Tackling reproductive failure in a beef herd starts with understanding what reproductive success looks like — and for most Alberta cattle operations, the usual measure of success doesn’t tell the whole story.
“A lot of people might think, great, I got greater than 90 per cent (pregnancy rate), that might mean success,” said veterinarian Dr. Blake Balog, who owns Bow Valley Livestock Health in Brooks.
“To me, it doesn’t mean a whole heck of a lot if I haven’t defined how long that breeding season is or the calving distribution.”
For Balog, who presented as part of a recent Beef Cattle Research Council webinar, the metrics that define reproductive stress are based on average breeding season and calving distribution targets. For cows, the breeding season should be around 60 days, or roughly three cycles, whereas for heifers, that number drops to 45 days.
“With that, if we’ve got normally fertile bulls and cows and heifers, we should see a 95 per cent preg check on a 60-day exposure and 85 per cent on a 45-day exposure,” said Balog, adding that some producers tighten up that timeline even further.
“We have a lot of clients around here doing anywhere down to 20 or 30 days, just pushing that reproductive momentum a little bit harder and selecting for the most fertile heifers.”
Calving distribution also plays an important role in determining reproductive success. Typically, 60 to 70 per cent of calving should be completed in the first cycle, as older calves generally weigh more when it comes time to sell.
“If we look at the metrics in terms of profitability, the herd that has the better calving distribution had about a $75-per-head advantage just from having a better calving distribution,” he said of one case study.
“So there are dollars and cents to having this better reproductive momentum.”
It’s also important to know what the average postpartum interval is, he added.
For a cow, that interval should be between 50 to 80 days, while for a heifer, it’s about 80 to 100 days.
“If we’ve done something wrong on those heifers — like dropped our body condition score — that’s going to delay the time frame that they’re going to get back cycling again,” he said.
“It also makes you think maybe we should be doing something with those heifers to get them to calve a little earlier than the cows we know have a little more time to catch back up.”
To that end, producers should be “paying a lot of attention to their heifers,” making sure that their body condition score is around 2.5 or 3.0 and that they’re on an “inclining plane of nutrition.”
“That’s where our momentum starts,” he said. “That means developing our heifers to an adequate weight — that usually means in the range of 55 to 60 per cent (of mature weight) and making sure they’re calving out at a reasonable weight as well.
“It’s really important for those critters you’re developing and for the cow herd you’re maintaining too.”
Breeding heifers early will also put some selection pressure on fertility, he added.
“It irks me when guys get a higher open rate and then the next year they figure they just want to put the bull out for longer. That’s really not the solution at all,” Balog said.
“The solution is putting better selection pressure on fertility in that herd and paying attention to nutrition.”
But every herd will have physiological, as well as regional, limitations, so producers will need to work closely with their veterinarians to optimize the reproductive success in their own herds.
“Every person’s situation is unique,” said Balog.
“We try to achieve the best situation that biology dictates is possible, but everyone’s herd-level dynamics will change things quite a bit.”