genetic markers and selection

[knabe]

interesting read.

translation.  even with different selection pressure, or lack of it, it's amazing how much polymorphism there is for some of these genes.

the reason i bring it up is because it's fairly obvious to me that even with literally decades of selection, it is extremely difficult to get animals homozygous for anything.

it's also pretty clear to be able to select for heterozygosity with selection pressure.  what would be really cool is to have two pure bred herds that were oppositely homozygous with terminal cattle as the hybrids, maximizing heterozygosity.

it's pretty amazing this happened.  amazing that selection pressure is so specific.

http://jas.fass.org/cgi/reprint/74/8/1784.pdf

from the text.

"The genetic background of a population
may prove to be an important factor as DNA markers
linked to QTL are identified.  Quantitative trait loci
influencing a trait in one population may have a
different effect, or no effect at all, in another
population due to epistatic interactions of the QTL
with background genes (Pomp, 1994).
Heterozygosity. It was expected that the Lents
population would have the lowest Hl and that the
pooled EPD population would have the highest Hl
because of known inbreeding levels. These expectations
were verified at the IGF-I, PRL, BM2113, and
PIT1 polymorphisms, but not at the K-Cas, B-Lac, or
GH polymorphisms. Selection or drift may be preventing
the latter loci from displaying the expected
consequences of inbreeding."

more interesting mumbo jumbo.

A significant effect of B-Lac on milk yield has been
reported, with increases consistently associated with
the A allele (Geldermann et al., 1985; Aleandri et al.,
1990; Bovenhuis et al., 1992; Cowan et al., 1992;
Bovenhuis and Weller, 1994). Bovenhuis et al. (1992)
and Bovenhuis and Weller (1994) also reported a
significant increase in fat percentage associated with
the B allele. A QTL influencing protein percentage
and yield closely linked to B-Lac was also identified
(Bovenhuis et al., 1992; Bovenhuis and Weller, 1994).
Results from the present study failed to detect a
significant effect of the B-Lac polymorphism on PR-m.
The GH polymorphism investigated in this study
results from a single point mutation that causes either
a leucine (A allele) or valine (B allele) to be
incorporated at amino acid position 127 of GH
(Seavey et al., 1971; Zhang et al., 1992). Eppard et al.
(1992) reported higher milk yields from dairy cows
that received recombinant-derived GH with valine at
position 127, compared to cows receiving GH with
leucine at position 127. These results are consistent
with the present study, in which the GH B allele was
associated with a significant increase in PR-m, explaining
5% of PR-m variability.

 

[aj]

You have brought up a good point knabe. You could really max out heterosis with this information. I would give up my good looks if I knew which Shorthorn bull out there was THE carcass bull of the breed.People could be sitting on genetic goldmines but this information isn't figured out yet and he could hypothetically go to the salebarn as a steer. I will probably be dead when it is all figured out though. Good topic.

 

[Dale]

If you are looking for homozygous, Shorthorns are mostly bred to max out the hybrid vigor (heterozygous).  Many of our Shorty's have various percentages of outcross genetics brought in through dual purpose (milkers), Irish, appendix (both on and off the pedigree).  By outcrossing, cattle tend to be more growthy & genetic recessives don't show up very often. 

A.J., we have tried some genetics from line-bred cattle including Rob Sneed's 034, some Irish, & Jazz.  About the only line-breeding I practice on purpose is that we like various Enticer descendants.  Years ago we purchased genetics with Frosty Acres bloodlines and the entire Bi-Ru herd hoping to improve Shorthorn carcass.  Often as not, we were barking up the wrong tree, except for marbling.  In recent times some carcass data has been made available through the sire summary; I'm not sold on it completely, since most are not high-accuracy.  I think the Smith calf that was 10th out of about 30 at Louisville recently was one we bred--he did not do well on foot, but it looked good that he graded Choice, when many were lower quality.  The one we bred was by Red Rider 844, a bull that also sires some of the outcross genetics in the breeder show.

Some people (even judges in this era of obese show cattle) don't get it that if thickness is fed on (not bred in), it is not red meat.  If it shakes when they walk, it is not muscle.  We have Shorthorns that kill very well.  Ask Barry Jordan about Waukaru Gold Mine 2109 data--they have the proof.  We also like 2109's daughters as replacements.  Since all the outside genetics came into Shorthorns, you can get anything you want (at Alice's Restaurant) if you look around--there's lots available.  Good carcass through Rodeo, Titleist 269, Dividend's Impact, etc.  For freezer beef I like some Improver 57th, since he is great on marbling.

