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

Supplemental findings

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

The following section includes additional informative data. This section also includes suggestions for further research.

Effects of under- and overgrazing

Both undergrazing and overgrazing appear to decrease pasture growth potential. Plants that become mature are producing no net growth. However they take up moisture, sunlight and soil nutrients while declining in feed value. Conversely, plants that have a majority of their leaf surface removed (grazed to 1 or 2 inches) have to withdraw energy from their root reserves for regrowth. Table 2 shows that when more than 50% of the leaf area is removed, root growth is severely retarded (Bartlett 1991).

Table 2. Leaf Removal Effect on Root Growth
% leaf volume removed 10-40% 50% 60% 70% 80-100%
% root growth stoppage 0% 2-4% 50% 78% 100%

Grazing heights

In general, the recommended beginning grazing height is 6-10 inches at which time there is approximately 2,000 to 2,500 pounds of dry matter/acre. Initial spring grazing is the one exception to this. Then a 3-4 inch beginning height is suggested so paddock growth is staggered and remaining paddocks do not overmature. Beginning grazing heights should not be more than 10 inches. This is because forages 10 inches and less are grazed from the top down, while those taller than 10 inches are bitten off at the bottom of the plant (Bartlett 1991). As noted earlier, the tops of the forage plants have higher RFVs and CP levels.

Seeding into existing sod

Only legumes should be seeded into existing sod. Attempting to seed grass into a grass sod is seldom successful because sod competes too greatly to allow establishment of the new grass seedlings (University of Wisconsin 1991).

Bypass protein supplementation

In general, high quality pasture forages are high in crude protein (CP) but low in non-degradable or bypass protein. A recent study reported that Holstein cattle grazing orchardgrass pastures and supplemented with a grain mix containing 47% of the CP as bypass protein produced slightly less milk (67-80 lb./day) than cows supplemented with a grain mix containing 62% of the CP as bypass protein. Bypass protein supplementation may be beneficial for reproduction as well as milk production (Linn 1994).

Bulk tank method records

Graziers in the study found the bulk tank method was an excellent, quick way of monitoring recent management strategies. However, it appears that none of the producers using this method keep written records of their daily observations. Perhaps developing a simple recording system to monitor bulk tank yield and daily feed would provide graziers with valuable information.

Impacts of grazing cattle on distribution of soil minerals

Grazing livestock ingest substantial quantities of mineral elements contained in the forage they consume. Typically, 70% to 95% of these ingested minerals are returned to the soil via excretory processes. Neither ingestion by grazing or redistribution by extraction are random functions. Both are dependent upon size and shape of pasture as it relates to proximity of water, landscape features and special features that serve as points of livestock concentration such as shade, water and supplemental feeding sites. Therefore, fertilization of pastures should be structured to apply nutrients only to areas from which livestock are removing nutrients to avoid further enriching areas of animal manure and urine concentration. Minimizing the development of single direction nutrient gradients in pastures should be considered during placement of watering equipment, shade and mineral feeders (Gerrish et al. 1994).

Suggested topics for future research

Dairy graziers and conventional dairy farmers face many similar challenges. However, information available on dairy grazing is immature when compared to that on confinement feeding systems. In many cases, information must be extracted from data pertaining to confinement feeding systems. While additional research on numerous topics would help dairy graziers, the authors believe the topics of dairy nutrition and economics are immediate concerns for dairy graziers and dairy farmers considering MIG. Additional areas for further research are environmental impacts of MIG and why some adopters of MIG have discontinued the practice.

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