The Role of Pastures in Grass Founder (Sand Cracks) (Nutrition Update, Volume 9)

Grass founder is the result of predisposed animals being exposed to a metabolic insult that results in hardship grooves on the claws. The development of these grooves appears to create a weak point in the hoof wall. This weak point splits due to the mechanical pressure of the bone on the hoof wall, resulting in sand cracks and lameness. Factors which predispose animals to sand cracks are inadequate mineral nutrition or a previous dietary imbalance, genetics, age (older, heavier animals are more susceptible) and an environment which results in mechanical injury. The metabolic insult is related to early spring turn out on to pasture.

• Early spring grass pastures have very high crude protein (20-30%) and low ADF (20-25%). An apparent deficiency in "functional" or "effective" fiber can also be present at spring turn out. Livestock which have been adapted to drylot feeds do not have the necessary microfloral balance in the rumen to utilize these very high nutrient, and low effective fiber levels. A rapid change-over to very high quality spring forage, coupled with rapid rates of digestion and low effective fiber levels, result in a shock to the rumen system. Lactic acidosis and subsequent laminitis occur.
  
  Practices to Reduce Potential Problems in Spring:
• Meet the nutritional needs of the animal with particular attention to mineral balance (eg. zinc) throughout the season to reduce their predisposition to grass founder.
• Utilize fall management practices to enhance residue on pasture. Reduce late summer/fall grazing on the pastures that will be used early in the spring to increase the fiber content in the diet. Rotational and complimentary grazing systems enable this approach.
• Reduce spring use of fertilized pastures. Deferred grazing of fertilized pastures to allow for increased fiber and reduced nutrient concentrations.
• Delay/defer spring turn out. Where economically feasible, animals could be retained in dry lot. However, this option must include increased summer pasture utilization to offset the economics.
• Turn out earlier in the spring. The development of a sacrifice pasture permits continued dry feeding as the animals adjust to emerging pastures.
• 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. 

Nutrition Update
Volume 9 No.1, May 1998