Livestock on Grass and Forage
Dickinson Research Extension Center
1089 State Avenue
Dickinson, ND 58601
and Calf Performance on Seasonlong and Twice Over
Rotation Grazing Treatments in Western North Dakota
L. Manske1, Mario E. Biondini1, Donald R. Kirby1,
James L. Nelson2, Douglas G. Landblom2, and Phillip J. Sjursen1
Range Sciences Department and
2Dickinson Experiment Station North Dakota State University
Livestock are the primary harvestable product of economic value from rangelands. Wildlife, water and aesthetics are also important "products" from rangeland that require sincere consideration for management decisions but it is very difficult for land owners to receive economic return from these. Maximum economic return from rangeland requires livestock to maintain production at or very near their potential for the entire grazing season. Anything short of this is lost potential capital. It is difficult to sustain maximum livestock production without crossing over a very fine line and causing detrimental effects to the range natural resource and its intrinsic values. Grazing livestock on native rangeland has a multitude of complex interactions and relationships between the plants and animals. Rangeland has a wide diversity of plant species. Each species has different needs for growth and development and respond differently to any given set of environmental factors. Animal performance is variable with the changes in the growth of plants. Scientists and managers need to understand the variations in weight performance through the grazing season in order to understand the ecology of grazing and evaluate the effects of any grazing management technique. Frequently animal performance on rangeland is evaluated by comparing single annual mean values of rate of gain and total weight gained for the entire season. Animal weight gain performance is not at the same rate during the entire grazing season and it is not the same for animals grazing on single pasture treatments and animals grazing on multiple pasture systems. This study was designed to describe and compare cow and calf rate of gain and change in accumulated weight gain for the grazing season during biweekly performance periods on three grazing treatments.
This study was conducted for five years between 1983 and 1987 at the Dickinson Experiment Station located in western North Dakota. The vegetation was the Wheatgrass-Needlegrass Type (Barker and Whitman, in press) of the mixed grass prairie. The dominant native range species were western wheatgrass (Agropyron smithii), needleandthread (Stipa comata), blue grama (Bouteloua gracilis) and sedge (Carex filifolia). Long term mean annual precipitation was 15.89 inches.
Three grazing treatments were included in this study, deferred seasonlong, seasonlong, and twice over rotation system. The deferred seasonlong grazing treatment had a delay of the starting date until mid July. This treatment was based on tentative interpretation of herbage production data collected from clipping studies in Canada (Campbell, 1952) with supporting herbage data collected in central North Dakota (Rogler et al., 1962) and western North Dakota (Whitman, 1954). This treatment was located at the Dickinson Experiment Station Pyramid Park area and consisted of one pasture of 600 acres grazed by one herd of 68 cow-calf pairs for 3.7 months from 16 July to 5 November in 1983 to 1985. These livestock were on several smaller breeding pastures prior to mixing and the start of this treatment.
The seasonlong grazing treatment was the control treatment of this study and consisted of a single 320 acre pasture grazed by one herd of 35 cow- calf pairs for 4.4 months from 18 June to 30 October, 1983 to 1987. It was located at Dickinson Experiment Station Ranch Headquarters. The pasture was not replicated.
The three pasture twice over rotation grazing system consisted of two 80 acre pastures and one 75 acre pasture for a total of 235 acres. Twenty-six cow-calf pairs grazed for 4.5 months from I June to 17 October, 1983 to 1987. These pastures were replicated twice but the data was combined and used as one replication. This grazing technique was based on ar. ur.proven hypothesis suggested by Sampson (1914 and 1954) and expressed by Heady (1975) that there were three critical periods for grass plants when grazing has greater detrimental effects than at other periods (Manske and Conlon, 1986). Each pasture was grazed for two periods with one period of 15 days and a second period of 30 days for a total of 45 days of grazing in each pasture per year.
Commercial crossbred cattle were used on all treatments in this trial. Dates grazed, number of total days grazed, number of cow-calf pairs, acres and stocking rates data for the three grazing treatments are shown in table 1.
