Calving Ease for GF

[smcgrath76]

http://www.iowabeefcenter.org/pdfs/bch/02120.pdf

This is a pretty good summary of the effects of various traits/factors on calving ease.
The original work in NA was done at Cornell by Drs. Quass and Pollock. At the time, with existing technology threshold analysis was cutting edge stuff.
As an example of heritabilities, and trait relationships, the estimates from the SM data are:
Heritability
BW 0.18
CE 0.18
MCE 0.19
Correlations are
CE / BW 0.41
MCE / BW -0.18
CE / MCE -0.13
These appear backwards but are only this way because of the way CE scores are transformed. 1 = unassisted, 4 = surgery
So in other words, as BW increases, CE score increases (more problems), as BW increases, MCE decreases (fewer problems), etc.
Remember that these correlations are across the entire random population. There are cattle out there that break this relationship. In general the theory behind the correlations is that lower birthweight genetics, have less growth, and tend to be smaller/less developed at first calving.
I know this creates arguments and various breed claims and discussion about fertility and age at maturity/first estrus, but this is what the data says happens (again - in general).
CE / MCE EPD can and do work. The latest cycle of MARC shows that SM have caught up to and perhaps passed the current AN population for calving ease.
I do agree with CS. I would prefer to use CE bulls over the other options, but we also look at MCE to try to overcome this negative correlation.

http://www.ars.usda.gov/Main/docs.htm?docid=6238
The USDA MARC Germplasm program results are at the link above. Of most interest is probably #22 and #23.

Actually, to me the work done by MARC has made Red Poll and interesting and probably overlooked breed of cattle. Unfortunately they have not done a lot of work with some other breeds of interest such as Galloway, Welsh Black and Luing, among others.

[grassfarmer]

Thanks Sean, there is a lot of reading material and I haven't ploughed through it all yet. So I wonder if the MCE results showing that lower birth weight calves can go on to produce difficult calvings themselves are in fact natures way of preventing cattle getting too small? If you get a line going that direction an unassisted difficult calving can soon terminate that line!
I can't say I've ever noticed this trend in our own cattle and I thought that as CS stated building generation upon generation of lower birthweight cattle would result in a stable easy calving line.

With regard to Red Poll cattle and also arguably Lincoln Red, Sussex and North(or Ruby)Devons they all have undiscovered potential. The populations of these breeds are not large in the UK but they certainly contain some valuable genetics. I wonder looking at them how different or how unrelated to Red Angus they really are? The history of many of these breeds predates that of the Aberdeen Angus in Scotland. I know that it is a well established fact that black Angus can throw the odd red calf hence the development of the Red Angus breed but of all the people I knew in Scotland that had Angus I never knew one that had a red calf. It seems strange that in the number that came to America there were enough red carriers to populate the world with it's most numerical breed in fifty years or so.

As an aside I add the comment Jim Lents, the hereford linebreeder made on Devons and their current importations from New Zealand by Gearld Fry's group. "I find it strange that they feel the need to re-import a breed whose last contribution to American posterity was pulling wagons on the Oregon Trail" - priceless!

[cowman]

I have always found that AI bulls from ABS pretty well deliver what they promise in regards to calving ease?
We used a Red Angus bull "Bootjack" that delivered exactly what they promised...low birthweight, good mothers. Used a popular Herford bull "Challenger" that had high birthweight and lots of frame...again exactly what they said!
I have not had much luck with some of the Canadian AI bulls...all over the map!
The days of those big monster Char and Sim calves are pretty well gone? In fact some of the black angus are going to throw some pretty huge calves that would put most Char calves to shame?
A good sized cow should be able to have a good sized calf? At the end of the day when you trot them off to the sale barn, you want a calf that the buyers think will make them a dollar.

[cswilson]

Examples???? I've used bulls from both companies too-start naming names .

[cowman]

Having some trouble remembering names because I haven't used either Western or Independent since the late 80s. Do know I used a Char bull from Western that wasn't what you could call an "easy calver" and one Sim from Independent who had low EPD for birthweight, who threw some very big calves. Used a Mckenzie Red Angus bull(Independent) that threw calves all over the weight range, but made very good cows.
Used the herford bulls Titan and Vigilante also in the early ninties. The Vigilante cattle were good.
Haven't AI'ed the last few years but am a firm believer in it for moving a cow herd forward.

[cswilson]

So you used Titan 7777 too-how you like those Simmental cross calves-that was about the last time I used an ABS bull-if I wanted to bredd Simmental I'd just buy Simmie semen-I got rattailed smokes off him and my Angus cows. Glad you expound the superiority of an American A'I' stud after widely sampling three Canadian bulls from three different studs in three different breeds-that's kind of R-Calf science there sunshine.

[smcgrath76]

Interesting. Perhaps the most important piece of info missing here is what was the accuracy of the EPD on those bulls?
I wouldn't use a low accuracy sire across my entire cowherd, but we have used high accuracy bulls on every cow before.
Also, in the late 80s most evaluations were not North American. Currently, pretty well all evaluations are North American (US and Canadian data) and all AI studs are getting their EPD from the same model and the same data sets.