Stocking rates on light land : Wongan Hills Research Station

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Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 4 Western Australia, Series 4

Volume 7

Number 10 1966 Article 3

1-1-1966

Stocking rates on light land : Wongan Hills Research Station Stocking rates on light land : Wongan Hills Research Station

R J. Lightfoot W. L. McGarry

Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/journal_agriculture4

Part of the Agricultural Economics Commons, Comparative Nutrition Commons, and the Sheep and Goat Science Commons

Recommended Citation Recommended Citation

Lightfoot, R J. and McGarry, W. L. (1966) "Stocking rates on light land : Wongan Hills Research Station,"

Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 7: No. 10, Article 3.

Available at: https://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol7/iss10/3

This article is brought to you for free and open access by the Agriculture at Digital Library. It has been accepted for inclusion in Journal of the Department of Agriculture, Western Australia, Series 4 by an authorized administrator of Digital Library. For more information, please contact [email protected].

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MORE SHEEP PER ACRE

Stocking Rates on Light Land — Wongan Hills Research Station

By R. J. LIGHTFOOT and the late W. L. McGARRY

T H E two most important things that determine the rate of return on invested capital in M e r i n o sheep breeding and grazing are the stocking rate and lambing percentage.

In many of the agricultural areas of Western Australia annual pasture production has increased enormously over the last 20 years or so. This increase is due largely to the use of new, better suited legume varieties, the correction of trace element deficiencies and more effective fertiliser use.

However, stocking rates have not increased proportionately with the increases in pasture production, resulting in waste of paddock feed and an enormous loss in potential income per acre.

This first stocking rate trial at Wongan Hills Research Station was one of the first in a series of experiments which aim to define the "safe upper limit" for stocking rates in various districts. The trial began in April, 1961.

The Experiment

Location and Site

Wongan Hills Research Station is on light sandy undulating country about 90 miles north-east of Perth. It receives an average of 14.7 inches annual rainfall, of which 10.75 inches falls between May and October.

An area of 36 acres of gently sloping country, as uniform as possible in soil type and pasture growth, was selected for the experiment.

This paddock was cleared in 1924 and sown to improved pasture in 1945. It was cropped in 1955 and again in 1958 after which the whole paddock was reseeded to Dwalganup subterranean clover. When the trial commenced in 1961 the paddock was in its third pasture year since cropping.

Applications of superphosphate since clearing total some 1,600 lb. The trial plots were top-dressed at 100 lb. per acre in 1961 and 90 lb. per year from 1962 to 1965.

Stocking Rates

The average stocking rate throughout the Wongan Hills district is 0.7 sheep per acre of pasture. Stocking rates of 0.5, 1.5 and 3.0 sheep per acre were chosen for the trial as representing lower than average, considerably higher than average and radical levels of stocking respectively.

Twelve sheep were run on each plot and paddock size was adjusted to give the required stocking rates.

Sheep

Thirty-six 11-month-old B u n g a r e e Merino wethers were divided at random into three groups each of 12 sheep. Average liveweight (off shears) at the start of the trial was 61 lb.

T H E AUTHORS: R. J . Lightfoot, B.Sc. (Agric)—Adviser, Sheep and Wool Branch, now at the University of Sydney, School of Animal Husbandry, where he holds a Wool Board Scholarship. M r . W . L. McGarry was, at the time of his death, Officer-

in-Charge of the Sheep and Wool Branch.

432

Journal of Agriculture, Vol 7 No 10 1966

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Supplementation

A ration of oaten hay fed at maintenance level was given to any treatment group when it was considered that sheep were likely to starve if a supplement was not given.

Observations

Liveweights were recorded at intervals throughout 1961 and 1962. From November 1962, sheep were weighed each month.

The wethers were shorn annually in April. Greasy fleece weights were recorded and a mid-side sample was drawn from each fleece for further measurements.

Records were kept of the supplementary feed given to each group.

RESULTS Supplementary Feeding

All groups received 1 lb. of oaten hay per head per day, from the inception of the trial on 21/4/61 until 15/6/61, to supplement eaten-out and burnt off paddock

feed.

