Selective Grazing and Grazing Management Lecture Notes

These flashcards cover the concepts of selective grazing, preference vs. selection, nutritive value of forage components, animal factors in diet selection, and fundamental grazing management terminology including stocking rates and defoliation parameters.

What is the distinction between 'preference' and 'selection' in the context of animal grazing?

Preference relates to what an animal would eat if there were no restrictions or constraints, whereas selection is what actually happens based on what is available in the environment.

According to research, what morphological component do animals prefer even when the nutritive value (such as $NDF$, $ADF$, or lignin) is the same?

Animals prefer leaves over stems.

In a grass monoculture, why do animals prefer grazing the top of the sward?

The top contains the youngest leaves which have higher digestibility and crude protein compared to bottom leaves.

What is the typical preference ratio for animals choosing between legumes and grasses?

$70\%$ legume and $30\%$ grass.

In a dairy cow trial, what was the percentage increase in intake when grass and legumes were offered in separate paddocks rather than mixed?

$11\%$ increase.

In the feedlot trial involving ryegrass, Lucerne, chicory, and plantain, how did the multi-forage choice affect animal performance?

Animals who could choose between species ate $50\%$ more and gained more weight, even though their selected diet had a lower nutritional value than the single-forage diet.

How did infection with the gastrointestinal nematode 'black scar worm' influence the diet selection of sheep?

Infected sheep selected a diet with higher crude protein content to meet the body's demands to fight the infection.

Define 'Forage Mass' as described in the lecture.

The amount of biomass that can be assessed in a paddock at a specific point in time, often measured using quadrants.

What is the difference between 'stocking rate' and 'stocking density'?

Stocking rate refers to the number of animals per total area, whereas stocking density is the number of animals in a given area at a specific point in time.

What is the 'carrying capacity' of a grazing land?

The maximum stocking rate that achieves a target level of animal performance over a defined time without deteriorating the land.

How is 'forage allowance' calculated?

$\frac{\text{kilos of dry matter}}{\text{kilos of live weight}}$ (e.g., if $10$ cows at $500\,kg$ graze $10$ hectares with $5000\,kg\,DM/ha$, the allowance is $10\,kg\,DM/kg\,\text{live weight}$).

What is the 'utilization rate' in a grazing system?

The proportion of the total amount of biomass produced that is actually consumed by the animals.

What is the estimated optimal utilization rate for extensive grazing systems in Australia?

$30\%$.

Describe the relationship between stocking rate and production per animal vs. production per area.

As stocking rate increases, production per animal decreases due to competition, while production per area increases up to a point before eventually decreasing.

What are the two primary parameters of defoliation that affect both plants and animals?

Frequency (how often the plant is grazed) and severity (how much of the plant is removed).

How is a well-managed 'continuous stocking' system maintained?

By adjusting the stocking rate to match the carrying capacity, which involves adding or removing animals depending on how fast the pasture is growing.

In the Sagebrush trial, what happened to the selection of undesirable species as forage allowance decreased?

The selection for undesirable species increased because animals were forced to consume them once they ran out of preferred feed options.