Preliminary observations on the effect of work (driving sugar cane press) on intake of pressed sugar cane stalk and urea-treated rice straw by buffaloes and cattle

Nguyen Phuc Tien* and T R Preston

University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City, Vietnam
* Goat and Rabbit Research Centre, Son Tay, Hatay province, Vietnam

Abstract

Six animals (three crossbred Sindhi*Chinese Yellow cows of 249±18 kg and three female buffaloes of 337±20 kg ) were used to study the effect of work (driving a sugarcane press ) on intake of pressed sugarcane stalk (PSC) and urea-treated rice straw (UTS) and on some parameters of metabolic stress. Two buffaloes were lactating and were assessed for effects of diet and work on milk yield. The buffaloes were fed PSC for the first two weeks and UTS the second 2 weeks. The cows received UTS in weeks 1 and 2 and PSC in weeks 3 and 4. The buffaloes worked during weeks 1 and 3; the cows worked in weeks 2 and 4. On the PSC diet a molasses-urea block was also fed. The UTS was not supplemented.

Intakes of dry matter on both PSC and UTS diets, adjusted by covariance for liveweight, were some 50% higher for the buffaloes than for the cows. The heart rate after working was significantly greater for the cows than for the buffaloes but there were no differences in the rate of grinding the sugar cane.

Dry matter intake was higher on the urea-treated straw diet then on the pressed sugar cane stalk. Buffaloes would not eat the molasses-urea block. By contrast, the cows consumed an average of 450 g/day. The heart rate of buffaloes after working was much greater when the diet was urea-treated straw compared with pressed cane stalk. Milk yield of the two lactating buffaloes was higher on the diet of urea-treated rice straw than when PSC was fed.

Key words: Buffaloes, cattle, pressed sugarcane stalk, urea-treated rice straw, feed intake, pulse, respiration rate, milk yield, work.

Introduction

In Vietnam, draught animals play an important role, especially for small-holders. Cattle and buffaloes are the most common domesticated species used for draught work and preferences for one or other of these species vary with the region. In areas where sugar cane is produced as the main crop, the farmers use cattle or buffaloes to drive the crusher to extract the sugar juice. Farmers prefer animal power as it is cheaper than an engine and does not require purchase gasoline or diesel. In addition, farmers can profitably use their available resources such as animals, local feeds and family labour to carry out this traditional work.

It has been suggested by Miah and Sarker (1990 ) that sugar cane crushing demands a much higher energy input from the animal than other farm activities such as ploughing and threshing. Therefore, knowledge of effects of sugar cane crushing on animal physiology as well as their performance may be useful for the smallholder farmer. Pressed sugar cane stalk is the residue after extracting the juice for artisan sugar production at smallholder level. The pressed stalk is usually air-dried and used as the fuel for evaporating the juice. When the juice is used as a replacement for cereal grain to feed livestock (Preston 1995), the residual pressed stalk can be used to replace firewood for cooking or as a feed for ruminants. The freshly pressed stalk contains some 20-25% of sugars (dry matter basis) which makes it a potentially more valuable feed resource than the bagasse produced in industrial sugar manufacture.

It is a common belief of farmers, but not apparently documented scientifically, that fibrous feeds of low nutritive value are eaten more readily, and utilised more efficiently, by buffaloes than by cattle.

The purpose of this experiment was to obtain some preliminary information on the relative responses of buffaloes and cattle when fed pressed sugar cane stalk, as compared with urea-treated rice straw, and subjected to a work load induced by driving a sugar cane crusher.

Materials and methods

Sugar cane crusher:

The vertical crusher had three rolls; two small ones of 80 cm circumference and a large one of 110 cm . The circle round which the animals walked to operate the crusher had a diameter of 7.3 m.

Experimental animals:

Six animals (three crossbred Sindhi*Chinese Yellow cows of 249±18 kg and three female buffaloes of 337±20 kg) were used to study the effect of work (driving a sugarcane press ) on intake of pressed sugarcane stalk (PSC) and urea-treated rice straw (UTS) and on some parameters of metabolic stress. Two of the buffaloes were lactating (3^rd and 5^th week of lactation, respectively). The cows were pregnant (3^rd to 6^th month).

Design and treatments:

The first replicate (one buffalo and one cow) was located at the "Ecological Farm" situated on the campus of the University of Agriculture and Forestry, near Ho Chi Minh City in South Vietnam. The second and third replicates (two buffaloes and two cattle) were located at the Goat and Rabbit Research Centre, in Hatay province in North Vietnam. As sugar cane stalk and rice straw are plant resources of relatively constant composition, unlikely to be affected significantly by latitude and soil, it was expected that responses to these two feeds would be similar in the two ecological zones.