Individual animals were weighed on and off each treatment and at 28 or 30 day intervals while on the treatments. Cow and calf mean weights for each treatment were adjusted to the 8th and 23rd day of each month of the grazing period. Biweekly performance periods of average daily gain and accumulated weight gain for cows and calves were used to evaluate each treatment from the start of the grazing period. Response surface analysis (Kerlinger and Pedhazur, 1973) with a repeated observation design (years as the repeated observation) was used to compare animal response curves among treatments. Simple mean annual average daily gain and gain per acre were calculated for each treatment and evaluated by unbalanced AOV (Mosteller and Rourke, 1973).
Cows grazing seasonlong and deferred seasonlong treatments steadily decreased in average daily gain from the start of the grazing period (fig. 1). There was no significant difference (P>0.05) in the response curves of the cow average daily gain between seasonlong and deferred seasonlong treatments. The average daily gain was negative for the cows in most years during the last six weeks of the grazing period for the two seasonlong treatments. There was no significant difference (P>0.05) for the cow mean annual average daily gain between the seasonlong and deferred seasonlong treatments (table 2). Cow performance on the seasonlong and deferred seasonlong was less than desirable. Cows on the seasonlong and deferred seasonlong gained an average of 77.1 and 50.0 pounds, respectively, during the early portion of the grazing season. Cows lost 24.1 and 24.9 pounds on the seasonlong and deferred seasonlong treatments, respectively, during the latter portion of the grazing period.
The cow average daily gain response curves were significantly different (P<0.05) between the twice over rotation treatment and the seasonlong and deferred seasonlong treatments (fig. 1). Cows on the twice over rotation treatment initially had a reduction in average daily gain but a period with no reduction occurred during the middle portion of the grazing period before cows lost weight at the end of the grazing period. Weight loss for cows occurred in most years only for the last two weeks of the grazing period on the twice over rotation grazing treatment. A significant difference (P<0.05) between twice over rotation treatment and seasonlong and deferred seasonlong existed for mean annual average daily gain (table 2). Cow average daily gain was more desirable on the twice over rotation treatment than the seasonlong and deferred seasonlong treatments. The period of weight loss that usually occurred on the two seasonlong treatments was delayed about four weeks on the twice over rotation system.
Accumulated weight gain for cows from the start of each grazing period was significantly different (P<0.06) between seasonlong and deferred seasonlong treatments (fig. 2). Accumulated weight gain was not different on the two seasonlong treatments but the rate of loss of accumulated weight during the latter part of the season was greater on the deferred seasonlong treatment. The upward slopes of the accumulated weight gain response curves were similar but the downward slope was greater on the deferred seasonlong treatment compared to the seasonlong treatment (fig. 2).
The cow accumulated weight gain response curve of the twice over rotation treatment was significantly different (P<0.05) from the response curves on the seasonlong and deferred seasonlong treatments. The upward slopes of these three curves (fig. 2) were not different. The downward slope for the cows on the twice over rotation treatment was significantly less steep than the two seasonlong treatments. Cows on the twice over rotation treatment gained an average of 87.4 pounds and lost 11.7 pounds. These cows gained more weight and lost less weight than the cows on the two seasonlong treatments. Cow weight performance on the twice over rotation treatment was more desirable than the performance of cows on the two seasonlong treatments. Cow gain per acre (table 2) was not different (P>0.05) between the deferred seasonlong and seasonlong treatments. Cow gain per acre was significantly greater (P<0.05) on the twice over rotation treatment compared to deferred seasonlong and seasonlong treatments.
Calf average daily gain (fig. 3) decreased with the progression of the grazing period. The rate of decrease was different for all three grazing treatments. The shape of the calf average daily gain response curves were not different but the downward slope of the deferred seasonlong treatment was significantly greater (P<0.002) than the seasonlong treatment. The downward slope of the twice over rotation treatment was significantly less (P<0.01) than the seasonlong and deferred seasonlong treatments. Average daily gain for calves on the twice over rotation treatment was more desirable than for calves on the seasonlong treatment which was more desirable than for the calves on the deferred seasonlong treatment. Average daily gain for calves on the twice over rotation treatment was steadier throughout the grazing period compared to the two seasonlong treatments.
