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Extension > Agriculture > Livestock > Dairy > Grazing systems > Knee deep in grass: A survey of twenty-nine grazing operations in Minnesota > Pasture management

Pasture management

Brian Loeffler, Helene Murray, Dennis G. Johnson, Earl I. Fuller
Reviewed 2008

Although no two farmers managed their pastures identically, many graziers' overall management strategies were similar. Two rules of thumb frequently cited are:

  1. cattle movement rates of 50,000 lb. of animal/acre and
  2. a 60:40 ratio of grass: legume mixture provides the preferred pasture composition

Cattle movement and stocking rates

Both cattle movement and stocking rates are calculated in animals/acre. The difference between the two terms is how the numbers are used. Movement rate refers to the number of cattle divided by the size of the present grazing area. The stocking rate is the number of cattle divided by the total pasture area. Over half the graziers moved the milking herd to fresh grass every 12 hours, after each milking. Respondents indicated that this kept grass fresh compared to adjusting the size of the grazing area to accommodate cattle for a period of 24 hours or more on the same paddock. Graziers moving the herd every 12 hours believed cattle were less likely to trample and soil forages, resulting in uniform grazing heights, increased consumption and less wasted feed. Also, graziers using this approach thought having fresh grass stimulated cattle to return to the pastures quickly and with little assistance. Other segments of the herd, such as dry cows and heifers, were generally moved every 3-7 days. Cattle movement rates for the milking group were calculated by dividing the size of the grazing area by the number of cattle grazing. Many graziers reported they tried to keep 50,000 lb. of animals/acre (about forty 1,200 lb. cattle/acre) in the grazing area. One grazier mentioned that this level of grazing pressure created competition among the cattle for feed and kept them grazing, not trampling the pasture. Movement rates varied with pasture productivity and pasture supplemental levels.

Stocking rates ranged from 0.40 to 4.11 animals/acre. Variations are thought to result from different levels of pasture supplementation, pasture productivity, animal stage of production and cattle breed. There may have been some correlation between stocking rate and land use. Farmers who reported being entirely grass based (no crop production) had lower stocking rates than many who were raising other sources of feed. Possibly the grass-based producers were attempting to lower the risk of depleting pasture resources, thereby reducing the possibility of having to purchase feed.

Pasture growth and rest periods

Twenty-eight graziers reported that they rely on visual observations as the main method of determining the length of the grazing rotation (time to cover the entire pasture). One grazier said he meticulously schedules pasture rest periods at the beginning of each season by using records from previous years as well as visual observations of the pastures during the season. Graziers noted that visual observation plus experience assisted them in determining where certain groups of cattle should be grazed on their farm during different times of the grazing season and under various weather conditions.

Graziers said that visual observation included the incorporation of these five factors:

  1. Examining forage regrowth. This involved observing forage regrowth rates and noting the differences of those rates among forage species, as well as the ability to recognize when specific forage species should and should not be grazed.
  2. Observing the palatability of different forages. This entailed noting which forage species cattle prefer.
  3. Observing milk production levels following each milking. Some farmers called this the bulk tank method.
  4. Regard for animal stage of production. Are they milk cows, heifers, young stock? Further attention to the milking group included consideration for their stage of lactation and recognition of different nutritional requirements of high- and low-producing cattle.
  5. Consideration of weather and season. This involved taking weather and time of the year into account when evaluating the first four factors.
"You can tell what's going on in your pastures immediately by looking at bulk tank levels."

Many graziers viewed observation of bulk tank levels as the best indicator of their recent management strategies. Commonly this was made by observing the level of milk in the bulk tank following each milking. Along with the quantity of milk produced, the producers also take into account weather, stage of production and the types and amounts of feed recently consumed. Farmers then try to answer questions such as, "How big should I make the paddocks tomorrow?" or "Should I feed more corn in the barn?" The bulk tank method helps indicate current forage quality and quantity as well as the need for changes in concentrate supplementation. One grazier noted, "You can tell what's going on in your pastures immediately by looking at bulk tank levels." Grazing rotation lengths varied with weather, season, forage species and experience, as well as present and previous grazing heights. Most respondents agreed that not allowing pastures to mature or head out encourages new growth. Many farmers clipped their pastures, especially during the spring, in order to keep forages from heading out.

Typical rotation lengths for cattle in a given paddock were approximately 8-14 days during the spring, 25-35 days during the summer and 45-65 days in the fall. Some graziers have increased the amount of time they allow pastures to rest compared to when they first began using MIG.

Grazing height

Like grazing length determination, graziers decided when to allow cattle into and when to remove them from a paddock by considering variables such as weather, forage species, animal stage of production and their experience. The reported beginning grazing height ranged from 8-12 inches, except at the very beginning of the grazing season when it was much shorter. Cattle were removed when the ending height ranged from 2-5 inches for the milking herd. To improve pasture quality and durability, many graziers had increased their beginning and ending grazing heights (at least for the dairy herd) as they have gained experience.

One grazier said, "I've reduced the number of grazing rotations (times grazing the entire pasture per season) from ten to six." This increased the beginning grazing height or allowed the pastures more time to rest. He also said that this has improved the durability of his pastures. Others noted forage quality is also improved with higher grazing heights (beginning 8-10 inches, ending 4-6 inches). They said this allows many desired forage species to better compete with undesired species.

