

National Institute of Animal Husbandry, Chem, Tu liem,
Hanoi, Vietnam

Abstract

Four local cattle of 100 to 120 kg initial weight were allocated to four treatments:  100% rice straw-chicken litter (RSCL); 70% RSCL + 30% urea-treated rice straw (URS), 30% RSCL + 70% URS and 100% URS according to a Latin square design with four 56-day periods. The Rice straw was chopped to 5-10 cm length and used as litter for 600 chickens raised from one-day-old until 60 days. Every two weeks, chopped dried rice straw was scattered on top of the old layer. At the end of the 60 days, the chicken bedding was sun-dried to reach 14-16% moisture. Urea treatment was by ensiling in big plastic bags (100 kg rice straw, 5 kg urea in 35 litres water). All animals received daily 4 kg fresh cassava peel (21% DM) and 0.5 kg of a concentrate mixture (56% cassava root meal, 18% groundnut cake, 25% rice bran and 1% bone meal). The straw component of the diet was fed ad libitum.

Nitrogen and ash contents were higher in RSCL (2.89 and 20.5%) than in untreated rice straw (0.66 and 16.9) and URS (1.69 and 17.2%). NDF and ADF were lowest in RSCL. DM losses in the rumen (48 hour incubation) were 47.7% for untreated straw, 50.8% for RSCL and 62.3%for URS. DM intake, liveweight gain and feed conversion increased with increase in the proportion of URS in the diet. The best method for utilization of rice straw chicken litter appeared to be in combination with urea-treated rice straw in a ratio of 30: 70%.

Key words: Rice straw, urea, chicken litter, dry matter degradability, gas production, growth, cattle

Introduction

Fodder supply during the dry season is a very important factor limiting livestock productivity in the tropics. In Vietnam, the rice crop occupies about 7.4 million ha and supplies nearly 32 million tonnes of  straw annually, which is the main feed for cattle and buffaloes in the dry season. Ammoniation of straw to raise the nutritive value has been very successful in China with widespread application on farms (Ørskov 1999), but the application in other countries has been to only a limited extent (Dolberg 1992).

In some areas in North Vietnam, rice straw has been utilized as litter for commercial broiler and laying hen enterprises. Poultry excreta and poultry litter have been used as feed resources for ruminants in many areas of the world (Muller 1980; Devendra 1983).  It has been estimated that the economic value of poultry litter in balanced animal feeds for ruminants may be 3 to 10 times greater than its value as a source of plant nutrients (Smith and Wheeler 1979).  However, we have not found any reports on the use of chicken litter based on rice straw as the major source of roughage for ruminants.

Materials and methods

Rice straw  treatment

The experiment was done at the Animal Breeding Station in Quoc Oai district of Hatay province. Six hundred one-day-old chickens were raised on the floor with chopped rice straw (5-10 cm length) at a depth of 3 cm as the initial layer of litter. Every two weeks, chopped rice straw was scattered over the existing litter at a depth of 2 cm. The feeding period was 60 days at the end of which the litter was sun-dried to a moisture content of 14-16%.  Rice straw from the same batch  as that used for litter was chopped and ensiled with urea in thick plastic bags 5 m long and 1.5 m diameter. Each layer of 100 kg straw was treated with 5 kg of urea dissolved in 35 litres of water. Treatment time was 21days.

Feeding trial

 Four local cattle (“Yellow” breed) of 100 to 120 kg liveweight were allocated to four treatments according to a 4*4 Latin square design with four 56-day periods.

100RSCL: 100% rice straw-chicken litter as the main roughage

70RSCL: A mixture of 70% RSCL and 30% urea-treated rice straw  (URS).

30RSCL: A mixture of 30% RSCL and 70% URS.

100URS: 100% urea-treated rice straw.

All the animals received daily a supplement of 4 kg fresh cassava peel (21% DM) and 0.5 kg of a concentrate mixture (56% cassava root meal, 18% groundnut cake, 25% rice bran and 1% bone meal) in two equal meals in the morning and in the evening. The straw component of the diet was fed ad libitum.

In sacco and in vitro gas production

One portion of each of the samples (untreated rice straw, urea-treated rice straw and rice straw chicken litter) was milled through a 1.0 mm sieve for chemical analysis and gas production (Menke and Steingass 1988). Another portion was milled through a 2.5 mm screen and used for dry matter degradation in sacco (Ørskov et al 1980).

The coarsely-milled samples (4.67 ± 0.30 g)  were incubated in nylon bags placed in the rumen of three cattle fitted with rumen cannulas. The cattle were fed a basal diet of ad libitum natural grass (DM 25.6 %, crude protein 10.2 % in DM) plus 1 kg /day of a concentrate mixture (10 % rice bran, 10 % groundnut cake, 80 % cassava meal) with DM and crude protein of the mixture of 89.2 % and 7.9 %, respectively, given  in two equal meals at 08.00 hours and 16.00 hours.  Incubations began one hour after the cattle were offered the first feed in the morning. The bags were withdrawn after 6, 12, 24, 48, 72 and 96 hours of incubation. Triplicate bags of each sample were suspended in the rumen and were removed as a group at the same time.

