Fertility

[dbirdsong]

I need someone to explain the correlation between scrotal circumference and heifer fertility. I have been analyzing all the genomics enhanced epds I’ve had done on my bull calves and I have noticed the bulls with the best hp also have the worst sc epds. I also have some bulls that have great sc genomic results but a lower hp number. Maybe I don’t understand how this works but I would thing a high sc result would also equal a high hp #. For instance one calf has a hp in the 35% and his sc is at 85% while the next calf has a hp at 75% and a sc at 20%. Any explanation would be appreciated.

 

[W.B.]

Hp epd and scrotal circumference are not a linear equation. I will also add that hp epd is more than heifer pregnancy. If that makes any sense. This is going to cause a firestorm I am sure but what the heck. Early embryonic death loss is being factored into the genomic test. Early in the game but I am seeing some positive results of selecting bulls that are high hp settling more cows. Probably going to only 60 percent correlation at this point but better that what we had previously.

 

[dbird33]

Open question, if you have to choose a bull and all other traits are equal except for HP and SC, which do you put more weight on to make your selection? In this hypothetical the bulls have similar phenotype and Epd's minus the two discussed here. I know the best option is to get a bull with both, but I'm curious how other folks' view these metrics.

 

[MO-Ruminants]

The following pertains to meat goats, and may be totally irrelevant.

The meat goat industry is light years behind the cattle industry in terms of EPDs, EBVs and almost every other area in the field of genetics. Use your own judgement, proceed with caution etc.

We have been told that +Scrotal Circumference often equates to earlier sexual maturity/puberty in the female. My thoughts are that earlier sexual maturity/puberty in the female can be positive, depending on ones program, but it is not exactly the same as fertility.

Many studies show that the fertility trait has a very low heritability. What exactly is the definition of fertility? Could it be that my females who can easily maintain good body condition are actually more "fertile" and that by selecting for "good doers", I am actually selecting for fertility?

 

[Ebenezer]

Scrotal Circumference often equates to earlier sexual maturity/puberty in the female.

Same for cattle. If large SC selection worked on increasing fertility then the HP EPD would never have been necessary. An opinion: if you select heifers using steer and bull type criteria then you will never make progress with the females.

 

[ALACOWMAN]

The following pertains to meat goats, and may be totally irrelevant.

The meat goat industry is light years behind the cattle industry in terms of EPDs, EBVs and almost every other area in the field of genetics. Use your own judgement, proceed with caution etc.

We have been told that +Scrotal Circumference often equates to earlier sexual maturity/puberty in the female. My thoughts are that earlier sexual maturity/puberty in the female can be positive, depending on ones program, but it is not exactly the same as fertility.

Many studies show that the fertility trait has a very low heritability. What exactly is the definition of fertility? // Could it be that my females who can easily maintain good body condition are actually more "fertile" and that by selecting for "good doers", I am actually selecting for fertility?

Though I love easy keepers ,I've never found that to be the case..

 

[NEFarmwife]

Definitely an interesting topic. Would love others to weigh in.

I believe that HP is that of only a heifer. How fast they'll mature and be able to be bred. I.E. for us, we breed our heifers at about 13-14 months of age. Some in that group may be slightly less because we sync heat heifers at same time.

I've not paid much attention to SC at all.

 

[Stocker Steve]

Many studies show that the fertility trait has a very low heritability. What exactly is the definition of fertility? // Could it be that my females who can easily maintain good body condition are actually more "fertile" and that by selecting for "good doers", I am actually selecting for fertility?

Though I love easy keepers ,I've never found that to be the case..

I think this depends on how much selection pressure you put on the females. If you feed well there may be no effect. If feed is short enough to put lactating females under stress, then it matters.

In the real world there are often multiple factors in play. If I select good doers I do see more fertility and longevity - - but in my herd these are often the Hereford x females descended from some moderate ranch cow types. So is it good keepers or cross bred vigor or lower milk production or higher stocking rate or a combination of...

 

[ALACOWMAN]

For the most part those British breeds are easy keeping, and highly fertile..add the right cross to it and bump that up..i always have too keep watch on the heifers I plan to retain...