The paddock carrying 3 sheep per acre was grazed bare by January, 1962, so this group was fed a maintenance ration of oaten hay, amounting to 1.35 lb. per head per day, until green feed was adequate in August.

The 1.5 sheep per acre group also received l i lb. of oaten hay per head per day following shearing in April, until early June. Subsequent experience has shown that this ration was not needed as the sheep weighed 92 lb. off-shears in April and the paddock contained enough feed

T a b l e 1.—Supplementary feeding (lb. oaten hay per head)

Period

Stocking Rate (Sheep/acre)

0.5 1.5 3.0

1st Year—21/4/61- 2/4/62 ....

2nd Year— 3/4/62- 7/4/63 3rd Year— 8/4/63-14/4/64 4th Year—14/4/64-13/4/65

Total

lb.

5

5 lb.

5 91

96 lb.

99 286 173 275 833

Wongan Hills Research Station is on light, sandy soils, four miles north of Wongan Hills. The annual average

rainfall is 14 i n . , of which 1 0 1 in. falls in the growing period.

On good subterranean clover pasture on the Station, 1£ wethers per acre proved t o be a safe and profitable stocking rate.

to carry the sheep through until after the break of the season.

In the following years supplementation of the 3 sheep per acre group began when the paddock bacame bare in summer and was continued until late winter, when pasture growth was sufficient to support the sheep. Table 1 shows the total amounts fed during each year of the experiment.

The 0.5 sheep per acre group maintained reasonable liveweights and did not require supplementation.

Mortality

The incidence of mortality in the three groups is shown in Table 2.

Of the six sheep that died on the 3.0 sheep per acre plot over the duration of the trial, two died partly as a result of malnutrition. These sheep failed to main- tain liveweight during stress periods even though supplements were available. The remaining sheep died as a result of entero- toxaemia, pneumonia and other miscellaneous causes

Table 2 . — N u m b e r o f deaths

Year

Stocking Rate

0.5 1.5 3.0

21/4/61- 3/4/62 4/4/62- 8/4/63 9/4/63-15/4/64 16/4/64-14/4/65 Totals

i

'

1

'

1 2 2(1*)

1*

6

* M a l n u t r i t i o n c o n t r i b u t e d t o death.

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Liveweight Trends

Regular monthly liveweight records were kept after November, 1962.

Table 3 shows liveweights taken on three occasions in the first year of the trial.

Table 3 . — A v e r a g e liveweight (lb. per head)

Date

21/4/61 15/11/61 3/4/62

Stocking Rate (sheep/acre)

0.5

62 125 I I I

1.5

61 I I I

92

3.0

61 95 71

The sheep used in this trial were wether weaners and were placed on the plots in April 1961, aged 11 months. At this time each group weighed 61 to 62 lb.

Had the sheep been ewe weaners they would have shown similar liveweight trends to those shown in the table above and would have been mated over the period December to March at 22 months of age.

Like the wethers in the trial, ewe weaners stocked at 1.5 and 3.0 sheep per acre would have been 14 and 30 lb. lighter respectively than those at only 0.5 sheep per acre. Ewe weight at mating is closely related to fertility, and a difference of

14 lb. in liveweight in maiden ewes at mating could be expected to result in a difference of about 10 per cent, lambs born.

Obviously, it is not wise to stock ewe hoggets at stocking rates as high as those recommended for adult sheep. If their stocking rate is too high, growth to maturity and fertility as maidens will be depressed.

Figure 1 shows liveweights trends in each treatment group over the last 30 months of the trial.

The 1.5 sheep per acre group averaged about 8 lb. lighter than the 0.5 sheep per acre group. It is obvious that throughout the period of the experiment liveweights in both groups were very good.

In contrast, 3.0 sheep per acre proved far too heavy a stocking rate, at least for this particular paddock.

Wool Production

Average greasy wool production over the 4 years of t h e trial on both a per head and per acre basis is shown in Table 4.

Other aspects of wool production t h a t were examined are summarised in Table 5.

Figures represent averages over the period of the trial.

