3 minute read
Herd Health
Semen testing of the yearling bulls is almost over and herd sires is just around the corner. When purchasing a bull whether purebred or commercial, producers always ask for a semen evaluation. Look at it thoroughly and make sure the pass box is ticked off. Then look for the specifics and whether the scrotal size if within normal parameters and is what you want. Back in 2013, the scrotal circumference minimums for age were changed just slightly, some not at all. The minimums are there for a very good reason, as almost every time you semen test a bull that is even one cm below the minimum, he likely would not pass based on semen quality. The Limousin breed has a minimum of 29 cm for yearlings up to 31.5 cm at 15 months. Even though this is less than many other breeds, the minimums are very true. I have found that Limousin do NOT need as big a testicles as some of the other breeds to produce high quality semen.
All purebred producers should have a scrotal tape and use it at culling or selection time on the young bulls. It gets you familiar with how to use it. I highly recommend the “reliabull” scrotal tape which has been the main one used in Canada because of the spring mechanism that keeps everybody consistent. You are then not surprised if one is a little short on scrotal size when your herd veterinarian semen tests them because you have also measured them. Producers and veterinarians can overall be very consistent this way. Measuring the widest part of the scrotum and pulling compressing scrotal skin until you see the red part of the plunger. This means stop and read it right then. The bulls can be measured at a younger age than a year but keep in mind your cut off for scrotal size will be a lot lower. I have seen an adjusted amount of .04 cm per day as an average predicted growth rate. You are trying to eliminate the real small ones and you may find badly misshapen or not fully descended testicles these are obvious culls. They are then removed early at a younger age before effort has been put into promoting, picturing, clipping videoing etc. Then even the castration will be easier on them and less risky. Go by the beef code and use the appropriate pain killers. Plus, you don’t have your veterinarian trying to semen test an inferior bull. This is why veterinarians’ initial pass rate on yearling bulls will be considerably higher on the preselected candidates.
You want to semen test only bull calves older than a year of age and preferably the closer to fifteen months the better, because under a year they are just not ready. If you are in an early sale, I would measure and palpate their reproductive organs, but would say they are too young to test and defer until a later date.
It is phenomenal to me how quickly breeders have increased scrotal size by selection. Scrotal size is moderately heritable so that has been accomplished generally in short order. I have always said on mature bulls anything above 39 is just bragging rights. In studies, they have found bigger bulls do not on average produce any more semen. I also worry that if we breed big testicled genetics to big testicled genetics, they can probably get too big. Bigger is not always better in the testicle world. Other veterinarians will vouch for me when we see yearlings being an abnormal amount above breed average, it may be cause for concern. The semen test will be the final reckoning but I have definitely seen abnormally big bulls fail.
I have heard many breeds say the testicles are not big but they are longer. There are differences in shape between bulls, but the scrotal circumference is easy to do reliably and puts everyone on the same page. Again if looking at US bulls or selling into that market, remember the US veterinarians just pull the tape snug and so their scrotal circumferences are going to be inflated 2 cm to Canadian readings. That is a fact and worth noting to yourself and telling others. In the early days, many a breeder of lots of the breeds brought in a highly touted American bull to increase scrotal size only to find he was the same size as ones they had in their own bull pen. ..continued on page 73
