Forage Crops

HCS612 Forage Crops
Grazing Management

	Grazing Frequency
	Grazing Intensity

Frequency

	The return period for grazing a field
	Measured as rotation length (days)
	The shortest frequency is depends on stocking rate – but under usual stocking rates with continuous grazing is ~15 days
	Typical frequencies are 20-40 days
	With 3-cut hay the frequency is 2-4 months

Continue

Intensity (handout pg 251)

The severity of grazing or cutting a field
Measured as residual height or mass after cutting or grazing

High intensity is <2.5 cm <1,000 kgDM/ha
Moderate intensity is 5-7.5 cm ~2,000 kgDM/ha
Low intensity is >10 cm >3,000 kgDM/ha

Utilization is the ratio:
post-grazing mass/pre-grazing mass

high intensity: utilization>80%
low intensity: utilization<50%

Continue

For fixed stocking rate, grazing frequency and intensity are related

		Frequency
		v. high (<15 days)	high (15-25 days)	medium (~30 days)	low (>40 days)	v. low (4-6 weeks)
Intensity	very high	overgrazing				hayfield
	high	overgrazing			slow rotation
	medium			average rotation
	low		rapid rotation		under-grazing
	very low	continuous grazing			under-grazing

Continue

Effect of high frequency (handout p258)

High defoliation frequency will suppress yield, since plants have no recovery period

This effect is greatest in spring when plant growth rate is greatest

High frequency grazing could be used for control of tall fescue

There appears to be little effect of grazing frequency on animal production

15- and 30- day rotations had similar animal production

High frequencies of rotation (e.g. 6 moves per day) have little effect on animal production

Back to top

Continue

Effect of intensity (at constant frequency)

	number of tillers	roots (g)	leaves (g)
not clipped	431	147	202
clipped at 12.5 cm	427	78	160
clipped at 7.5 cm	192	30	59
clipped at 3.8 cm	53	7	18

Continue

Species and intensity

	species vary in tolerance of defoliation intensity (text pg220)
	orchardgrass, alfalfa, tall fescue red clover are intolerant of intense defoliation (especially frequent-intense defoliation)
	ryegrass, kentucky bluegrass, white clover are more tolerant of intense defoliation

Continue