Professor Jo-Anne Murray
PhD, MSc, PgDip, BSc (Hons), BHSII, RNutr, PFHEA University of Glasgow Veterinary School
What is copper?
Copper (Cu) was first discovered many thousands of years ago and was initially used to construct metal objects. Looking back at ancient records, it would seem that copper was believed to have antiseptic properties. Back in the early 1800s researchers found copper in plants and then later discovered that copper was also present in human and animal tissues. Having said that, it wasn’t until the early 1900s that scientists recognised the essential requirements for copper in the diet of humans and animals.
What does copper do?
Copper is now considered as an essential mineral because it has a number of vital roles within the body. Copper is stored and metabolised in the horse’s liver. It is an essential co-factor (a substance that helps enzymes cause a reaction) for numerous enzymes in the body making it an important mineral, even though it is only required in small amounts, which is why it is known as a micro (or trace) mineral.
Copper is essential in maintaining healthy connective tissues (e.g. tendons and ligaments); it supports antioxidant functions in the body; it is used to produce melanin (the pigment that determines coat colour) and it is necessary for the mobilisation of stored iron in the body. Copper deficiency can result in abnormal bone growth in young horses and weakened connective tissues in mature animals.
How much copper does my horse require?
A 500 kg mature horse at maintenance (not working) or in light work will require 100 mg of copper per day. This increases to 125 mg of copper per day for a 500 kg broodmare in the last few months of pregnancy and throughout lactation, and for a horse with a heavy workload. Copper requirements for growing horses are 0.25 mg of copper per kg bodyweight; thus a 300 kg yearling would require 75 mg of copper per day.
The amount of copper required by growing horses has been debated for many years, but what appears to be clear is that it is essential that pregnant mares receive adequate amounts of copper in their diet to supply the growing foetus with copper for bone and cartilage development. Studies conducted to evaluate the effect on copper supplementation of broodmares and foals have shown that the foals of mares supplemented with copper during pregnancy had lower inflammation of their bone growth plates (physitis) and fewer cartilage lesions than those that were not supplemented. In addition, the foals of the mares supplemented with copper had higher copper stores in their liver at birth, which is considered important for healthy skeletal development during the period of postnatal growth.