Pasture Management and Grazing Systems

Pasture Management

Whatever the kind of pasture, the goals of grazing management will incorporate the following principles: maintain or improve pasture condition for livestock and wildlife; maintain economical animal performance; reduce animal selectivity; improve livestock distribution; improve the ease and flexibility of management (Sindelar 1989).

A grazing system is a planned schedule of pasture use and defines when and where livestock will graze during the season to accomplish the desired goals (Abouguendia and Dill 1993). The system may include annual and/or perennial forages, seeded pastures and/or native range.

The most common grazing systems are:

• Continuous;
• 'Complementary' use of seeded and native range; and
• Various rotational grazing schemes.

Russian wildrye is a cool-season grass, that is, most of its production is during the months of April, May and June. This usually coincides with the best soil water conditions. After spring, grazing management of Russian wildrye involves the management of stockpiled forage. Russian wildrye is superior to most grasses at the same date because the stored forage is of higher palatability and better quality. Therefore, it may be grazed at any time of the year from April until December or later depending on available forage and weather.

Whatever the season, forage supply and quantity must meet the needs of the grazing animal. About 10-12.5 cm (4 or 5 inches) of growth should be available before a pasture is grazed. This will equal about 654 - 872 kg/ha (600 to 800 lb) forage per acre. It may be grazed to 5 - 15 cm (2 to 3 inches) 327 -436 kg/ha (300 to 400 lb/acre residue) before productivity (average daily gain, milk production, body condition) of the animals will begin to decline.

In general, in semiarid climates, maximum yields of annual or perennial crops are obtained in one harvest per year. Thus, hay harvest or once-over rotational grazing will provide maximum forage yields. Quality will not necessarily be optimized by a one-harvest system but should be adequate for most livestock classes. Frequent harvests of immature forage will provide higher quality forage but will reduce plant vigour and lead to elimination of such species as alfalfa, intermediate wheatgrass and many native grass species if rest is not provided. Heinrichs and Clarke (1961) have shown that Russian wildrye tolerates frequent clipping much better than several other introduced or native grasses. This characteristic, too, may be considered when planning a grazing system which includes Russian wildrye and other grasses.<

Different pasture species may need to be managed differently or grazed at different times to optimize palatability or quality. For example, native range should be fenced and grazed at a different time than seeded pastures. Crested wheatgrass should be fenced out from Russian wildrye to use each grass in its prime. Russian wildrye may be sowed in mixture with forages of similar livestock acceptance, such as slender wheatgrass or Dahurian wildrye and/or a legume, with the expectation that the pasture will be uniformly grazed. It is very important that alfalfa is not selectively grazed out of the grass-alfalfa mixture, which is possible when the only regrowth available is that of alfalfa, such as in mid-summer.

Stock density is a very important management decision. Stock density can be managed to reduce selective grazing. This will depend on the period of use and expectations of productivity. If 1 animal unit month per acre use can be expected, then the stock density will be 1 animal unit per acre if one month's grazing is expected. If the pasture will be continuously grazed for five months, then the stock density will be 1 animal unit per five acres given the expected productivity of 1 animal unit month grazing per acre.

To satisfy the second principle of grazing management in maximizing animal returns, pasture quality is matched with the animal type. Forage digestibility, protein, and many quality factors decline from first growth in spring until dormancy in fall. In spring, Russian wildrye or Russian wildrye-alfalfa will provide high quality grazing for cows with calves and 'flushing' cows for re-breeding. This pasture will support excellent calf gains and maintain or improve cow condition summer long. The stockpiled forage will maintain the non-lactating pregnant cow into fall and winter. Yearlings will gain 1.0 kg/day (2 lb/day) on Russian wildrye-alfalfa pasture from April until August at which time average daily gains may decline. By this date, the Russian wildrye may need supplementation or the steers are removed.

Grazing systems for Russian wildrye

Russian wildrye or Russian wildrye-legume pastures may be used in a variety of grazing systems. Russian wildrye will tolerate early season use much better than native grasses. However, crested wheatgrass is more productive for early season use. Russian wildrye will tolerate frequent clippings better than other grasses (Heinrichs and Clark 1961). Despite this trait, rest is important to allow the plants to recover for re-grazing. Because of its quality in stored forage, Russian wildrye may be grazed late into the season with acceptable livestock production.

Russian wildrye or Russian wildrye-legume may be grazed continuously but utilization should be less than if rotationally grazed. Plants within the sward are given an opportunity to improve vigour through under-utilization. Russian wildrye quality supports season-long use. Minerals, salt or supplements may be used to improve cattle distribution in large fields. Variability in year-to-year production will need to be addressed in long term plans.

If native range is available, then Russian wildrye is often used to 'complement' the native pasture. The Russian wildrye is used for early season use to allow the native grasses to flower before use. The Russian wildrye is rested until the following year. This system allows the seeded pasture to maintain its vigour while the native range improves in condition.

Rotational grazing is the preferred system of use of any pasture. This will provide for a rest period for the plants to recover and replenish root reserves. Utilization may be increased to 75%, if rest is provided before the next grazing. The rest period may be one year or longer depending on precipitation and usage. In all cases, pastures used late in one season must be given time to recover the following year before re-use.

A twice-over system may be used for seeded pastures. Use during the first rotation in spring is reduced and plants allowed to re-grow for later summer or fall grazing. There is a quality benefit of removing seed tillers as seed stems are prevented. 'Dormant' season grazing will reduce the forage available for early grazing the next year.