[Whittsend]

 Replying to a post by Oh lal la, Marches farmer mentioned keeping lambs( ewes) off long wet grass in the mornings as a precaution to prevent bloat.  I had no idea that  long grass with dew on could cause bloat .
I can't think why it would cause a problem. Do they swallow the longer stalks without chewing it properly so that it sticks together and digestion takes too long or is it to do with the sugars in the grass in certain weather conditions?

[ladyK]

Good question - I'm interested in understanding this better too!

[Marches Farmer]

Long, wet grass, particularly if rich in things like clover, causes excessive bubbles in the rumen and foam will form.  The tiny bubbles in the foam make it impossible for the sheep to belch and it can quickly die from respiratory or circulatory failure because of the excessive pressure on the diaphragm.  "Belching" is usually a very small burp, so unless you're downwind, while foot-trimming, say, you probably won't be aware it's happening on a regular basis!

[Whittsend]

Thank you for that explaination Marches Farmer. my bottle reared lamb is thirteen weeks old now but comes for head scratches several times a day, and does a good line in burping, so  I was aware how frequently sheep need to get rid of stomach gases. I am still a bit confused as to why this  build up of bubbles is more likely to happen if they eat  grass that is is long, and wet with dew, in the mornings ( or rain , I assume,? ).  There must be a scientific explaination and I would love to understand it, rather than just worry about it happening .

[OhLaLa]

My lad is doing fine now, once I had pinned down what his ailment might be (with thanks to some guys on here), swot that I am I did a fair bit of reading up. The grasses ferment. For comparison; Haylage/silage is baled with a higher water content than for hay and then wrapped. It ferments inside the wrapping.

"The rumen is a large fermentation vat. It contains billions of microorganisms, including bacteria and protozoa, which allow ruminants to digest fibrous feeds such as grass, hay, and silage that other animals cannot efficiently utilize. Fermentation in the rumen produces enormous quantities of gas that ruminants get rid of by belching (burping). Anything that interferes with belching is life-threatening to the ruminant and may result in a condition called bloat"

My mental image of it is imagine a demi-john without the air lock in the top, just a cork. All that fermentation, thick foam on top and nowhere for the bubbling gases to escape to.

The last two links below explain it best.

http://www.uwex.edu/ces/forage/pubs/bloat.htm

http://www.farmanimalshelters.org/care_sheep.htm

http://www.sheep101.info/cud.html

http://ag.ansc.purdue.edu/sheep/articles/pasbloat.html

[Whittsend]

Many thanks for those links OhLaLa, they tell me everything I wanted to know.
Basically, like any animal, a change of diet that happens too quickly e.g.  fast growing pasture that is wet,  or too much of a new feedstuff before the animals gut has had time to adjust (as can happen when lambs are being weaned), has the potential  to cause bloat problems.  I have a horse that has just spent six weeks in his stable, on a strict diet, because he developed laminitis when the Spring grass came through.  Friends ,who have been visiting us, were  amazed that an animal, evolved to eat grass, could be in such pain ( not to mentioned in a potentially life threatening condition) from eating grass!  Our pasture is unimproved, and full of herbage, yet still brought him to a standstill overnight!  It's a complex topic, but the more I learn the more confident I feel about identifying symptoms and handling problems when they arrive, thanks again.

[kelly58]

Good info Oh La La 

[ladyK]

Thank you for the detailed explanation & links! 

[waterbuffalofarmer]

Here is some information with regards to bloat.
http://www.esgpip.org/PDF/Technical%20bulletin%20No.31.pdf

[landroverroy]

Long, wet grass, particularly if rich in things like clover, causes excessive bubbles in the rumen and foam will form.  The tiny bubbles in the foam make it impossible for the sheep to belch and it can quickly die from respiratory or circulatory failure because of the excessive pressure on the diaphragm.  "Belching" is usually a very small burp, so unless you're downwind, while foot-trimming, say, you probably won't be aware it's happening on a regular basis!

You will see from the above, and from the link provided by waterbuffalofarmer that they both mention legumes eg clover.
It is the presence of a large proportion of legumes/clover that is the problem -  not the long wet grass  on its own. If wet grass were going to cause bloat then you would have to move your sheep every time it rained or there was a heavy dew!
Our grass has a maximum of 20% clover and in Spring it is pretty long. But in 30+ years sheep keeping it has never caused bloat.
 

[Whittsend]

Good point, Landroverroy, clover contains more sugar, carbohydrate and protein than grass. That's the main reason horse owners ( particulary those who own " good doers" or equines prone to Laminitis) don't like to see an increase in the proportion of clover in paddocks. Seed mixes for horse and pony paddocks will advertise the fact that they don't contain clover seed.  Many horses/ponies tend to eat around clover plants if they have plenty of grass, which allows the plants to multiply, but sheep/cows seem to really like clover. Seed mixes for agricultural use make a point of including clover seed.  You mention that your grassland contains about 20% clover. Is that percentage achieved naturally, from being grazed, or do you have to do something to control that?

[landroverroy]

That's just a rough estimate of the clover content after long term grazing by sheep and cattle.
If you use a fertiliser high in phosphate you get an increase in clover, but with high nitrogen it is supressed.

[Marches Farmer]

Can also depend on the susceptibility of the animal in question. We have lost only one sheep to bloat and she was an old ewe on grazing with little other than native (unimproved) grasses but it was long and we had a week of very heavy morning dewfall.  One evening she was fine, next morning dead from bloat.