And while those plans tend to prioritize finding our next herd bull, or finalizing planned matings between cows and A.I. sires, your nutritional management program should also be at the forefront of planning for a successful breeding season.
Let’s face it – reproduction is a lowly heritable trait, which means the environment generally has more influence on an animal’s reproductive outcome than its genetics. Fortunately, or unfortunately (depending on how you look at it), nutrition makes up the majority of that environmental component.
While there are a number of nutritional factors that influence reproduction – protein and energy nutrition are at the forefront. This is because cattle partition (a fancy word for prioritize) the use of these nutrients for their survival and the survival of the calf at their side before diverting them toward other uses.
And while the list of those specific uses is fairly long and complex, reproduction always finds itself at the bottom.
In order to preserve reproduction, she needs to be in a nutritional state that tells her body she can not only support herself and the calf at her side, but that she’s ready to support another. When she receives those hormonal cues, she resumes normal estrous cyclicity.
This generally requires one of two things: either she’s consuming enough energy and protein to meet those demands, or she has enough “excess” condition to fill the void.
Is her body telling you she’s ready?
Body condition score (BCS) at the time of calving is inversely related to the postpartum interval to return to estrus. As BCS at calving decreases, the amount of time it takes for her to start cycling again increases – ultimately increasing the amount of time it takes for her to breed back.
A cow that calves at a BCS of less than 5 is far less likely to breed back within the amount of time for her to calve annually, when compared to a cow that calves at a BCS of 5 or greater.
To that end, body condition acts as a form of insurance for reproductive efficiency. If her needs aren’t met, the excess condition she brings to the table will help fill the void and ensure her productivity. But if she doesn’t have condition to spare, she has no reserve to pull from and reproduction suffers.
Evaluating body condition at set points throughout the year can provide you with the opportunity to adjust feeding or supplementation in enough time to actually make a difference. Weaning and the beginning of calving season are two ideal times to do so.
If BCS is less than 5 or 6 at calving, and your forage resources are fixed, identify your most economical options in terms of supplemental feeds that can provide a sufficient amount of energy and protein to meet her needs. Just keep in mind, cattle require a certain amount of nutrients, rather than a percent.
So even if a supplement contains a high amount of these nutrients, the cattle must consume enough to make up for what the forage lacks. If those resources aren’t fixed, consider purchasing a more “nutrient-dense” forage, or utilizing pasture resources higher in quality or that have greater forage abundance.
Sorting cattle into groups based on age and condition, and then feeding them accordingly, can be a useful addition – especially if your forages or feed resources differ in quality.
And while their nutrient values are often unknown, conducting a forage analysis can be an invaluable tool when paired with any of these management practices. Doing so has the potential to yield a huge return on a minimal investment, as it allows you to be proactive in preventing an issue before the damage is done.
Is she on an uphill or downhill slope?
Plane of nutrition also affects reproductive efficiency, even when body condition is less than ideal. When her nutritional status is increasing, it tells her body that times are getting better, and she can think about producing another calf. So she begins to cycle again.
Ionophores such as lasalocid and monensin, as well as grains or feeds that contain a high amount of starch, such as corn or corn-based feeds, are quite effective at stimulating estrous cyclicity. The one thing they share in common is they cause a shift in ruminal fermentation – favoring production of a greater amount of propionate.
That increase in propionate causes a hormonal cascade that induces ovarian function, which stimulates the cow to return to estrus. In a way, that acts as a “jump-start” to the ovary.
Just keep in mind that inducing ovarian function isn’t necessarily a silver bullet for ensuring reproductive success, as there is not an equally effective substitute for sending a cow into the breeding season in ideal condition. But if we want to be successful at not only getting her bred, but also ensuring she stays bred when her body condition isn’t ideal, we can’t just trick her – because she’ll return the favor.
If we feed her something that signals to her body that times are getting better, they need to get better. Otherwise, we run the risk of losing that pregnancy.
To follow suit, consistency and adaptation are also key during the breeding season. Research at South Dakota State University suggests cattle need to be adapted to the environment if they’re going to be placed in it after breeding.
Breeding cattle in a drylot setting, then immediately turning them out on lush spring or summer grass generally decreases pregnancy rates, unless they’ve been in that grazing setting before.
This is because grazing is a learned process. If cattle don’t know how to graze effectively, their nutritional status may only suffer for a shorter period of time; however, that short period is often enough to have a negative effect on reproduction.
What does your mineral program look like?
Aside from energy and protein nutrition, mineral nutrition also plays an important role in reproduction. We hear a lot of discussion about which specific mineral element is most important when it comes to reproduction. While some may be more influential than others, the reality is almost all required mineral elements play some role in reproduction.
In most situations, forages alone or forages supplemented with only white or trace-mineralized salt, will not meet the mineral requirements of cattle. Luckily, there is a plethora of different mineral formulations that can help ensure mineral status will not be a factor that limits reproduction in your herd.
Work with your extension personnel or nutritionist to determine which option (or options) are the most appropriate for your operation.
Ultimately, we have a lot invested in a female by the time the breeding season rolls around. This is true regardless of whether she’s a 3-year-old or if she’s been in the herd for more than a decade. And this remains true whether we’re using natural service sires, A.I. or embryo transfer to put a calf on the ground.
So to help ensure your genetic investment isn’t a wash for the year, focus on your nutritional management program. Use it to equip your cattle with tools they need to be successful for this breeding season and to ensure your genetic improvement efforts are an investment rather than an expense. 
PHOTO: A lot of time and money is invested in a female by the time breeding season rolls around. Make sure she has what she needs nutritionally to help her succeed. Staff photo.
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Jason Smith
- Assistant Professor - Extension Beef Cattle Specialist
- University of Tennessee
- Email Jason Smith
