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Calving times and pasture composition

May 13, 2008 10:50 AM, By David Bennett
Farm Press Editorial Staff

In recent years, Ken Coffey and research colleagues have studied the options novel endophyte fescue (NEF) offers Mid-South cattlemen.

“We’ve had fall and spring calving cows here for years and we’ve looked at their performance,” said the University of Arkansas professor of animal science, who spoke at the Livestock and Forestry Branch field day outside Batesville, Ark., on April 15. “But we’ve never had them in the same study, in the same pasture area. So it was hard to compare them.”

In the past, Coffey has worked with cows running on NEF year-round and others on toxic fescue. He’s found that changing a pasture’s makeup isn’t always easy.

“On my property, I can’t tear the whole pasture up and put it in NEF. Some of it will stay infected fescue and I know some of yours will too. Some places on (the station), we’re happy to see anything green that’ll stay.”

So, a few years ago, Arkansas livestock researchers gathered to pinpoint needed areas of trial research. One thing that came up: put fall and spring calving cows in the same study.

Typically, on the worst station locations, “we’ve had 90-plus percent conception rates with fall calving cows. In summertime, they stay in better body condition than the spring calving cows.

“We thought, ‘Well, maybe we can do okay with fall calving cows.’

“Then, we seeded the pastures — half are in toxic Kentucky 31 and half are NEF. We aren’t using the MaxQ but the HiMag4. That’s what we have in four pastures here.”

The researchers then sought data on how valuable the NEF would be “if we worked toward establishing it farm-wide. Or, how much benefit would there be if I take a small acreage in a NEF and use it at strategic times of the year?”

The study involves both fall and spring calving cows. “Either all acreage those cows graze is toxic fescue or 25 percent is replaced with NEF.”

Small, good pastures were planted in NEF “to use it at certain times of the year. In our case, that means moving calves onto the NEF one month prior to weaning. Or, we move the cow-calf pairs to the NEF one month before breeding. That way, hopefully, we can flush some of that toxin out of their systems before those critical times.”

Coffey said the year of data collected so far — including a positive control of cattle that stayed on NEF year-round — is enlightening.

For example, he pointed to hair scores. “Are the cows looking any better on NEF? Are we offsetting 100 percent of the cost?”

The cows grazing NEF year-round had the best hair score of 1.6, “which means they’re slick and look good. That’s compared to the fall calves at 4.3, which means they have rough hair on about 75 percent of their body. The spring calves, at weaning, were at around 3.5, which means a bit over half their body has rough hair. So, appearances probably aren’t being helped that much by going with 25 percent NEF compared with the positive control.”

Looking at calf weaning weight as a percent of cow body weight, there isn’t much difference across the board. However, differences really showed up in things like cow reproductive rates and weaning weights.

“We had to start the study somewhere. We ended up starting it after the fall breeding season. We’re waiting on those cows to calve this fall before we get that data.”

Even so, looking only at spring calving cows, “we’re at over 90 percent on cows that stay on NEF year-round. That’s what we were hoping for.”

Unfortunately, for those that stay on toxic fescue, the calving rate is a bit below 40 percent. The previous two years, the rate was running 45 percent. The toxic fescue “is hammering” reproductive rates.

How about the cows on 25 percent NEF? “The numbers actually land about halfway between the NEF and toxic. So, with just a small part of pasture in NEF — and using it at the right times — we’re offsetting roughly 50 percent of the damage. Economically, that starts making a whole lot more sense. Maybe we don’t have to plow out and replace 100 percent of our pasture at the cost of establishment and $4 per pound of seed and everything else. If we use it right, a little bit of NEF will go a long way.”

Another efficiency measure looks at calf value per cow, exposed — calf value at the time of weaning. “The 25 percent NEF (a bit over $300) splits the difference between 100 percent NEF (about $500) and toxic fescue (just under $200).”

As for weaning weights, “there’s about a 98 pound difference between those on 100 percent NEF and those on 100 percent toxic fescue. The 25 percent NEF offset about 37 percent of the reduction in weaning weight.”

For weaning weights, “we’ve typically had spring calving cows on some bermudagrass. And the spring calving cows weaned off calves that are 50 pounds heavier than fall-calving cows. But when given the same access to the same pastures — we don’t cheat one — the fall calving cows actually had heavier weaning weights by an average of about 50 pounds.”

Coffey is aware of only one other study that’s looked at spring and fall calving cows on fescue. In that one, which occurred years ago, open cows were given another chance in the next breeding season. By the end of the 4-year study, 80 percent of the cows were fall calving.

“So, if we’ve got toxic fescue and must live with it, based on what we’re seeing so far maybe we should consider fall calving. The problem, of course — and the reason I’ve never been a big fan of fall calving — is what to do with the calves after weaning?”

On the station, when spring-born calves are weaned and go to winter annuals, “that puts a lot of weight on them. We have steers now averaging around 850 pounds and hoping to put another 40 or 50 pounds on them before shipping to a feedlot.”

Fall-born calves are weaned off and put on bermudagrass. There have been years when they weighed the same when loaded on the truck for the feedlot as they did at weaning.

“That turns me off. However, when you consider the data from the current study, fall calving looks a lot better. Hopefully (further research) will figure out how to get better quality forages into the bermudagrass so we can put more rapid rates of weight gain on those weaned calves.

How long are the breeding seasons?

“Both breeding seasons are about 62 to 65 days. We’re not synchronizing cows and there is no (artificial insemination) work. The bulls are just turned in around May 10 or May 15, for the spring breeding season. In the fall, the bulls go in the Monday following Thanksgiving.”

Is the study being conducted on pure stands?

“When we check species composition, we’re running over 70 percent fescue. But most of the other grasses in these pastures are low-producing grasses. There’s very little bermudagrass in these pastures — maybe 10 percent along with some crabgrass and some spring annual forages. There’s a bit of rescuegrass in some along with a bit of Kentucky bluegrass.”

How can an operation prevent contamination of infected with NEF?

“In the spring, when we rotate to the NEF from toxic, there’s no seed head formation to transport. They won’t come back on the novel pastures until fall in mid-September. By then, all the seed is off the infected pastures. We are doing a rotational grazing program to reduce those chances.”

e-mail: dbennett@farmpress.com