There is an obvious decline in yield and staple length with increasing stocking rate. Both of these factors would be

Table 4 . — W o o l production per head and per acre (4 year average)

Stocking Rate 0 . 5 1.5 3 - 0

Wool Production per

head (lb.) 14.8 Wool Production per

•era (lb.) | 7.4 14.0

21.0

10.4

31.2

"Stratified" regeneration of heavily-stocked four-year-old pasture, where heavy grazing has prevented the spread of clover from the original seeding rows. This section, stocked at 3 sheep per acre, contrasts with the even spread of pasture

(background) stocked at 1.5 sheep per acre

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Table 5.—Aspects of wool quality

Stocking Rate

Greasy fleece wt. (lb.)

Clean scoured fleece wt. (lb.) ....

Per cent, yield

Per cent. wt. skirted fleece to total greasy fleece

Staple length (in.)

0.5 14.8 10.2 69.3 71

3.9 1.5 14.0

9.4 67.4 75

3.8 3.0

10.

6.

65.

74 3.

expected to reduce the value of the fleece on a greasy basis. The decline in yield appears to be associated with higher levels of sand and dust contamination in the fleece as stocking rate increases.

Economic Analysis

Although wool production per head fell slightly, there were large increases in wool

production per acre as the stocking rate was increased. Obviously many costs (on a per acre basis) are increased as the stocking rate rises and so the farmer must make a decision as to when increases in wool production are profitable and when they are not. The answer will depend on the balance between costs and returns.

Table 6 uses the results from the year 1964-65 to illustrate the method of calcula- tion in arriving at an estimate of net return per acre at the three different stocking rates. The budget assumes that all wool is sold at 48c per lb., that the annual mortality rate is 5 per cent, at each stocking rate and that the wethers were mulesed in the first year of the trial and did not require additional treatment other than shearing and crutching thereafter.

160

150

no

1 30-

120

no

100

90

80-

70

Shear ing

0.5 sheep/acre 1 .5 sheep/acre 3.0 sheep/acre

• • > > • i • • — • — > » t i » i i i ' i i i t — •

N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J

'362_4*.

1963

+^

¹⁹⁶⁴ ^{^ K -} ^{196 5}

Fig. 1.—Liveweight trends at the three stocking rates 437

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Table 6.—Costs and returns per acre—1964/65

Returns—

Wool (lb.)

Money from wool (at 48c per lb.)

Costs—

Supplementary feed (Hay at

$20 per ton)

Shearing ($40 per 100 sheep) Crutching ($7 per 100 sheep) Dipping, inoculation and

drenching (up to 10c per sheep)

Labour—Miscellaneous (up to 40c per sheep)

Interest on cost at 5% (up to 40c per sheep) Annual depreciation (up to

60c per sheep)

Annual loss (up to 30c per sheep)

Total costs per acre Net return per acre

0.5 sheep/

acre

7.1

$3.41

$0.20

$0.03

$0.05

$0.20

$0.30

$0.15

$1.13

$2.28 1.5 sheep/

acre

20.4

$9.79

$0.60

$0.10

$0.15

$0.60

$0.90

$0.45

$3.40

$6.39 3.0 sheep/

acre

33.9

$16.27

$7.37

$1.20

$0.21

$0.30

$1.20

$1.80

$0.90

$14.18

$2.09

On this basis the average net return per acre for each stocking rate over the four- year period 1961-65 can be calculated as in Table 7.

Although greasy wool production per acre was highest at 3.0 sheep per acre, this stocking rate was by no means the most profitable.

Wool Prices

The average price per lb. received for the fleece wool fell slightly as the stocking rate increased. The grouped 12 fleeces obtained at each shearing on each of the

Table 7.—The effect of increasing stocking rate on net return per acre

Year

1961/62 1962/63 1963/64 1964/65

4 years' average

Stocking Rate 0.5

$2.44

$2.76

$2.22

$2.28

$2.42

1.5 3.0

$5.55

$6.32

$7.40

$6.39

$6.41

$4.77

$0.18

$3.88

$2.09

$2.73

three stocking rate treatments were re- garded as individual clips, fleeces from each "clip" being sorted into the appro- priate bulk class bin types at the stock agent's wool store. Using the average price (greasy) for each of the relevant bin types over the 1963-64 and 1964-65 wool selling season, the average price per lb. for each

"clip" was calculated. The values obtained in this way are shown in Table 8.

