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Processed and unprocessed sorghum stover in beef finishing rations

T.A. Mohammed, A.E. El-Tayeb, A.F. Mustafa and H.M. Khogali
Department of Animal Nutrition, Institute of
Animal Production, University of Khartoum
P.O. Box 32, Khartoum North, Sudan.


Abstract
Introduction
Materials and methods
Results
Discussion
References

Abstract

Two eight-week feeding trials using entire male cattle were conducted to evaluate the effects of incorporating processed and unprocessed sorghum stover in traditional concentrate diets used for finishing cattle in the Sudan. In the first trial milled sorghum stover was used to replace the concentrate mix at the rate of 0, 25, 35 and 45% (W/W). In the second trial the experimental animals were offered unprocessed sorghum stover ad lib in addition to the concentrate mix which was offered at 100, 75, 65 and 55% of the ad lib level of intake.

The first trial showed that incorporation of milled sorghum stover in the diets had no effect on the performance of the animals.

Animals in all treatments consumed an amount of feed equivalent to 3.0% of their body weight and gained at an average rate of 1.40 kg/d.

The results of the second trial showed that the intake of unprocessed sorghum stover increased as the amount of concentrate offered was decreased. The rate of gain of the experimental animals was not affected by the treatment and was about 1.0 kg/d. However, the efficiency of feed utilisation was higher when the animals were offered the concentrate mix ad lib than when the concentrate mix was limited.

Introduction

The Sudan ranks among the top African countries owning livestock. Statistics indicate that there are about 21 million tropical livestock units (TLU) composed respectively of 15.0, 16.0, 12.0 and 2.3 million head of cattle, sheep, goats and camels. Most of those livestock are kept under extensive management systems and are fed exclusively on rangeland grazing resources.

Livestock commercial offtake rates were low prior to 1973 and have been increasing since. Today it is estimated that 2.61 million TLU are transported annually to feedlots in the major urban centres for finishing before slaughter or export. Approximately 60-70% of the animals finished are cattle.

Cattle are finished on ad lib feeding of concentrate rations composed of equal parts of ground sorghum grain and cottonseed cake for a period of 8 weeks. The availability of the two ingredients and the simplicity of the formulation are the reasons behind the popularity of this feeding regime.
However, recent increased local and export demands for sorghum grain and cottonseed cake elevated prices to levels that limited the expansion of the growing feedlot operations in the country.

Arable farming in the Sudan has grown considerably since independence in 1956, and areas under cultivation today are estimated at 15-20 million feddan producing 7-9 million tons of crop residues, of which 60-70% is sorghum stover. The bulk of the sorghum stover produced is of little use to cultivators and is normally disposed of by means other than feeding to animals.

A research project was initiated in the Sudan by IDRC with the intention of maximising the use of agro-industrial byproducts in livestock feeds. Results of on-farm trials conducted during the earlier phases of the project (Mohammed Salih, 1986) suggested the possibility of incorporating relatively high levels of processed and unprocessed sorghum stover in beef finishing rations.

The objective of the on-station trials reported in this paper was to investigate the effects of partial replacement of the traditional concentrate ration with processed and unprocessed sorghum stover. The trials were designed in response to the reactions of feedlot operators involved in on farm trials during earlier stages of the project.

Materials and methods

Twenty-four feeder bulls, 5-6 years old and of the western Sudan type were used in each of the trials for a finishing period of 8 weeks. The bulls used in each of the trials were stratified according to body weight into 8 groups of 3 bulls each. In each trial the groups were allotted randomly to four treatments (2 groups/treatment).

In trial 1, chopped and milled sorghum stover was incorporated into the traditional basal concentrate mixture at rates of 0, 25, 35 and 45%, and offered ad lib. Ingredients and chemical composition of the diets are shown in Table 1.

Table 1. Ingredient and chemical composition of diets used in trial 1.

Item

Level of milled sorghum stover (%)

0

25

35

45

Ingredient composition (%)

Ground sorghum grain

49.5

37.0

32.0

27.0

Cottonseed cake

49.5

37.0

32.0

27.0

Milled sorghum stover

-

25.0

35.0

45.0

Salt

1.0

1.0

1.0

1.0

Chemical composition (%DM)

DM

95.5

94.4

95.4

95.5

OM

91.2

88.4

88.6

88.3

CP

22.8

18.2

16.8

15.4

ADF

25.0

28.4

32.5

34.1

EE

4.2

3.4

3.1

3.9

Ash

4.3

6.0

6.8

7.2

In trial 2, unprocessed sorghum stover was offered ad lib to all animal groups together with the traditional basal concentrate mixture at 100, 75, 65 and 55% of the ad lib intake. The ad lib intake of the traditional concentrate mixture was adjusted weekly. The unprocessed sorghum stover and the traditional concentrate mixture were offered simultaneously in two adjacent mangers once in the morning and refusals were collected the next morning. Chemical composition of the traditional concentrate mixture and sorghum stover used in trial 2 are presented in Table 2. Feeds were analysed using standard methods (AOAC, 1980).

