New insights into trace element supply in cattle: towards smarter and safer supplementation

Trouw Nutrition R&D therefore investigated how the natural homeostatic regulation of animals can be utilised to prevent both deficiencies and excesses. The findings have been published in Animal and can be read via LINK. The researchers defined two important thresholds:

• The lower limit, at which the animal’s maximum absorption efficiency becomes insufficient to meet the net requirement.
  The upper limit, at which the body cannot further reduce absorption and undesirable accumulation occurs.
• Lower limits: when does absorption efficiency become a limiting factor?
  An extensive literature review shows that the maximum achievable absorption efficiency varies greatly between minerals. A maximum of 17% was established for zinc, and only 0.45% for manganese. For copper, this varies between 2.1% and 3.7%, depending on the presence of antagonists such as molybdenum or sulphur. When rations fall below these lower limits, animals can no longer compensate for their requirements through more efficient absorption.

Upper limits: when does regulation become overloaded?

At higher intake levels, the opposite problem arises: the body cannot further reduce absorption and excess minerals accumulate. For example, a longitudinal  study in dairy cattle demonstrated that the copper balance became positive as soon as copper intake exceeded the net requirement, i.e. 0.625 mg/day/kg body weight. Similar thresholds were established for zinc and manganese.

What does this mean in practice?

Using random simulations, calculations were made to determine how many animals are at risk of deficiencies or excesses at different supplementation levels. It is striking that:

• Zn supplementation during lactation remains essential, as 88.7% of cows would otherwise be at risk of a deficiency.
•  Mn requirements are often met by roughage and concentrates, except in some rearing animals.
• Cu supplementation must be carefully dosed, as even 8 mg/kg DM of extra Cu in lactating cows can lead to the tolerance limit being exceeded in 21.8% of the animals.

Conclusion

This new risk- -based gestuurde approach provides a much more accurate framework for trace element supply. By taking into account both biological limits and variation in requirements and basal intake, nutritionists can formulate rations that are healthier, more sustainable and more economically efficient.