Inbred Regression?

I'm wondering at what point you can expect to see inbred regression expressing itself as reduced growth and stature? I'm starting to think I can see reduced growth and stature in some of our young cattle that have IBC scores of 14-17% which would be earlier than I was expecting to see it if this is indeed the cause.
TIA

Grassfarmer wrote:

I'm wondering at what point you can expect to see inbred regression expressing itself as reduced growth and stature? I'm starting to think I can see reduced growth and stature in some of our young cattle that have IBC scores of 14-17% which would be earlier than I was expecting to see it if this is indeed the cause.
TIA

Isn`t there some regression as soon as you make a breed?,,,but my limited experience says you are seeing things about right...I got the promise of genomic measured IBC`S today,,,I want to check the real levels against the expected "average" in the few tightbreds that I pictured...

MKeeney wrote:

Grassfarmer wrote:

I'm wondering at what point you can expect to see inbred regression expressing itself as reduced growth and stature? I'm starting to think I can see reduced growth and stature in some of our young cattle that have IBC scores of 14-17% which would be earlier than I was expecting to see it if this is indeed the cause.
TIA

Isn`t there some regression as soon as you make a breed?,,,but my limited experience says you are seeing things about right...I got the promise of genomic measured IBC`S today,,,I want to check the real levels against the expected "average" in the few tightbreds that I pictured...

Mike will you please elaborate on genomic measured IBC's.

If a person starts with 7 animal/cow families all somewhat related how long can you keep mixing the families together before you see regression? Occaisional new genetics will be introduced via AI.

patb wrote:

MKeeney wrote:

Grassfarmer wrote:

I'm wondering at what point you can expect to see inbred regression expressing itself as reduced growth and stature? I'm starting to think I can see reduced growth and stature in some of our young cattle that have IBC scores of 14-17% which would be earlier than I was expecting to see it if this is indeed the cause.
TIA

Isn`t there some regression as soon as you make a breed?,,,but my limited experience says you are seeing things about right...I got the promise of genomic measured IBC`S today,,,I want to check the real levels against the expected "average" in the few tightbreds that I pictured...

Mike will you please elaborate on genomic measured IBC's.
Simply looking at the individual genotypes and measuring true homozygousity rather than theorectical average expectations

If a person starts with 7 animal/cow families all somewhat related how long can you keep mixing the families together before you see regression?
won`t regression occur immediately relative to the degree of homozygousity created?[/color]

Occaisional new genetics will be introduced via AI. why?

what if the genetic theory of overall homozygousity creating regression was wrong; and regression was controlled by only a segment of the genotype?

Occaisional new genetics will be introduced via AI. why?

The bull customers like to see AI sires close up in the pedigree. The other reason to keep the percent inbreeding under controll.

patb wrote:

Occaisional new genetics will be introduced via AI. why?

The bull customers like to see AI sires close up in the pedigree. The other reason to keep the percent inbreeding under controll.

I'm reminded of a comment by one of the old guys that founded our breed "The customer may always be right - it depends if that customer is worth catering to" For the guys that "want to see AI sires close up in the pedigree" I'd be happy to forgo their business as they obviously don't get it. There are always plenty "Jims" down the road who can supply the star struck customers.

patb wrote:

Occaisional new genetics will be introduced via AI. why?

The bull customers like to see AI sires close up in the pedigree. The other reason to keep the percent inbreeding under controll.

10 points out of 10 for honesty and a sad commentary on the state of the industry

How does one know that you are dealing with regression rather than genetics that may be relating back to the average?

