We're at the crucial stage now, and I'm finding it a struggle. Not as much of a struggle as the birds are, but here goes...
The meat hybrid pullets are now at 20 weeks of age. Apart from the one with major leg trouble a few weeks ago these birds have all stayed active and mobile. I'm letting them out once every couple of days under supervision; I'd do it daily only the goshawks are very good at noticing. So far, so good.
The combs have all reddened and the girls have been squatting for some time. Unfortunately a week ago the first two eggs that appeared were soft shelled. Even more ominously no eggs appeared after that for several days. And then yesterday egg material was expelled freely.
The trick at the moment is balancing the birds' high energy needs (so much muscle needs a lot of feeding) without adding to fat in the cavity, which is going to cause problems with laying. They mustn't get fatter but they must get enough excess protein and energy to produce eggs. However with shells not being developed properly there's a third element: getting the mineral absorption right.
I believe this isn't a supply issue as the birds are given 3.5% shell grit in the feed, and there is also an ad lib hopper in each pen. Phosphorus in excess amounts compared to calcium can cause soft shelled egg laying, and it's true that milk has an improper ratio, but I'm only giving kefir once a day at about a cupful per 10 birds. Perhaps the skim powdered milk is higher in phosphorus than even straight milk, but even so it shouldn't cause this effect at the amounts I'm feeding; not when the layers are doing well with good hard shells on the same diet. It's not a vitamin D issue (D is required for the absorption of calcium) as their pen gets sufficient sunlight. I'm left with either a virus like EDS (Egg Drop Syndrome), which doesn't make complete sense given that they've come directly from a hatchery and haven't contacted many other birds; and gut issues affecting absorption.
What to do next?
First thing will be to slightly reduce protein so the laying stops for a short time (a week or two should help). That gives them a breather, though some may keep laying internally, which will be a bad thing in every way. EDS is improved by a break from laying, typically during a moult. Sometimes I feel a break can give the shell system time to catch up to ovulation as well.
Secondly I'll worm them. I haven't done so yet because they haven't shown signs of needing it (no diarrhoea, no weight loss), but they will almost certainly carry parasites, and these birds would very definitely have been bred without parasite resistance in mind. They might well have a few too many worms that are inhibiting calcium absorption by damaging the intestines. The layers of course aren't showing these problems, but whereas layers are bred to last 18 months before starting to fail (in the commercial setting) meat hybrids have only been bred to last 8-10 weeks. For this reason I feel their immune systems are likely to be massively more under par than those of their comparatively long-lived cousins.
Lastly on the thin-egg front I'll switch to commercial pellets (layer feed) for a while. This can be useful to find out if the mix I've been giving them isn't ideal. Actually they've been on half commercial mix for a while, given the problems I've had post-lupins (trying to source high protein feedstuffs) so this isn't a major change. And as I said the layers are doing quite well on the same feed. But it's worth a shot in case I've missed something.
So that's the current picture... A balancing act in the extreme! I hope I can sort out the laying as they really are friendly handsome birds. They're too huge for their own good, but they're inquisitive and quite gentle. They seem to know that their huge size puts them ahead of other birds when it comes to shaping up for a tussle. They're just a neat no-drama creature that's unfortunately been bred too far down a particular line.