A JASSA study on animal nutrition to achieve better quality beef in the cattle- rearing agricultural sector in Zimbabwe.A study was carried out in July 1996 to assess the potential of sorghum grain (high tannin) in high energy beef finishing diets. The effect of polyethylene glycol (PEG) on the utilization of sorghum grain based diets was also examined. Forty steers were blocked by weight and then randomly allocated to five treatments. One group was assigned to direct slaughter. The remaining groups were offered the following diets containing 33 percent grain: 1.100 percent maize (100M); 2.50 percent maize: 50 percent sorghum (50M:50S); 3.100 percent sorghum (100S);
4. 100 percent sorghum + 3g PEG per day (100S PEG). Dry matter and metabilizable energy (ME) intake were highest with 50M:50S and lowest (P<0.01) with the 100S PEG diet. Steers on the 50M:50S diet had the highest (P<0.05) growth rates and carcass gains. PEG did not improve the utilization of the high tannin sorghum grain

Chihora, R.M.

Hatendi, P.R.

Magadzire, Z.

Ncube, S.

JASSA Journal of Applied Science in Southern Africa

English

IDS OpenDocs

JASSA
Journal of Applied Science in Southern Africa 
The Journal of the University of Zimbabwe
Volume 7 • Number 1 • 2001 ISSN 1019-7788
CONTENTS
Editorial
Utilization of sorghum grain in high energy beef finish diets
S. Ncube, Z. Magadzire, R. M. Chihora and P. R. Hatendi.
Assessment of small holder irrigation perform ance; m anagem ent of 
conveyance  and distribution infrastructure (at Murara and 
N yam atanda, north east Zimbabwe)
K. E. Motsi, J. Zirebwa and L. Machingambi.
A survey of the distribution of and consum er preference for dried 
fruits and vegetables in the Harare-Chitungwiza m etropolis
E. Manzungu and R. Machiridza.
Reproductive perform ance of Tuli beef heifers m ated as yearlings 
and synchronised for oestrus with gonadotrop in  releasing hormone 
and prostaglandin F2p
W. Murwi, C. Chakoma, H. Hamudikuwanda and N. Kusina.
A review of current concepts on sex determ ination in animals
V. Muchenje and Z. Dube.
Dropout rate during prolonged physical stress training in the military 
m ay be determ ined by haem ato log ica l changes
Mudambo K.S.M.T., Zivawose C. J., Mandisodza A.R., Dzuda C., 
Cakana A.Z., Siziya S. Tafirenyika A., Tandayi M. and Zenda E.
JASSA
Journal of Applied Science In Southern Africa 
The Journal of the University of Zimbabwe
Vol. 7 No. 1 • 2001 
ISSN 1019-7788
CONTENTS
Utilization of sorghum grain in high 
energy beef finish d ie ts ...................
Assessment of small holder irrigation 
performance; management of 
conveyance and distribution 
infrastructure (at Murara and 
Nyamatanda north east of 
Zimbabwe)..........................................
A survey of the distribution of and 
consumer preference for dried 
fruits and vegetables in the Harare- 
Chitungwiza metropolis..................
Reproductive performance of Tuli 
beef heifers mated as yearlings 
and synchronised for oestrus with 
gonadotropin releasing hormone 
and prostaglandin F2p....................
S. Ncube, Z. Magadzire, R. M. Chihora 
and P.R. Hatendi............................. 1
r - -  -
i
i
I > / 1
K. E. Motsi, J. Zirebwaafra ej ' /
L. Machingambi ....l-nl l ....... .S:........9 I
\i\ ^ *
/  v /
/ >''
ft , °
E. Manzungu and R^  Mafchiridza........23
W. Murwi, C. Chakoma, H. 
Hamudikuwanda and N. Kusina.... 41
A review of current concepts on sex 
determination in animals...............
Dropout rate during prolonged 
physical stress training in the 
military may be determined by 
haematological changes.
V. Muchenje and Z. Dube................... 53
K. S. M. T. Mudambo, C.J. Zivawose, 
A.R. Mandisodza, C. Dzuda,
A.Z. Cakana, S. Siziya, A. Tafirenyika, 
M.Tandayi and E. Zenda..............61
© University of Zimbabwe 2001
Published by University of Zimbabwe Publications 
P.O. Box MP203, Mount Pleasant, Harare, Zimbabwe
Typeset by University of Zimbabwe Publications 
Printed by MG Printers
Journal of Applied Science in Southern Africa •  Vol. 7 No. 1 • 2001