What about environment, perhaps rainfall or a lack of it may be the culprit? Even if the grass doesn't suffer or explode with growth doesn't mean that the cattle aren't reacting to it, does it?

dunc, I don't know very much about anything but I am starting to see some of my cattle smaller among their contemporary groups - same grass/feed/rainfall and they have a certain look about them that I can't describe. They all look of one type and it just looks like the characteristics of the breed are more concentrated in them. These are the cattle that are the closest bred I have got 14-18% IBC scores and they are starting to stand out in the crowd as being different. I have one small bull that I never noticed much in his life other than to see he was growing poorer than the rest - all of the sudden I can see he has a distinct type about him and I want now to breed him to some relatively unrelated purebreds of a different body type and see what the offspring turn out like. I'm hoping that if what I'm seeing is caused by inbred regression he might already have a level of prepotency for the characteristics of the line he comes off.
Pure guess work on my part at the moment but it's fun studying the cattle and trying to understand what is going on.

dunc wrote:

How does one know that you are dealing with regression rather than genetics that may be relating back to the average?

What about environment, perhaps rainfall or a lack of it may be the culprit? Even if the grass doesn't suffer or explode with growth doesn't mean that the cattle aren't reacting to it, does it?

If you had some cattle that weren't lined up tight running with them I guess you could use that for enviroment.Other than that someone smarter than me will have to tell us.

Whats the big deal about regression if the outcross works? Might some regression mean the linebreeding worked?
Edit
Grassfarmer kinda beat me to it on tne second part.

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I have one small bull that I never noticed much in his life other than to see he was growing poorer than the rest ...

What you didn't say was if he was inbred. If not, he might just be a dud.

Quote :

Whats the big deal about regression if the outcross works?

The expected effects of regression and the lack of curb appeal.

I have probably told this story before but it is an example where inbreeding regression did not "follow the rules". Dr. Leroy Boyd was at Mississippi State University and wanted to develop a flock of heat resistant Polled Dorset sheep. He also was working towards resistance to internal parasites. So he started with about 25 ewes and two or three rams. Within about a year all sheep were dead or gone except one ram and two ewes. One ewe was bigger and growthier. One ewe was smaller and more prolific. When he retired and the flock was sold, the flock never exhibited any regression and each generation was larger in mature size than the previous, all based on the three sheep. I do not know how sheep were in the entire flock but I assume 100+ and the work went on for years. I think that he did bring in a ram on an occasion that was very kin to the original ram.

It seems to me that we start with what we have and the genetic potential of the animals defines the success of the program. It either can end quickly, prolong the average or improve the overall. Much of it is beyond human control. The success is not in the breeder but the unseen genetics we start with and how strong, durable or flawed they may be. So, providence is involved with the success. There is an ability to select breeders and we all wish that we had the xray eyes to be able to say we were 100% on all selections.

EddieM wrote:

Quote :

I have one small bull that I never noticed much in his life other than to see he was growing poorer than the rest ...

What you didn't say was if he was inbred. If not, he might just be a dud.

Quote :

Whats the big deal about regression if the outcross works?

The expected effects of regression and the lack of curb appeal.

I have probably told this story before but it is an example where inbreeding regression did not "follow the rules". Dr. Leroy Boyd was at Mississippi State University and wanted to develop a flock of heat resistant Polled Dorset sheep. He also was working towards resistance to internal parasites. So he started with about 25 ewes and two or three rams. Within about a year all sheep were dead or gone except one ram and two ewes. One ewe was bigger and growthier. One ewe was smaller and more prolific. When he retired and the flock was sold, the flock never exhibited any regression and each generation was larger in mature size than the previous, all based on the three sheep. I do not know how sheep were in the entire flock but I assume 100+ and the work went on for years. I think that he did bring in a ram on an occasion that was very kin to the original ram.

It seems to me that we start with what we have and the genetic potential of the animals defines the success of the program. It either can end quickly, prolong the average or improve the overall. Much of it is beyond human control. The success is not in the breeder but the unseen genetics we start with and how strong, durable or flawed they may be. So, providence is involved with the success. There is an ability to select breeders and we all wish that we had the xray eyes to be able to say we were 100% on all selections.

based from or closed to three sheep genepool? scientific paper or folklore? no selection for size; just heat resistance?lambing rate?