The mean annual average daily gain (table 2) for calves was significantly different (P<0.05) between the deferred seasonlong treatment and the seasonlong and twice over rotation treatments. There was no difference (P>0.05) for calf mean annual average daily gain between the seasonlong treatment and the twice over rotation treatment. Simple annual average daily gains have been used for a long time to evaluate animal performance but should not be the only method to evaluate animal performance when comparing grazing treatments. This technique did not detect the differences in calf average daily gain between the seasonlong and twice over rotation treatments.
Accumulated weight gain for calves was significantly greater (P<0.004) on the seasonlong treatment when compared to the deferred seasonlong treatment (fig. 4). Calf accumulated weight gain for the twice over rotation treatment was significantly greater (P<0.0001) than on the seasonlong and deferred seasonlong grazing treatments. The greatest differences between these three performance response curves occurred toward the latter portion of the grazing period. The dip towards the latter portion of the grazing period for the calf accumulated weight gain curves (fig. 4) tended to follow the same trend as the downward slopes of the cow accumulated weight gain curves (fig. 2) for each treatment. The greatest downward slope occurred for the cows and calves of the deferred seasonlong treatment. The least downward slope occurred for the cows and calves of the twice over rotation treatment. The seasonlong treatment was between the other two treatments.
Calf gain per acre (table 2) was not different (P>0.05) for the three grazing treatments. Gain per acre values would be important to livestock producers but these values did not detect the differences between the three treatments in this study.
The performance response curves for cows (fig. 1) and calves (fig. 3) on the three grazing treatments show that cows and calves do not gain weight at the same rate for the entire grazing period and different grazing treatments cause differences in cow and calf weight performance. Simple annual average daily gain values (table 2) do not show variation in rate of gain during the grazing period and they mayor may not show differences between grazing treatments.
Livestock production in western North Dakota has three major problems that need to be overcome by management in order to have maximum potential performance from cows and calves on rangeland. A) Western North Dakota has only a three month period, May, June and July, in which range grasses complete most of their growth (Goetz, 1960). Water is usually a limiting factor after July and very little new growth occurs in the latter portion of the grazing season. B) Lactating cows that are around 1000 pounds require 9.9% protein from their diet in order to maintain body weight and average milk production (NRC, 1984). The major grasses in western North Dakota drop below this level after mid July (Whitman et al., 1951). C) Grazing native range too early in the spring (May) reduces total herbage production by 40 to 60% of the potential growth (Campbell, 1952; Whitman, 1954; and Rogler et al., 1962).
These three problems limit maximum cow and calf production on rangeland in western North Dakota when management of grazing treatments ignores the negative effects of these factors. The standard seasonlong grazing treatment with a six month grazing season from mid May to mid November was the traditional grazing management in western North Dakota. This treatment was not included in this study because a set of data with six months grazing in one pasture did not exist. We can by apriori reasoning explain the effects of this treatment. The stocking rates would need to be low because of the loss of potential herbage production by grazing early. The average daily gain of cows and calves would be low because 3.5 months (58%) of the grazing period would be on mature vegetation that would be below nutritional requirements. On seasonlong grazing treatments with early starting dates the animals tend to select for green growing vegetation from choice species and most grass leaves are grazed before they are fully expanded. These immature leaves are very nutritious but below their potential weight. Under seasonlong grazing, it requires a larger number of plants with immature leaves to provide daily fol-age requirements for each animal. There is only a limited number of desirable plants available and this increases the number of times each plant is regrazed which keeps the leaves below potential weight. This repeat grazing reaches a point that is detrimental to the plants and inhibits growth which considerably reduces quantity and quality of adequate forage. The grazing animal then must turn to the plant species that initially escaped the selection and regrazing process. By this time, these plants would be in various stages of late senescence and below the nutritional requirements for the livestock. The animals lose weight during the latter portion of the grazing season.
