SC

cowboy_nyk said:

-XBAR- said:

cowboy_nyk said:

No scrotal measurements = fertility???. 

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Is scrotal measurement an indicator of fertility or age of puberty?

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From what I have read there is a very high positive correlation between scrotal circumference and fertility.  This stays true to a point then tapers off at more extreme measurements.  I don't disagree with you that it also measures the speed of maturation of the bulls as well, which is also a desirable trait in my opinion.

Some breeds have a heifer pregnancy and/or a stayability EPD that would ~directly measure fertility in females but I am not familiar with the details.

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Interesting.  My understanding is that the relationship only refers to age of sexual maturity.  Maybe I'm wrong.  I had the discussion not too long ago with a friend and he, like you, felt the relationships were synonymous: earliest sexually maturing = most fertile. 

I had 2, 15 month old heifers calve this summer and, last week, after witnessing one of my 7 month old bull calves service, not ride,  a 6 month old heifer who was in standing heat, I've thought about this topic a lot. 

I just wonder if we've put too much emphasis on early maturing.  Selecting for early maturity to the point where females are cycling long before they're physically capable of calving seems like overkill in terms of selection pressure.  I don't really know how I should address the situation though. Will measures to select gainst (this) early maturing ultimately have a negative effect on overall herd fertility? 

What are the antagonism to super early sexual maturity?  Any correlation w/ longevity?

How do you address this in your selection protocol?

How are other producers managing this issue within their own herds?  Are you separating your bull prospects and their dam? from the rest of the herd?  Maybe I'm going to have to start pulling bulls earlier too. I've always just left bulls out and then just pulled them when the cows started calving so they won't breed back too early. 

Had a friend last weekend wean all of his bull calves born in the spring. He had a couple March bulls riding and he didn't want to take any chances. I had a friend back in college 10 years ago or so get a show heifer in when she was about a yearling in late spring and I told her that I thought she looked bred and she said that she hadnt seen her cycle to breed yet. Come to find out she was bred and calved that July at 15 months or so. That means she was bred when still on the cow before she ever bought her.

This has been the theory that has been accepted and many still believe it very strongly today.  However we have seen a few breed associations try to discredit the scrotal measurement and EPD saying that it has nothing to do with fertility or maturity.

This is the definition of our Scrotal EPD trait:

SC (Scrotal) (cm) – This trait is used as an indicator of a bull’s ability to transmit scrotal size to his male progeny.  In theory, the larger a bull’s scrotal circumference, a bull’s daughter’s will reach puberty at a younger age and therefore a higher probability they will conceive to calve at two years of age.  This trait is measured in centimetres (cm), with a larger number being more desirable and is only important if males or females will be kept as replacements.

From my interpretation of that definition, sc is an indicator of age of sexual maturity with the only constraint on fertility being that they have to cycle by the time they're 15 months old.  15+9 =24

  Seeing as how the results we're experiencing are occurring in animals under half the age of the standard, why is sc still given consideration?  It seems to me, if there is this direct correlation between sc and age of sexual maturity,  we need to lower the standard of what is desirable/acceptable in terms of sc.  With continuous upward pressure on sc, how long will it be before we have offspring cycling at 4 months? or earlier?

Interesting discussion.  I have always believed that SC is a measure of fertility, and it appears it is, but not in such a clear way as I may have been lead to believe. Here's an article that discusses fertility in depth:

http://pas.fass.org/content/25/5/517.full.pdf

Page 7 has some good stuff on scrotal measurements.

As for how I deal with early maturing females and bulls, we have always split the bull calf pairs from the heifer pairs post breeding (bulls are always pulled) OR weaned the older bull calves earlier to prevent heifer pregnancy.  Some "teen" pregnancies still occur but I accept that as part of the deal when you want to sell yearling bulls for breeding.

XBAR - higher isn't always better.  I think that's what's different in this case.  There is a threshold and most people know that (I think).  If people strive to use bulls with approximately avg SC# there shouldn't be a lot of upward pressure.  The key is to weed out the very low SC bulls, and potentially the very high ones as well. As a side note, the breed associations keep increasing the min SC to pass a BSE, so as a breeder I need to meet that number, for better or worse.

FWIW my Feb calves are already weaned and split.

If average sc bulls are going to give me heifer calves that are cycling at 6 months, then I don't know that I want an average sc bull.  It seems to me that at this point, we need downward pressure on sc.

As is, many of these heifers are coming in heat 7-8 times before they're even old enough to breed. 

The problem is that the brothers of those heifers are expected to be able to breed 20 females at 16 months of age in 6 weeks or less.  Without that early maturity that won't happen.  Double edged sword.

Cowboy_nyk hit the nail on the head. It has some pressure on early sexual maturity but it is not the only factor. I would stick to BIF standards on scrotal. Too big and you negatively affect male fertility in inclement weather. We think we know more than we do. In terms of selection eliminate the small but just run your cows like commercial and it will sort itself out.