Utilization of sorghum grain in high 
energy beef finishing diets
S. Ncube1, Z. Magadzire1, R. M. Chihora2 and P. R. Hatendi3
1Matopos Research Station, P B K 5137, Bulawayo, Zimbabwe.
2 National Foods Pvt. Ltd, P. O. Box 648, Bulawayo, Zimbabwe.
3 Cattle Producers Association, P. O. Box WGT 390, Westgate, Harare, Zimbabwe.
A study was carried out in July 1996 to assess the potential of sorghum 
grain (high tannin) in high energy beef finishing diets. The effect of 
polyethylene glycol (PEG) on the utilization of sorghum grain based 
diets was also examined. Forty steers were blocked by weight and then 
randomly allocated to five treatments. One group was assigned to direct 
slaughter. The remaining groups were offered the following diets 
containing 33 percent grain: 1.100 percent maize (100M); 2.50 percent 
maize: 50 percent sorghum (50M:50S); 3.100 percent sorghum (100S);
4. 100 percent sorghum + 3g PEG per day (100S PEG). Dry matter and 
metabilizable energy (ME) intake were highest with 50M:50S and lowest 
(P<0.01) with the 100S PEG diet. Steers on the 50M:50S diet had the 
highest (P<0.05) growth rates and carcass gains. PEG did not improve 
the utilization of the high tannin sorghum grain.
Keywords: cattle, sorghum grain, finishing diets, polyethylene glycol, tannin
Introduction
In Zimbabwe the standard high energy diet for fattening cattle is based on maize. 
Maize is becoming more expensive and is sometimes unavailable for stockfeeds. 
With the increase in human population, the competition between humans and 
livestock for maize will increase. Although sorghum grain is also a source of 
energy, it has not been routinely used because it has been considered less valuable 
than maize grain because of its highly variable chemical composition and feeding 
value. The lower feeding value of sorghum grain has been attributed to 
environmental and varietal differences (Hulse eta/.,1980).
Sorghum grain contains some antinutritional factors (secondary compounds). 
The presence of secondary compounds (mainly tannins) limits the feeding value of 
sorghum grain (Maxson et a/., 1973; Butler, 1989). In addition to effects on feeding 
value sorghum tannins exhibit toxic effects which require absorption from the 
digestive tract (Butler, 1989). Despite these limitations sorghum grain offers a 
substitute for maize in high energy diets for cattle in the drought prone areas of the 
country as it is more drought tolerant than maize. Sorghum can replace maize, on
p1-8
2 JASSA • Vol. 7 No. 1 • 2001
average, with an efficiency of feed utilization of 89 percent (Topps and Oliver, 
1993). Polyethylene glycol (PEG) has been shown to preferentially bind with 
tannins (Barry and Duncan, 1984) resulting in better utilization of nutrients, 
especially protein (Jones and Mangan, 1977). The objective of this study was to assess 
the potential of sorghum grain in high energy finishing diets. The effect of polyethylene 
glycol (PEG) on the utilization of sorghum based diets was also examined.
Materials and Methods
Animals and treatments
Forty steers (28 Hereford*Simmental and 12 Brahman’Simmental crosses) were, on 
arrival, dosed against endoparasites with 70 ml of a 2.5 percent Levamisole and 3.4 
percent Oxyclozanide solution (TRAMIZAM). Their initial average live-weight 
was 304kg (range 286 to 325). The steers were blocked by weight and breed then 
randomly allocated to five treatments. One group was assigned to direct slaughter. 
The remaining groups were offered the following diets containing 33 percent grain:
1. 100 percent maize (100M).
2. 50 percent maize:50 percent sorghum (50M:50S).
3. 100 percent sorghum (100S).
4. 100 percent sorghum + 3g PEG per day (100S PEG).
The composition of the diets is given in Table 1.
Table 1: Diet composition (g/kg), chemical composition (g/kgDM) and 
metabolizable energy (ME MJ/kgDM) of diets containing 100 percent Maize 
(100M), 50 percent Maize:50 percent Sorghum (50M:50S) and 100 percent 
Sorghum (100S).
100M 50M : 50S 100S
