SASKATOON — A recently published study shows bulls can eat feed contaminated with ergot alkaloids without affecting their breeding soundness.
Researchers at the University of Saskatchewan found minimal impact on breeding condition and dispelled questions about the impact of ergot alkaloids.
“Our research group has been hearing about concerns from producers that bulls exposed to ergot was potentially affecting cows getting pregnant. There are a lot of question marks about that desire from producers to know if there’ll be an effect on the bulls,” said Vanessa Cowan, who holds a PhD in toxicology from the U of S and is completing her final year of veterinary medicine at the Western College of Veterinary Medicine in Saskatoon.
“It’s a gap in the scientific literature. Female reproduction is more well studied when it comes to exposure to ergot alkaloids, but there’s no consistently effected parameter in adult bulls. So, we’re really interested in trying to bridge the gap and hopefully provide some practical information to producers, veterinarians and regulators,” said Cowan.
Ergot alkaloids are produced by Claviceps purpurea, a fungus that infects cereal grains and grasses. When the fungus overtakes the seed head, it forms characteristic black kernels called sclerotia that contain ergot alkaloids.
The history of ergot is long and colourful, said Cowan. In the Middle Ages, people were poisoned by ergot-contaminated rye flour used in bread. The syndrome was called St. Anthony’s Fire because the alkaloids constrict blood flow, causing a burning sensation in the limbs, possibly followed by gangrene in fingers and toes.
Ergot-contaminated grain sometimes makes its way into livestock feed. Over time, high levels of ingested ergot alkaloids lead to toxicity, which can cause blood vessel constriction.
Over the past decade, Cowan said testing for ergot in animals has increased as it has become more routinely detected in grain.
“We speculate that this could be due to changing weather conditions and other factors, but requests for testing of feed is very common at Prairie Diagnostic Services right now,” she said.
Until now, most research was done in the United States with bulls and stallions, looking at a similar condition of ergotism called fescue toxicosis.
“There are some indications that perhaps sperm motility was affected, or maybe ergot constricts the blood flow that goes to the testicles and that affects sperm production. But really nothing about Claviceps purpurea itself and the ergot alkaloids that we have here (in Canada),” she said.
“So, our information was anecdotal in many cases. We were hearing that people were concerned that, ‘I have ergot in my feed, and I don’t think my cows are getting pregnant as a result.’ That’s kind of where our jumping off point was.
“A bull has one job and if there’s something that’s causing him not to do his job, well then, it’s certainly something concerning for producers. Perhaps if it’s feed related, then they can change the feed. So that’s what we’re concerned about as well.”
Two groups of range bulls were purchased for the one-year study, which started in December 2017 at the university’s Livestock and Forage Centre of Excellence Goodale Research Farm.
“We made sure that all the bulls passed the breeding soundness evaluation before they were enrolled into the study, since we wanted to see if there’s any effect on that,” Cowan said.
The 14 bulls were put into two groups and fed an ergot-free diet. Semen and blood were collected every two weeks during a control period of 12 weeks.
The two groups then received different feed for the following nine weeks. The first group of eight bulls were fed daily rations of grain-based pellets containing 1,100 micrograms per kilogram (mg/kg) of ergot alkaloids, while the second group of six bulls was given pellets containing 2,200 mg/kg of ergot alkaloids.
“We based our concentrations on what’s currently permissible in Canada. The guideline for Canada right now for cattle feed is 2,000 to 3,000 micrograms per kilogram of grain.
“We fed the bulls every day for a period of nine weeks, which corresponds to one cycle of spermatogenesis, so production of sperm,” Cowan said.
The bulls then went through a 10-week post-treatment period where sperm concentrations and morphology were calculated. Body weight and scrotal circumference were also measured.
Researchers also measured prolactin. Lower levels of this hormone are commonly cited as a factor when animals are exposed to ergot.
“We did observe in both groups that their hormone prolactin was (decreased). This was interesting to us because in our previous studies, we didn’t observe any decreases in the hormone prolactin.
“We’re not exactly sure what the implication of that would be. The bulls didn’t lose weight. They’re scrotal circumference was not greatly affected, so they seemed to do fine in terms of productivity.”
The researchers concluded that ergot had a mild impact on fertility indicators in the bulls.
“In our high ergot group (2,200 milligrams per kilogram), we observed a decrease in progressive motility, the percentage of sperm swimming forward, which is important for them to do their job.
“We saw a decrease in live sperm as well. But this returns to kind of its normal value (about two weeks) after we took them off the ergotized feed. We observed a change maybe in the energy status, but these effects were pretty mild overall. And we don’t think that one would be able to tell that these bulls were exposed to ergot based on looking at their sperm profile,” Cowan said.
“There’s other kinds of toxins out there or poisons that can have a negative effect on sperm and induce morphological changes and totally shut down motility, but it’s just not what we observed.”
While the data found that bulls exposed to ergot are unlikely to fail a breeding evaluation, one caveat was the effect on blood vessels at lower concentrations.
“Keep in mind that those studies were completed in the summer where it’s already quite warm out. But in the winter is when ergot really has its most drastic effect because it constricts blood flow. And frostbite constricts blood flow as well, so animals are at a higher risk during the winter.
“So, we don’t want to say that it is safe to feed the 2,200, but we can say that if bulls get a concentration around that in their feed, it is unlikely to have an effect on their breeding soundness,” said Cowan.
Future research will explore whether cryo-preserved sperm from these bulls is affected during artificial insemination.
“So, semen that was thawed from these bulls exposed to ergot, would cows have trouble getting pregnant? That would be the next piece to this study because we know that passing a breeding soundness evaluation isn’t necessarily a guarantee for fertility.”
