Why I Do Not Run Many Summer Programs (and What I Do Run Is Brahman)

Producers ask me about summer AI and ET programs every year. My honest answer is that I do not run many of them on Angus cattle. The biology is hard enough in a Southeast summer that I would rather have the calendar conversation up front than try to explain a disappointing preg check three months later. Most of my Angus work runs from fall through spring. The summer work I do take on is almost all Brahman or Brahman-influenced.

What heat stress does to English-breed reproduction

Sustained Southeast heat and humidity — what extension services call severe heat stress once the heat index pushes past 80, which is most Florida summer days — disrupts reproduction at several points. During sync, heat stress around ovulation hurts egg quality, follicle development, and the response to GnRH. In early pregnancy, an elevated core body temperature is fatal to the embryo for the first several weeks, before the cow's body even knows she is pregnant.

For AI on English-breed cattle in Florida, the published numbers are stark. Florida studies report summer AI pregnancy rates in the teens for lactating cows — roughly 13 to 18 percent — versus 40-plus percent in cooler months.¹ ² That data is largely from lactating dairy, but the underlying mechanism applies to beef cattle of the same general background.

For frozen ET, the recipient still has to hold the early pregnancy through whatever conditions she is in. The embryo itself was collected and frozen elsewhere under good conditions — that part is not the limit. But the recipient's uterine environment, CL function, and the first 35 days of pregnancy are still working against the heat. A summer Angus recipient pool that has been baking through July is not the same biological system as the same cows in October.

I do not run many summer programs on Angus cattle in Florida. The biology stacks the deck. I will run them if a producer asks and understands what the season costs, but I am up front that the same protocol on the same cows would do better three months later.

Why Brahman cattle are the exception

Brahman and Brahman-influenced cattle handle heat in ways that Angus simply do not. Skin pigment, sweat gland density, shorter hair coat, and a different metabolic profile mean a Brahman cow under the same Florida July conditions runs a lower core body temperature than an Angus cow standing next to her. The reproductive consequences follow: ovulation, embryo survival, and early pregnancy all hold up better in Brahman genetics through summer heat.

That is why most of the summer work I do is Brahman programs. The biology cooperates, and the producers running registered Brahman operations in Florida understand the heat tolerance of their cattle is part of why they run that breed in the first place.

Brahman cattle do respond to standard CIDR-based protocols, but they tend to react to progesterone differently than Angus and other English breeds — published Bee Synch protocols were developed specifically for Brahman-type cows because the standard 5-day CO-Synch does not always hold them through to AI.³ Protocol selection on Brahman work deserves a separate conversation, and is one I have with producers before the program starts.

Management adjustments when summer work is required

When a summer program does run — Brahman or otherwise — early-morning handling is the single most consistent improvement available. Cattle moved, sorted, and worked before the day's heat peaks spend less time hot during the procedure. Shade in holding areas matters even for short waits. Water supply has to keep up with the much higher intake of cattle under heat stress.

GnRH days are where I push hardest on scheduling, since the hormone response is more reliable before the peak heat of the day. That is not always possible to fit around producer schedules, but when it is, it helps.

When to delay rather than push

If the embryos and the breeding window are not time-sensitive, the calendar conversation is worth having before committing to a summer Angus program. A program started in October — when temperatures have dropped, cattle have recovered, and are usually on improving feed — will materially outperform the August version. For Brahman programs the calendar is more flexible because the cattle handle the heat. For Angus programs in the Southeast, I would rather take the time to wait.