This brief outlines results of some research carried out to show the impact of mineral supplementation for productivity of cattle grazing native pasture in Zimbabwe

1. Phosphate supplementation for beef cattle on range
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By Eddington Gororo
Chinhoyi University of Technology, Zimbabwe
E-mail: gororoeddington@yahoo.com
Extensive areas of phosphorus-deficient soils occur throughout the world, especially in
tropical and subtropical areas (Zimbabwe included), and a deficiency of phosphorus
can be regarded as the most widespread and economically important of all the
mineral disabilities affecting grazing livestock (McDonalds et al, 2010). Phosphorus is
the most significant nutrient in short supply on green summer grazing. Summer
phosphate supplementation of beef cattle offers a simple and relatively cheap means
of increasing returns by a very considerable margin. Research in the sour-veld and
mixed-veld (Agro-ecological Zones I-III) areas of the country has indicated that
phosphorous supplementation in summer can result in increases in weight gains, in
fertility and in calf viability (Gammon, 1993). However, cattle have shown little or no
response to phosphorous supplementation in the sweetveld (mostly natural farming
regions 4 and 5) of the low veld areas of Zimbabwe.
The heavily leached soils of the high and middle veld areas and the resultant forages
are low in phosphorous and have for a long time been held responsible for low
production and reproduction problems in grazing cattle. For instance, in 1929,
Bisschop and DuToit showed that phosphorous (steamed bone meal) supplementation
increased weight gains of oxen by 30%, while supplemented cows weighed 20% more
and produced 30% more calves (van Niekerk, 1978). Following extensive research on
the subject at both Makoholi and Grasslands Research Stations, Ward (1968) and Grant
(1976) reported that phosphorous supplementation of breeding stock increases
summer gains by 18-45kg, calving rate by 4-5% and weaning weight by up to 10%. This
converts to more than a 20% increase in total weaner production per cow per year.
Table 1 below summarises the findings made by Grasslands Research Station when
they supplememnted steers on veld in summer. The experimental group was given a
50/50 mixture of monocalcium phosphate (MCP) and common salt.

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Table 1 Summary of performance of steers given a phosphate supplement in
summer at Grasslands
Parameter Control (No P) Supplemented (P)
Induction mass (6/11/1975) 186.5 184.0
Finishing mass (23/6/1976) 256.0 298.5
Total summer gain (kg) 69.5 114.5
Response to supplementation (extra LW, kg) - 45.0
Live mass into pens 256.0 298.5
Live mass at slaughter 409 441.5
LW Gain in pens 153.5 143.0
Days in pens 111 83
Feed Consumed (kg) Std pen diet 1070.8 878.8
Average Feed intake (kg/day) 9.647 10.587
LWG in pens (kg/day) 1.383 1.723
FCE (kg feed/kg LWG) 6.976 6.145
Carcass mass at slaughter (kg) 220.2 231.5
The supplemented group of steers gained 45kg more weight than the unsupplemented
group and took less time to finish in pens. This would certainly reduce the farmer
feed bill and increase turn over.
Table 2 summarises the results of research on phosphorous supplementation carried
out at Matopos, Makoholi and Grasslands research stations. The trials at Makoholi and
Grasslands were conducted on granite sands while the Matopos trial was done on red
clays. The increased weight gains due to phosphorous supplementation ranged from
14 to 18kg at the lower rainfall sites (Matopos and Makoholi) to 34-45kg at the higher
rainfall site (Grasslands). In the trials the supplement was given free choice (ad lib) in
mixtures containing monocalcium phosphate (MCP) and salt, or other carriers.
Phosphorous intake per head ranged from 2.5g to 4.7g per day at the drier sites, and
from 7.0g to 13.7g per day at the wetter site.

