E L S E V I E R Bioresource Technology69 (1999) 129-132

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Digestibility and composition of broiler litter, as affected by gamma irradiation

M.R. A1-Masri*, M. Zarkawi Division of Animal Production, Department of Agriculture, Atomic Energy Commission, P.O. Box 6091, Damascus, Syria

Received 17 September 1998; revised 10 October 1998; accepted 14 October 1998

Abstract

An experiment was carried out to study the effect of six doses of gamma irradiation (0-350 kiloGray, kGy) on in vitro organic matter digestibility (IVOMD), digestible energy, gross energy (GE), total nitrogen (N), crude fibre (CF), neutral-detergent fibre (NDF), acid-detergent fibre (ADF) and acid-detergent lignin (ADL) of wood sawdust broiler litter. The results indicated that gamma irradiation increased the IVOMD and IVDE, except the dose of 50 kGy, and decreased the values of CF, NDF, ADF and ADL significantly (P<0.05). Digestible energy increased by 1030, 1040, 1330 and 1510 kJ/kg DM for 100, 150, 250 and 350 kGy, respectively, compared with the control. The dose of 350 kGy had the highest effect, resulting in reductions of 33% in both CF and ADL, 30% in NDF and 24% in ADF. There was no significant (P > 0.05) effect of irradiation on GE and N. © 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Broiler litter; Irradiation; Digestibility; Cell-walk

1. Introduction

Recycling of the agricultural and animal wastes and their utilization as alternative energy sources for biogas production or animal feeding is important for econom- ical and environmental aspects. In developing countries, broiler litter has been introduced into ruminant diets as protein supplement and energy source. It appears, however, that the nitrogen in the broiler litter could be made more available to ruminants to improve the productive performance and to minimize the requirement for expensive protein feeds (Jakmohla et al., 1988). In addition to the nitrogen, broiler litter can also contain large amounts of wood sawdust rich in lignocellulosic materials but poor in digestible energy. Chemical treatments using urea or ammonia to improve the degradation rate of fibre contents of roughage and of poultry litter (Schneider and Flachowsky, 1990; Sunstol, 1984), or to improve the organic matter digestibility (Lobor et al., 1992), have been utilized. On the other hand, physical treatment using irradiation has been used in order to

*Corresponding author.

sterilize pathogens in the poultry litter (Messer et al., 1971), instead of chemical treatments (Caswell et al., 1975). Irradiation doses of 25-35 kGy are suitable for sterilization of animal diets (Ito and Iizuka, 1979). Gamma irradiation (50-200kGy) has been used to decrease the cell-wall constituents in some agricultural residues rich in lignocellulosic materials (A1-Masri and Zarkawi, 1994a,b; A1-Masri, 1998a).

The objective of this experiment was to study the changes in the digestible energy and total nitrogen of broiler litter as affected by different doses of gamma irradiation. Crude fibre and cell-wall constituents in treated broiler litter were investigated to explain the changes in the digestibility of energy.

2. Methods

Samples containing poplar wood sawdust, beech wood sawdust and a mixture of both were collected from three different broiler farms where birds (8/m 2) were kept for a period of 50 days. Samples from each location were dried separately under natural conditions (temperature: 20-24°C, relative humidity: 40-60%),

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130 M.R. Al-Masri, M. Zarkawi/Bioresource Technology 69 (1999) 129-132

for about one week. After good mixing for each dried sample, three equal amounts from the three collected samples were taken and well-mixed again to obtain one representative sample before the irradiation treat- ments. This step was important to avoid any differ- ences in the chemical compositions among the three collected samples. The nutritive components of the representative broiler litter sample were 150 crude ash, 313 crude protein, 116 crude fibre, 32 crude fat (g/kg dry matter, DM) and 682 STE, starch equivalent/kg DM. The representative sample was divided into six treatment samples and each put in a long glass beaker (volume: 600 ml, length: 15 cm) and irradiated at doses of 0, 50, 100, 150, 250 or 350 kiloGray (kGy) by 137Cs irradiation (Gammator) at a dose rate of 8.17 Gy/min under the same conditions of temperature (about 24°C), and humidity (about 50%). Due to the rotary movement of the sample around the source inside the Gammator, the dose of irradiation was the same in the whole sample. The samples were, thereafter, stored frozen at -20°C in sealed nylon bags for later analyses.

In vitro organic matter digestibility (IVOMD) was determined according to the Tilley and Terry (1963) method in two stages using rumen-fistulated Awassi rams to obtain the rumen liquor. Stage 1: samples were incubated with the rumen liquor and buffer at 38°C for 48 h. Stage 2: samples were incubated with pepsin-HC1 at 38°C for 48 h. The buffer solution was made up generally according to McDougall (1948), but half of the amounts of NaHCO3 and Na2HPO4.12H20 were used to obtain a pH of 6.7 for incubation (Bekendorf, 1993). Rams were given daily feeds containing 93 g digestible protein and 459 STE/kg. The period between the last feeding and rumen liquor collection was 17 h.

The gross energy (GE) was determined by a calori- meter (HC 10, HAAKE, Germany). The in vitro digestible energy (IVDE) was calculated from the obtained energy and the digestibility of organic matter values. Total nitrogen (N) was determined using the AACC (1983) method. Crude fibre (CF) content was estimated according to Naumann and Bassler (1976). Neutral-detergent fibre (NDF), acid-detergent fibre (ADF), and acid-detergent lignin (ADL) were deter- mined using the method of Goering and Van Soest (1970). Each sample was analyzed in triplicate (n = 3). Results were subject to analysis of variance (ANOVA) using the Statview program 4 on a personal computer to test the effect of doses for each nutritive component using Fisher's LSD at the 0.05 level.

