Mineral Supplementation: Focus on Phosphorus

Comprehensive flashcards covering the importance, physiological roles, mobilization, and diagnostic methods for phosphorus supplementation in grazing ruminants based on the lecture notes.

What is the 'law of the minimum' as applied to animal production?

The law states that production is limited by the nutrient that is in the least quantity relative to its demand, meaning increasing other nutrients will not affect production until the most limiting one is addressed.

What is the hierarchy of nutrient importance for grazing ruminants in Australia?

1. Metabolizable energy, 2. Crude protein, 3. Phosphorus.

Why is phosphorus particularly significant for grazing ruminants in Northern Australia?

It is frequently the most limiting nutrient in forage sources in that region, despite nutrients like potassium and calcium having higher total requirements.

In which specific scenario might calcium be more limiting than phosphorus?

In a dairy grazing system where cows are at the peak of lactation.

What are the primary physiological roles of phosphorus mentioned in the lecture?

It is present in DNA and RNA, and it is part of biochemical reactions related to energy, such as ATP and energy transactions.

Where is phosphorus absorbed in the ruminant body?

Phosphorus is absorbed in the small intestine rather than the rumen.

How does the animal body act as a 'bank' for phosphorus?

When there is a surplus, phosphorus is stored in the bone; when there is a deficiency, the animal mobilizes those minerals from the bone to supply the body.

What is the phosphorus concentration requirement for microorganisms in the rumen?

Between $50$ to $80\,mg$ per liter of rumen fluid.

Approximately how much phosphorus can be mobilized from the skeleton of a $400$ to $500\,kg$ breeder cow?

About $0.9\,kg$ of phosphorus (from approximately $3\,kg$ of skeleton).

How much phosphorus is required per liter of milk produced by a cow?

Approximately $1.6\,g$ of phosphorus per liter of milk.

What are the roles of osteoblasts and osteoclasts in bone turnover?

Osteoblasts are cells responsible for bone formation (producing new bone), while osteoclasts are responsible for bone resorption (breaking down bone).

What is CTX1 and what does its concentration in the blood indicate?

CTX1 is a component of the bone matrix released during resorption; high concentrations in the blood indicate high activity of osteoclasts and bone mobilization.

What is the relationship between phosphorus intake and dry matter intake (DMI)?

There is a high linear correlation; low phosphorus concentration in the diet significantly reduces DMI over time.

Which diagnostic strategy is most recommended to determine if a herd needs phosphorus supplementation?

Measuring plasma inorganic phosphorus (PIP) concentration in the blood, often alongside an assessment of the dry matter digestibility of the pasture.

Why is fecal phosphorus considered less precise than plasma inorganic phosphorus?

While it has a good relationship with intake, its coefficient of determination ($0.69$) is lower than that of plasma inorganic phosphorus.

According to the Northern Territory grazing trial, what was the impact of phosphorus supplementation on pregnancy rates?

Pregnancy rates were $25$, $39$, and $63$ percentage units higher over the three years assessed.

What was the economic return on investment for phosphorus supplementation in the Northern Territory trial?

Each dollar invested returned an extra $7.80 in production.

What is the recommended supplementation strategy for phosphorus-deficient country?

Supplement year-round, including both wet and dry seasons, ensuring phosphorus is associated with protein or non-protein nitrogen during the dry season.

What happens to the bone of a cow that received high phosphorus during pregnancy but low phosphorus during lactation?

The bone undergoes demineralization as the animal consumes its own bone reserves to sustain the high mineral requirements of lactation.