The Role of Pastures in Grass Founder (Sandcracks and Hardship Grooves)

Grass founder occurs when predisposed animals experience a metabolic disturbance that leads to the formation of hardship grooves on the claws. These grooves weaken the hoof wall, creating a structural weak point. As the animal bears weight, mechanical pressure from the underlying bone causes the weakened area to split, resulting in sandcracks. These grooves weaken the hoof structure, making it more prone to broken toes and vertical splitting.
Although their exact cause is not fully understood, several factors—including nutrition, pasture management, cow age, and body weight—influence their development. These vertical splits can be extremely painful, leading to lameness, reduced body condition, poorer breeding performance, and increased culling.
 
Causes and Development
The hoof wall grows downward from the coronary band at approximately 4 mm per month. This means the timing of stress events can be estimated by measuring the distance from the groove to the coronary band and dividing by four.
Hardship grooves form when normal hoof growth is disrupted. Common sources of stress include:
  • Handling or aggression
  • Nutritional changes
  • Disease
  • Pain
  • Weather or environmental shifts
Nutritional Stress
A major contributor to hardship groove formation is a sudden change in forage quality. For example:
  • Cows moving from preserved hay in winter to lush spring pasture experience:
    • A sharp increase in protein
    • A drop in fibre
  • Without a gradual adjustment, this can trigger metabolic disorders such as acidosis, disrupting hoof growth and causing groove formation.
Trace mineral imbalances—particularly involving zinc, copper, manganese, molybdenum, and vitamins A and E—also affect hoof health.
 
Control and Prevention
Effective prevention focuses on minimizing nutritional shocks, supporting consistent hoof growth, and managing animal selection.
Grazing and Nutritional Management
  • Avoid abrupt turnout onto lush spring pasture.
  • Delay spring turnout to allow forage to mature.
  • Manage pastures to ensure residual forage is available in the fall.
  • Do not graze fertilized pastures first thing in spring.
  • Provide good quality preserved forage for the first 10 days of spring grazing.
  • Ensure year‑round nutrient requirements are met.
  • Feed hay/straw/silage on spring pasture. Continued availability of roughage over the first three weeks of pasturing would enable higher dietary fiber levels and dilute the high nutrient levels found in spring pastures. 
Mineral and Vitamin Support
  • Provide balanced trace minerals—especially Zn, Cu, Mn, Mo—and Vitamins A and E.
  • Biotin supplementation can reduce the incidence of sandcracks.
  • Regularly feed test forages and pastures to ensure nutrient adequacy.
 
Genetic and Herd Management Considerations
Recent research indicates sandcracks have a heritability of 0.45, meaning genetics play a meaningful role in susceptibility. As a result:
  • Cull affected cows and related lineages to reduce long‑term incidence.
  • Older, heavier cows experience higher rates of sandcracks; they may warrant targeted culling.