Pasture Composition

Generally speaking, as stocking rate increased the proportion of subterranean clover in the sward increased and the proportion of grasses fell.

In no instances in this experiment did

"clover dominance" occur. On the other hand there was an almost complete absence of clover at low stocking rates where capeweed and brome grass, particularly capeweed, have got away earlier at the break of the season, crowding out the developing clover plants. As stocking rates increased the proportion of brome grass in the pasture was reduced, which also reduced the infestation of grass seeds in the fleece.

Some changes in pasture composition became obvious over the four years that the trial was in progress.

At the lowest stocking rate—half a sheep per acre—pasture quality and the propor-

tion of capeweed and brome grass increased at the expense of the clover.

The stocking rate was obviously inade- quate as large areas of pasture were completely deviod of clover and the animals grazed only a relatively small area immediately surrounding their camping ground. In the summer, the paddock had a long, rank, grassy appearance typical of under-stocked pastures.

Table 8.—The effect of stocking rate on price of greasy fleece wool

Stocking Rate

0.5 1.5 3.0

Year 1962/63 1963/64 1964/65

76.9 74.8 74.9

72.6 72.4 72.3

71.9 71.3 70.9

3-year average

73.8 72.8 72.7

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Contrast in pasture available in early winter on plots stocked at 3 sheep per acre (left) and 1.5

per acre

At the highest stocking rate, three sheep per acre, the ground was denuded of all plant cover from February until June each year. Pasture regeneration following the break of the season was extremely slow as the developing plants were kept closely nipped to the ground and the pasture did not produce enough bulk to support grazing animals until August.

Clover, erodium and capeweed were the most common species and grass was virtually absent.

The paddock grazed at one and a half sheep per acre improved over the duration of the trial and at its conclusion was a well-balanced sward with a higher proportion of clover than occurred in the lower stocking rate plots. Capeweed, erodium and grasses were present, although the proportions of brome grass and capeweed were obviously less than those at the lower stocking rate. The pasture regenerated well and maintained plant cover throughout the summer and autumn months.

It is interesting to note that during the third year of the trial sheep on the 1$

per acre paddock maintained higher body weights throughout summer, and cut more wool per head, than those run at the lower

stocking rate of £ sheep per acre. This appears to be a consequence of the better clover pasture developed at the higher stocking rate during the growing season in that year, resulting in a better quality dry summer feed.

Teeth Wear

Observations revealed that there was considerable teeth wear at the higher stocking rates.

The effect seemed to be confined to the two front incisors which, particularly in the sheep run at 3.0 per acre, were fre- quently worn below the level of the adjacent teeth. In such cases the wear had formed a marked bevelling, exposing the dentine layer. These teeth were, however, still quite firmly embedded in the gum.

At the conclusion of the experiment in April, 1965, the measurement from the base of the gum to centre of the top line of both front incisor teeth was recorded for each sheep. Averages for each treatment were:

Stocking rate 0.5 1.5 3.0 Teeth length (mm) 15.8 14.3 12.4 Teeth wear may be an important factor in determining the productive life of a sheep.

439

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Further observations on this aspect are being made on a larger, more compre- hensive stocking rate trial begun in 1963 and is still in progress.

CONCLUSIONS

One and half wethers per acre is a safe and profitable level of stocking on good sub clover pastures in the Wongan Hills district.

Ewe hoggets can not be run well at the same stocking rate as adult sheep; this could reduce their liveweight at mating and their fertility as maidens.

• Some aspects of wool quality—

particularly percentage yield and staple length—are reduced as the stocking rate increases.

• There is no indication that production per head is maintained over even a small increase in stocking rate. Production per head declines and production per head increases as the stocking rate is raised.

The "best stocking rate depends not only on the economics of production but also on the farmer's willingness to accept increased risk as a consequence of increased production per acre.

440

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