3. Results and discussion

The changes in gross energy and in vitro digestible energy in the broiler litter treated with different doses

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17500

15000 : l '-' 12500

"" 10000

75O0

5OO0

25O0

0 OGE

[ ] WDE 0 50 100 150 250 350

Irradiation Dose (kGy)

Fig. 1. Effect of gamma irradiation on gross energy (GE) and in vitro digestible energy (IVDE) in broiler litter.

of gamma irradiation are shown in Fig. 1. The digest- ible energy values (kJ/kg DM) increased by 1030, 1040, 1330 and 1510 for 100, 150, 250 and 350 kGy irradia- tion dose, respectively, compared with the control. These increases in the digestible energy values of broiler litter as a result of irradiation were mainly attri- buted to the changes in the values of organic matter digestibility, since there was no effect on gross energy values, and this agrees with A1-Masri (1998b) using laying-hens excreta irradiated at doses of 10-150 kGy. There was no significant (P > 0.05) effect of irradiation on digestible energy between the control and the 50 kGy dose.

The results indicated that organic matter digestibility increased significantly (P<0.05) compared with the control (Fig. 2). These increases could be explained as a result of decreasing the contents of CF and cell-wall constituents.

There were significant (P<0.05) reductions in CF (Fig. 2), NDF, ADF, and ADL contents in irradiated samples, except the dose at 50 kGy, for CF, ADF and ADL, in comparison with the control (Table 1). The highest reductions in the CF and cell-wall constituents using the dose of 350 kGy were: 33% in both CF and

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80

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~ 80 50

~ 40 30

20

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[] CF 0 50 100 150 250 350 m IVOMD Irradiation Dose (kGy)

Fig. 2. Effect of gamma irradiation on crude fibre (CF) and in vitro organic matter digestibility (IVOMD) in broiler litter.

M.R. AI-Masri, M. Zarkawi/Bioresource Technology 69 (1999) 129-132 131

Table 1 Effect of gamma irradiation on total nitrogen (N) and cell-wall constituents in broiler litter (% dry matter, n = 3)

Dose (kGy) N NDF ADF ADL Cellulose Hemicellulose

0 5.00 + 0.09 34.71 -I- 0.24 15.87 __+ 0.06 4.59 __+ 0.04 11.28 __+ 0.28 18.84 + 0.28 50 5.01 + 0.02 32.53 __+ 0.26 15.61 + 0.09 4.49 +__ 0.07 11.12 + 0.09 16.92 __+ 0.3 l

100 5.02 __+ 0.04 30.32 __+ 0.34 14.90 -t- 0.17 3.84 +__ 0.11 11.06 __+ 0.21 15.42 __+ 0.50 150 4.99 + 0.04 29.21 __+ 0.23 14.68 _____ 0.15 3.63 __+ 0.09 11.05 + 0.06 14.53 __+ 0.14 250 5.02 __+ 0.04 27.83 __+ 0.11 14.47 +__ 0.22 3.47 __+ 0.17 11.00 __+ 0.17 13.36 + 0.33 350 5.06 __+ 0.09 24.34 + 0.15 12.11 __+ 0.03 3.10 __+ 0.07 9.01 +__ 0.08 12.23 __+ 0.14 LSD 0.10 0.42 0.24 0.18 0.23 0.55

NDF, neutral-detergent fibre; ADF, acid-detergent fibre; ADL, acid-detergent lignin. Values are expressed as sample means _+ standard deviation. LSD, least significant difference at the 0.05 level.

ADL, 30% in NDF and 24% in ADF. However, calculated hemicellulose ( = N D F - A D F ) and cellu- lose ( = A D F - A D L ) values in the treated broiler litter decreased by 35% for hemicellulose and 20% for cellulose. Fibre levels may be reduced in direct propor- tion to the level of irradiation due to depolymerization and delignification (Sandev and Karaivanov, 1977). It appears that radiation resulted in random depolymer- ization and decomposition of cellulose (Jerome et al., 1952), and seriously weakened the cellulosic fibre (Gilfillan and Linden, 1955). AI-Masri (1998b) indicated reductions in poultry excreta treated with 100 kGy of gamma irradiation reaching 12%, 5%, 6% and 3% of CF, NDF, ADF, and ADL contents, respec- tively. Regardless of the dose, these differences in the reductions could be attributed to the broiler litter containing wood sawdust which is rich in lignocellulosic materials, as compared with poultry excreta. Gralak et al. (1989) reported that NDF, ADF, and ADL contents in beech sawdust decreased and the digestibility increased in samples treated with 1100 kGy of gamma irradiation.

In the present experiment, there was no significant (P > 0.05) effect of gamma irradiation on total nitrogen (Table 1), and this agrees with Udes et al. (1971) and Ford (1979) using rat diets treated with gamma irradia- tion at doses ranging between 50 and 1000 kGy.

Irradiation treatment has the potential to increase the nutritive value of broiler litter used as feedstuffs for ruminants. For economical and environmental reasons, we would like to recommend that, in the long run, ruminants should be fed as much as possible on agricultural and animal wastes and other feeds which are not in competition with human food.

Acknowledgements

The authors would like to thank the Director General and the Head of the Agricultural Department of the Atomic Energy Commission of Syria for their support.

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