Vita: Began to think and realized I came to the point that I'm not sure what the real correlation is of feet and leg skin with SARA. I believe that this is a cause of acidosis. Discomfort and poor housing (short beds) leads to less feed intake, poor appetite and sorting. From the other hand it can be consequence of very bad general health due to acidosis and came from too long laying down.
Thoughts by Joep Driessen
You are right: bad beds makes bad things happen with hock skin.
In order of importance (best guess based on experience only...)
Acidosis kills rumen bacterias. Toxins come free in the rumen. Get absorbed in the blood vessels. Toxins ruin the endothelial cells (inside layer of blood vessels).
When you put pressure on these vessels they start leaking blood under the skin. This happens in the hocks only in combination with hard beds!
And under the claw sole : Laminitis! Only in combination with hard floor (concrete) and too much standing time (for example 3 or more hours waiting for milking).
Swollen hocks will also rub more over the hard stall floor and you get more hair loss.
1: hard stall floor
2: rough wood particles in bedding material( saw dust)
3: lameness: too much time (1 or more hours) resting on one side: bed sores
5: too short bed: legs half out of the bed
6: empty deep beds: hard back curvbis irritating skin
Thoughts by Jan Hulsen
The relation between ruminal acidosis and hock lesions is complex. Farmers often talk about it and I believe that their observations are correct: episodes with symptoms of ruminal acidosis often come with an increase of swollen hocks. Probably because the beds are quite hard and ruminal acidosis is the trigger to increase the impact of this on the hocks of the cows.
The mechanism Joep describes, histamin release due to endotoxins which causes higher vulnerability of capillary blood vessels, is a hypothesis and makes sense. But there are more possible reasons, that can contribute:
Ruminal acidosis also leads to loss of body condition score, which decreases the fat cushions in the claws and makes the claws more vulnerable for solar hemorrhages (a symptom of laminitis). Solar hemorrhages are very painful, so the cows ly down for longer periods, which increases the load on the hocks. It is often cows with low bcs that show thick hocks. Perhaps the fact that in these cows there is also hardly any fat under the skin of the hock and that their lying position puts more load on the hocks, increases the risk for thick hocks.
Often cows with ruminal acidosis also have lower resorption of minerals, trace elements and vitamins. This reduces the quality of the hoof horn and might increase the sensibility for laminitis.
On top of this, cows with ruminal acidosis more often have ketosis, which again reduces the quality of the hoof horn and might increase the length of lying bouts (episodes of lying).
And last but not least: the risk group for ruminal acidosis are cows in the first weeks of lactation. These animals have a lot of stress and often show increased standing times (more load = more hoof problems = more hock problems). Plus these animals often have subclinical hypocalcemia, which might reduce the quality of the hoof horn.
On the photo, the coronary band looks quite red and a little swollen. This can be a sign of laminitis but also of infectious hoof problems (digital dermatitis, heel horn erosions). This needs to be checked.
My first impression is that the beds are very rough and quite hard. Did you do the back-of-hand-rub-test to test for roughness? Did you do the knee-test to test for hardness? I always ask the farmer and farm staff to join me in these tests.
When cows have soft and comfortable beds, there are very little hoof and hock problems even with ruminal acidosis.
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