After removal from the rumen, the bags were washed under running cold water until the rinse water was clear. The bags were then dried at 70 °C for 48 hours. Washing losses were estimated by soaking two bags per sample in warm  water (39 °C) for one hour followed by washing and drying. The pattern of the degradation of the feeds was described by fitting the DM loss values to the exponential equation

P = a + b (1 - e ^-ct)……….. (Ørskov and McDonald (1979)

The index value (IV) of each feed was calculated using the formula:

IV  =  A + 0.4*B +  200*c……………. (Ørskov.and Ryle. 1990)

where : A = Washing loss value, B = (a+b) and “a” “b” and “c” are from the exponential equation of Ørskov and McDonald (1979)  

In vitro gas production

The finely ground samples were incubated in vitro with rumen fluid in calibrated glass syringes as described by Khazaal and Ørskov (1994) following the procedures of Menke and Steingass (1988). About 200 ±3 mg dry weight of the sample were weighed in triplicate into calibrated syringes of 100 ml. The syringes were pre-warmed at 40 °C before the injection of 30 ±1 ml rumen fluid-buffer mixture into each syringe, followed by incubation in a water bath at 39 ± 1 °C . The syringes were shaken twice  during the first 2 hours and once at every reading, which was taken 3, 6, 12, 24, 48, 72 and 96 hours after incubation. The gas volume readings (mean of three triplicate runs) were fitted to the exponential equation:

 P = a + b (1-e^-ct) (Ørskov and McDonald 1979).

Chemical analysis

Dry matter (DM) was determined by drying the samples at 100 °C  overnight and ash by igniting the sample in a furnace at 550 °C  for 6 hours. NDF and ADF were determined with an automated analyzer (FIBERTEX SYSTEM)  according to the procedure of Goering and Van Soest (1970).

 
Measurements

Feed offered and refused was recorded daily and liveweight every two weeks.  Rate of liveweight gain was estimated by the linear regression of liveweight on time.

The data were analysed by the General Linear Model option of the  ANOVA software (Minitab Version12.1).

Results

Chemical composition of the roughage 

The rice straw-chicken litter had the highest content of nitrogen, followed by the urea-treated rice straw with the lowest value for the untreated straw (Table 1). There was a similar trend for ash values while NDF and ADF trends were in the opposite direction. 

In sacco DM degradability 

Dry matter losses in the rumen of urea-treated rice straw were always highest, and of untreated straw lowest, at all incubation times. Most of the DM was lost during the first 48 hours. There were no significant differences in washing loss values among  the samples although the value for rice straw- chicken litter tended to be higher than the others (Table 3). The percentage of the insoluble but fermentable fractions (B) and the potential degradability (A+B) were highest in urea-treated rice straw.

In vitro gas production.

The trends in gas production rate had the same tendency as DM degradation in sacco (Tables 4 and 5).

 
Growth rate, feed intake and feed conversion

Intake of dry matter, rate of liveweight gain and dry matter feed conversion were improved significantly as the rice straw – chicken litter was replaced by urea-treated rice straw (Table 6; Figures 1 and 2).  

Figure 1:  Consumption index (kg DM/kg liveweight) for cattle fed different
ratios of chicken litter rice straw (RSCL) and urea-treated rice straw (URS)

Figure 2: Liveweight gain of cattle fed cattle fed different ratios of
 chicken litter rice straw (RSCL) and urea-treated rice straw (URS)

Discussion

An important finding from this study is that the chemical and degradability parameters were no guide to the real nutritive value of  a feed such as chicken litter.  The dry matter degradability parameters (in sacco and in vitro) as derived from the exponential equation (P = a + b (1 - e ^-ct),  did not reflect the nutritive value differences between untreated rice straw and rice straw – chicken litter, since the predicted values for “b” and “c” tended to be less for the chicken litter than for untreated rice straw.  Only the washing loss (13.2% for chicken litter versus 10.2% for untreated straw) was indicative of expected differences in nutritive value. Similarly, the chemical analyses for nutritive value (nitrogen, NDF and ADF), indicated that the chicken litter was better than the urea-treated rice straw, but the animal performance data showed the opposite. The INDEX VALUE, derived from degradation parameters, was also a poor predictor  of animal feed intake since the values for urea-treated straw (IV = 45.4) were not significantly different from those for the chicken litter (IV = 43.9), yet actual roughage intakes were almost 50% higher for the urea-treated straw (3.73 compared with 2.38 kg DM/day). 

Urea-treated rice straw was clearly a better feed than the chicken litter when given as the only roughage source.  However, there was only a small difference between 100% urea-treated rice straw (daily liveweight gain 520 g/day; DM conversion 9.2) and the combination of 70% urea-treated straw and 30% chicken litter (480g/day and 8.7).

Conclusions

Chicken litter with untreated rice straw as a base, when  offered in combination with urea-treated rice straw (30:70 ratio), supported a rate of animal growth and feed conversion only slightly inferior to that with urea-treated rice straw alone.

Chemical and degradability measurements were unreliable indicators of the nutritive value of chicken litter based on rice straw. For such an unconventional feed it is obvious that the only dependable way to assess the nutritive value is in a feeding trial with animals.

References

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Received 14 March 2001

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