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Scrotal Measurements

Posted: Mon Mar 06, 2017 7:24 am
by AGN
Opinions on selecting bulls.....

How important are above average measurements? Is bigger always better? Or is there a sweet spot above minimums but not too big? Or are minimums there for a reason and anything above is fine?

And is the popular opinion that the larger the measurement, the more fertile the females produced will be? Is there scientific data to back this up?

Re: Scrotal Measurements

Posted: Mon Mar 06, 2017 8:21 am
by Soapweed
Here is one of my observations from over fifteen years ago. My perspective hasn't changed. I think some of this stuff ranks right in there with "climate change," but people seem to like to measure things. :cboy:

Some More "Bull"
Dec 20, 2002
It was February of 1977. Dad was running mostly straight Hereford cattle at the time, and about a third of his cattle were registered. He usually marketed about 70-100 head of bulls at his annual October sale. Dad had gone to a couple bull auctions in January, and purchased five new herd bulls. These Hereford coming-two-year-olds had been close to our ranch headquarters for a couple weeks, but we were getting about ready to start calving and Dad wanted to make room for more cows. This particular beautiful sunny day, Dad decided to drive the five new bulls east of the house about a mile where there were about 35 or 40 other older bulls. The weather report was for things to go haywire, but there was adequate protection from the wind where these other bulls were located.

I had just acquired a brand-new Canon FTB camera, so was packing it along as I fed hay. My feed-outfit was an International 1066 tractor pulling a Lahman stack-mover equipped with a Hydra-fork. Dad rode by looking pretty sporty on his paint horse, "J.R.". He was wearing his hat on this beautiful 50 degree day, so I got out of the tractor and took his picture.

Things went to heck in a hand backet that night, as the predicted "Alberta Clipper" came along packing snow and high winds. The temperature went from the balmy plus 50 degrees to a miserable minus 50 degree wind chill, in essence a 100 degree drop. The old bulls didn't allow the five new bulls to share wind-break space, so the five drifted off to the southeast corner of the meadow where there was no protection.

Back in those days, no one really cared about scrotum size. It has since become desirable, as it seems to be linked to both fertility and greater maternal qualities in the female offspring of so-endowed bulls. Two of these bulls had large "desirable" scrotums and the other three didn't. As it turned out, the two more masculine well-endowed bulls froze their scrotums and were later pronounced to be ruined. The other three came through the storm with flying colors, and went on to sire some pretty good calves. There is no further point to this story.

Kind of along the same topic, though, I think the larger scrotum-more fertility aspect is worthy of consideration if you are buying a bull with the idea of keeping future daughters as replacements. If you are buying a bull to use as a terminal cross (selling all offspring as feeders) don't worry about scrotal circumference.

Re: Scrotal Measurements

Posted: Mon Mar 06, 2017 8:28 am
by rancherfred
The "settled science" of larger scrotal size leading to earlier puberty in daughters is now being questioned as more recent research is indicating the correlation to be more tenuous than thought. There are a whole host of other factors that I look at long before I ever get to the point of worrying about scrotal size. My only real concern for that is that if the factory is too small they won't be able to cover as many cows as they should. If memory serves me correctly our vet's cutoff is 30cm on yearling bulls. Our homeraised bulls can usually do that at about 14-15 months of age. Occasionally we get a sire group that has trouble meeting that cutoff but for the most part it is not an issue.

Re: Scrotal Measurements

Posted: Tue Mar 07, 2017 3:02 pm
by AGN
Thanks for the feedback. The BSE criteria that our vet uses is 16-30 months....35 cm is an acceptable minimum measurement. Our bulls are approx 21 months at testing. We don't personally worry about anything that measures on the lower end at 35-37 just cause we know our bulls could be 200 lbs+ heavier at time of testing to be truly comparable to bulls at most sales. The extra conditions they carry at sale time adds cm to their scrotal measurements but doesn't mean that they are truly higher in actual scrotal measurements. Just our opinion. We had some discussions with customers recently on this topic so was just wondering what others thoughts were.

We've had bulls that fell into 35-37 at time of testing that developed into 40+ as mature bulls (5+ yr olds).

Re: Scrotal Measurements

Posted: Thu Mar 09, 2017 11:49 am
by RSL
This is an interesting topic to me. In the Great White North a lot of work and emphasis has been placed on scrotal size. In the last year of two the Society of Theriogenology updated the minimum scrotal requirements and added an extra centimetre to the requirements for yearling bulls. Scrotal is a growth trait and will vary dramatically based on age and diet. The same calf backgrounded to 2 pounds per day will have a lot smaller testicle size than that calf fed to be 4.5 pounds per day at a year of age. There is some question about the relationship to female fertility, some positive relationship to age at puberty for daughters (again I think that is growth rate related) and a positive relationship with volume of sperm production. I think we push it way too hard here and actually wreck a lot of bulls trying to accomplish big growth numbers. We don't usually buy bulls at minimum scrotals, but there are just as many problems with oversized as under in my estimation. Some of our most fertile, aggressive breeding bulls with good daughters have been average scrotal size. The semen test result is more important to me than the scrotal size and even that doesn't tell the whole picture...