At each site the experimental design was the same (Table 1). Measurements were made during 4 weeks with each animal receiving each of the diets for two successive weeks. Each period was of one week and animals, activities and feeds were alternated in succeeding weeks (Table 1). The work load of driving the sugar cane press was imposed every morning beginning at 07.00 am. For the second and third replicates, one cow and one buffalo were worked consecutively in order to complete the design within 4 weeks.

Table 1: Layout of treatments (replicate 1)
Period	Buffalo	Cow	Buffalo	Cow
1	W	R	PSC	UTS
2	R	W	PSC	UTS
3	W	R	UTS	PSC
4	R	W	UTS	PSC
W Working ; R Resting; UTS urea-treated straw; PSC pressed sugar cane stalk.

Feeding management:

Sugar cane stalks were passed three times through the 3-roll mill, being doubled on the second and third pass as is done traditionally in artisan sugar production. Extraction rate (kg juice from 100 kg stalk) was in the range of 45-50% at both sites. The pressed sugar cane stalk (PSC) was collected immediately after the crushing operation, chopped into lengths of approximately 15 cm and fed at 200% of intake together with a molasses-urea (MUB) block. The block contained (% as fed): urea 10, dry clay 10, cement 5, salt 5, rice bran 30, "A" molasses 40. The urea-treated straw (5 kg urea, 50 litres water, 100 kg rice straw) was fed with minimum refusal (about 16 kg/day for the buffaloes and 12 kg/day for the cows). No other supplements were given.

Measurements:

Dry matter was measured on representative samples of PSC and UTS, both the offered material and the refusals. The intake of nitrogen was estimated using data reported in the literature (Preston 1995; Chenost and Kayouli 1997). The animals were weighed every week when the treatments changed. Respiration and pulse rate were taken before and after working. The time to grind sugar cane (70 kg in replicate 1 and 50 kg in replicates 2 and 3) was measured every day. Milk yield of the buffaloes was determined by weighing the calf before and after suckling which was restricted to two periods of 20 minutes morning and afternoon.

Statistical analysis:

For most traits the data were collected on a daily basis and analysed with the general linear model (GLM) of the Minitab software package (Release 10) for effects of species, diet and activity, correcting the data by covariance for differences in liveweight. The error term was the interaction of days x animals.

Results

The effects of animal species, diet and activity on intake, metabolic stress and sugar cane grinding rate are shown in Tables 2, 3 and 4. The limited number of animals available for the experiments is acknowledged but it is considered that the results are interesting and may be useful as the basis for planning more elaborate work on this topic which is important for many developing countries where cows and buffaloes are the main source of power in agriculture.

Effect of species

Buffaloes consumed more dry matter than cows (P=0.001) and appeared to be less stressed by working as measured by the heart rates after working (Table 2). The greater dry matter intake by the buffaloes compared with cows was observed equally on both diets (49 and 48% greater intake for PSC and UTS, respectively, Table 5). There were no differences between species for effect of work on respiration rate or the observed rate of grinding the sugar cane. Species and physiological state were partially confounded (two of the buffaloes were lactating while the cows were dry and pregnant) which might have affected the voluntary intakes as it is well known that lactation stimulates intake.

Table 2: Mean values for effects of animal species (3 buffaloes and 3 cows), on dry matter intake (DMI), and heart and respiration rate. The data were adjusted by covariance for differences in liveweight.
	Buffaloes	Cows	SE/Probability
DMI, kg/day	3.71	2.50	0.14/0.001
Heart rate, beats/min
Before work	50.1	49.0	1.1/0.51
After work	65.0	73.2	0.69/0.001
Respiration rate, breathes/min			Hp
Before work	26.5	26.1	0.45/0.45
After work	39.0	40.1	0.69/0.3
Grinding rate of sugar cane, kg/min	2.19	2.38	0.086/0.17

Effect of diet

Dry matter intake was higher when the diet was urea-treated straw rather than the pressed cane stalk (P=0.03; Table 3) and the relative increase was similar for cows and buffaloes (Table 5; P=0.73 for the interaction: species x diet). However, for both feeds the rate of refusal was high and the dry matter content of the residue was higher than of the offered material (56±0.9% vs 37±2.0% for PSC and 42±1.0% vs 39.0±1.9% for the UTS). As a result the dry matter intake was low. The buffaloes did not eat the molasses-urea block despite the deficiency of nitrogen in the pressed sugar cane stalk. In contrast, the cows consumed on average 460 g/day of the block which provided 46 g of urea. Nguyen Van Thu (personal communication) also observed that swamp buffaloes in the Mekong Delta would not eat molasses-urea blocks. The problem was overcome by making a soft "cake" rather than a "block" and in some cases mixing the cake with water to form a slurry which was force-fed using a bamboo tube. By contrast, in India milking buffaloes (Murrah breed) readily consumed molasses-urea blocks (Kunju 1986). We have no explanation for this apparent difference in response to molasses-urea blocks between the different strains of water buffalo. The estimated intake of nitrogen was highest for the buffaloes fed the urea-treated straw (80 g N/day), followed by the cows fed the same diet (53 g N/day), then the cows on PSC plus block (34 g N/day) with lowest intake being for buffaloes fed PSC (16 g N/day).

