Apparently here in the UK crop and gizzard impaction is an increasing problem as a result of the increase in popularity/demand for free range.
In my experience this is more often a case of hens who do not free range often, or which were raised in cages, suddenly being granted access to long pastures. Among my animals, those raised free range on grass I've never seen suffer crop impaction or gizzard impaction. Those brought in from cage reared backgrounds are prime suspects/candidates for it. But there's a few things that influence it too, like how intact or otherwise their instincts are.
For example RSLs are commonly known to be severely lacking in instinct regarding things other chickens know to avoid. With high production breeds usually raised in intensive and highly artificial environments, with the first few generations you can take the chicken out of the cage but can't take the cage out of the chicken's mind, so to speak. Others adapt quicker.
Hens having access to lush pasture, particularly at this time of year are tempted to gorge on the sweet grass and if it is too long it gets ravelled up into a ball and clogs.
I put that down to desperation and lack of experience, not the length of the grass being the risk but rather the hens' lack of experience with it. Hens raised free range know better to eat long strands of fibrous material and if they can't break a piece of grass they use a foot to remove it from their mouths, not swallow. Cage stock just keep swallowing.
Cage stock that are given grass cuttings are also more likely to eat lengths they should not, but so are all chickens and all other caged animals that eat grass, just because they cannot easily break them up from the length provided. Given a chance they 'cut' their own length, often from half a centimeter long to an inch but almost never longer than that.
You could make a similar comparison here with sheep suddenly being let out into a lush paddock from a dry one and getting bloat and scours and dying. The fault is not the grass, it's the human management. In the wild they don't all drop dead whenever the rains bring fresh green grass, because not only is the amount available staggered, they are experienced enough and instinctively intact enough to know to not gorge. When I let my cage-bred/reared new stock onto grass for the first time, I restrained them in small mobile runs on very short and tender grass for about a week so they could learn how to handle it before being let free range; even so, occasionally I'd see one of those hens (never a free-range-reared one though) consuming grass too long for it, and I'd make a mental note and give it an olive oil drench later the same day, or just add more oils to their feed mix. Keeping their natural oil levels high prevents basically all egg binding and prolapse because the mucosal membranes of the body, from mouth to vent and everything in between, are kept supple and lubricated. I've always followed that 'old wife's tale' piece of advice and never had a single egg bound or prolapsed hen, even with those known to be predisposed genetically or via health issues. It's likely also had a huge impact on my extremely low occurrence of crop and gizzard binding and when I did get a gizzard bound bird that's what I treated it with.
Unfortunately I'm not sure of an enzyme that will break down fibre like this but will research it.
Can't quite recall what, but there is an enzyme used in the equine industry for a very similar problem; it's naturally sourced, meaning they don't administer it in pill or injection form or anything ike that... I think it's something naturally occurring in some grasses, and/or in their digestive tracts' microflora or probiotics or similar.
It is treatable if it is just the crop that is affected but once the gizzard is impacted it suggests there is no hope. Obviously you can feel when the crop is impacted, but Dolly's crop was empty as it had all moved down and jammed in her gizzard.
Pretty unfortunate and incorrect that they suggest there's no hope! Plenty of people lose chickens with gizzard impactions but plenty manage to save them too. But it can be a fickle thing to try to address especially because in many cases you don't see symptoms until it's pretty advanced.
Anyway, none of the others are acting poorly yet (just a couple with slightly dry looking combs) and all are eating enthusiastically and it is now several days since the horses last had grass cuttings, so hopefully we are over the danger point.
If anyone knows of any supplements/foods that promote fibre break down that are safe to use on hens, then I'm happy to give them a go and see if those 2 hens' combs return to normal. They have access to plenty of grit already.
How large and sharp is the grit?
Many people provide the sort of grit that would do for a cage bird, like a canary, and expect that to do the job for chickens, and it's certainly better than nothing, but left to their own devices they also choose pieces around a centimeter wide/long, and sometimes alarmingly sharp, like in cases where they will make do with plastic, broken glass, metal etc, often without dying from it too. Their guts are tough and for fibre they need sharp pieces, not rounded and small ones. Some chickens prefer rounded rocks, too, like gravel, not sure why the discrepancy in choices there. But most I've seen pick usually triangular and sharp, often slightly curved pieces of very hard matter.
Best wishes.
