Pennsylvania copper challenge - forage analysis and ratios

By Blake Jackson

Forage analysis is crucial for designing a balanced feeding program for sheep, goats, and cattle. While we often focus on basic measures like moisture, protein, and fiber, a deeper dive into trace minerals provides invaluable insights.

Traditionally, owners rely on mineral supplements, assuming they address trace mineral needs. However, ignoring forage analysis and rumen interactions can lead to imbalances. This article highlights the importance of understanding trace mineral availability, particularly copper, in Pennsylvania's unique context.

Copper: A Balancing Act

Copper plays vital roles in nerve function, respiration, immunity, and pigmentation. Sheep are sensitive to both deficiency and excess, making them a prime example of the complexities of copper nutrition.

Rumen Roulette: How Molybdenum and Sulfur Play Their Part

The rumen environment in ruminants like sheep adds another layer of complexity. Molybdenum and sulfur interact with copper, forming thiomolybdates that bind and reduce its absorption. The type and amount of thiomolybdate formed depends on factors like rumen pH and dietary molybdenum and sulfur levels.

Beyond Molybdenum and Sulfur: More Players in the Game

Iron, zinc, and even water sources can influence copper availability. Iron competes with copper for absorption, while high dietary zinc can trigger the production of a protein that binds both minerals, reducing uptake. Pennsylvania's water often contains high iron and sulfates, necessitating water analysis for a complete picture.

Clinical vs. Subclinical Deficiency: The Subtle Shades of Mineral Imbalance

Clinical copper deficiency presents obvious symptoms like loss of pigmentation and anemia. However, subclinical deficiency is more common and presents vague issues like reduced immunity and fertility. In Pennsylvania, we've observed increased parasite loads, stillbirths, and reproductive problems linked to subclinical copper deficiency.

Testing and Monitoring: Putting Knowledge into Practice

Trace mineral analysis should be part of your routine forage testing, with molybdenum and sulfur as optional add-ons. Analyzing liver copper concentrations during necropsy can further confirm deficiencies.

Balancing the Scales: Achieving the Perfect Ratio

Research suggests a dietary ratio of copper to molybdenum of at least 6:1 to prevent deficiency. Ratios below 4:1 are risky, while exceeding 12:1 raises concerns about copper toxicity. Unfortunately, no definitive recommendations exist for copper-to-sulfur ratios but keeping dietary sulfur below 0.3% of dry matter is advisable.

Beyond Ratios: Remember the Bigger Picture

While ratios are important, remember that total copper intake is equally crucial. Work closely with your nutritionist to design a diet that meets your animals' specific needs and prevents copper-related issues.

Photo Credit: istock-heebyj