 

[Son of Butch]

Open question, if you have to choose a bull and all other traits are equal except for HP and SC,
which do you put more weight on to make your selection?

SC is .51 heritable (3 times more heritable than HP)
HP is only .15 heritable and is mostly influenced by environment.

Never give up SC for HP especially if the HP is low accuracy.
I consider the HP epd with less than .50 accuracy as almost meaningless.

 

[Nesikep]

SC is positively correlated to earlier heifer heat cycles, but it's MINIMAL, from the studies I've seen.. as in not worth bothering with for that alone...
I've never had a problem with heifers not coming into heat in time to breed.. and I'm also not that fond of them coming into heat at 6 months old and getting bred.

Seems with EPD's if some is good, more is better, or that's the popular view.

 

[Son of Butch]

Scrotal circumference is positively correlated to male fertility and if you plan on selling bulls it would be unwise to ignore. Mature Height and SC are the 2 most heritable traits in cattle breeding (other than color or horned/polled)

 

[NEFarmwife]

Scrotal circumference is positively correlated to male fertility and if you plan on selling bulls it would be unwise to ignore. Mature Height and SC are the 2 most heritable traits in cattle breeding (other than color or horned/polled)

I understood it to be male fertility but doesn’t influence their female progeny fertility, correct? Wouldn’t it just be their own fertility?

 

[Rydero]

Pulled from beefresearch.ca
"We all recognize fertility (in both sires and dams) as a trait that has the biggest impacts on profitability. But fertility has relatively low heritability, meaning that cumulative environmental influences (e.g. nutrition, weather, etc.) generally have a larger impact than genetics. In Canada, some genetic evaluations do not report any EPDs at all for ERTs related to female fertility. While most evaluations include scrotal circumference (indicator), it actually has a near zero relationship with heifer pregnancy rate (ERT), though bulls with a larger scrotal circumference tend to have daughters that reach puberty earlier."

 

[Son of Butch]

Testicles are the male equivalent of ovaries in the female. When an embryo is choosing to
become female or male what would become the ovaries if female become testicles if male.

There is some belief that testicle size, shape and health does have a minor correlation to fertility
of the daughter's ovaries. But yes NEfarmwife you are correct, SC is accepted as being far more
influential in male fertility than female.

 

[Son of Butch]

Pulled from beefresearch.ca
"We all recognize fertility (in both sires and dams) as a trait that has the biggest impacts on profitability. But fertility has relatively low heritability, meaning that cumulative environmental influences (e.g. nutrition, weather, etc.) generally have a larger impact than genetics. In Canada, some genetic evaluations do not report any EPDs at all for ERTs related to female fertility. While most evaluations include scrotal circumference (indicator), it actually has a near zero relationship with heifer pregnancy rate (ERT), though bulls with a larger scrotal circumference tend to have daughters that reach puberty earlier."

It would stand to reason with HP (Heifer Pregnancy) being .15 heritable = HP is 85% environment.

Since the Dam is 1/2 of the equation, sire only contributes .075 leaving 92.5% influenced by dam
and environment. Which is why I said if HP epd is less than .50 accuracy it is almost meaningless.

SC is .51 heritable = other 49% of SC is environmental... ie nutrition ect.

 

[Dsteim]

I think it’s fairly heritable but you have to use the same type of bull that was used to produce the fertile cow.

 

[W.B.]

I get it that fertility is lower heritability but to me it means we should be all the more diligent in its selection. I really believe that this is one trait that genomic testing can really help because it takes environment out of the equation. Just food for thought.

 

[NEFarmwife]

Question:

I have a few donors. 2 donors provide an average number of embryos.

1 donor is exceptionally high. 15-22 with 20 being the average. Very lucky.

Would it be safer to assume that a line of pathfinders is a good indicator or do you think it’s just luck? Since HP doesn’t actually indicate “fertility”.

Do you suppose that is heritable? Would it be fair to assume that one of her daughters would also provide a good number of embryos?

 

[Son of Butch]

Who knows, exceptionally high production of embryos could also be .15 heritable.
It could become a selling point in the commotion/promotion world of cattle sales.