Knowing the sire helps producers when culling bulls

Taking DNA samples from calves helps determine which bull is performing

LANIGAN, Sask. — Preliminary DNA information is raising more questions than answers about multi-sire breeding, according to University of Saskatchewan researchers working in conjunction with the Western Beef Development Centre.

Stacey Domolewski and Crystal Ketel, along with their supervisor, Bart Lardner, recently presented the first of three years of data collected for a DNA parentage project on multi-sired breeding pastures in Saskatchewan.

While many producers pick bulls on traits important to them, decision-making basically stops after the bulls are turned out.

“There’s not really any concrete way to follow those bulls through and really understand actually what they’re doing and how many calves they’re producing and what those calves are doing down the line,” said Domolewski during the International Rangeland Congress in July.

“So that’s why we’re doing this project and looking at DNA parentage testing.”

More than 500 delegates from 55 countries attended the week-long conference, which had as its theme Future Management of Grazing and Wild Lands in a High-Tech World.

The DNA parentage study involves six co-operating ranches in Saskatchewan that have multi-sired pastures using three to 12 bulls.

Domolewski said management practices vary widely in the number of sired calves and researchers are trying to determine related trends between bulls.

Researchers are also looking closely at the economics.

“If you’re a producer, does paying the $12 to test every calf pay off? Are you able to cull those bulls that aren’t doing anything within the first year and then not pay the cost to overwinter them?

“We all know it costs the same to overwinter a bull that sires three calves or a bull that sires 30 calves.”

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Before the study, Domolewski said producers often said the older bulls sired more calves than the younger ones.

“In some cases that’s true but in others we were finding that it’s those yearling bulls in the pastures that were going out and siring more calves,” she said.

Statistics are not yet available but it appears the bull to cow ratio and the number of bulls in a pasture is the cause of most variation.

“The pasture where we have the 12 bulls on, that’s where we’re seeing bulls that are siring anywhere from three times the amount of calves that they should be siring to one or two cows,” said Domolewski.

Crystal Ketel brought cattle ears and tails she procured from a meat processing plant to demonstrate how DNA samples are collected using tissue and hair.

Using a modified Y-Tex ear tagger, she cut a tiny piece of flesh from the ear for the DNA sample.

“You can do the samples while you’re tagging the calves or branding or vaccinating or doing any routine management processes,” said Ketel.

Collecting DNA from a full-grown bull is more dangerous, so hair samples from the tail switch are used, said Ketel as she held a tail in one hand and pulled hair with the other.

About 15 to 20 hair follicles are needed to provide choice for the lab. And while it’s more complicated for the lab to extract DNA, there are greater advantages to collecting hair samples compared to using ear tissue.

“They like to use them with bulls because if you have to go back and look at calves further down the line, there’s a lot more of the 
sample,” said Ketel.

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Ear flesh must be preserved immediately or its DNA starts to degrade.

“For the hair samples, as long as it’s in a dry, cool place, it doesn’t matter. It can stay in storage for years and still have a good root ball to collect DNA from,” said Domolewski.

Researchers said DNA testing is all about exclusion and finding out which bulls in the pasture are not siring calves.

“For a paddock that has five bulls, you will exclude four bulls from being the sire of one particular calf, but that is also a 99.99 percent chance of being correct. They never say that is 100 percent correct that is the sire,” said Ketel.

Added Lardner: “So by process of elimination, you’re left with possibly one and then you make the assumption that one would be the sire.”

He said one of the biggest challenges producers face after a calf is born is the short turn-around time for putting bulls out for the next breeding season.

“You only have a 60-to-90 day window where once you have sampled the calves that are born that year and get the information on who their sire was, you can eliminate those sires who are not producing calves for you,” he said.

“And you hope the lab can get that information back to you in time so you can make an informed decision.”

Added Domolewski: “What producers participating on this have learned is the sooner you can take those calf samples, the better.”

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