Whether home raised or purchased, open replacement heifer candidates are one of your biggest investments on the ranch.
Heifers experiencing dystocia or a difficult calving are less likely to mother up and breed back and more likely to wean lighter calves. Assisted calves are more likely to become sick or die before weaning.
Proper heifer bull selection is absolutely crucial. Here are some tips to help identify the perfect heifer bull for your operation.
Expected progeny differences (EPDs) are used to evaluate the difference between one animal’s progeny compared to another’s.
For many years, birth weight EPDs were the go-to tool for heifer bull selection. A bull with a birth weight EPD of +3 indicates that on average, calves sired by that bull will weigh three pounds more compared to a bull with a birth weight EPD of 0.
This means that bull birth weight EPDs with a negative value are preferred. However, just because a calf has a low birth weight doesn’t necessarily mean delivery will proceed without a hitch.
Calving ease EPDs are an absolute game changer and have a distinct advantage over simply using birth weight EPDs. They do the work for you by factoring in birth weight, but also the calving ease history of that bull, as well as his sire, dam, grand sires, grand dams, siblings, and progeny if available.
This is where the true value of the calving ease EPD truly lies. Here, factors such as calf shape and gestation length play a role. So don’t be surprised if calves sired by bulls with high calving ease EPD values have a more streamlined appearance and drop a few days earlier than expected. Depending on what you are looking for, it may be important to consider both calving ease direct (abbreviated as either CE or CED), as well as calving ease maternal (abbreviated as CEM or MCE).
Calving ease direct (commonly termed just calving ease) indicates how easily that sire’s calves will be delivered by first-calf heifers compared to calves sired by other bulls within that breed.
Here, positive values are desired.
So a bull with a calving ease direct EPD of +5 will have on average six per cent fewer calves requiring assistance during delivery compared to a bull with a calving ease EPD of -1. But there are many factors determined by the heifer that also impact calving ease. Calving ease maternal can be used in the same fashion to predict how easily a sire’s daughters will calve at two years of age when compared to the daughters of other sires.
If you plan to sell all heifers born to your first-calf heifers, then you only need to evaluate calving ease direct.
However, if you envision keeping some heifers as replacements, then both calving ease direct and calving ease maternal EPDs should be considered. It is important to note, if true calving ease is what you are after, then birth weight EPDs should be ignored. Evaluating both will result in less genetic improvement as you will overemphasize birth weight and underemphasize calving ease, which is the more critical component.
Average calving ease EPDs across breeds are constantly changing.
A true heifer bull will have calving ease EPDs well above breed average. However, in most cases, bulls within maternal-based breeds such as Angus, with only moderately high calving ease EPDs are suitable to use on well-developed heifers within continental breeds such as Simmental. (See table for current breed averages for all calves born during 2018-19.)
A balance of all other EPDs is desired.
Bulls with below-average birth weight and above-average weaning weight or yearling weight EPDs are termed ‘curve benders.’ Expect to pay up for these boys as they likely offer adequate calving ease without compromising on the performance side.
Steer clear (no pun intended) of bulls with exceptionally high milk EPDs or extremely low gestational length EPDs. The age-old saying of ‘too much of a good thing’ holds true when it comes to these two traits. Genetic potential for milk should be matched to environment and forage availability to avoid compromising on feed efficiency or reproductive performance. Though calves born early weigh less and are more likely to be delivered with ease, selecting very heavily for short gestational length and even extreme calving ease is believed by some researchers to lead to slightly premature calves with underdeveloped lungs, reduced vigour, and decreased overall compatibility with life.
That being said, there are distinct breed differences when it comes to gestational length. Hereford calves typically drop around the commonly referenced 285 days, whereas Angus calves tend to come earlier around 280 days. Continental calves, such as Simmental and Charolais, wrap up closer to around 290 days.
Keep in mind breed averages are constantly changing and EPDs should never be compared across breeds without using proper adjustment factors.
Good conformation and disposition
A bull is only valuable insofar as he can settle heifers. Physical soundness is absolutely crucial. When evaluating your heifer bull prospect at an upcoming sale make sure you get him off the bed pack and on flat ground where he can get out and walk. Evaluate his gait, his feet, and overall structural soundness. Short-strided bulls with inadequate angle and flex to their hock are more likely to endure stifle injuries or turn up lame.
Evaluate the shape of their head and shoulders.
Heavy-boned bulls with a large blocky head or extremely wide, coarse shoulders are more likely to sire calves with similar characteristics that may negatively impact calving ease. Keep your eye out for a bull that is well balanced with a pleasant disposition. Heifers already tend to be more flighty than the mature cow herd. Adding a high-headed bull to the mix can make the group even more difficult to handle, not to mention, their calves.
A clean bill of health
Most heifer bulls make their debut as yearlings and, as such, the value of a breeding soundness evaluation cannot be overemphasized. A satisfactory breeding soundness evaluation result is needed to ensure that bull has reached sexual maturity and is not affected by wart or persistent frenulum that could negatively affect his ability to settle heifers.
Be sure to double-check for adequate vaccination and health history. Bulls should be vaccinated with a modified live or intranasal respiratory vaccine and a seven- or eight-way clostridial vaccine at branding, weaning, and boostered at least once prior to breeding.
Those with a history of any disease should be avoided.
If the bull is from an operation that is not on a vaccination program guaranteeing against the birth of calves persistently infected (PI) with BVD, then the bull should also be tested for PI status before purchase. Negative status for other infectious diseases such as Johne’s or carrier-free status for common genetic defects such as arthrogryposis, hydrocephalus, dwarfism, etc. are also ideal.
Purchasing a virgin bull to use on heifers is preferred. Non-virgin bulls should be tested for trichomoniasis, regardless of the age group they are turned out with. New additions should be isolated and quarantined for 30 days.
The value of crossbred bulls and positive impacts of hybrid vigour should not be ignored.
A crossbred heifer bull has the ability to give you the calving ease you need to sleep at night while still packing enough punch to help your calf crop tip the scales. Luckily, we are seeing more crossbred heifer bulls on offer in sale catalogues with each passing year. Talk to seedstock producers about their value and versatility.
Regardless of the breed or breeds you buy, always keep in mind that a heifer bull’s residency on a ranch may be short lived. Heifer bulls no longer suitable to use on replacement heifers (either because of large size or risk for inbreeding) may not be economical to use on the mature cow herd. Though there are true curve benders out there, you are likely giving up too much performance to justify keeping a true heifer bull around. This is something that should be considered when establishing your budget.
Also consider the number of replacement heifers a bull is expected to cover, which is roughly equivalent to their age in months. For example, a 16-month-old bull should be able to cover 16 head in a 60-day breeding season. This rule of thumb holds true until a bull reaches his maximum breeding capacity at approximately 36 months of age.
Lastly, have fun!
Bull sale season is a great opportunity to get out, admire some fantastic bulls, eat good food, and visit with friends. Here’s to wishing you the best of luck and the top bid as you search for that perfect heifer bull candidate and a restful, dystocia-free 2020 calving season.
Elizabeth Homerosky is a veterinarian and partner at Veterinary Agri-Health Services in Airdrie and operates a small commercial cow-calf herd near Cremona.