Angus at Work

Can You Program Fertility?

March 01, 2022 Angus Beef Bulletin Season 1 Episode 3
Angus at Work
Can You Program Fertility?
Show Notes Transcript

Replacement heifers are an incredibly important, yet expensive part of our operations. Wouldn't it be great if we could program fertility in our replacement heifers? Shelby Rosasco from the University of Wyoming tells us that nutritional management of weaned heifers can help program puberty attainment, fertility, and the ovarian reserve. 

Hello everyone. And welcome to Angus at Work. I’m your host Kasey Brown.

If you are familiar with the Angus Beef Bulletin, you know that the editorial team gets to travel to some really cool places. We get to meet some really interesting people, who either make strides in management or marketing, or the researchers who are doing the work that we share with you to make your operations thrive.

Kasey Brown:

Now, I've been with the Bulletin and previously the Journal for 10 years now. I'm not quite sure how that happened already. But for the last five years, with the birth of my kids, I've been voluntarily grounded for the most part. However, I do get to hit the road every once in a while. So, back in November, I ventured to Rapid City, South Dakota, for the Range Beef Cow Symposium. This is one of my favorite events that we cover because it's full of really practical information that you can just take home and use now. And the speakers always bring up some really good questions. Like, wouldn't it be great if we could program fertility in our replacement heifers? They are an incredibly important, yet expensive of our operation. You've likely heard about fetal programming in recent years, but today, we're talking about another yet similar concept that can help program fertility.

Kasey Brown:

Dr. Shelby Rosasco from the University of Wyoming tells us that nutritional management of weaned heifers can help program puberty attainment, fertility, and something called the ovarian reserve. So let's dig into the work and hear from Dr. Rosasco herself.

Kasey Brown:

Welcome to the podcast. Thanks for joining me.

Shelby Rosasco:

Yeah, I'm excited to be able to be here.

Kasey Brown:

Great. Tell us a little bit about your background in the beef industry.

Shelby Rosasco:

So I actually grew up in California on a cow-calf operation and really enjoyed that. Then, I went on to do an ag education degree at Fresno State University in California. I actually went back to the ranch for a couple years and helped out on the family ranch. And then, I decided I really wanted to be able to help producers, and do a little more. And so, I went out and actually went to New Mexico State University and I did my I master’s and my Ph.D. there in beef cattle reproductive physiology.

Kasey Brown:

So, what made you interested to specialize in reproduction?

Shelby Rosasco:

I just really enjoyed it, and my focus has always been on the heifer development side of things. I really enjoy kind of that interaction between nutrition and reproduction. And reproduction and fertility is so important in our cow herd. There's actually some really interesting data that shows pregnancy rates are four times more economically important, or impactful, than a lot of our other production traits. And so focusing on that, I think, is a really good way to help producers to be more efficient in their operation.

Kasey Brown:

Absolutely. And with heifers, how long does it take them to breakeven, or start paying their way?

Shelby Rosasco:

So, it does take some time. Typically, if you go into the research, which isn't always the perfect place to look, they usually say it's about three to five years. But it's going to depend on what your input systems are. Especially with feed prices the way they are this year that can, certainly, increase our input costs and that can increase how long it takes those heifers to break even.

Kasey Brown:

So, you were talking today about developmental programming. Not fetal programming so much as developmental program. Can you tell us the difference between those two?

Shelby Rosasco:

So, they're kind of the same thing, but different at the same time. Fetal programming, certainly, falls under developmental programming, but there we're really talking about how we're managing those animals, especially from a nutrition standpoint, is what we often hear and how that impacts that fetus during gestation. The developmental programming, or nutritional programming I was focusing on today was postnatal. So, once that calf's born, there's actually certain developmental windows where we can have an effect, especially with nutrition, and see some positive impacts on reproduction.

Kasey Brown:

Cool. You were saying kind of that sweet spot was like the full year after they're born, right? Can you tell us a little bit more about that?

Shelby Rosasco:

Yeah. So within that first year, if you think about that heifer, even though she did a lot of development during gestation she's still going through a lot of changes, she's working on attaining puberty that has a big impact on her reproductive tract development, as well as actually development within the brain, and how that heifer is functioning from a hormone profile. But that window, we really are able to see a lot of impacts when we use different management strategies. And so, it's kind of an ideal time, especially for producers, there's still a lot of things we can do to alter management.

Kasey Brown:

Excellent. You were telling us today about some different studies comparing stair-step, or constant gain. Can you tell us about those studies and what came out of them?

Shelby Rosasco:

So, the first study we talked about there was kind of a stair-step type study was the preweaning study, where they looked at puberty attainment. And that one was really interesting because it showed that when we had a higher constant trait diet between three and six months of age, we could actually almost induce precocious puberty, or puberty really early.

Shelby Rosasco:

They did a second stair-step diet in that one where they fed a higher rate of gain between six and nine months of age. And we actually saw really good timing of puberty attainment between 11 and 13 months of age, which is really ideal and what we want in our heifers. And then, we talked about some stair-step diets in the postweaning period. That's where my research has been. We were able to show that those stair-step diets, closer to the breeding season —so closer to between 10 and that 14- or 15-month-age time period, using a stair-step diet, so a low rate of gain, and then a high rate of gain can actually have a really positive impact on the ovarian reserves. So, the number of microscopic follicles within the ovary in those efforts, potentially, positively influence longevity.

Kasey Brown:

Talk us through a stair-step diet. How is that something that a cattleman could use themselves?

