Whenever someone gets a new truck, there are always two questions you have for them:
1. What engine does it have in it?
2. What transmission did you get?This translates perfectly to bull sale season in that when you purchase a bull, aside from all the major upgrades and features available for your future herd sire, there are two things I want to look at – his engine and transmission.
The feet are the basis of the transmission
Besides basic structural soundness, there are two major issues I like to look for in bulls: founder and screw claw. While the two can be easily confused, at the end of the day, any bull suspect to either should not be considered.
Founder (laminitis) is a condition that results in the weakening/separation of the layer of tissue between the hoof wall and coffin bone. The reason this is of concern in sale bulls is that it is very closely associated with ruminal acidosis. This is often linked to diets that are not properly managed and contain high levels of fermentable carbs, such as grains, which are typically used when developing bulls. In addition to being lame or tender footed, hoof elongation and curling of the claws is typically a sign of founder.
The more bull sales I attend the more screw claw I seem to be seeing. That’s not to say it is in every herd, but it is out there. While it is a recessive trait, screw claw is heritable. Most commonly it is seen in the outer claw of the hind legs and is caused by a misalignment of the foot bones. The screw claw is typically longer and narrower than the other claw and has an inward and upward spiral rotation of the toe.
This causes the animal to not bear weight properly on the sole and results in major lameness issues. The issue with screw claw in sale bulls is that it typically does not show up until the animal is three years or older, making it easy to miss or something that will show up after the purchase. Remember, it is heritable, so if there are issues in the rest of the herd, there are likely issues in the young bulls – another reason to go look at the cow herd before sale day. Take some time to go through the cows, ask the seedstock producer if they are getting those mature cows’ feet trimmed and why.
Make sure you are doing a good job looking at the feet and legs of the bull. If a bull does not have a great set of feet and legs on him, it will struggle to travel and mount cows.
These are just two things to be on the lookout for when evaluating your potential new bull’s transmission. More extensive information can be found at “Beef Conformation Basics” and “An Approach to Corkscrew Claw,” a factsheet from the American Association of Bovine Practitioners Lameness Committee that goes into detail about screw claw.
The testicles are the engine
A bull has one purpose on the ranch: to successfully get cows bred. So, take a good look at his scrotum – this is the engine of the entire machine you are purchasing. The shape and size of the testicles can tell you a lot about that young bull.
First, let’s talk scrotal circumference (SC). It is positively correlated with fertility in the bull’s offspring (replacement heifers), which translates into other important reproductive and longevity factors for the cow herd he will create. In addition to the genetically heritable link to SC and daughter fertility, research has also shown us that SC is a great indicator of spermatogenic function. A study by Palasz et al. in 1994 found that SC was positively linked to normal sperm cell production and bulls with a SC less than 31 centimeters tended to have lower peak testosterone levels.
So, what about the shape? Yep, it matters too. We have talked in the past of about how critical it is to control the temperature of the testicles. The two main functions of them are the production spermatozoa and the production of testosterone. The shape of the scrotum can impact their ability to thermoregulate and will ultimately impact their ability to perform their main functions.
There are three basic shapes of scrotums: normal/bottle shaped, wedge shaped and straight-sided. Figure 1 is a graphic from “Fertility and Breeding Evaluation of Bulls” that helps visualize the desired shape of the scrotum. Remember, any deviation from normal can cause issues with thermoregulation and result is sperm quality and production issues in a bull. In addition, Dr. Stephen Boyles from Oklahoma State Extension does a great job expanding on this topic in “The Bull's Scrotum and Testicles.”
At the end of the day, the last thing you want to see is for the check engine light to come on or to feel your transmission slip in your truck. To make sure you don’t have issues with that in your bull battery, select good-footed bulls that were developed correctly from a herd that is free from lameness issues and that have nice scrotal conformation and circumference. Happy bull hunting. 
PHOTO:
Kalyn Waters
- Agricultural Agent
- University of Florida Extension
- Email Kalyn Waters
