Grazing Intensity Research On Coteau Rangelands


Livestock Response

Table 3 shows the average daily gains and gains/acre of cattle on the trial each year from 1989 to 1999. The average body condition scores for each treatment from 1994 to 1999 are also shown on table 3. This is a visual ranking of the amount of fat on an animal's body with 10 being extremely fat and 1 being extremely thin. This ranking was made because of concern that the animals on the extreme grazing treatment were coming off in poor condition. Figure 2 shows the relationship between stocking rate and average daily gain, figure 3 shows the relationship between stocking rate and gain per acre and figure 4 shows the relationship between stocking rate and economic return for 1991 to 1999. Reference lines indicate the average stocking rate of each of the four grazing treatments in the study. The figures for economic return do not include the costs for land, labor or management which vary widely from one operation to another. The years 1989 and 1990 are not included in these graphs because none of the pastures were stocked heavily enough to significantly reduce average daily gains. As the grazing intensity increased, average daily gain decreased. Gains per acre increase until they reach a certain level and then begin to decline, and profit per acre shows the same pattern. As is apparent from figure 2, the relationship between stocking rate and average daily gain differs significantly between years (p<0.0005). These differences may be due to variations in forage quality, the effect of weather on the animals, class of animal, their initial weight, or their potential to gain. Table 4 A shows the stocking rate which would have resulted in the maximum gain per acre in each year. We can't predict what stocking will result in the maximum gain in the future so its impossible to stock each year for the maximum gain in that year. In retrospect if we were to pick one constant stocking rate for the past nine years which would have provided the greatest gain per acre for this period it would have been 2.449 AUMs/acre. This is the point labeled as "optimum" in figure 3.

Table 3. Average daily gains and gains per acre from different stocking intensities 1989-1999.

  Average Daily Gains (lbs/head/day)
Desired
Grazing
Intensity
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
Light

Moderate

Heavy

Extreme

LSD(0.05)

2.18

2.35

2.03

2.00

NS2

1.01

1.23

1.17

1.05

NS

1.42a1

1.13ab

0.91b

0.69b

0.48

2.04a

1.89a

1.70a

1.20b

0.44

1.56a

1.56a

1.68a

1.06b

0.40

1.10a

0.90ab

0.74b

0.20c

0.26

1.05a

0.94a

0.86a

0.55b

0.29

1.07a

0.93a

0.81ab

0.44b

0.39

1.63a

1.46a

1.20ab

0.83b

0.45

1.53a

1.31ab

1.03b

0.60c

0.38

1.40a

1.30a

1.19ab

0.96b

0.25

  Average Gain (lbs/acre)


1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
Light

Moderate

Heavy

Extreme

LSD(0.05)

16.84c

33.27bc

41.28ab

61.00a

22.35

13.69c

27.63b

36.47b

52.87a

9.95

16.86b

43.10a

58.83a

61.90a

20.35

18.60d

54.33c

105.58b

129.22a

22.49

13.82c

45.34c

119.31b

166.77a

44.42

20.10b

38.70ab

57.23a

26.64ab

30.75

12.78c

42.37b

70.45a

77.04a

24.30

14.14c

30.10bc

53.25a

45.38ab

22.79

30.27c

66.05b

110.13a

71.10b

27.85

28.29c

62.25b

97.86a

67.98b

29.59

36.50b

59.73b

93.93a

108.49a

24.31

  Condition Score


1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
Light

Moderate

Heavy

Extreme

LSD(0.05)

          5.19a

4.84ab

4.80ab

4.21b

0.64

5.08

5.13

5.16

4.74

NS

5.19a

5.11a

4.91ab

4.37b

0.58

5.35

5.24

4.93

-- 3

NS

5.81a

5.71ab

5.21b

4.65c

0.53

5.72a

5.65ab

5.54bc

5.41c

0.18

1Means in the same column followed by the same letter are not significantly different at p=0.05.
2Means not significantly different.
3Not available





 


Table 4 B shows what the gain/acre would have been in each year if we had stocked at this rate. Table 4 C shows what the gain per acre would have been if we had stocked at a moderate stocking rate. It is important to note that the pastures which are stocked at the heavy and extreme rates were in good condition at the beginning of the study and that their condition has slowly deteriorated over the course of the study. As these pastures have deteriorated we have seen the "optimum" stocking rate gradually decline and we expect that we will see it decline further as the study continues.

If cattle prices were constant, return per acre would peak at a stocking rate somewhere below maximum gain per acre with the exact point depending on carrying costs (interest, death loss, salt and mineral, vet cost, transportation, labor and land). However, fluctuating cattle prices make determining an optimum stocking rate difficult. For example, in May 1991 we stocked our pastures with bred heifers weighing an average of 800 lbs. An 800 lb heifer was valued at $702.26. Our carrying cost for the season for this animal was $35.29, so if we had sold her in September when the cattle were removed from the trial we would have had to get $737.55 to break even. To get this price, assuming a 5% shrink, she would have had to come off the pasture weighing 941 lbs which would be an average daily gain of 1.18 lbs/day. Average daily gains were not very good in 1991 therefore reducing economic returns. In May 1992, we stocked our pastures with bred heifers averaging 750 lbs. Heifers of this weight were valued at $560.33 in May and at $620.33 in August at the end of the grazing season. Carrying costs for this animal in 1992 were approximately $19.77 which would have returned $40.13 even without a gain in weight. This difference in beginning and ending value of the animals made it possible for the stocking rate with maximum return/acre to exceed the stocking rate with maximum gain/acre in 1992.