Follow-up groups

Follow-up groups of heifers or dry cows were used at least occasionally on eight farms and had been used previously on one farm. Graziers using follow-up groups typically removed the milking herd at higher than normal residue heights, typically at 5-8 inches instead of the 2-5 inches. They then allowed follow-up groups to finish grazing to an end height of 4-6 inches. Some graziers reported that pastures could be evened up by forcing follow-up groups to graze pastures very short or 2 inches. Follow-up group users reported that the milking group had access to the higher quality forages in the top few inches of the plants, thereby eliminating or reducing the number of acres grazed solely by dry cows and heifers.

Forage testing

Eight graziers had used pasture forage analysis (usually 1-3 times a year) to assist them in pasture management and concentrate supplementation. Five graziers had discontinued testing forages. They thought the results were not useful in helping them accurately formulate rations because of the difficulty in calculating pasture forage intake, also known as dry matter intake or DMI. Reported results of pasture forage analysis showed that relative feeding values (RFV) ranged from 140-220 and crude protein (CP) ranged from 24% to 35% (DM basis). RFV is an index which combines important nutritional factors (potential intake and digestibility) into one number for a quick, easy and effective method of evaluating feed value or quality. The values reported by graziers in the study are considered to be high (Grade 1 to Prime). Graziers noted, however, that the forage analysis results varied depending upon the height at which the sample was taken. It appears that RFVs and protein levels are much higher at the top of forages than near the bottom. Thus, many graziers are motivated to top graze the milking group.

Grazing dates

The grazing season is typically expected to begin the last week of April through the first week of May for southeastern and south central Minnesota graziers. Graziers in the northern regions indicated that they expect to start grazing in mid- to late May. One farmer stated that he begins grazing selected paddocks "as soon as the snow disappears." This was done to retard normal forage growth in those paddocks, thus staggering pasture growth. This farmer claimed that staggered pasture growth enabled him to reduce the need for clipping rapidly maturing cool season forages in early to mid-June. In other words, this extended the window in which cool season grasses head out. Therefore, grazing could be used to keep up with maturing forages on more acres. The grazing season in all regions of Minnesota appeared to continue until mid- to late October. Several farmers reported they continued to graze cattle, including the milking group, until snow made it impossible.

Pasture inspection and fencing

Most graziers reported spending 10-20 minutes per day moving portable fences for the milking group and inspecting pastures. Graziers reported they are usually able to accomplish both simultaneously. They noted that it is important to inspect the entire pasture regularly, not just the paddocks closest to the milking parlor. Several graziers used all terrain vehicles (ATVs) to help move fencing equipment and inspect pastures. Many graziers claimed that pasture inspections were an integral part of their pasture and cattle management. Additional time was periodically required to move dry cows and heifers. Fences were not usually moved daily for groups other than the milking herd.

Weed control

Essentially all respondents agreed that Canada thistle is the only plant cattle refuse to eat. Consequently, it was considered a weed by many. Alfalfa was considered a weed by some graziers, but usually little was done to control or eliminate it from pastures. These graziers consider it to be a weed because it has low RFV when it is actively growing. Additionally, they reported that dairy cattle find fresh alfalfa unpalatable and that grazing dense stands of alfalfa can lead to bloating. Respondents who previously grazed their pastures continuously noted fewer weed problems since adopting MIG. Clipping and managed grazing were the primary methods of weed control for most graziers. Clipping was done on almost all pastures. It is also done to mechanically harvest feed and to keep ahead of lush pasture growth so it doesn't mature. Farmers commonly used haybines and hay mowers. Some producers reported they clip thistles by hand during pasture walks. Only one farm used herbicide to help control thistles.

Farmers managed grazing to discourage the growth of many undesired forage species. Creating a competitive environment that encourages the desired species was a tactic used by several graziers to discourage weed growth. Having an understanding of the growth and regrowth traits of desired and undesired forage species was reported to be necessary to accomplish this goal.

Soil testing

Eleven graziers reported they recently tested or will be testing pasture soil fertility. Nitrogen and pH management appear to be the most common reasons for testing. Seventeen respondents said they have not tested and do not test pastures for soil fertility while one farmer had discontinued the practice. Some did not believe that results from conventional ways of measuring soil fertility were helpful in determining the overall soil health of their system. Some of the graziers did not want to apply inputs on their land and consequently felt the money would be ill-spent.

Mechanical harvesting of pasture

Many farmers harvested (baled and chopped) pastures to supply feed during other times of the year. This also helped control weeds and to keep ahead of lush pasture growth. Mechanical harvesting was most common during the spring and on farms with low stocking rates. It appears pastures designed for strip grazing were better suited for mechanical harvesting than rectangular paddocks because there was less fence to move or avoid while harvesting.

Other types of management

"I'm trying to increase bio-diversity on my farm... it will make the farm a stronger system, and in turn make me more money."

Many respondents were critical of using alfalfa in the pasture mix. However, one farmer strip grazed pure stands of alfalfa with no bloat problems reported. This grazier indicated that grass production was very poor on his farm's soil type and had originally planted the alfalfa as a soil-building crop. He now reseeds the alfalfa every two years in rotation with potatoes and sweet corn. As noted earlier, one farm used only a perimeter fence and did not use any paddocks to direct grazing. This farm had the entire dairy herd in 160 acres of pasture. Cattle movement was directed by harvesting 10-15 acres of pasture hay weekly. The grazier claimed that the cattle automatically followed the regrowth of the harvested areas. According to this grazier, "the cattle follow (graze) the harvested areas by roughly two weeks." Harvested hay was stored and typically used during the winter.

Eleven farmers considered native plants and wild animals when planning their pasture management strategies. One grazier said, "I'm trying to increase bio-diversity on my farm... it will make the farm a stronger system, and in turn make me more money."

Some actions included:

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