EddieM wrote:

Quote :

I have one small bull that I never noticed much in his life other than to see he was growing poorer than the rest ...

What you didn't say was if he was inbred. If not, he might just be a dud.

I would call the bull line-bred rather than inbred but that's my definition. He is the product of a half brother/half sister mating in that his grand-dam is the same on both sides. His grand sires are a father and son on the respective sides so he has a 18.75% IBC score according to Kintracks. To be honest I never paid much attention to him as a calf - he weaned OK, just a little under average and his performance since weaning has been lackluster although part of that was my feeding regime last winter. What struck me the other day was that this year's heifer calf from the same cow also weaned just under average (within 10lbs) as did the identically bred heifer calf out of her full sister. Despite this year's calves being off a different but closely related sire they all look to be the same type with the same growth pattern and I'm wondering if this is the start of a standardized type appearing? I kind of like the growth pattern because it mirrors that of the old cow (the grand dam in these cases) behind my line-breeding program. She weaned at the exact same weight these grand-daughters have and ranked 26/70 on WW but her YW ranking was 56/66. I have often wondered if this is the trade off on growth required to produce a fertile cow that bred until 23 years old or if it is a mere coincidence?

This is a different thought process and probably irrelevant to the topic, but...
We have a national cow herd at 1950s numbers, but pounds of beef production is well above 1950s. Even with reducing cow numbers over the last decade, beef production is relatively stable.
Have we been using 'outlier genetics' for so long that we have move the entire national cow herd ( save a few nonconformist) to the point that 'outlier genetics' have become 'normal'? When we close a herd to outcross or crossbreeding genetics and select for average functional cattle, are we seeing 'regression' or simply a return to a true genetic normal?

Ag producers have been production driven for over 50 years...are we better off today than 50 years ago?

Quote :

based from or closed to three sheep genepool? scientific paper or folklore? no selection for size; just heat resistance?lambing rate?

Not sure of all the questions, but not folklore. I have a file on them from back in the 80's but cannot find it. I visited breeders in SC and also visited the flock at MSU. However, with the ivory towers, MSU moved on beyond sheep so they do not worry about finding any of the information that they have on had. Definitely selected for increased size so outliers were used as breeders,(lowest IBC selection in my opinion). Each new generation was like a stairstep when viewed in the pastures. Heat resistance was well documented from rectal temps while grazing in the summer heat while comparatives were panting in the shade with elevated temps. One ewe line had more twinning and one was more of a growth influence.

Lambing rates are largely based on nutritional levels immediately prior to and during breeding as well with the weather conditions (heat/cold) during early gestation. So, you can genetically select or nutritionally select twinning to some degree. I'm not sure how much the parasite resistance got increased but was selected. The loss of many of the orignal sheep was from indirect selection: they died out!! "Survival of the least wormy"!

I don't know how much I buy into the idea of inbred regression. Is it regression or reversion to the mean (average)? If you aren't happy with the mean (average) then maybe you have the wrong cattle. I think I read some where that the reversion or regression lasts for three generations before the mean starts to climb. Four herds come to mind when I think of inbred cattle. Jim Lents, Pinebank, Wye and possibly Holdens. If those herds are evidence of regression then I'll take it anytime in mine!

farmboy236 wrote:

I don't know how much I buy into the idea of inbred regression. Is it regression or reversion to the mean (average)? If you aren't happy with the mean (average) then maybe you have the wrong cattle. I think I read some where that the reversion or regression lasts for three generations before the mean starts to climb. Four herds come to mind when I think of inbred cattle. Jim Lents, Pinebank, Wye and possibly Holdens. If those herds are evidence of regression then I'll take it anytime in mine!

All four herds you mention limit inbreeding so as to avoid regression...you certainly have the wrong herds to prove your disbelief in regression; in fact, just the opposite, they are testament to regression occuring.