Grazing Systems

All these pasture features influence the intake and production of individual animals. However, for the sheep producer, it is ultimately production per unit area that

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Fig. 2 Typical changes in dry matter (DM) digestibility of pasture during the growing season. (View this art in color at www.dekker.com.)

drives profitability. A key element in sheep nutritional management is then the identification of the stocking rate, which will strike the balance between optimum (not maximum) nutrient intake per animal, and animal production/ha.

The sheep producer must also select a system for grazing groups of animals on the available areas of pasture. Grazing management systems range from true set stocking (all the animals graze all the land all the time), through rotational grazing (animals shifted between areas at intervals of one to several weeks), to very rapid rotational grazing (large flocks or mobs of sheep graze on small areas, with frequent shifts referred to as cell grazing or mob stocking). Which of these is the best system is the subject of continuing argument. Because most sheep-production systems

250-

Fig. 1 Effect of amount of pasture (75% digestibility) on the intake of a 50 kg sheep. [Data derived using GrazFeed decision support tool. (From Ref. 4.)]

Amount of pasture (t DM/ha)

Amount of pasture (t DM/ha)

Table 1 Minimum amounts of green pasture (kg DM/ha) required for different classes of sheepa

Digestibility of pasture (% DM)

Sheep class

75

68

60

Non pregnant, non lactating

400

600

1,200

Ewes, mid pregnancy

500

700

1,700

Ewes, late pregnancy

700

1,200

Nb

Ewes, lactating, 1 lamb

1,000

1,700

N

Ewes, lactating, 2 lambs

1,500

N

N

Young stock growing at: 75 g/d

400

700

1,700

125 g/d

600

1,000

N

225 g/d

1,600

N

N

aYoung growing stock 4 month old, 32 kg crossbred lamb from ewe of mature live weight 55 kg. bN production target cannot be maintained under defined pasture conditions. (Adapted from Ref. 1.)

aYoung growing stock 4 month old, 32 kg crossbred lamb from ewe of mature live weight 55 kg. bN production target cannot be maintained under defined pasture conditions. (Adapted from Ref. 1.)

operate below their optimum stocking rates, it is likely to be more useful to concentrate effort on defining the appropriate stocking rate for the enterprise rather than to become preoccupied with the system of grazing management.

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