Chemical composition and in sacco and in vitro fermentation of dried rice straw-chicken litter
and urea-treated rice straw

Tran Quoc Viet, Dao Duc Kien, Le Viet Ly 

National Institute of Animal Husbandry, Hanoi

  

Abstract

Four local cattle of 100-120 kg initial weight were used in a feeding trial according to Latin square design with 4 56-day periods and 4 treatments: RS-CL100:100% rice straw-chicken litter as main fodder ad libitum; RS-CL70: 70% RS-CL + 30% urea-treated rice straw (U-RS); RS-CL30: 30% RS-CL + 70% U-RS; RS-CL0: 100% U-RS.

Before using for urea-treatment and broiler bedding, dried rice straw was chopped to 5-10 cm length. Rice straw was ensiled in big plastic bags with 5 kg of urea dissolved in 35 litres of water for every 100 kg of drice rice straw. Six hundred one day old chickens were raised for 60 days on the ground with initial chopped rice straw layer of 3 cm depth. Every two weeks, chopped dried rice straw was scattered on the old layer as new one. After the feeding period the chicken bedding was collected and dried under sun-light to reach to the moisture content of 14-16%. This form of chicken litter was used as feed for experimental animals and collected as samples for in sacco and in vitro gas production procedures.

 

Nitrogen and ash contents of RS-CL were highest (2.89 and 20.5% vs 0.66, 1.18 and 16.9, 17.2%) in comparison with N-RS and U-RS. But in contrast, NDF and ADF concentrations were lowest in RS-CL (144 and 66.6 mg. g^-1 DM vs 289, 293 and 165, 182). Most in sacco  DM losses of N-RS, U-RS and RS-CL took place in the first 48 hours: DM  loss of N-RS, U-RS and RS-CL after. 48 hr incubation : 47.7, 57.9, 50.8% and after 96 h, 52.4, 62.3, and 53.9. Washing loss values were: 10.2, 12.5 and 13.2% for N-RS, U-RS and RS-CL respectively.  Gas production rates of the three samples showed the same tendency as the in sacco data.

 

Key words : Urea-treated rice straw, chicken litter, DM degradability, gas production. 

 

Introduction

Fodder supply during dry season is a very important factor limiting livestock productivity (Ogle 1989) and this is truly a big problem for animal production in North Vietnam, especially for ruminant production. Being a tropical country with about 80 % of the Vietnamese population engaged in horticulture and/or agriculture, rice is a main crop with approximately 7.4 million ha supplying nearly 32 million tones of  residues annually as a basic roughage resource for ruminants. For very long time, rice straw has been used as a main fodder for cattle and buffaloes in the dry season. Use of urea-treated straw (mainly wheat straw) has been successful in China (Guo Ting Shuang et al 1995), but upgrading of cereal crop residues has yet to have an impact in Vietnam.

 

In recent years, together with rapid development of commercial chicken production in some rural areas in North Vietnam, rice straw has been also utilized as a bedding for broiler and laying hen raising. Traditionally, poultry excreta or litter is applied to farmland as a fertilizer.

 

Poultry excreta and poultry litter have been known as a valuable feed resource for ruminants in many areas of the world (Devendra 1982). The economic value of poultry litter as feed components in balanced diets for several classes of ruminants may be 3 to 10 times greater than their value as plant nutrients (Smith and Wheeler 1979). However, little is known about nutritive value of poultry litter as an important feed for ruminants. Also there are no reports or studies on utilizing poultry litter in Vietnam.

 

This study aimed to evaluate the feeding value of rice straw-chicken litter and urea-treated rice straw using the in sacco and in vitro gas production methods.

 

Materials and methods

Material preparation

Chicken litter preparation

Before using as bedding for raising broiler chicken, dry rice straw was chopped into pieces of 5-10 cm long. Six hundred one-day-old chickens were raised on the floor with depth (3 cm) of chopped dry rice straw as initial layer of litter. The duration of the feeding period was 60 days. Every two weeks, chopped rice straw was scattered on the old layer of chicken bedding with the depth of 2 cm. After the raising period, the chicken litter was collected and dried in the sun until reaching a moisture content of 14-16%. 

Urea treatment of rice straw

Dried and chopped rice straw were ensiled with urea at the level of 5% in thick plastic bags of 1.5 m diameter and 5 m long. Every layer of 100 kg dry rice straw was treated with 5 kg of urea dissolved in 35 litres of water. The duration of the treatment was 21 days.

