More about Bone Development in Horses

5th February 2019

The correlation between bone development and horse nutrition has been researched extensively over the past few years. That a foal can be standing within 20 minutes of birth and within hours be ready to run yet at this stage of life has less than 20% of their mature bone mineral content highlights the careful balance taking place between growth, nutrition, bone strength and development, body weight, and the forces applied to bone to achieve optimal growth.

Developmental Orthopaedic Disease

The term developmental orthopaedic disease (DOD) refers to a variety of disorders involving bone malformation in foals and young horses including bone cysts, osteochondrosis and osteochondritis dissecans which are a consequence of cartilage failing to develop correctly into bone and can be caused by factors including rapid growth or nutrition deficiency as a result of poor knowledge of the nutrient requirement of horses, leaving weak bones open to disease.
Very simply put, there are two kinds of bone in horses, flat bone (mainly found in the skull and pelvic area) and long bone (found in limbs and thighs). Flat bone is a protective type of bone and is formed by a process known as intramembranous ossification. Long bone is formed by endochondral ossification.

Bone Formation and growth

Endochondral ossification is the process by which growing cartilage is systematically replaced by bone through a serious of developmental steps. The first is Hypertrophication – the growth of chondrocyte cells. The second is Calcification and the hardening of the hyaline cartilage matrix. Thirdly, in Cavitation chondrocytes die and leave cavities in the bone for periosteal bud invasion where nutrients are delivered to the bone in the blood vessels and nerves also enter. After the nutrient source is delivered to the centre of the bone, Diaphysis Elongation can take place as the diaphysis region has the resources to elongate as cells divide in the primary centre of ossification. This elongated region is known as the medullary cavity, which is where the bone marrow is contained. Finally, Epiphyseal Ossification occurs just before birth as the ends of the bone or Epiphysis develop their own centres of ossification. These secondary centres of ossification can’t remain as cartilage or they would be structurally weak, and they go through the same process as the primary centre of ossification: hypertrophication, calcification, cavitation, and periosteal bud invasion.

What can be done to promote healthy & natural skeletal development, how and when.

Endochondral ossification is the particular area, the growing area in utero where bone formation in horses has proved to be influenced by certain diet additives. Calphormin manufactured by TRM in Ireland has data and trial results to prove that the inclusion of sodium zeolite in the form presented helps enhance bone calcification.
Correct feeding for Mares in foal should start in the third trimester as bone formation is taking place. Nutrients are carried forward in the mare’s milk and foal creep pellets will improve the skeletal development of the foal and help in the prevention of Epiphysitis and equine Osteochondrosis later in life.
Other nutritional elements include calcium and phosphorus – fed at the correct ratio to each other as an excess of phosphorus relative to calcium will result in reduced calcium absorption. Chelated copper, zinc and lysine for horses are also essential elements in maintaining soundness.
We recommend involving qualified experts, your vet and nutritionist, for the best horse feed advice to assist in horse breeding programmes to ensure your youngstock the best start in life for later success and health.

Written by Bernadette Hewitt