One of the best studies on heterosis I've ever seen was at an American University research farm. I think it was U of Nebraska if I remember right but don't quote me on it. That study changed the way I looked at crossbreeding after reading it in the Canadian Gelbvieh magazine. They had done studies on using F-1 cows with F-1 bulls VS. purebreds VS. F-1 bulls on purebred cows VS. F-1 cows with terminal sires. All F-1 cows were of mainly British origin, and the 'terminal' sires were continental. The conclusion was that, under the same conditions - apples to apples - the terminal sires on F-1 british cows produced something like 24-26 pounds more of weaned calf. I'll try and find the article tonight and post it.
The article also stated that you have to consider all of your own factors - of course - b/c terminal sires on F-1 cows just doesn't work for everyone. We can't all at once take our mongrel cows to market and replace them the same day w/F1 females. So, when I took into consideration all of my factors, and got involved in a niche market for Galloway and Highland beef, I ended up with Galloway bulls on an Angus based cow herd, FOR NOW. The goal is Galloway cross females that I can breed any way I like. But for our beef program, the calves must be at least 50% 'Celtic' heritage, so we'll have to plan accordingly.
Now something else that vexes my mind, is how much is that extra 25 pounds of calf really worth when using continental sires, when you add in the extra work of calving problems with larger frames? 25 pounds is 25-35 dollars extra per calf, but a couple of vet bills for c-sections or prolapses, not to mention your own time, will eat that up pretty quick. So in my opinion it still comes down to whatever works for you. There is a huge amount of room for improvement in most herds I see, but you still can't just go by numbers and data. Black and white will make gray on paper, but when it comes to mixing genetics, it's not quite so clean cut.