Intake of the complete diets (trial 1), concentrate mixture and unprocessed stover (trial 2) were recorded daily and animals were weighed weekly. At the end of each week feed conversion ratios were computed.

Table 2. Chemical composition of traditional concentrate mixture ¹ and sorghum stover ² used in trial 2.

Item

Traditional concentrate

Sorghum

mixture

stover

DM

95.5

95.7

CP

22.8

3.5

ADF

25 0


Lignin

6.2

11.5

Price LS/ton

717.8

200.0

1. The traditional concentrate mixture is composed of 49.5% sorghum grain, 49.5% cottonseed cake and 1.0% salt.

2. Cost of milling sorghum was LS 75/ton.

Data were analysed using analysis of variance (Steel and Torrie, 1980). When differences were significant (P<0.05) Duncan's multiple range test was employed to detect differences among treatment means.

Results

Performance parameters of bulls used in trial 1 are presented in Table 3; treatments had no effect on dry-matter intake, rate of body weight gain or food utilisation. Irrespective of the treatment daily feed consumption and rate of body weight gain average 131 g/kg metabolic body weight and 1.4 kg, respectively. Average feed conversion (kg feed/kg gain) was 7.7.

Performance parameters of bulls used in trial 2 are presented in Table 4. They show that treatment significantly (P<0.05) affected dry-matter intake and feed utilisation but had no effects on rate of body weight gain. It was observed that total dry-matter intake progressively increased (P<0.05) as the amount of concentrate offered was decreased. Feed consumption/kg metabolic body weight increased from 117 g for the ad lib and 75% ad lib treatments to 126 g for the 65 and 55% ad lib treatments. The increase in the total dry matter was a result of increased (P<0.05) consumption of unprocessed sorghum stover as the amount of concentrate offered was reduced. The consumption of unprocessed sorghum stover increased from 1.0 kg when concentrate was offered ad lib to 3.5, 5.1 and 6.2 kg when the concentrate was offered at 75, 65 and 55% ad lib respectively. A decrease in concentrate offered by 1 kg is substituted for by consumption of approximately 1.5 kg of unprocessed sorghum stover. The feed conversion ratio was significantly (P<0.05) lower for bulls offered the concentrate ad lib than bulls offered other treatment.

Table 3. Performance of bulls used in trial 1.

Parameter

Level of milled sorghum stover(%)

0

25

35

45


Initial body weight (kg)

364.0

365.0

363.4

365.2

4.7

Final body weight (kg)

443.0

442.3

442.6

445.0

6.2

Finishing period (weeks)

8.0

8.0

8.0

8.0

-

Daily gain (kg)

1.41

1.38

1.41

1.43

0.4

Daily feed intake (kg)

10.44

11.04

10.70

11.38

0.4

Daily feed intake (g/kg0.75)

125.3a

132.5

128.8

136.6

1.7

Feed intake (% body wt)

2.9

3.0

2.9

3.1

0.04

Feed conversion






(kg feed/kg gain)

7.4

8.0

7.6

7.9

0.11

Cost of feed (LS/kg gain)

4.28

4.10

-

5.31

4.86

Values with the same letter script are not significantly different (P>0.05).

Discussion

El Hag and Kurdi (1986) concluded that milled sorghum stover. could be included in beef finishing rations to levels not exceeding 30% (W/W). In this study milled sorghum stover was incorporated in concentrate finishing rations to levels as high as 45% (W/W) without negative effects on basic performance parameters. This is in agreement with Lamming et al (1966) who used milled barley straw as a substitute for maize in beef finishing rations. It was concluded that the traditional system of feeding (concentrate mix ad lib) is wasteful; since the replacement of the concentrate mixture with milled sorghum stover to levels as high as 45% had no effect on feed consumption, rates of body weight gain and feed utilisation.

Under the prevailing conditions in the Sudan the milling of sorghum stover is inconvenient to some users and definitely increases the costs of production. Nevertheless it was thought that the feasibility of using high levels of milled sorghum stover. as a substitute for the concentrate mix in traditional beef finishing rations would be more tempting to feedlot operators.

Table 4. Performance of bulls used in trial 2.