I don't think anyone should be trying to change any breed to reaching puberty later. It may be an inconvenience to have to separate your cows with heifer calves from your cows with male calves before weaning, or wean them earlier, but in the long run, it is a very important trait. I remember a meeting several years ago where a group of well known cattlemen were in a panel and were entertaining questions from the audience. One question to them, was " if you could only use one selection trait in your breeding program what would it be?"  The first panel member said that he would select weaning weight, and explained why he felt this was important. The second person to answer this question was Jim Leachman, Leachman Cattle Co, Billings Montana. Jim said that this question was not hard for him to answer, as he felt that age at puberty was the most important selection trait. He was quite convincing in his reasoning why this was the most important selection trait. Since hearing his comments I have read several research studies that compare the economic value of females who have varying ages at puberty. In almost every study I have read, the early maturing ( puberty) females produced the most value over their lifetime.
I have always felt that you get your best producing, most maternal and fertile females from bulls with above average testicle size. In the past couple years though, I have seen some Angus breeders here in Canada, starting to criticize bulls with the extra large testicles. They seem to think that these bulls are siring daughters that aren't as easy to keep in good condition. There may be something to this, as in ranch conditions, you can have females that are " too maternal".

I give every weaned female an abortion shot. Its easy and justs solves any problem. The one year I think we had a calf got bred at 5 months of age. It had to been bred by a sibling bull.

Where is the proof that heifers that cycle at 6 mos have the longest production?


In many animals, early maturity equals early death and smaller mature size.


I'm sure the records on heifers that cycle at six months and have a calf for 12-15 years are pretty sparse.

knabe said:

Where is the proof that heifers that cycle at 6 mos have the longest production?


In many animals, early maturity equals early death and smaller mature size.


I'm sure the records on heifers that cycle at six months and have a calf for 12-15 years are pretty sparse.

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I tend to agree... continental breeds>late maturing>15 years of productive life
                          british breeds>early maturing>10 years of productive life

The heifer has to do more than just cycle at 6 months, she needs to breed in the first 21 days of exposure. 

Time and time again people find and studies have shown that heifers that conceive early tend to have longer productive lives.

My experience has only been with the Shorthorn breed but based on what I have seen over the past 42 years I would say that scrotal circumference has very little if any influence on fertility.My first experience was with the duals and I quickly learned to wean early or separate the sexes. I visited several herds bred similar that had to manage calves the same way.Stories abounded of how many cows these bulls could breed in a season.The testicles on a lot of these bulls could be called modest at best by today's standards.I would also point out that 15 and 16 year old cows were not uncommon in a lot of the established herds of this strain.I tried what I like to call the Continental Shorthorns on them next.These bulls had large testicles but I didn't have to worry about heifers cycling early anymore in fact 31 of 35 cows that I put into production by one of those bulls were culled for fertility before they were 6 years old.My management of the herd has changed very little over the years and if anything the offspring of those C.shorthorns should have benefited from some hybrid vigor.

hamburgman said:

The heifer has to do more than just cycle at 6 months, she needs to breed in the first 21 days of exposure. 

Time and time again people find and studies have shown that heifers that conceive early tend to have longer productive lives.

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Can you post links that detail age at first cycling, how this was confirmed,and the age of the cows when she exited production.

r.n.reed said:

My experience has only been with the Shorthorn breed but based on what I have seen over the past 42 years I would say that scrotal circumference has very little if any influence on fertility.My first experience was with the duals and I quickly learned to wean early or separate the sexes. I visited several herds bred similar that had to manage calves the same way.Stories abounded of how many cows these bulls could breed in a season.The testicles on a lot of these bulls could be called modest at best by today's standards.I would also point out that 15 and 16 year old cows were not uncommon in a lot of the established herds of this strain.I tried what I like to call the Continental Shorthorns on them next.These bulls had large testicles but I didn't have to worry about heifers cycling early anymore in fact 31 of 35 cows that I put into production by one of those bulls were culled for fertility before they were 6 years old.My management of the herd has changed very little over the years and if anything the offspring of those C.shorthorns should have benefited from some hybrid vigor.

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I have experienced a lot of the same as rn reed so far. I think Shorthorns are also known for early maturity or at least are suppose to be known for that. I have seen a lot of large testicled, perfect scrotum bulls that have had really bad fertility and on the contrary the lower SC bulls with slight twists have been very fertile. I think there is something to the size but I don't think it is as much as what some people think. I believe the show ring has put a lot of emphasis on scrotums that has really fogged the research especially with the Shorthorn breed.

hamburgman said:

The heifer has to do more than just cycle at 6 months, she needs to breed in the first 21 days of exposure. 

Time and time again people find and studies have shown that heifers that conceive early tend to have longer productive lives.

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But do the studies show that heifers who start cycling at 6 months are anymore likely than those who start cycling at 10 months to conceive in the first 21 days of exposure at 14 months?

JTM said:

I believe the show ring has put a lot of emphasis on scrotums that has really fogged the research especially with the Shorthorn breed.

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There could be some merit to that-- As opposed to the testicles being a secondary characteristics indicative of virility,  I can see how the show crowd's applying of direct selection pressure to the appearance of the testicles could skew the usefulness of the indicator. 

Is it selection pressure or age?

When we sell bulls they have to pass a semen test and part of that is meeting the breed's minimum requirements. If they don't meet that they fail the test. I had a great looking bull that left us some beautiful calves but almost every son failed his semen test on SC, rather hard on bull sales. I have had some heifers that bred as calves but they were from various sires and bloodlines so can't say there was a specific pattern related to SC size of the sire.

r.n.reed said:

Is it selection pressure or age?

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I would say both...