Cotton seed meal 71 70 70
Roughage component 70 70 70
Whole cotton 100 100 100
Maize 33T 166 —
Sorghum — 166 332
Wheat bran 300 300 300
Salt 3 3 3
Molasses 100 100 100
Limestone flour 27 27 27
Vitamins and minerals 1 1 1
Dry matter 927 929 929
Crude protein 140 142 145
Crude fibre 106 105 105
Fat 55 52 48
Ash 75 75 76
Tannin-Van-HCl (CE) 2 6 12
ME 12.1 11.9 11.8
JASSA • Vol. 7 No. 1 • 2001 3
Feeding and housing
The steers were individually penned. During the first two weeks of the experiment 
steers were offered eight kg (as fed) of the appropriate treatment diets only. After 
this initial period, the diets were fed ad libitum twice per day at 0800 and 1400 hours 
for 97 days. The amount of feed offered was adjusted to allow about 20 percent 
refusals. Refusals were collected daily prior to morning feed, weighed and sub 
sampled and stored to await analysis. Water was available at all times.
Chemical analysis
Feed was analysed for dry matter (DM), crude protein (CP), crude fibre (CF) and 
ash (Association of Official Analytical Chemists, 1975). Tannins were estimated by 
the vanillin-HCl method (Burns, 1971; Broadhurst and Jones, 1978). Metabolizable 
energy (ME) of the feed was estimated according to equation 73 (Ministry of 
Agriculture Fisheries and Foods, 1984);
ME (MJ/kgDM) = 12 + 0.008CP + 0.023EE - 0.018CF - 0.012ASH
Statistical analysis
Analysis of variance was carried out using the SYSTAT Statistical package 
(Wilkinson, 1987). Differences among treatment means were tested for significance 
using Student’s t test. A polynomial regression, with week as a dependant variable, 
was fitted for each animal using SAS (SAS/STAT, 1987). A polynomial of order one 
was significant (P<0.001) for all animals. The gradient (b-value) which is the rate of 
weight gain was therefore, used in Least-squares analysis of variance using the 
General Linear Model (GLM) procedure of Statistical Analysis System (SAS) (SAS/ 
STAT, 1987) and fitting a fixed model in which the effects were diet, breed, and 
initial weight. Rate of weight gain was fitted as an independent variable in the 
univariate analysis.
Results
One animal died from bloat in the PEG diet. Two other animals, one from the 100 
percent maize diet and the other from the 50M:50S diet were removed from the 
experiment because they did not adapt to the treatments. The rest of the animals 
maintained good health throughout the experimental period.
Feedlot performance
The CP contents of the diets were as predicted and were similar for all treatment 
diets. The sorghum based diet contained the most tannins. The energy values were 
slightly lower for sorghum than for maize-based diets (Table 1).
Intake and growth performance of steers is shown in T able 2. Dry matter and ME 
intake were highest with the 50M:50S diet and lowest (P<0.01) with the 100S PEG 
diet. The maize and sorghum-based diets had similar intakes. Steers on the 50M:50S 
diet had the highest growth rates and the sorghum plus PEG diet the lowest
4 JASSA • Vol. 7 No. 1*2001
(P<0.05). Although there were no significant differences between treatments (P>0.05), 
feed conversion ratio was better with the 50M:50S diet and least with sorghum- 
based diets.
Table 2: Feedlot performance of steers fed sorghum based diets containing 
100 percent Maize (100M), 50 percent Maize:50 percent Sorghum (50M:50S), 
100 percent Sorghum (100S) or 100 percent Sorghum + PEG (100S PEG).
100M 50M : 50S 100S 100S PEG Sed
Number of animals 7 7 7 8
Daily feed intake
Dry matter (kg) 9.7ab 10.7b 10.0ab 8.6a 0.71
ME (MJ) 117ab 127b 118ab 101a 8.4
Liveweight changes
Initial (kg) 305 304 302 305 5.90
Final (kg) 436ab 456b 430ab 422a 14.7
Daily gain (kg) 1.33a 1.56b 1.32a 1.18a 0.148
Feed conversion ratio
KgDM/kg gain 7.3 6.8 7.8 7.8 0.68
ME MJ/kg gain 88.0 80.9 91.2 91.6 7.99
abMeans in the same row with different superscripts are significantly different (P < 0.05). 
Carcass traits
Carcass traits of the steers are shown on Table 3. Daily carcass gains were highest 
