Selenium in New Zealand pastures

Area of Science:

• Agricultural Science
• Soil Science
• Animal Nutrition

Background:

• Selenium is an essential trace element for animal health.
• Pasture selenium content is influenced by plant species, soil type, and environmental factors.
• Selenium deficiency can lead to unthriftiness in grazing livestock.

Purpose of the Study:

• To investigate selenium concentrations in various pasture species.
• To determine factors affecting selenium levels in pastures.
• To establish critical selenium thresholds for grazing lambs.

Main Methods:

• Analysis of selenium concentrations in different pasture plant species (grasses, clovers, lucerne).
• Assessment of selenium variation based on soil type, season, and plant growth rate.
• Correlation of pasture selenium levels with observed unthriftiness in lambs.

Main Results:

• Highest selenium concentrations were found in the leaves of grasses and clovers.
• Selenium levels varied significantly across different soil types (3-1500 ng/g).
• Lower selenium levels (<20 ng/g) in spring pastures were associated with selenium-responsive unthriftiness in lambs, while >30 ng/g was adequate.

Conclusions:

• Pasture selenium content is highly variable and influenced by multiple factors.
• Plant species, growth rate, and soil type significantly affect selenium accumulation.
• Establishing adequate selenium levels in pastures is critical for preventing deficiency disorders in grazing lambs.