Dissertation: How does the musculo-skeletal system and gait develop in precocial animals?

Precocial animals are animals that are able to leave the nest shortly after hatching or birth, such as chickens, hares, horses, cows and pigs. Veterinarian Ben Gorissen has studied how the musculo-skeletal system copes with the extreme changes in loading after birth in foals and calves.

Foals can walk exceptionally quickly after they are born, but little is known about how they develop their ability to move, and how their skeleton deals with associated loading so soon after birth. As they grow, the foals’ legs grow longer and their speed at walk and trot increases. However, despite the increase in their speed of movement, the bodyweight normalised peak vertical loading on their legs remains fairly stable. There is also a clearly measurable improvement in the foals’ coordination and balance. 

Bone architecture and development around birth

Foal bone is characterised by a relatively large amount of bone tissue. Calves have relatively less bone tissue at birth, but the structure of the trabeculae is more in line with the mechanical strain. These differences may be explained by the differences in the animals’ anatomy, and therefore the loading of these specific anatomical regions. Bone volume in Shetland ponies is even higher than that in Dutch Warmblood foals listed in the Royal Warmblood Studbook of the Netherlands (KWPN), probably due to the higher growth rate KWPN foals experience in the womb. After they are born, the amount of bone increases as the horses grow. However, the direction of the trabeculae and the collagen network does not change. This means that before the foal is born, its skeleton is already preparing for the loading it will experience after birth.

Gorissen has also studied the effects on bone and cartilage development of the non-steroidal anti-inflammatory drugs meloxicam in young piglets. Long-term administration of meloxicam did not cause side effects in the bone tissue and growth paltes in growing piglets, which indicates that the drug may be a suitable choice for treating pain in young pigs. 

PhD Candidate Gorissen also examined the function of osteoclasts; cells that can ‘eat’ the bone and which are essential for bone growth. A low concentration of oxygen inhibits the development of osteoclasts, but does not influence their long-term capacity to clear away bone, Gorissen concluded.