with the 50M:50S diet and lowest (P<0.01) with the 100S PEG diet. Dressing 
proportions were similar for all treatments. Carcass fleshing grades were lower 
(P<0.01) for steers offered 100S PEG compared to the other treatments.
Table 3: Carcass characteristics of steers fed sorghum based diets containing 
100 percent Maize (100M), 50 percent Maize:50 percent Sorghum (50M:50S), 
100 percent Sorghum (100S) or 100 percent Sorghum + PEG (100S PEG).
100M 50M:50S 100S 100S + PEG Sed
Carcass weight changes
Initial (kg) 164 164 164 164 5.90
Final (kg) 246ab 254b 243ab 233a 7.8
Daily gain (kg) 0.84ab 0.93ab 0.82ab 0.71a 0.165
Dressing proportion (g/kg) 586 580 580 572 9.4
Dressing proportion (g/kg) •586 580 580 572 9.4
Fleshing grade 2.86ab 2.14a 2.75ab 3.14b 0.532
Back fat (mm) 9.14 7.71 10.0 7.00 1.829
abMeans in the same row with different superscripts are significantly different (P<0.05).
JASSA • Vol. 7 No. 1-2001 5
Fleshing grade was coded; A+ = 1, A- = 2, B+ = 3,---------E+ = 9, E- = 10, where 1 = very well
fleshed and 10 very poorly fleshed (Cattle Producers Association, 1991).
Discussion
The sorghum used in this experiment was brown in colour and high in tannins (61.6 
g/kg DM). In sorghums, a significant correlation between seed colour and tannin 
content has been observed (McMillian et al., 1972; Harris et al, 1970). Brown 
sorghums tend to have a higher tannin content than white or red sorghums (Arora 
and Luthra, 1974). Amira (1992) recommends a maximum of 30 percent of brown 
sorghum inclusion and no upper limit or restriction for white sorghums in pen 
finishing diets. The grain inclusion in this experiment, at 33 percent, was in the 
range reported by Amira (1992).
The results (Table 2) are similar to the work by Smith et al., (1992) who 
substituted maize with sorghum at the rate of 0, 25, 50, 75, 100 percent in pen 
finishing diets for steers at a grain inclusion rate of 70 percent. The 50:50 maize to 
sorghum diets gave the best animal performance. On the other hand, these results 
differ with those of Loyacano et al (1973) who observed that the level of sorghum 
in the ration had a significant effect on average daily gains and feed conversion ratio 
both worsening as the level of sorghum in the ration increased. The rates of gain are 
comparable with those found by other workers in pen finishing trials. Meissner 
(1995) found an average daily gain of 1.5 kg per day in feedlot (range 0.9 to 2.1 kg). 
The best diet in this trial, 50M:50S, had a rate similar to the average and the others 
fell within the range.
The relatively poor performance on the PEG-containing diet is consistent with 
earlier report (Smith et al, 1992). In other experiments PEG has been shown to 
improve intake and digestibility of high tannin feeds (Barry and Forss, 1983; Jones 
and Mangan, 1977). The amount of PEG given in these experiments is usually 1.5 
parts per part condensed tannins (weight:weight) (Waghorn, 1990). The PEG 
offered in this experiment was below (3g/day vs 149.6g/day) the recommended 
level (Waghorn, 1990). In this experiment PEG might have destroyed the positive 
effects of tannins in protecting protein from deamination in the rumen. Barry and 
Manley (1986) observed increased nitrogen retention in sheep fed high tannin than 
low tannin Lotus pedunculatus. This was attributed to an increased supply of amino 
acids to the small intestines as a result of protection of protein from proteolysis in 
the rumen.
The results of this work indicate that high tannin sorghums are useful as a 
source of energy in pen fattening diets without adversely affecting animal 
performance. The potential of the mixed diets (maize with sorghum) in pen 
finishing rations needs further investigation.
ACKNOWLEDGEMENTS
We thank National Foods Pvt (Ltd) and the Cattle Producers Association for 
funding the project.
6 JASSA • Vol. 7 No. 1-2001
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Utilization of sorghum grain in high energy beef finish diets

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