Grazing methods affect forage, cattle production

Grazing methods affect forage, cattle production

Grazing methods are a component of grazing management that have the potential to increase animal and forage production.

*Joao Vendramini is an associate professor of pasture and forage management at the University of Florida Range Cattle Research & Education Center in Ona, Fla.

GRAZING methods, which include rotational or continuous grazing, are a component of grazing management that have the potential to increase animal and forage production.

Rotational grazing is defined as alternating periods of grazing and rest for two or more paddocks in a grazing management unit throughout the grazing season. Continuous grazing is a method of grazing livestock on a specific unit of land where animals have unrestricted and uninterrupted access throughout the grazing season.

It is important to note that the most critical grazing management decision is not the grazing method but the stocking rate. Stocking rate is defined as the amount of land allotted to each animal during the grazing season. If the stocking rate is not right, then neither rotational nor continuous grazing will correct the problem.

So, the first and most important step in developing a grazing program is to choose the correct stocking rate for a specific condition. After that is done, changing the grazing method may allow producers to fine-tune their grazing system.

Production of new growth after grazing depends on the amount of residual leaf and carbohydrate reserves, because they will supply energy for plant growth. Rotational grazing with the correct stocking rate will maintain adequate stubble height and carbohydrate reserves after grazing to maximize forage regrowth.

Stewart et al. (2005) verified that bahiagrass (Paspalum notatum) can produce more forage under rotational grazing than under continuous grazing (Table). Rotational grazing with one, three, seven and 21 days of pasture occupation (21-day rest period between grazing periods) resulted in greater forage production than pastures that were grazed continuously.

In addition to increased regrowth rates, rotational grazing at the proper stocking rate also aids in pasture persistence by allowing better stubble height control. Controlling the target stubble height on rotationally grazed pastures is important not only to maximize forage regrowth but also to extend the life span of the pastures.

Overgrazing can result in the loss of desirable species and an increase in weeds. Results from Florida studies confirmed the beneficial effect of rotational grazing on persistence of some grasses.

For example, Callie bermudagrass pastures were rotationally or continuously grazed for two years at the same stocking rate (Matthews et al., 1994). Pastures contained 90% Callie and 10% common bermudagrass at the beginning of the study.

After two years of grazing, the percentage of Callie was 86% in rotationally grazed pastures and 62% in continuously grazed pastures. Callie persisted better under rotational grazing because, during the rest period between grazings, it grew taller and shaded common bermudagrass, while under continuous grazing the lower-growing common bermudagrass was not shaded nearly as much.

The nutritive value of forage is usually not affected by grazing method. In Florida, crude protein, phosphorus and digestibility in bahiagrass were not affected by grazing method or the length of the grazing period of rotationally grazed pastures (Dubeux et al., 2005).

In general, grazing method does not affect the average daily gain of beef cattle; however, the increased forage production and utilization allow for greater stocking rates that typically result in greater liveweight gain per unit of land.

Matthews et al. (1994) found that stocking rates could be increased by as much as 20% when bermudagrass pastures were rotationally versus continuously grazed. Average daily gains of cattle did not differ between grazing methods and averaged 1.10 lb. per day. However, the increase in stocking rate with similar average daily gains resulted in greater liveweight gains per acre.

Grazing cattle retain approximately 20% of the nutrients ingested from forages, with the remaining 80% excreted through feces and urine. Feces and urine are important sources of nutrients for forages, mainly for grazing systems with low inputs. However, in warm climates, the animals tend to concentrate their excreta close to water and shade.

Under continuous grazing in warm climates, animals deposited 80% of the excreta in 30-40% of the pasture area (Matthews et al., 1996).

Rotational grazing increases the uniformity of distribution of the excreta. Dubeux et al. (2005) showed that feces were more uniformly distributed on bahiagrass pastures grazed rotationally than continuously. At times of increasing fertilizer costs, better distribution of the excreta likely will result in improved use of the nutrients by forages and may reduce the amount of commercial fertilizers used in the long run.

Rotational grazing allows producers to make management decisions based on seasonal variability in forage production and animal requirements. During the months of the year with excessive forage production, rotational grazing allows some pastures to be deferred and used for hay production or to stockpile forage for the winter.

In addition, the producer utilizing rotational grazing has the opportunity to better match animal requirements with the pasture's ability to supply nutrients. Animals with greater nutrient requirements (i.e., replacement heifers and first-calf heifers) can have access to pastures first and graze the forages with greater nutritive value. They can be followed by cattle with lower nutrient requirements (i.e., mature cows). Last, the periodic handling of the cattle permits managers to inspect the herd frequently so that timely herd management decisions can be made.

The main disadvantages of rotational grazing compared with continuous grazing include the initial investment in fences, water and feed bunks, labor availability to move the animals and additional management decisions.

 

The Bottom Line

No single grazing management program will be appropriate for all forages in all environments. Because of the likelihood of greater forage production and pasture persistence, rotational grazing has the potential to increase animal production on beef cattle operations.

The choice of grazing method will depend on the characteristics of a particular beef cattle enterprise, including the forage being grazed, the stocking rate used and the economics of production.

In general, rotational grazing will be most needed when stocking rates are high or the forage being grazed requires more careful management for long-term survival.

 

References

Dubeux, J.C.B. Jr., R.L. Stewart Jr., L.E. Sollenberger, J.M.B. Vendramini and S.M. Interrante. 2006. Spatial heterogeneity of herbage response to management intensity in continuously stocked Pensacola bahiagrass pastures. Agron. J. 98:1453-1459.

Matthews, B.W., L.E. Sollenberger and C. Staples. 1994. Dairy heifer and bermudagrass pasture responses to rotational and continuous stocking. J. Dairy Sci. 77:244-252.

Matthews, B.W., L.E. Sollenberger and J.P. Tritschler II. 1996. Grazing systems and spatial distribution of nutrients in pastures — Soil considerations. In: R.E. Joost and C.A. Roberts (eds.). Nutrient Cycling in Forage Systems. PPI/FAR, Columbia, Mo. p. 213-229.

Stewart, R.L. Jr., J.C.B. Dubeux Jr., L.E. Sollenberger, J.M.B. Vendramini and S.M. Interrante. 2005. Stocking method affects plant responses of Pensacola bahiagrass pastures. Forage & Grazinglands.

 

Herbage accumulation rates on rationally grazed pastures with different grazing periods (rest period of 21 days for all) and under continuous grazing during 2001-03

 

Herbage accumulation,

Treatment

lb. of DM/acre/day

Rotational, days

  1

58

  3

61

  7

64

  21

67

Continuous

37

Adapted from Stewart et al. (2005).

 

 

Volume:86 Issue:16

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