The deferred seasonlong grazing treatment used in this study delayed grazing until nearly all the vegetative growth had been completed and after the nutritional quality of the major grass species had dropped below the minimum requirements of the animals. Most of the grass leaves available were fully expanded and at later stages of senescence. The cows were able to select forage early in the grazing period that provided adequate nutrition and were able to gain weight. Shortly after midway into the grazing period the animals were unable to select adequate forage to maintain body weight and presumably milk production.
The cows lost weight and calf production was greatly reduced. The calf average daily gain and rate of accumulated weight gain decreased after the cows started to lose weight.
The seasonlong grazing treatment used in this study delayed the start of grazing until mid June. Vegetation was still growing but initial leaves on several grass species were fully expanded at or near full weight and all major grass species were above minimum nutritional requirements. The initial mean average daily gain for cows on the seasonlong treatment was greater than for the cows on the deferred seasonlong treatment. The cows on the seasonlong treatment had a steady decline in average daily gain and lost weight during the latter portion of the grazing season the same as the cows on the deferred seasonlong treatment. The loss in weight occurred after July when mast of the vegetative growth had been completed and the available vegetation had dropped below nutritional requirements. Calf average daily gain and accumulated weight gain decreased during the latter portion of the grazing period after the cows started losing weight.
Loss of weight by cows in late summer was not harmful to the health of the animals but it did indicate that they were unable to maintain body weight and lactation on the forage available. Milk production for cows from the same experiment station herd but on another study grazing seasonlong showed that daily production of milk increased from May to June and then steadily decreased until weaning (Landblom et al., 1988). Cow body weight and milk production on seasonlong grazing treatments followed the same downward trends as the season progressed.
Grazing on the twice over rotation treatment was delayed until early June. No grazing occurred in May when the effects of grazing on young immature leaves reduce total potential herbage. In early June grass plants were still actively growing with several leaves fully expanded at full weight and still above minimum nutritional requirements. The livestock were moved to all three pastures one time during the early portions of the grazing period prior to mid July so that each pasture was grazed while the vegetation was growing and the nutritional quality was above the minimum requirements. Average daily gain for the cows decreased during the first rotation in the early portion of the grazing period presumably because the fully expanded leaves were decreasing in nutritional quality. The nutritional quality was still above requirements and the cow weight gain remained positive and weight was accumulated. During the second rotation the cows were still able to select forage that met their nutritional requirements in the first two pastures and the cows were able to maintain positive weight gain. The cows did not lose weight until the second rotation of the third pasture.
Cows on the twice over rotation system prolonged weight gain late into the grazing period and delayed weight loss. The reason for this was thought to be that a higher amount of leaves consumed by the cows during the first rotation were near full weight and that fewer plants were required to fulfill the daily needs of the animals. This would allow a high number of immature leaves to escape grazing during the first rotation and be available as fully expanded leaves during the second rotation. This would explain the increase in total available herbage and the ability to increase stocking rates on rotation grazing systems over seasonlong treatments.
Light grazing during the early portion of the grazing season seems to stimulate grass plant tillering which would increase plant density and the number of leaves available for the grazing animal during the second rotation and possibly the following year. The leaves from the new tillers would be phenologically less developed than the leavts from the older plants of the same species and relatively higher irl nutritional quality. Calf performance on the twice over rotation treatmerlt was also benefited. The average daily gain did not drop off during the latter portion of the grazing period as much as the calves on the deferred seasonlong and seasonlong treatments.
Cow and calf production from rangeland can not be maximized to the potential of the natural resource if the cows lose weight for long periods and calf average daily gain decreases well below their potential.
During this five year study cows and calves grazing on the twice over rotation grazing treatment had greater average daily gain and accumulated weight gain than cows and calves on the seasonlong and deferred seasonlong treatments. Cows on the two seasonlong treatments had a steady decrease in average daily gain and lost weight during the latter portion of the grazing period. The calves on the two seasonlong treatments had decreases in average daily gain during the latter portion of the grazing period. Cows on the twice over rotation grazing treatment gained weight for a longer period and delayed and shortened the period of weight loss at the end of the grazing period. Calves on the twice over rotation treatment had only a slight decrease in average daily gain during the latter portion of the grazing period.
