Grazing Management Systems and Stocking Strategies

Comprehensive flashcards covering grazing terminology, standard animal units, management strategies for continuous and intermittent stocking, and the biological principles of plant regrowth in temperate and tropical systems.

What is the primary difference between the terms 'continuous grazing' and 'continuous stocking'?

The term 'continuous grazing' implies animals graze all the time, whereas 'continuous stocking' accurately reflects that animals (the stock) are present in 100% of the paddock 100% of the time, regardless of their immediate activity.

In Northern Australia, how is an 'adult equivalent' ($AE$) specifically defined?

It represents a $2.2$ year old Bos Bostaros steer weighing $450\,kg$, maintaining its current weight, and walking $7\,km$ per day.

How much energy and daily dry matter intake is associated with one Dry Sheep Equivalent ($DSE$)?

One $DSE$ requires approximately $7.6\,MJ$ per day and has an intake of about $1.1\,kg$ of dry matter per day.

What is the standard conversion factor between adult equivalents ($AE$) and dry sheep equivalents ($DSE$)?

One adult equivalent is approximately equal to $7.5\,DSE$.

How is the total daily dry matter requirement for a mob of animals calculated using adult equivalents?

By totaling the $AE$ value for all animal classes in the mob and multiplying that sum by the estimated intake per $AE$ (approximately $8\,kg$ of dry matter per day).

According to the Jones and Sandler model, how does increasing the stocking rate affect production per animal versus production per hectare?

Increasing the stocking rate decreases gain per animal due to competition and less grazing selection, but increases production per hectare up to a certain point before eventually declining.

What is a major economic constraint of 'set stocking' during environmental fluctuations like droughts?

It is not economical to frequently sell and rebuy animals to match fluctuating pasture production, which can lead to overgrazing and the need for expensive supplemental feeding.

In a research trial in Northern Australia, how was 'heavy stocking rate' expressed in terms of area?

It was expressed as $4\,ha$ per adult equivalent ($AE$).

What is the difference between short-term and long-term carrying capacity?

Short-term carrying capacity fluctuates based on seasonal pasture production (the 'red line'), while long-term carrying capacity is an average calculated across multiple years to maintain stability.

What is the recommended 'pasture allowance' for cattle based on their body weight?

The allowance should be $3$ to $5$ times the daily animal intake, which equates to roughly $6$ to $10\%$ of the cattle's live weight.

Name four methods mentioned for estimating pasture biomass in the field.

1. Pasture cuts (manual), 2. Satellite images, 3. Rising plate meter, and 4. The botanau (visual estimation) technique.

Why is 'green leaf allowance' considered a better indicator than total 'forage mass' in tropical pastures?

Tropical pastures have high rates of stem elongation; measuring only total weight includes stems and dead material, while green leaf allowance focuses on the most nutritional component the animal actually consumes.

Why is it important to manage the 'sward height' of perennial ryegrass at approximately $20\,cm$?

Experimental data shows that at this height, live weight gain is maximized both per individual animal and per area (hectare).

According to the lecturer, how does the frequency of stocking rate adjustments relate to system intensity?

More intensive systems (using irrigation and fertilizer) require stricter and more frequent adjustments (every $15$ to $30$ days), similar to the control needed when 'driving a Ferrari' versus a slow truck.

What are the core characteristics of Adaptive Multi-Paddock ($AMP$) grazing?

It uses multiple small paddocks (often more than $40$) with high stocking densities ($>60$ animals per hectare) and short grazing periods followed by long rest periods ($>40$ days).

What is the scientific rationale for grazing perennial ryegrass at the $2$ to $3$ leaf stage?

This stage allows the plant to replenish its water-soluble carbohydrate reserves used for regrowth and avoids senescence, as ryegrass tillers only maintain a maximum of $3$ leaves at a time.

How does stubble height affect the regrowth of tillers and roots?

Higher stubble heights ($50\,mm$) allow for faster replacement of daughter tillers (approx. $5$ days) and quicker root elongation compared to shorter stubble heights ($20\,mm$).

Why can excessive 'trampling' of high-biomass pasture hinder regrowth?

A dense mat of organic matter can block sunlight from reaching the base of the tillers, which is the most critical factor for plants to reshoot.

What is the critical 'light interception' ($LI$) threshold for grazing tropical pastures to maximize efficiency?

The recommended threshold is $95\%$ light interception; beyond this, the plant shifts from leaf production to significantly more stem elongation and dead material.

In the tropical pasture trial, how did the $95\%\,LI$ strategy compare to the $100\%\,LI$ (maximum) strategy regarding milk production?

The $95\%\,LI$ strategy resulted in a $51\%$ increase in milk productivity per hectare because animals had a higher intake of leaves and the stocking rate was higher due to more frequent rotations.

How does earlier grazing (lower sward height) in tropical pastures affect methane efficiency?

While the daily methane production per cow remains similar, it is 'diluted' because the increased milk production makes the methane produced per kilo of product significantly lower.