Parameter

Traditional concentrate mixture SE offered (% ad lib)

100

75

65

55


Initial body weight (kg)

313.8

313.2

313.2

313.8

5.1

Final body weight (kg)

375.4

363.6

374.8

375.4

3.0

Finishing period (weeks)

8.0

8.0

8.0

8.0

-

Daily gain (kg)

1.1

0.9

1.1

1.1

0.1

Daily DM intake (kg)

9.5

9.7

10.5

10.5

0.5

Daily sorghum stover intake (kg)

1.0a

3.5b

5.1c

6.2d

0.4

Daily concentrate intake (kg)

8.5

6.2

5.4

4.3

0.3

Substation rate (cone. roughage)

-

1.5

1.6

1.5

-

Feed intake (% body wt)

2.7

2.7

2.9

2.9

-

Daily feed intake (g/kg 0.5)

117.0

119.0

125.0

128.0

-

Feed conversion (kg feed/kg gain)

8.6a

10.8b

9.5c

9.5c

0.3

Cost of feed (LS/kg gain)

5.73

5.73

4.43

3.92-

-

Values with the same letter script are not significantly different (P>0.05).

Studies on the use of unprocessed sorghum stover in beef cattle rations are scarce. Lofgreen et al (1981) demonstrated that calves given concentrate diets consumed significantly less feed than those given limited concentrate and roughage free choice. In this study (trial 2) the feeding of limited amounts of all concentrate diet stimulated bulls to consume more of the unprocessed sorghum stover which resulted in higher total dry matter intake.

Montgomery and Baumgardt (1965) observed that ruminants adjust their voluntary feed intake to their physiological demands for energy. In this study it was noted that bulls consumed more of the unprocessed sorghum stover than the replacement increment from the concentrate.

Average daily gains were the same for all treatment groups used in trial 2. This confirms the earlier conclusion that the systems based on the exclusive feeding of an all-concentrate diet is wasteful. Bulls fed the limited concentrated diets not only gained at similar rates as those offered the concentrate diet ad lib, but had the additional advantage of consuming significantly (P<0.05) greater amounts of unprocessed sorghum stover.

Lister et al (1968) reported that feed per unit gain was significantly (P<0.05) greater for steers fed roughage only compared with those fed roughage plus a high concentrate diet. In trial 2 the feed conversion ratio was significantly (P<0.05) better for bulls fed the concentrate diet ad lib than for those fed limited concentrate amounts together with unprocessed sorghum stover. However, it must be borne in mind that the inexpensive unprocessed sorghum stover represented a significant proportion of the feed consumed in the latter diets. It is apparent that these diets would be adopted more by feedlot operators looking for convenience and reduced production costs.

It was concluded that the traditional system of free choice concentrate feeding is wasteful. Concentrates could be replaced by as much as 45% with milled or unprocessed sorghum stover. without undesirable effects on the performance of finishing bulls.

References

A.O.A.C. (Association of Official Analytical Chemists). 1980. Official methods of analysis. 13th ed. AOAC, Washington, D.C.

El Hag, M.G. and Kurdi, O.I. 1986. Prospects for efficient utilisation of agro-industrial by-products and crop residues for ruminant feeding in the Sudan, with emphasis on quantification, nutritional composition, constraints and research results. In: T.R. Preston and M.Y. Nuwanyakpa (eds), Towards optimal feeding of agricultural by-products to livestock in Africa. Proceedings of a workshop held at the University of Alexandria, Egypt, October 1985. ILCA, Addis Ababa, Ethiopia.

Lamming, G.E.; Swan, H. and Clark, R.T. 1966. Substitution of maize by milled barley straw in beef fattening diets and its effect on performance and carcass quality. Anim. Prod. 2: 303.

Lister, E.E.; Heaney, D.P. and Pigden, W.J. 1968. Performance of Holstein-Friesian steers fed on all-concentrate diet diluted with ground hay. J. Dairy Sci. 51: 1946.

Lofgreen, G.P.; El-Tayeb, A.E. and Kliesling, H.E. 1981. Millet and alfalfa hays alone and in combination with high energy diet for receiving stressed calves. J. Anim. Sci. 52: 959.

Mohammed Salih, G.M. 1986. Effect of sorghum straw feeding on feedlot performance of cattle. M.V.Sc. thesis, University of Khartoum, Sudan.

Montgomery, M.J. and Baumgardt, B.R. 1965. Regulation of feed intake in ruminants. 1. Pelleted rations varying in energy concentration. J. Dairy Sci. 48: 569.

Steel, R.G. and Torrie, J.H. 1980. Principles and procedures of statistics. 2nd ed. McGraw-Hill Book Co., New York.


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