In order for livestock producers in western North Dakota to maximize production and economic return from rangeland they need to move away from seasonlong grazing treatments and implement rotation grazing systems.
|Table 1. Dates and total days grazed, number of cow-calf pairs, acres and stocking rates for three grazing treatments.|
|Treatment||Dates Grazed||Total Days||Number
|16 Jul - 5 Nov||112±6.3||68||600||0.45±0.03|
|Seasonlong||18 Jun - 30 Oct||134±2.4||35||320||0.36±0.03|
|Twice Over Rotation||1 Jun - 17 Oct||138±1.7||52||470||0.43±0.04|
|Table 2. Mean annual average daily gain and gain per acre for cows and calves on three grazing treatments.|
Average Daily Gain
Gain Per Acre
|Twice Over Rotation||0.87±0.22b||2.21±0.07b||8.0±1.4b||28.4±3.0a|
|Means of same column followed by the same letter are not significantly different (P<0.05).|
Barker, W.T. and W.C. Whitman. (in press). Vegetation of the Northern Great Plains. Rangelands.
Campbell, J.B. 1952. Farming range pastures. J. Range Manage. 5:252-258.
Goetz, H. 1963. Growth and development of native range plants in the mixed grass prairie of western North Dakota. M.S. Thesis, NDSU, Fargo, N.D. 141 pp.
Heady, H.F. 1975. Rangeland Management. McGraw-Hill Book Co., New York, N.Y. 460 p.
Kerlinger, F.N. and E.J. Pedhazur. 1973. Multiple Regression in Behavioral Research. Holt, Rienhart and Winston, Inc. New York.
Landblom, D.G., J.L. Nelson, L.L. Manske, and P.J. Sjursen. 1988. The brood cow efficiency study -a progress report. N.D. Farm Res. 46(1):6-10.
Manske, L.L. and T.J. Conlon. 1986. Complementary rotation grazing system in western North Dakota. N.D. Farm Res. 44(2):6-10.
Mosteller, F. and R.E.K. Rourke. 1973. Sturdy Statistics. Addison- Wesley Publishing Co., Mass. 395 p.
NRC. 1984. Nutrient requirements of domestic animals, No.4, Nutrient requirements of beef cattle. National Academy of Science.
Rogler, G.A., R.J. Lorenz, and H.M. Schaaf. 1962. Progress with grass. N.D. Agr. Exp. Sta., Bull. 439. 15 p.
Sampson, A.W. 1914. Natural revegetation of range lands based upon growth requirements and life history of the vegetation. J. Agr. Res. Vol. 111(2):93-147.
Sampson, A.W. 1952. Range Management Principles and Practices. John Wiley and Sons, Inc., New York. 570 p.
Whitman, W.C. 1954. Yield characteristics of native grass ranges. Proc. N.D. Academy of Science. pp. 14-19.
Whitman, W.C., D.W. Bolin, E.W. Klosterman, H.J. Klostermann, K.D. Ford, L. Moomaw, D.G. Hoag, and M.L. Buchanan. 1951. Carotene, protein, and phosphorus in range and tame grasses of western North Dakota. N.D. Agr. Exp. Sta., Bull. 370. 55 p.
Figure 1. Cow average daily gain response curves for deferred seasonlong (top), seasonlong (middle), and twice over rotation (bottom) treatments.
Figure 2. Cow accumulated weight gain response curves for deferred seasonlong (top), seasonlong (middle), and twice over rotation (bottom) treatments.
Figure 3. Calf average daily gain response curves for deferred seasonlong (top), seasonlong (middle), and twice over rotation (bottom) treatments
Figure 4. Calf accumulated weight gain response curves for deferred seasonlong (top), seasonlong (middle), and twice over rotation (bottom) treatments.
[ Back to 2001 Annual Report Index ] [ Back to Grassland Topical Index ]
[ DREC Home ] [ Contact DREC ] [ Top of Page ]