Table 4. Comparison of gain per acre from selected stocking rates.
  A

B

C
  Stocking rate that would result in the maximum gain/acre in each year. Stocking rate that if held constant would result in the maximum gain/acre over the nine-year period. Gain/acre over the nine-year period if stocking rate were held constant at 0.97 aums/acre, the average of the moderate treatment over this period.
Year aums/acre gain/acre aums/acre gain/acre aums/acre gain/acre
1991

1992

1993

1994

1995

1996

1997

1998

1999

2.258

2.681

3.406

2.268

3.076

2.036

1.919

2.082

3,179

62.526

134.753

175.776

58.117

84.690

56.957

92.431

91.219

111.371

2.449

2.449

2.449

2.449

2.449

2.449

2.449

2.449

2.449

62.070

133.718

160.343

57.740

80.989

54.311

84.289

87.905

104.992

0.974

0.974

0.974

0.974

0.974

0.974

0.974

0.974

0.974

41.842

78.665

76.214

38.704

43.149

39.403

66.486

61.021

52.609

9yr. ave. 2.545 96.427 2.449 91.810 0.974 55.344

Table 5 A gives the stocking rates with the maximum predicted return per acre for each year from 1991 to 1999. These values correspond to the peaks of the curves in figure 4. Just as we can't predict what stocking will result in maximum gain per acre we can't predict what stocking rate will provide the greatest economic return in any future year. With cattle prices of the last nine years, and the gains that we achieved on these pastures, the one constant stocking rate which would have given us the greatest economic return over the last nine years was 1.844 AUMs/acre. This is the point labeled optimum in figure 4. Table 5 B shows what the return/acre would have been if we had stocked at this rate. Table 5 C shows what the return would have been if we had stocked at a moderate rate. Although the average return per acre is higher under the optimum rate there were three years with negative returns while all years had positive returns under the moderate stocking rate. (Cost for land, labor and management have not been subtracted).

Table 5. Comparison of return to land, labor and management from selected stocking rates.
  A

B

C
  Stocking rate that would result in the maximum return/acre to land, labor and management in each year. Stocking rate that if held constant would result in the maximum return to land, labor and management over the nine-year period. Returns/acre to land, labor and management over the nine-year period if stocking rate were held constant at 0.97 aums/acre, the average of the moderate treatment over this period.
Year aums
/acre
returns
/acre
gain
/acre
aums
/acre
returns
/acre
gain
/acre
aums
/acre
returns
/acre
gain
/acre

1991

1992

1993

1994

1995

1996

1997

1998

1999

9 yr. ave.

0.882

3.125

2.387

0.669

1.439

2.060

1.113

1.012

3.240

1.769

$4.10

$97.11

$105.10

$1.99

$2.05

$31.83

$13.35

$2.11

$56.58

$34.91

38.764

130.956

158.275

28.489

59.491

56.948

73.542

63.066

111.327

80.095

1.844

1.844

1.844

1.844

1.844

1.844

1.844

1.844

1.844

1.844

-$2.76

$80.20

$99.53

-$5.86

$0.94

$31.44

$ 6.91

-$ 4.81

$44.92

$27.83

60.379

121.290

134.723

56.036

70.429

56.384

92.269

89.834

89.843

85.687

0.974

0.974

0.974

0.974

0.974

0.974

0.974

0.974

0.974

0.974

$ 4.04

$49.40

$67.25

$ 1.46

$ 0.60

$21.90

$13.12

$ 2.09

$25.84

$20.63

41.842

78.665

76.214

38.704

43.149

39.403

66.486

61.021

52.609

55.344

Comparing tables 4 and 5 it can be seen that in all but three years, 1992, 1996, and 1999 the stocking rate with the greatest economic return was less than the rate with the greatest gain per acre. Again it must be stressed that the pastures stocked at the heavy and extreme rates were in good condition at the beginning of the study. As these pastures have deteriorated in condition the "optimum" stocking rate has gradually declined. As the study continues we expect that we will see further reductions in livestock gains on these heavily grazed pastures as they continue to deteriorate, which should have the effect of lowering stocking rate with the "optimum" return.

This trial is continuing and these relationships need more study before we can recommend the stocking rate which will give the greatest return in the long run. Stocking at the rate which produced the greatest economic return in 1999 would damage the pasture and, if prices are low, it could result in substantial financial losses. The returns from a moderate stocking rate are "moderate," higher than the "optimum" stocking rate when prices are poor, and lower when prices are good. We cannot yet recommend the 1.844 AUMs/acre in table 5 because it is only based on nine years of data and changes in forage production, particularly as a result of range deterioration, or cattle prices could make it inappropriate. Also producers should keep in mind that an optimum stocking rate for a stocker operation may not be optimum for a cow-calf operation. In the future we hope to provide more information to help the livestock producer make a sound decision.



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