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Table 2 Summary of research on phosphate supplementation carried out in
Zimbabwe
Site Stock
category
Period
(days)
P. Intake
(g/d)
Extra LW
(kg)
Extra LW
value $1.40/kg
P. Cost
($8.00/kg)
Net Value (P)
($/head)
Makoholi Lactating
Cows
210 6 26.2 36.68 10.08 +26.60
Makoholi Yearling
steers
180 2.5 18 25.20 3.60 +21.60
Grasslands Yearling
steers
179 11 44.8 62.72 15.75 +46.97
Grasslands Yearling
steers
210 7 34 47.60 11.76 +35.84
Grasslands Yearling
steers
210 10 38 53.20 16.80 +36.40
Grasslands Yearling
steers
229 7.8 34 47.60 14.29 +33.31
Grasslands Yearling
steers
229 13.7 45 63.00 25.10 +37.90
Matopos Yearling
steers
167 3.4 16.1 22.54 4.54 +18.00
Matopos Yearling
steers
167 4.7 14 19.60 6.28 +13.32
Matopos Yearling
steers
155 3.4 12.1 16.94 4.22 +12.72
*Economic evaluation is based on a standard 15kg, 7% phosphate block, selling at $7.80 each
In the Makoholi cow experiment, conducted over a six-year period, 26.2kg is the
average increase in weaner weight produced per cow per year. This amounted to an
increase of more than 20% per cow per year, made up by 7% increase in calving
percentage, 16% increase in weaning weight and a small reduction in calf mortality.
Products that can be used for phosphorous supplementation include monosodium
phosphate, bone meal, monocalcium phosphate, and dicalcium phosphate, usually in
combination with common salt for intake control. With ruminants, there appears to
be no difference among the above substances as sources of phosphorous and the
choice of supplement should be determined by the cost per kilo of phosphorous.
However, use of steamed bone meal is restricted due to the BSE scare; although its
use is still lawful when the beef product is not intended for export. In the medium
rainfall areas (+/- 600mm) the optimum levels appear to be 2.5-4.0g/day for young
stock and 6.0-9.0g/day for lactating cows. In the higher rainfall areas the optimum
levels are probably in excess of 8g/day for young stock and 10g/day for older
lactating cows.

4. The economics
In spite of such overwhelming research evidence in favour of supplementation, a
surprising number of farmers do not make use of phosphate to increase summer gains,
conception rates and cow productivity. This may be due to a lack of awareness. But in
most other cases it is due to the feeling that the difference between animals doing
well in summer and those doing extremely well is not important. However, gaining
extra weight in summer is as important as reducing weight loss in the drier season
months. Many other farmers do not supplement phosphorous because they think that
it is not profitable. It should therefore be beneficial to analyse the economics of
phosphorous supplementation at present costs. The current cost and returns for
supplementation in each of the experiments has been included in Table 2 above. A
standard summer (7% phosphate) block on the market in Zimbabwe costs about $7.80
(which translates to approximately $8.00/kg P) and the increased live weight gain is
valued at $1.40/kg live mass.
It is then clear that a farmer could greatly increase profit per head by amounts
ranging from $12.00 to over $37.00 through phosphorous supplementation. The lowest
return per dollar invested would be 1:2.5 according to the analysis. At current beef
and phosphate prices, supplementation during the growing season in the sour and
mixed veld areas is highly profitable. The farmer will benefit superior animal
performance on penning and a shorter fattening and production period.
Conclusions
 Supplemental phosphate is most critical during the wet season when animals
are gaining weight rapidly and energy and protein supplies are adequate.
Research has indicated little or no response to phosphate supplementation in
the dry season when grazing cattle are in a negative protein and energy
balance and are losing weight.
 There is little or no response to phosphate supplementation of cattle grazing in
the sweetveld of the lowveld areas of Zimbabwe.
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 Consistently high conception rates in excess of 80%, high summer gains and
minimal winter weight losses can be achieved by supplementing adequate
protein in the dry season and adequate phosphorous in the growing season.
 Phosphorous sources available to the farmer include monocalcium phosphate,
dicalcium phosphate, monosodium phosphate, steamed bone meal and
commercial phosphate products such as licks, blocks and meals.
 Economic return on phosphate mineral supplementation is high.
Reference
Gammon D. M. 1993. Advice on summer phosphate supplementation. The Farmer,
January 14 1993: 9.
Gammon D. M. 1997. Phosphorous supplementation of beef cattle on veld. The Farmer
November 6/13, 1997.
Grant JL 1974/1975. Division of Livestock and Pastures. DR&SS Annual Reports
1974/1975. Department of Research & Specialist Services, Harare.
McDowell L. R., Ellis G. L., and Conrad J. H. 1984. Mineral supplementation for
grazing cattle in tropical regions. World Animal Review 52:2-12

6. 5
 Consistently high conception rates in excess of 80%, high summer gains and
minimal winter weight losses can be achieved by supplementing adequate
protein in the dry season and adequate phosphorous in the growing season.
 Phosphorous sources available to the farmer include monocalcium phosphate,
dicalcium phosphate, monosodium phosphate, steamed bone meal and
commercial phosphate products such as licks, blocks and meals.
 Economic return on phosphate mineral supplementation is high.
Reference
Gammon D. M. 1993. Advice on summer phosphate supplementation. The Farmer,
January 14 1993: 9.
Gammon D. M. 1997. Phosphorous supplementation of beef cattle on veld. The Farmer
November 6/13, 1997.
Grant JL 1974/1975. Division of Livestock and Pastures. DR&SS Annual Reports
1974/1975. Department of Research & Specialist Services, Harare.
McDowell L. R., Ellis G. L., and Conrad J. H. 1984. Mineral supplementation for
grazing cattle in tropical regions. World Animal Review 52:2-12