Biodegraded rice husks in laying bird's diet: 1. Performance and egg quality parameters

A Z Aderolu, E A Iyayi^*, A A Onilude^** and I Eniola^***

*Department of Animal Science, University of Ibadan
**Department of Botany and Microbiology, University of Ibadan
***Department of Animal Science Ladoke Akintola University Ogbomosho
dezaid@yahoo.com

Abstract

Rice husks were subjected to biodegradation using the fungus Trichoderma viridii, and included in traditional diets for laying hens at rates of 20, 30 and 40%; a diet with 20% undegraded rice husk was used as control.

Biodegradation of rice husk led to improvements in nutritional composition (higher crude protein; less fibre)  than the untreated material. However, there was no difference in feed intake or hen-housed egg production between the diets with undegraded or biodegraded rice husk at the 20% level.  Increasing the level of biodegraded rice husk from 20 to 40% resulted in a linear decrease in egg production.

Keywords: Biodegradation, egg production, egg quality, laying birds, rice husk, Trichoderma viridii

Introduction

Biodegradation, a process defined as the application of biological principles for the purpose of converting foodstuffs into more palatable, nutritious or stable foods (Larry 1995), has potential to improve the nutritive value of fibrous agricultural byproducts. T

Rice husk (RH), an agricultural by-product of rice milling, is available in abundance in Nigeria and presently constitutes a nuisance to the environment (Belewu 1998). Presently, it has no direct nutritional value and in most rice mills it is left to rot or used as fuel. According to Shqueir et al (1989) attempts at feeding it to poultry resulted in poor growth performance as a result of low nutritional quality, high fibre and lignin content.

This study evaluated the biodegradation of rice husks using the fungus Trichoderma viridii, and the inclusion of the biodegraded rice husks in diets for laying hens.

Materials and Methods

Biodegradation of rice husk

The rice husk used in this experiment was purchased from a commercial miller in Ibadan Nigeria. The process of biodegradation, which lasted for 10 days, was carried out according to the method of Aderolu et al (2002) using the fungus Trichoderma viridii. The rice husk (50kg) was autoclaved at 121ºC for 15 minutes after which it was allowed to cool down and then inoculated with 5 plates of the fungi culture (plate size 10cm diameter) and moistened with distilled water at the rate of 300 ml per kg of rice husk. After a period of 10 days, the action of the fungus was stopped by oven drying the substrate at 80 ºC for 24 hours. The dried material was then incorporated into the diets.

Feeding trial with layers

Seventy-two Isa brown laying birds of about 28 weeks of age were randomly selected and assigned to four dietary treatments, with three replicates per treatment and three birds per replicate in a cage with dimensions of 38 by 40cm. The cages were double-decked in an open-sided naturally ventilated house within the University of Ibadan research and training unit.

The treatments consisted of a control diet with 20% undegraded rice husk (URH) and three different levels of biodegraded rice husk (BRH20, BRH30, BRH40 representing 20, 30 and 40%, respectively in the diet). Each of the treatments was assigned to the cages in a completely randomized design. All diets were formulated to meet the NRC (1994) standards. The increasing levels of biodegraded rice husk replaced maize in the diet (Table 1)

Feed and water were supplied ad-libitum. The hens were exposed to 16 hours of light. Performance data included egg production, hen-day production, feed efficiency, feed intake, egg weight, egg length and width, shell weight, thickness and shell surface area. Yolk weight, colour, height and width were measured on a weekly basis over the 16 weeks of the experiment. Mortality was recorded.

Data were analyzed using the general linear model (GLM) procedure of  SAS Institute (SAS 1990). Differences among treatment means were identified using the Duncan multiple range method (SAS 1990).

Results

Biodegradation resulted in an improvement in the proximate composition of the rice husks; the fibre fractions were drastically reduced and the crude protein doubled, compared to the undegraded rice husk (Table 2).

The feed intake of the birds fed diet BRH20 was significantly higher than  for birds on the BRH40 diet but did not differ from the URH and BRH30 diets (Table 3). Hen-day production was lower on the BH40 diet than on diets URH and BRH20. Egg quality traits did not differ among treatments.

Discussion

The increase in crude protein content of the biodegraded rice husk was probably be due to the growth of the mycelia of the fungus used for the biodegradation process. A similar finding was reported  by Belewu (1998) and Aderolu et al (2002). However, despite the apparent increase in nutritive value of the biodegraded rice husk, as indicated by the chemical analysis, this was not  translated into improved egg production, which did not differ between diets having 20% undegraded or biodegraded rice husk  Increasing the level of biodegraded rice husk resulted in a linear decrease in egg production (Figure 1). This was to be expected due to the decreasing energy density of the diets,  as the biodegraded rice husk with 20% crude fibre (Table 1) replaced maize which has only 2% fibre (Göhl 2000).

Figure 1: Hen-housed egg production on diets with 20% undegraded rice husk (URH)
and increasing levels of biodegraded rice husk (BRH)

Conclusion

• Biodegradation of rice husk with the fungus Trichoderma viridii increased the level of crude protein and reduced the fibre fraction.
  
  
• At 20% rice husk in the diet there was no apparent improvement in egg production due to the biodegradation process while, at higher levels of biodegraded rice husk, egg production  was depressed probably because of the increase in the crude fibre content of the diet.

References

Aderolu A Z, Iyayi E A and Ogunbawo S T 2002 Nutritional status of Palm kernel meal inoculated with Trichoderma harzanium. Tropical Journal of Animal Science 5 (2): 103-108

AOAC 1990 Official methods of Analysis. Association of Official Analytical Chemists. Washington, D.C.

Belewu M A 1998 Biodegradation of sorghum stover by fungi and the feeding of resulting stovers to rat. 3rd Annual Conference of Animal Science Association of Nigeria, Ikeja Lagos pg 17-19.

Göhl 1971  Tropical Feeds (Updated HTML version prepared by A W Speedy and Nick Waltham.  http://www.fao.org/ag/AGA/AGAP/FRG/afris/default.htm

Larry R B 1995 Application of biotechnology to indigenous foods. Food Technology January 1995, 86-90

NRC 1994 Nutrient requirement of Poultry. 9^th edition (Washington,DC, National Academy press).

SAS  1990 Users guides Statistic 1990 education. SAS Institute Statistical Analysis Systems, Cary NC.

Shqueir A A, Brown D L and Klasing K C 1989 Canavanine content and toxicity of Sesbania leaf meal for growing chicks. Animal Feed Science Technology. 25: 137.

Received 3 July 2004, resubmitted 18 July 2004;  Accepted 21 October 2004

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