To this day, one of the age-old problems facing cattle producers is knowing which calf arose from which parents. For the most part, it is fairly easy to determine the dam of a calf (although mistakes can slip in). Sire's determination, especially in the light of multiple bull matings and close neighboring herds, can be a whole lot trickier. One way of reducing this ambiguity would be to break up breeding herds into single sire groups, to have more control over breeding, but even this is not a foolproof method as bulls can break through or jump fences to get to available cows. The introduction of artificial insemination (AI) added yet another variable in confidently determining parentage as these calves, when using the 283-day calendar, are seldom born on time. No matter the system in place, it can be difficult to determine whether a calf was sired naturally or through artificial insemination. 

 

 

DNA testing and parentage verification have taken away a lot of the guesswork in assigning the correct set of parents to the correct calf. The main goal in adding parentage verification to your breeding program is to provide breeders and their customers with accurate, reliable information. This is true not only for seed stock producers but for commercial farmers as well. Having access to parentage results not only ensures correct pedigrees but can provide producers with the information they need to make important herd management decisions. An example of this is a producer who makes use of multiple sire matings may feel that it is unnecessary to establish the parentage of a calf if all the bulls within his group have similar expected progeny differences (EPDs) for calving ease. Even with similar EPDs, some bulls may still cause calving problems.

 

Without knowing which bulls sired which offspring and therefore were subsequently the cause of the calving problems, producers won’t know which bulls to exclude from their breeding programs moving forward. Breeders making use of AI, followed by natural service sires may have difficulty in determining parentage when the birth dates are too ambiguous. This is especially important for producers who wish to only move forward with AI-sired heifers for seed stock replacement. Accurate parentage verification also plays an important role when calculating EPDs.  

 

How parentage is determined:

A single marker, viewed by itself, will not be very useful in determining the parentage of a calf. However, when several markers are viewed together, they become a powerful tool in creating unique DNA profiles for offspring and potential parents. An important concept to remember when it comes to parentage testing is that it is based on excluding animals from being the true parents, rather than the misconception that parentage testing confirms parentage outright. Genetic markers are used to exclude animals as possible parents, leaving only nominations that are the most likely parents. Table 1 below provides an example of a typical multi-sire parentage investigation:

 

 

The nominated dam has provided the calf with the alleles shown in grey. The remaining alleles need to be provided by the nominated sire. Sire 1 has all the remaining required alleles available at all markers tested. He can therefore not be excluded as a parent. Sire 2 has several markers (indicated in red), where his available alleles do not match that of the calf. Sire 2 is therefore excluded as the parent alongside the dam, leaving Sire 1 as the most likely parent. 

 

Sample taking guidelines:

 

The most common sample to send in for DNA analysis is pulled hairs from the tail. Roughly 20 – 30 pulled hairs (with their roots still intact) are enough to extract sufficient DNA for several tests. Hairs should be dry when pulled and not cut, then placed in a paper envelope. The roots of the hair should not be taped together as this may rip off the DNA-rich roots upon removal. For blood samples, a minimum of 200µL of blood can be drawn into a purple top EDTA tube. An ear-notching tool can also be used to collect a small skin sample (roughly the size of your thumbnail) from the outer portion of the ear. Finally, full or used semen straws can be sent in for analysis. All samples (except blood tubes) should be placed in paper envelopes to ensure their continued preservation. As DNA is fairly robust and stable, samples can be shipped at room temperature. 

 

Parentage verification can be a feasible tool in both stud and commercial production when used to address multiple bull breeding, AI, embryo transfers, switched calves, and ambiguous data or record keeping. Not only does parentage verification help establish accurate pedigrees, help in EPDs calculations, and aid in identifying potential problem bulls, it is also a welcome tool to manage record keeping during busy calving periods and can help guide decisions for improved herd management.