Lucerne is the ‘king of folders’ because it provides high quality, high protein feed all year round. This is particularly significant in the subtropics where tropical grasses are frosted and lose their nutritive value in the winter months.
The feed value of lucerne is greatest during its early vegetative phase (Table 9.2). However, utilisation at this stage will sacrifice some dry matter (energy) production and will need to be accompanied by careful spelling management to ensure persistence. Early grazing may also predispose animals to bloat.
Table 9.2 Nutritive value of lucerne at three growth stages
Compared with other feeds (Table 9.3), the protein and calcium contents are usually high, while the metabolisable energy and phosphorus content are usually low. The phosphorus content of lucerne is generally lower than that needed by dairy cows. Supplementing dairy cows with phosphorus is recommended.
Table 9.3 Comparative feed values of four fodder crops used by dairy cows
# Very early growth with heavy nitrogen applications.
* Early growth.
Some form of rotational grazing is recommended for lucerne, whether sown in a grass/legume pasture or as a pure stand. Well-managed lucerne will persist for three to seven years.
The persistence of lucerne is increased where rotational grazing management is employed in intensively grazed lucerne stands, particularly those used by dairy cattle or sheep. Lucerne responds well to heavy grazing for short periods, followed by a stock-free period that enables the plants to regrow and replenish root reserves. The stock-free period should be at least four weeks, and up to eight weeks in the winter months. The optimum grazing period should be short and no more than three weeks. This usually means a minimum of three, and up to eight, paddocks in the rotational sequence.
In extensive dryland grazing systems, strict rotations are not practised for economic reasons, although some paddock spelling and the movement of stock are generally employed. The use of a multi-paddock grazing system also facilitates cutting for hay from one or more of those paddocks during wet times, when the forage produced is in excess of the needs of the stock. Haymaking is of particular benefit before the onset of dry weather in conserving dry matter, before the lucerne stand loses leaf and quality.
It is still important to give the lucerne pasture at least one, and preferably more, stock-free periods a year. These should coincide with the most active growing periods when feed is available elsewhere on the property, or during the late summer — early autumn when lucerne dry matter production slows and the plant seems to divert its energy into replenishing its root reserves. To be effective, a spelling period of six to eight weeks, or long enough to allow the stand to flower, should be provided.
Other management practices that will increase the life of extensive, less managed lucerne stands include:
• low stocking rates;
• ensuring that the lucerne is well established before grazing;
• sowing palatable species with lucerne so that the lucerne component is not preferentially grazed;
• using disease-resistant dormant and semi-dormant cultivars with low crowns instead of winter-active cultivars with more erect crowns.