Bill, you say you've used the Dorper ram in years past. What was the growth on last year's lamb crop sired by him?
I only have experience with a Coopworth sire and Texel sire so don't have the Dorper background, but our mid February pure Texels are ranging 104-140 lb mid Sept on pasture alone (creep fed for a month before pasture came on, just a minute amount compared to your grain program), weaned late (4 months) and pasture that is now waning. Just now getting a bit of hay to augment the forage left. Backfat is .10-.34 with the ewe lambs at the higher range. They are out with their mothers (weaned a while back and reintroduced). Ram lambs and wethers are separated.
Texel sired crosses are ranging all over the board depending on the ewe breed and were born in March-April but range from 75-125 lb. Mid Sept
Pure Coopworth born in March-April are 75 (set of quads are light) to 115 lb.
Here's the interesting part....we did a late lambing with our ewe lambs from last year. They lambed in June and July, Texel sired, all singled (which I wanted for ewe lambs) and their lambs have been on grass from the get-go, no creep feed. They were 35-55 lb mid August, haven't weighed them since. Many were gaining 1 1/4 lb a day...I know, they are singles and still nursing but nothing has been put into them as far as feed costs. Plus, I didn't have to get up in the middle of the winter all night to check on lambing, etc. We just went outside each summer morning to find lambs nursing and doing fine. I'm wondering...why don't we do it like this with all of them? Well, you know the reasons, purebred folks want breeding stock early in the season, market lambs need to be ready for my locker lamb customers by October and Superior Packing only has buy days in WA until October, so we have to have lambs ready to market at market weights (120-130) a tad bit earlier.
Wormed a couple of times as needed.
Sorry, I digressed on the subject matter. Do you have figures from last year on the Texel versus Dorper sired lambs? It might be "the year". We had a drought last year and had lower ADG's but this year a bit of rain here and there did the trick. My rams are on a diet (waning poor pasture) as they got so fat having a pasture to themselves all summer.
I also have no experience with grain feeding as we are basically too cheap to buy grain except for flushing ewes for a few weeks right now. I am assuming since you have this in your program, it's something in the past that has worked well for you for finishing out those lambs. Could it be a parasite problem or a mineral depletion of some sort? Just thinking out loud, looking at the variables.
Texel and Coopworth Sheep