Who’s your daddy? Find the answers via sire parentage verification

LANIGAN, Sask. — A sire parentage verification study is beginning to bear fruit for researchers and ranchers.

“The producers co-operating in this study have learned as much as we’ve learned,” said Bart Lardner from the Western Beef Development Centre in Lanigan.

Year two of the three-year study just wrapped up, which is evaluating the use of DNA sire parentage verification in multi-sire breeding pastures.

For the 2015 through 2017 calf crops, five co-operating ranches across Saskatchewan plus one breeding pasture at the beef and forage research centre have been providing DNA samples of their calves for sire parentage at Quantum Genetix Lab in Saskatoon.

The bull to cow ratio varies between operations depending on a number of factors (like bull’s age), but generally it’s about 25 cows to a bull, said economist Kathy Larson.

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“Some of you push the limit and put out 40 to 50 cows for a bull. Depending on topography, maybe you’re at 17 cows per bull,” she said.

Larson said WBDC’s breeding pasture put out 100 cows and four bulls.

“We had a breeding pasture here at 25 to one and I guess the expectation is if we had four bulls out there that each of them is going to service 25. What we’ve learned through DNA parentage testing is that just isn’t so,” she said.

“So the whole point is we make assumptions on these 25 calves per cow, but we may end up in situations where that bull is costing us significantly more.”

Testing is anywhere between $12 to $20 per animal and in order to make the investment pay it depends on the bull’s purchase price related to the number of cows serviced.

Using a modified Y-Tex ear tagger, tiny plugs of flesh are punched from the calf during tagging, branding, vaccinating or any routine management process. Samples then need to be kept cold and dry for accurate lab analyze.

Collecting DNA from a bull is done using hair samples from the tail. The hair root must be attached for accurate testing.

“They prefer tissue samples on the younger animals because they can get a better DNA sample from it simply because the tail hair isn’t as developed as a root ball to grab the DNA from,” she said.

A large variation between bull performances is one of five key points researchers and producers have learned over the past two years of study.

“We had as low as 15 calves per bull on our 100 cow pasture, but we had operators that had bulls that only sired one calf. So they’re going out there expecting to sire 25 to 30 and they only threw one,” said Larson.

However, she said they also expected some bulls would sire well over 25 and that did occur. One bull sired 66 calves.

“So it’s not unreasonable to expect your bulls to breed that 50 cows, but some of the producers have said they expect that the way they make their breeding pastures,” she said.

Good record keeping is a prerequisite in order to make the best use of the DNA parentage testing.

Breeding groups need to be recorded to provide the lab with potential sires for each calf. Calf date of birth, birth weight and wean weight is also helpful.

However, record keeping was one of the biggest challenges in making the parentage testing work, said Karmen McNabb.

She and her husband, Jason, were one of the five ranches that partnered with the WBDC during the three-year study.

They have a 450 commercial cow-calf and backgrounding operation in the Cypress Hills. Typically, they use four breeding groups with three to seven bulls in each group.

Calving is on pasture, newborns are tagged daily and they use a calf table for branding. Calves are usually kept until approximately 900 pounds.

“I thought I had pretty good records. I had a little calf book and I took that information and put it in an Excel spread sheet. So I had stuff listed out pretty well, but if you’re going to do this in detail — this seems crazy, but you need to actually know which cows gave which calves. And if you’re calving on pasture that’s not as easy as it looks,” she said.

McNabb said 98 percent of the time they would know which cow had which calf.

“The other two percent — there’s one wandering over there or there’s a twin from over there — so there are some that are a lot tougher than it looks,” she said.

Another issue for complete accuracy is knowing which breeding pasture the cows were in the previous year.

“That’s fine for 95 percent of your cows, but the fine detail is a little bit tougher,” she said.

She said if a producer really wants to know how many calves the bulls threw, then dead calves also need to be sampled, which isn’t easy.

“On our place sometimes a dead calf doesn’t last long. There’s not much left of it by the time you find it. So you pick out a piece that doesn’t have too much coyote DNA on it and bring it home,” she said.

Tight timelines are another key factor to consider in getting calf samples. Larson said producers will not be able to get results back before the next breeding season if testing all calves after a 60 day breeding season.

“It’s been suggested by previous researchers if you just test the calves born in the first 21 days you can get results back in time and still end up with results that can tell you which are the most prolific sires in your group,” she said.

Another major point learned is that non-matches do occur and it happens 5.4 percent on average in every herd.

“What that means is that we’ve used sibling bulls in our breeding pastures. You’ll end up with inconclusive results,” said Larson.

She said submission of dam DNA can help resolve the issue.

“Some of you make selections like that, buying bulls that are brothers because you want a more uniform calf crop and might end up in a little bit of a hurdle to get through.”

Larson uses a bull prolificacy index (BPI) to compare “apples to apples.”

She said producers are using cow to bull ratios and different lengths of breeding seasons, but the BPI brings all the data sets and different operations together to compare them.

The BPI is essentially the number of calves that a bull sired divided by the number of calves he was expected to sire, adjusted for conception.

“So if the bull threw you 25 calves and that’s kind of what his equal share would have been — you had him in a field of 100 cows and four bulls — then his BPI would be one,” said Larson.

“(The data) showed that there was definitely a lower number of calves sired by the younger bulls and more sired for the more mature bulls but there was also more variations amongst the older bulls.

“Some very interesting results there.”

McNabb said after the samples come back from the lab it’s important to put the data to work.

“There’s two main avenues you’re looking at. One would be how many calves are those bulls siring, but the next thing is, now that you know who actually sired those calves, maybe you could use that data as well,” she said.

“We had a bull whose feet grew out badly and we said, are we keeping his heifers? I don’t want feet like that. So we’ve gone back and looked at our yearling numbers to see who he sired and make sure we don’t keep any of those heifers,” she said.

“We have culled a couple of bulls because of poor performance….The trouble with that is timing. We only keep a bull for maybe four seasons. His results come back the first season and he’s only sired 15 calves so we keep him one more year, but the results don’t come back until three days after bull turnout (July 16). So really you’ve kept him another year and you discover his second year results were bad too … the timing is challenging,” she said.

“You have to actually do something with the data to add value.”

Lardner said the next step is to look at repeatability of results from two years of study and also look at other technologies that may help producers interpret the findings.

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