Shelby Rosasco:

Yeah, so a stair-step diet's really simple. It's not necessarily anything specific nutrient wise, or specific gain wise. It's really like an actual stair-step, we're going to have periods where they're on a low rate of gain. And then, we step them up to a period of a high rate of gain. And that can be reversed, we start them on a high rate of gain and then drop them down to a low rate of gain. We can have multiple steps within that. The really cool thing about those is that they utilize periods of compensatory growth. So, when we're on a low rate of gain, and then step those heifers up to a high rate of gain, we get some added growth, and compensatory growth that happens. And so, we're actually way more efficient during that time point.

Kasey Brown:

Oh cool.

Kasey Brown:

And so, you were saying kind of stepping back, what I was hearing was we don't want to induce precocious puberty, so we don't really need to push them so hard between that 3- to 6-month period. But the 6- to 9-month period was kind of that sweet spot to get them to attain puberty when we want them to, is that right?

Shelby Rosasco:

Yeah, that's exactly right. And precocious puberty is really hard in certain production systems, if they start attaining puberty before weaning, they may actually, if you still have the bull in there, would be an opportunity for them to become bred way too early in their life. And that could be really detrimental to that heifer from a developmental standpoint. We really don't want that. That's where some of those studies actually showed that pushing nutrition between that 6- to 9-month time point, we can actually time when that puberty is occurring, avoid precocious puberty, and have the majority of those heifers attain puberty between about 10, 11 months, 13 months of age.

Kasey Brown:

Oh cool. You said timing of nutrition affects ovarian reserve and the primordial follicles. Can you kind of give us an overview of what that means? Why is that important? Why should we care about it?

Shelby Rosasco:

Yeah. And so, our primordial follicles, that's the pool of follicles that's formed during gestation. And then, that's what that heifer has to use over her lifetime. And so, we want a nice big pool of follicles for her to use because it's really indicative of what her reproductive longevity might be in the herd.

Shelby Rosasco:

Now, we don't think that she's ever going to run out of those follicles but, certainly, she reaches a time point in her life where fertility drops, she doesn't have as many follicles left. And so, what we're doing with these nutritional diets is trying to see if maybe we can decrease the rate we're using these primordial follicles, so she'd have more over her lifetime to utilize, and that would potentially increase reproductive longevity, increase fertility in that heifer.

Kasey Brown:

Cool. And you were talking about one of your, I guess, more recent studies, or it was when you were in New Mexico. Tell us about how you were figuring out how to do this on the range also.

Shelby Rosasco:

Yeah, so a lot of the studies have been done in a drylot scenario, which is really important. We have really great control over nutrient intake, especially when we're individually feeding animals we can control their rate of gain really well. But there's a lot of producers that develop their heifers out grazing native range.

Shelby Rosasco:

And so, one of the things I wanted to answer was could we use this stair-step diet by supplementing those heifers to follow a stair-step rate of gain and still see the same result? And so those heifers were out grazing the majority of the day... Or the majority of the week. Three days during the week they got brought in the morning, we individually supplemented them on those three days to try to target that stair-step diet. We actually had kind of the stair-step diet happened naturally that year because we had a really nice green up in 2019 for New Mexico. But it was really nice to be able to see that we saw that increase in the primordial follicle numbers in the native range developed heifers, as well as the drylot developed heifers. And so, it gives producers options, so they can target a stair-step style of gain, whether they're in the drylot or out on pasture.

Kasey Brown:

Absolutely.

Kasey Brown:

And you mentioned you don't want to pick a development percentage. I mean, you've got people who are in either camp, and that's fine. But more of that there are options to develop efforts in their own environments. Can you talk to that a bit?

Shelby Rosasco:

Yeah. I think, each operation is unique and so I don't know that specifically picking 65% or 55%, I don't think of that as the way to look at it. I think let's look at your environment. What's feasible? What kind of resources do you have? What makes the most sense for how you manage your cattle? If that's 65%, great. Let's develop a system of how to do that at 65%. If pushing those heifers to 65% is going to cost you too much money and not be feasible then, let's look at using a more extensive grazing system or developing those heifers to a lower percent mature body weight. And what that research has really shown is that we can still be successful, whether we're at 65% or 55%.

Kasey Brown:

Heifer development, we could probably talk about this for ages. But where are some resources that you would recommend if our listeners want to find out some more about how they need to best develop their own heifers?

Shelby Rosasco:

There's a lot of resources when it comes to heifer development. The Reproductive Task Force is a group of individuals from around the United States, they put together a lot of information, not only on estrous synchronization, but they put a lot of information together on heifer development. Most of your state extension services are going to have articles on heifer development. The University of Nebraska–Lincoln has a lot of great ones, South Dakota State, Colorado State, and Wyoming all have really great resources when it comes to thinking about heifer development.

Kasey Brown:

Awesome. I always like to end our podcast on a high note because we all know that the cattle business is really a people business. Tell me something good that has happened to you recently, whether it's professional, personal, or both.

Shelby Rosasco:

As far as things good that happened, I'm just really excited to get to go home and see my family for Thanksgiving. It's been a little while, so I'm excited to get to go home next week, and get a chance to visit with them and see my niece and nephew.

Kasey Brown:

All right. So going home to California?

Shelby Rosasco:

Yep.

Kasey Brown:

All right. Well good. Well safe travels. I hope that goes so well.

Kasey Brown:

Thank you again for your time. Thank you for your insight today, to all the attendees at Range Beef Cow Symposium.

Kasey Brown:

Listeners, if you want to learn more, you'll find coverage of the Range Beef Cow Symposium in both the Angus Beef Bulletin, and the Angus Beef Bulletin EXTRA. So, be sure you're subscribed to both of these publications. You can do that, or access both magazines, and our digital and audio extras at angusbeefbulletin.com/extra. That's E-X-T-R-A.

Kasey Brown:

This has been Angus at Work. Now, let's get our hands dirty. Thanks for joining us.