 

[xxcc]

the reason i bring it up is because it's fairly obvious to me that even with literally decades of selection, it is extremely difficult to get animals homozygous for anything.

it's also pretty clear to be able to select for heterozygosity with selection pressure.  what would be really cool is to have two pure bred herds that were oppositely homozygous with terminal cattle as the hybrids, maximizing heterozygosity.

in regard to the first statement, it is pretty clear god intended it to be this way.

in regard to the second, I'm pretty sure it says in the Bible to not mix seed types when planting your field.....this can be interpreted in MANY ways, and totally shows how the club calf industry is without a doubt "in bondage with sin."

 

[r.n.reed]

I wish it were so simple.First define what is the ideal carcass/feedlot animal and then the ideal maternal animal and then what production model you are basing those types on.Then what happens when you cross those 2 lines.We had 2 distinct types in the early 70's english and continental,I new a guy that bred his 900lb Angus cows to Charolais.He never did it again!Actualy I'm glad its not so simple,it makes life interesting.I would also say that God has humbled me over the years when I look back on some of the breeding decisions I've made and some that were made for me.

 

[simtal]

I wish it were so simple.First define what is the ideal carcass/feedlot animal and then the ideal maternal animal and then what production model you are basing those types on.Then what happens when you cross those 2 lines.We had 2 distinct types in the early 70's english and continental,I new a guy that bred his 900lb Angus cows to Charolais.He never did it again!Actualy I'm glad its not so simple,it makes life interesting.I would also say that God has humbled me over the years when I look back on some of the breeding decisions I've made and some that were made for me.

The idea has always been to mate low input cows to high growth/carcass/terminal bulls

About the article, all I know that Macneil thinks that what ever publishes is gospel and the rest can go to hell

 

[aj]

So in theory...if you had a f1 cow....say Angus-Shorthorn cross and bred her to a terminal breed, The calf in the feedlot would be a quarter Shorthorn. Under this scenario The Shorthorn breed shouldn't select strictly for carcass traits. However to be significant in the industry the Shorthorns would need to bring something to the table for commercial cattle people. I think it should be marbling ability and fleshing ability. If the producer was using a 2 way cross, carcass traits would be a more signifigant concern. I would think you could select against poor rib eye measurements and maybe not so much for huge rib eyes. I don't know know if rib eye selection would be antaganistic with maternal traits or not. All I know is if we are to break the black side barrier we need to have something to offer. The goldmine bull may be the way to go. Is the high growth in the feedlot antagonistic to fleshing ability. I had some shorthorn calves in the proof positve Shorthorn feedlot that gained just over 4 pounds aday and won the reserve pen for gain. But they didn't grade so hot.Wakuru won the total value and gain awards so maybe the Goldmine bull is the way to go.Sorry for high jacking your thread knabe. ;D

 

[knabe]

Sorry for high jacking your thread knabe. ;D

hijack away..  to me, it just appears that the majority market is red meat, and there is enough higher end and lower end to meet those markets.  that's why the pressure to market the higher end to drive up demand.  most of the old timers around me don't bother with the quality market.  one guy asked me if i could invent a feed additive to break down chlorophyll faster as he wants to take older culled grass cow and fatten them up as quick as possible as the differential has room for him to buy them, fatten them, but the delay to get them white is too long to make it easy.

 

[r.n.reed]

Knabe,Thanks for submitting this article it was very interesting and thought provoking.AJ in response to your last post I think the most significant thing the Shorthorn breed has to offer today's commercial cow herd is hybrid vigor.With the high input cost structures in place today cattlemen are looking for ways to improve efficiency and cannot afford to ignore hybrid vigor.So much better if you have a linebred herd.After that its fine tuning and certain bloodlines will be stronger in some traits than others.

 

[aj]

The jsf no problem 46u bull looks interesting to me. He had a 1.54 rea/cwt.    14.14 rea, on a 4.4 frame. He sold out to Denver.Small bwt,easy keeping,polled,clean genetically,...I wonder if he might be a real tool.