Table 3: Mean values for effects of diet (pressed sugar cane stalk [PSC] or urea-treated rice straw [UTS]) on dry matter intake (DMI), heart and respiration rate and milk yield*. The data were adjusted by covariance for differences in liveweight.
	PSC	UTS	SE/Probability
DMI, kg/day	2.93	3.28	0.11/0.03
Heart rate, beats/min
Before work	49.6	49.4	1.1/0.12
After work	68.7	73.6	0.69/0.001
Respiration rate, breathes/min
Before work	25.6	27.0	0.45/0.45
After work	39.0	40.1	0.69/0.3
Grinding rate of sugar cane, kg/min	2.29	2.27	0.074/0.88
Milk yield*, kg/day	1.45	1.77	0.05/0.001
* Two buffaloes only

Metabolic stress due to work, measured as increase in heart rate, was higher on urea-treated straw than on the pressed cane stalk and the effect was more pronounced in buffaloes than in cattle (Table 5) (interaction: species x diet P=0.01). There were no differences between diets for respiration rate. The rate of grinding sugar cane was not affected by diet (Table 3). Milk yield in the two buffaloes with calves was higher on the urea-treated straw diet than on the pressed sugar cane stalk diet (P=0.001) (Table 3).

Effect of work

Working appeared to have no effect on dry matter intake nor on milk yield (two buffaloes only) (Table 4).

Table 4: Mean values for effects of activity on dry matter intake (DMI) and milk yield*. The data were adjusted by covariance for differences in liveweight.
	Resting	Working	SE/Probability
DMI, kg/day	3.24	2.97	0.11/0.00
Milk yield*, kg/day	1.55	1.66	0.05/0.14
* Two buffaloes only

Table 5: Mean values for effects of diet on feed intake and heart and respiration rate in buffaloes and cows
	Buffaloes		Cows		Probability*
Intake, kg/day	PSC	UTS	PSC	UTS
DMI	3.51	3.91	2.25	2.65	0.73
MUB	0.00		0.462
Nitrogen#	0.016	0.080	0.034	0.053
Heart and respiration rate after work, beats (breathes)/min
Heart rate	65.0	73.2	72.3	74.0	0.001
Respiration rate	38.7	39.4	39.4	40.8	0.71
Grinding rate of sugar cane, kg/min	2.27	2.10	2.31	2.44	0.16
* Probability of interaction (species x feed) # Estimated from literature values of the feeds

Discussion

The cows were more stressed than the buffaloes by the work of grinding cane as shown by the higher heart rate after working. However, this was not reflected in the rate of grinding the sugar cane and therefore the work force exerted (Miah and Sarker 1990).

An interesting finding was the faster heart rate, caused by working, when the diet of the buffaloes was composed of urea-treated rice straw compared with the pressed sugar cane stalk (Table 5). The main difference between the two diets was the much higher content of nitrogen in the urea-treated straw. Both cows and buffaloes had free access to a multi-nutritional block containing 10% urea. The cows were able to regulate their urea consumption on the PSC diet to an estimated 34 g/day. By contrast, on the treated straw diet they were forced to consume almost twice as much (an estimated 53 g/day). The contrast for the buffaloes was even greater since, without exception, they refused to eat any of the urea-containing block thus N intake (from the pressed cane stalk) was estimated at only 16 g/day, while on the treated straw diet they were obliged to consume about 80 g/day. It is therefore possible that the greater metabolic stress of working, suffered by the buffaloes when the diet was urea-treated straw, could have been related to the effect of metabolising and excreting an overload of dietary nitrogen, in a production system (physical work) for which the demand for nitrogen (protein) is minimal. This is an obvious topic for future research.

In contrast with the negative physiological effects of the urea-treated straw for working, there was a significant improvement in milk yield of the buffaloes on this diet compared with the pressed cane stalk. This may have been a direct consequence of insufficiency of dietary nitrogen on the diet of pressed sugar cane stalk, since the buffaloes did not consume any molasses-urea block when the pressed sugar cane was fed, and the nitrogen content of this feed is negligible (less than 0.5% in the dry matter).

Acknowledgements

This work was partially supported by the Feed Resources Group, Animal Production and Health Division, FAO, Rome through a Letter of Agreement.

References

Received 6 December 1997

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