Touched on a point that has been discussed with some friends. You want to put selection pressure on your ewes for early breeding and twinning. Continued use of homonal minulation to cycle your females , will result in what the dairy industry has . females that will not cycle at all without drugs.
I used cidrs in my ewe lambs last year. No pg600. The youngest one had twins. The nice thing was concentrating the lambing for a gruop, or so I thought. They still lambed over about a 10 day period. The one ram was a long gestation and one was short. So did have 3 lambing events. One for each ram used.
I considered cidrs for my matures this year. Opted not to. Concentrated on making sure ewes were in breeding rig( condition score 3) and a core gruop(25 head) that I wanted bred earlier and tight were isolated from rams for 60 days.
Seems to have worked
Rams been in about 10 days . Have not checked ,but count yesterday was 35 ewes marked. Historically ,98 percent of my ewes settle on single service. Not all ewes were introduced to rams at one time, as I want some lambs with different birthdates.
I can not see any reason to use pg600 this time of year. If your ewes are so unfertile that they can't drop more than 1 embryo, are they worth propegateing.?
One if my friends has exposed his ewes 2 weeks earlier than I have for many years. He has saved ewe lambs from those ewes over the years. He has a flock that natuarlly cyles early and has a very prolific flock of bf wether dams, normally approaching a 200 drop rate.
He implemented an aggressive ai plan 3 years ago. Saving a lot of those daughters, along with natural daughters. This year an aggressive cidr / pg 600 plan used with natuarl cover of rams. As his second cyle is about half way through, it appears that I have more ewes settled than he. It appears either the rams are not fertile enough to cover his groups, or the ewes are cycling, but may not be ovulating. Either way, lots of remarks and will now be later lambing.
His ewes are also in condition score 3 and most were isolated from rams for at least 60 days. No right or wrong In this deal, but my retained ewes will be from early born twins from non hormone induced ewes or retained flush ewe lambs.
I will continue to cidr ewe lambs as it is a nice way to manage that gruop. No pg600 . cidr will be in10 go 14 days.Most lambs are sold out of that gruop, as they don't fit my management scheme . I will be using a ram lamb from that gruop. The one twin born out of the ewe lamb that had twins.
She lambed at 12 .5 months of age . Sire of those lambs was a ram lamb that sired lambs at 5.5 months are age.
Good luck .