In theory, sub-acute rumen acidosis occurs when pH in the rumen gets to lower than 5.5 (acidosis is lower than 5.0) but in reality, Margerison said the length of time that the pH is below ideal is an important factor.
“Individual cows are genetically predisposed, or not, to cope with that. Some will function perfectly well at low pHs and others will have problems.”
The acidosis can result in a halt in claw horn growth and could cause a split to develop just below the coronary band – the point where the hoof meets the hairy skin on the cow’s foot. It is an individual farm diet-based issue.
“There are quite a few micronutrients we can use – they’re involved in skin and horn production,” Margerison said.
Hoof horn is a composite of cylindrical tubules held together with a cementing material. The quality of both is determined by factors like diet and exposure to moisture. Supplementing micronutrients can improve that quality, it’s just a matter of examining the farm system and seeing what is lacking.
“Biotin’s one of the most successful ones. The assumption is that ruminants produce enough biotin in the rumen, but often they do not.”
While Margerison said not all herds would benefit from biotin supplementation, those that spend time on feedpads and are fed a more acidotic-type of diet might see some improvement over time.
Zinc is another common additive that could be beneficial. It can be used in the diet or as an external application from a mat depending on the advice from vets or consultants.
Results from dietary micronutrient supplementation happen over time. They are not instant fixes but over the longer term can improve hoof horn hardness.
Margerison said Friesians tend to have a greater incidence of lameness than Jersey cows, with crossbreds somewhere in between. Research suggested hoof horn colour – white or black – had no impact on occurrence of lameness, but breed clearly has.
