Heterosis......Again........

Help Support CattleToday:

MikeC

Well-known member
Joined
Apr 11, 2005
Messages
7,636
Reaction score
3
Location
Alabama
4/25/2007 10:27:00 AM


Cow Calf: Heterosis…Hype Or Legit?



For as long as the beef industry has existed, crossbred commercial cattle operations have made up the lion's share of the beef cattle population, and those "in the know" were telling producers to "clean up their acts." Now, it seems every publication you read or every expert you hear is talking about heterosis. So, you ask, "What's this fancy word 'heterosis,' and can I capitalize on it in my herd?" Well, simply put, heterosis is hybrid vigor. At the Noble Foundation's recent Beef Cattle Female Selection School, livestock specialist Clay Wright defined hybrid vigor as "the added advantage in performance of a crossbred over the average of its purebred parents." So, you say, "Hey, I've been doing things right all along and didn't even know it, right?" Well, not so fast...



There is more to hybrid vigor than just taking a crossbred cow and breeding her with any old bull. Numerous studies have been conducted over the years to look at this very subject. If you want to take full advantage of this phenomenon, there has to be some thought put into the process.



Hybrid vigor is most fully expressed when you use bulls and cows of known ancestry - not just breeding any bull to a cow you pick up from Joe down the road or you bought at the sale barn because the price was right. Work conducted at Texas A&M University by Dr. Jim Sanders has shown a 10 to 20 percentage point increase in calf crop born to F1 cows (a cow which is a first-generation cross between two breeds) when compared to straight-bred cows. The advantage will fall dramatically when F2 (F1 x F1 bred cows) or greater cows are used.

One of the most effective and simplest ways for calves to exhibit hybrid vigor is to use an F1 cow and a pure-blood bull of known performance and ancestry; this is what the Foundation livestock specialists have been suggesting to certain cooperators. Use of a pure-blood bull allows the producer to have some predictability of how the bull's progeny will perform. The prediction is made through the bull's EPDs. In the Foundation publication Crossbreeding Beef Cattle for Western Range Environments, Don Kress and Michael MacNeil stated that an average F1 crossbred cow returns up to $70 more per cow per year than the average straight-bred cow. To arrive at this number, they looked at the various traits (Table 1) that cross breeding affects and the advantage that hybrid vigor afforded to or detracted from the calf.



Source: Robert Wells, Ag Specialist, Ohio State University, Noble Foundation
 
Heterosis isn't all roses either. Keep in mind that when you avail yourself of the advantages of heterozygosity, you're also sweeping all kinds of unexpressed genetic garbage under the rug. One day, those undesireable traits that are carried can and will surface randomly in the subsequent filial generations.
 
Only if the parent stock isn't "clean".

I've only seen problems like this when guys went back to a couple generations of straightbred.

Can't believe the problems coming out of the woodwork in some of these cattle. Weak calves, cleft palates, dwarfism.

All because the purebreds going in are not clean, not because the cows are crossbred.

Badlands
 
BRG,

I mean "no genetic defects", the simple recessive sort generally. Implied is economic importance for the commercial cattleperson.

Badlands
 
MY":1hwyzsuo said:
Heterosis isn't all roses either. Keep in mind that when you avail yourself of the advantages of heterozygosity, you're also sweeping all kinds of unexpressed genetic garbage under the rug. One day, those undesireable traits that are carried can and will surface randomly in the subsequent filial generations.
that can happen as well in a purebred operation . theres alot of unexspressed garbage that you wont ever hear about there. probably more so than a good quality cross bred system
 
Badlands,

Where did those genetics defects come from, originally?
 
BRG,

I guess there are some defects that have been specific to certain breeds. But all breeds have some defects.

Originally? It depends on what problem you are talking about.

Badlands
 
when is the Royal Family going to do something about those ears-Prince Charles is living proof that linebreeding doesn't always nmake a phenotypically pleasing individual-don't think Camilla will help much either.
 
I am jus curious where these problems came from. Are they from linebreeding, single trait selection, sneeking Hostien into Angus in the frame race, or was it something that has always been there.

I have never seen any genetic defects in Red Angus. But I am sure they are their somewhere. And if they are, will crossing these type cattle with the problem genes cause them to pop up more regular, because heterosis does make cattle more fertile, wean more pounds, etc, will it also bring these genes out stronger as well?
 
alot of great cattle could have a genetic defect lurking just waiting for that right mating to surface. and linebreeding would cause it too show up even quicker. but i dought linebreeding is the culprit of most defects
 
Linebreeding can not CAUSE a genetic defect.

Linebreeding increases homozygosity, which allows us to SEE the homozygotes, but it doesn't CAUSE defects.

Using CAPS not to YELL, but to better make the point than italics.

Mutations are always occuring, we just don't see them all. Most of the bad ones tend to be recessive, so it takes two copies of the gene to see them expressed.

So, any sort of selection scheme doesn't CAUSE a defect. When we sometimes see mutations popping up in lines of animals, it is generally just an associated trait that way already underlying things, but with extreme selection we tend to narrow the gene pool, so then inbreeding increases which ALLOWS us to see the defects, but it didn't CAUSE them.

Certainly when plowing new genes into a breed, if those new cattle are carrying defects, they can pop out later on. I wonder about it sometimes, but I don't know if there is a point to that.

Knowing a breed carries KK defect shouldn't stop us from using that breed, it should just make us cautious about checking the bloodlines of the cattle we want to use from that breed.


Badlands
 
Badlands":2mtghd75 said:
Linebreeding can not CAUSE a genetic defect.

Linebreeding increases homozygosity, which allows us to SEE the homozygotes, but it doesn't CAUSE defects.

Using CAPS not to YELL, but to better make the point than italics.

Mutations are always occuring, we just don't see them all. Most of the bad ones tend to be recessive, so it takes two copies of the gene to see them expressed.

So, any sort of selection scheme doesn't CAUSE a defect. When we sometimes see mutations popping up in lines of animals, it is generally just an associated trait that way already underlying things, but with extreme selection we tend to narrow the gene pool, so then inbreeding increases which ALLOWS us to see the defects, but it didn't CAUSE them.

Certainly when plowing new genes into a breed, if those new cattle are carrying defects, they can pop out later on. I wonder about it sometimes, but I don't know if there is a point to that.

Knowing a breed carries KK defect shouldn't stop us from using that breed, it should just make us cautious about checking the bloodlines of the cattle we want to use from that breed.


Badlands
hope you dont think i said linebreeding did cause them if you will read my post
 
No, alacowman!

BRG had asked about how some of those things might work.


Badlands
 
ok badlands im gonna ask a question of you. not because i know but because i want to know. i read were someone stated that livestock aint meant to be homozygious. do you think that they are more likely to have defects to surface than hetero's?
 
Top