Effect of ammonium bicarbonate treatment and rapeseed meal supplementation on growth rate of Huzhou lambs receiving rice straw

J X Liu, Z M Chen, J Q Yu^*, B R Fei*, W D Wang and J F Zhang

Zhejiang Agricultural University, Hangzhou 310029, P R China
^*Tongxiang Animal Production Station, Tongxiang 314501, P R China

Abstract

Seventy-two growing Huzhou lambs were used in a 2 x 4 factorial design to determine the effect of ammoniation (10% ammonium bicarbonate) of rice straw (RS) and rapeseed meal (RSM) supplementation on productive performance. The lambs were given free access to RS or ammoniated RS (ABRS) along with 100 g of rice bran per day per head. The RSM was supplemented at levels of 0, 100, 200 or 300 g/d. Each dietary treatment involved a total of 9 lambs kept in 3 pens. A mineralized salt block and drinking water were freely available at all times. The trial lasted for 60 days, the first 15 days of which were for adaptation. Ammoniation increased the RS intake by about 32%. The dry matter intake of both straws was not affected by RSM supplementation up to 200 g/day but decreased significantly with 300 g/day RSM. Supplementation with RSM increased liveweight gain of sheep offered either RS or ABRS, but the nature of the response differed according the type of straw. In order to obtain a similar daily liveweight gain, larger amounts of RSM were needed for the RS than for ABRS-based diets. This indicates that the benefits of ammoniation of straw are highest when the supplement level is low and least when the supplement level is high. With ammoniated straw, 100 g/day RSM raised liveweight gain from 20 to 63 g/day whereas 200 g/day of RSM had to be supplied to obtain the same liveweight gain with untreated straw.

Key words: Ammoniation, ammonium bicarbonate, rapeseed meal, supplementation, rice straw, intake, daily gain, conversion, Huzhou lambs

Introduction

One of the most effective methods to improve the nutritive value of cereal straws is treatment with ammonia derived from anhydrous ammonia or urea (Chenost and Kayouli 1997). In our region of China, ammonium bicarbonate is the least expensive source of ammonia and is readily available. It has been used effectively as an alternative to urea for the treatment of cereal straws (Liu J X et al 1995).

When cattle are fed only ammoniated straw and minerals the growth rate is low but that there are dramatic increases in performance when sources of bypass nutrients, such as oilseed cakes, are supplied (Zhang Weixian et al 1994; Liu 1995). Our region is abundant in rapeseed meal (RSM) used mainly for swine and poultry. Information is limited on the use of RSM as a protein supplement to ruminants offered a basal diet of rice straw treated with ammonium bicarbonate.

The present study was conducted to determine the effect of supplementing with different levels of RSM on growth rate of Huzhou sheep offered rice straw (RS) or rice straw treated with ammonium bicarbonate (ABRS) as their basal diet.

Materials and Methods

Ammoniated straw was prepared in a ceramic container of 200 litres capacity traditionally used to store water (Image 1). Each container held about 50 kg of straw. One tonne of the chopped RS was treated with 100 kg ammonium bicarbonate and 400 kg water for 30 days at ambient temperature of 15-20ºC. The treated straw was exposed to the air for a minimum of 24 h before feeding to animals to allow free ammonia to escape.

Seventy-two female sheep were used in a 2*4 factorial arrangement of four levels of RSM (0, 100, 200 and 300 g/day) and untreated rice straw (RS) or rice straw treated with ammonium bicarbonate (ABRS). Each sheep was also offered 100 g/day of rice bran and free access to mineralized salt block and drinking water. The initial liveweight of the sheep was about 21 kg with an initial age of approximately 5 months. Animals were randomly allocated to 24 pens with 3 lambs in a pen. Nine sheep from three pens formed a group to receive one of eight dietary treatments.

The feeding trial was conducted in Tongxiang Liuliang Sheep Farm over a period of 60 days (April-June 1997) with the first 15 days for adaptation and the subsequent 45 days for measurements. The mixture of RSM and rice bran was offered in two equal meals daily (0900 and 1600h). Each sheep was weighed for two consecutive days on arrival, and at the beginning and the end of the trial. Weights were also taken on days 15 and 30 of the trial. The straw intake was measured for two consecutive days coinciding with the dates for measuring liveweight.