 

In sacco and in vitro gas production

Sampling

One portion of each of the samples (untreated, urea-treated rice straw and chicken litter) was milled in a hammer mill through a 1.0 mm sieve for analysis and gas production. The rest was ground through a 2.5 mm screen and used for DM degradation in sacco.

Dry matter degradation in sacco

DM degradation was determined by incubating about 5 g of  sample in nylon bags in three rumen fistulated cattle. The cattle were fed a basal diet of ad libitum natural grass (DM 25.6 %, crude protein in DM 10.2 %) plus 1 kg /day of a concentrate mixture (10 % rice bran, 10 % groundnut cake, 80 % cassava meal with DM and crude protein (in DM) of the mixture of 89.2 and 7.9 %, respectively)  in two equal meals at 8 h 00 h and 16 h 00.  All the bags were consistently incubated 1 h after the cattle were offered feed. The bags were withdrawn after 6, 12, 24, 48, 72 and 96 h 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, bags were washed under running cold water until the rinse water was clear. Bags were then dried at 70^oC for 48 h. Washing losses were estimated by soaking two bags per sample in warm  water (39^oC) for 1 h followed by washing and drying As before. The course of degradation of the feed was described by fitting DM loss values to the exponential equation of Ørskov and McDonald (1981):   

 

P = a + b (1 - e ^-ct).

In vitro gas production

The samples were incubated in vitro with rumen fluid in calibrated glass syringes as described by Khazaal et al (1993) and Khazaal and Ørskov (1994) following the procedures of Menke and Steingass (1988). About 200 mg dry weight of the sample were weighed in triplicate into calibrated syringes of 100 ml. The syringes were pre-warmed at 40^oC before the injection of 30 ± 1 ml rumen fluid-buffer mixture into each syringe, followed by incubation in a water bath at 39 ± 1^oC. 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 hr after incubation. The results of the gas volume reading (mean of three triplicate runs) were fitted to the exponential equation of the form :

 

P = a + b (1 - e ^-ct).

 

Chemical analysis

Dry matter (DM) was determined by drying the samples at 105^oC overnight and ash by igniting the sample in a oven at 550^oC for 6 hours. Crude fibre was determined by the automated analyzer (FIBERTEX SYSTEM), neutral detergent fibre was determined according to Goering and Van Soest (1970).

 

Results and discussion

Chemical composition

In this study the nitrogen content of the rice straw  treated with urea was nearly two times higher than in the untreated straw (Table 1). There was little variation in NDF, ADF and lignin content among the samples. The rice straw-chicken litter sample had the highest nitrogen and ash content in comparison with untreated and urea-treated rice straw. The increase in nitrogen in the rice straw-chicken litter can be attributed to the poultry excreta including uric acid as the main nitrogen source (Fuller 1985). The cell wall components (NDF, ADF and ADL) in the rice straw-chicken litter were much less than in rice straw with and without urea-treatment. These results indicate that utilisation of dried rice straw as bedding to raise broiler chicken is a promising means to produce an alternative feed resource high in crude protein for feeding to cattle in the dry season.

 

Table 1: DM, ash, nitrogen, neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin (ADL) concentrations of  the untreated, urea-treated rice straw and rice straw- chicken litter
	Untreated rice straw	Urea-treated rice straw	Rice straw-chicken litter
DM, %	88.2	62.6	86.5
In the dry matter, %
Nitrogen, %	0.66	1.18	2.89
Ash, %	16.9	17.2	20.5
In the dry matter, mg/g
NDF	289	294	144
ADF	165	182	67
ADL	17.8	18.8	9.76

 

 In sacco DM degradability

Dry matter losses in the rumen from the urea-treated rice straw were always higher than from untreated rice straw and rice-straw chicken litter at incubation times from 24  to 96 h. Most of the DM was lost during the first 48 hours of incubation. There were no significant differences in washing loss values between the samples. The percentage of the insoluble but fermentable fractions and the potential degradability were highest in urea-treated rice straw. 

 

 

In vitro gas production

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

 

 

 

Based on the results of chemical composition and in sacco, and in vitro gas production, it appears that the potential benefit from utilizing rice straw-chicken litter derives from the enrichment with nitrogen and ash from the poultry excreta. Rumen degradability and in vitro gas production rates did not differ between untreated and rice-straw-chicken litter samples, indicating that the fermentability of the cell wall fraction had not been increased by use of the straw as litter for broiler chickens.

 

Acknowledgements

This study was partially financed by the SAREC research fund

 

References