The results were analyzed as a two-way factorial design and the difference between means was tested using Duncan's new multiple range test.

Results and Discussion

Mean values for feed intake and change in liveweight are in Table 1. Intake of both RS and ABRS was not affected when supplementary RSM was raised from 0 to 200 g/day but decreased significantly when the RSM level was further increased to 300 g/day. On average, ammonia treatment increased the intake of straw DM by 31, 39, 33 and 26% and of total diet DM by 26, 27, 20 and 13% for RSM levels of 0, 100, 200 and 300 g /day, respectively.

Table 1. Feed intake and body weight change of Huzhou sheep fed untreated or ammoniated rice straw and increasing levels of rape seed meal (3 groups of 3 lambs per treatment)
Rice straw	Untreated					Ammoniated
RSM, g/day	0	100	200	300		0	100	200	300
DM intake, g/day
Rape seed meal	0	88	175	263		0	88	175	263
Straw	432	404	406	343		566	562	541	431
Rice bran	88	88	88	88		88	88	88	88
Total	520	580	669	694		653	738	804	782
Weight change, g/day	-19c	15b	69a	67a		20b	63a	74a	77a
Feed conversion, g feed DM/g ADG
Total DM		37.9	9.7	10.4		33.4	11.8	10.9	10.2
Supplement DM		11.5	3.8	5.3		4.5	2.8	3.6	4.6
SEM Weight change ± 11.6; abc Means in rows without letter in common are significantly different

Figure 1. Liveweight change of Huzhou sheep receiving untreated or ammoniated rice straw and supplemented with different levels of rape seed meal

Treatment of RS with ammonium bicarbonate resulted in a significant improvement in body weight change of sheep and in feed conversion rate (both total diet DM and supplement DM per unit liveweight gain). Supplementation with RSM increased liveweight gain of sheep offered either RS or ABRS, but the nature of the response differed according the type of straw (Figure 1) . In order to obtain a similar daily liveweight gain, larger amounts of RSM were needed for the RS than for ABRS-based diets. This indicates that the benefits of ammoniation of straw are highest when the supplement level is low and least when the supplement level is high. A similar result has been reported by Creek et al (1984), who used concentrate mixtures as supplements to cattle offered untreated or ammoniated rice straw.

The optimum level of RSM with ammoniated straw was 100 g/day whereas 200 g/day had to be supplied to obtain the same liveweight gain with untreated straw. At existing prices (Yuan/kg 1.50 for RSM, 0.22 for RS and 0.27 for ABRS), there is a benefit of Yuan 0.08/day for ammoniation, equivalent to Yuan 7.20/sheep for the normal fattening period of 90 days.

Acknowledgements

The present work was financially supported by the Zhejiang Provincial Commission of Science and Technology, P R.China. The authors wish to express their sincere thanks to Mr.Ge Shengfa, Director of Tongxiang Liuliang Sheep Farm for his kind permission to carry out the feeding trial in the Farm, and to the farm staffs for their assistance and care of animals.

References

Chenost M and Kayouli C 1997 Roughage utilization in warm climates. FAO Animal Production and Health Paper Number 135, FAO: Rome pp 226

Creek M J, Barker T J and Hargus W G 1984 The development of a new technology in ancient land. World Animal Review. Number 51:15-20.

Liu J X 1995 Supplementation of low quality crop residues. In: Agricultural Science for Biodiversity and Sustainability in Developing Countries (Editors: F Dolberg and P H Peterson). Jordbrugsforlaget. Copenhagen, Denmark.

Liu J X, Wu Y M and Xu N Y 1995 Effects of ammonia bicarbonate treatment on kinetics of fibre digestion, nutrient digestibility and nitrogen utilization of rice straw by sheep. Animal Feed Science and Technology. Volume 52:131-139

Zhang Weixian, Gu Chuan Xue, Dolberg F and Finlayson P M 1994 Supplementation of ammoniated wheat straw with hulled cottonseed cake. Livestock Research for Rural Development. Volume 6, Number1: 18-26

Received 2 July 1998

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