Studies Show Breeding, Calving
Dates Have Big Impact In Texas

By David Bowser

PLANO, Texas — Environmental differences can affect livestock production and must be taken into account when planning a breeding calendar, says a beef cattle specialist and research scientist.

Different areas have different types of grasses, different soils, and different amounts of rainfall, says Dr. L.R. Sprott, Texas A&M University professor and Extension beef cattle scientist. What might be an ideal calving period in the Midwest could be a wreck in Texas.

"Be aware of what your environment is," Sprott admonishes.

What's right for one rancher may be different for another rancher in another region, Sprott told producers at the Extension Service's annual Metroplex Cattlemen's Conference this fall.

"You can hear all sorts of philosophies and stories as you visit with different producers and different educators," Sprott said.

Their philosophies and stories are probably right, even though they differ from one to another.

"You're going to have to decide for yourself based on the kind of environment you live in as to when you should be breeding your cows and when they should calve," he noted.

One of the important questions is how long the breeding and calving seasons should be.

"Our philosophy a lot of times is the longer we breed on these cattle, the more likely they are to get pregnant," Sprott said.

While there is some merit to that philosophy, the length of breeding season does not dictate whether or not the cows get pregnant.

"What dictates pregnancy in these animals and their ability to get pregnant is nutrition," Sprott insisted. "I'm becoming more and more of a proponent of good forage management. If we can develop forage systems that will allow us to become less dependent on high levels of supplement, that's really our goal, not that we will never have to feed anything."

Producers have to develop systems that provide more quantity and a little additional quality at times when they really need it.

The time of year when cows calve directly affects the types and timing of many herd management practices. The start of calving is dictated by the start of breeding. Cows calving in the fall normally need more supplemental feed in the winter than do cows calving in the spring unless cool season pastures are available. Unless producers retain ownership of the calves past weaning, fall-born calves will be marketed in the spring and calves born in the spring will be marketed in the fall.

The decision of when to calve is complicated by numerous factors, and ignoring these details can affect costs of production, animal performance, income and profitability, Sprott cautioned.

There is no single date that is best for the start of calving because differences in climate can affect the availability and conditions of natural resources, Sprott said, but for Texas producers and those in the southern United States, there are dates that probably should be avoided.

There are several principles to remember concerning breeding, Sprott continued.

Perhaps the first is the health of the herd, but fertility among cows is also variable. Fertility is highest in cows that conceive at first service. Cows requiring more than two services during the breeding period are the least fertile in the herd.

Ranchers have to identify and cull sub-fertile animals. A cow that's seven years old and has produced three calves probably needs to be sent to the sale barn.

Something else to consider, Sprott said, is narrowing the calving season.

"It takes the age variability out of those calves," Sprott pointed out.

When the producer takes the age variability out, he takes the weight variability out.

Sprott admitted that costs went up as much as $70 a cow in some of the research herds as ranchers implemented such management changes, but he said production improved by as much as 73 percent.

"They were producing more total pounds of beef per animal than they were prior to that," Sprott explained. "It effectively reduced their breakeven cost of production by about 20 percent."

In other words, they were getting more production for every dollar they spent.

Sprott said late-calving cows are late-conceiving cows.

"They are the sub-fertile animals," he said.

If they are eliminated, it will increase the overall fertility of the herd.

Producers must also recognize the importance of properly feeding cows so they can show estrus early in the breeding period. Cows which display estrus within the first 21 days of breeding have higher pregnancy rates.

"What we'd like to do is identify our most fertile cattle," Sprott said, "and provide an adquate forage base so they can come in heat right quick, early in the breeding season."

Pregnancy rates will increase in herds where the cows come into heat quickly, Sprott contended, noting that most pregnancies in a herd occur in cows with the highest fertility.

Some 95 to 97 percent of all pregnancies are attributed to cows conceiving at their first or second estrus. Only three to five percent are attributed to cows that conceive at their third estrus.

These principles regarding cow fertility lead to the question of what month the breeding season should start to optimize the chances that the most fertile cows will conceive, Sprott said. This is extremely important, since temperatures during certain months are stressful and can reduce fertility.

Research data from studies in Kansas and Texas indicate that if cows show their first estrus after the month of June, the chances of conceiving are dramatically reduced. In the two herds of Texas cattle studied, one near Waco and one on the Gulf Coast, pregnancy rates in cows showing their first estrus during July through September were less than 17 percent. That indicates that summer breeding in Texas is not recommended.

"Down on the Gulf Coast it does get ugly quick," Sprott pointed out.

In hot weather, fertility drops in both cows and bulls.

He said his research was the result of some studies in Nebraska that favored breeding in July and August.

"I tell you," Sprott said, "July and August in Nebraska ain't near what they are in Texas."

He cautioned ranchers to understand their environment.

In far West Texas, it may take some late summer showers to push the grass up to get the cattle onto a higher plane of nutrition.

"West Texas Augusts are hot but not very humid," Sprott pointed out. "Humidity is the terrible factor on these cattle, especially when it's hot, but even when it's cold."

Sprott said data from recent research in West Texas is still being studied.

Central Texas cows bred during the months of November, December and January have acceptable reproductive performance.

"Temperatures during Central Texas winters are not so stressful that fertility is compromised," Sprott noted.

The data also shows a lower pregnancy rate in herds with nutritional problems. In those studies, when the nutritional problems were corrected, herd pregnancy rates improved.

"Proper nutrition is required," he reiterated.

In a study of 500 calves born in the central and Gulf Coast regions of Texas, data shows that performance drops in calves born in the months from May through September. Calves born in those months had adjusted weaning weights below that of calves born in cooler months. August-born calves were 124 pounds lighter than their April-born herd mates. September-born calves were 99 pounds lighter than their February-born peers, and August-born calves were 57 pounds lighter than their March and December-born counterparts.

Targeting a specific month to calve based on this data is not recommended since there is some variation in the data between locations, but what can be gleaned from the data is that high temperatures are stressful on summer-born calves and will reduce their growth.

"Unless a producer can retain ownership of summer-born calves, they are unlikely to generate acceptable income," Sprott said.

Even then, data from a fourth Gulf Coast herd with summer calves shows that summer calves would have to be retained until they are 12 months old before they reach an acceptable sale weight. Their herd mates reached that weight at seven months of age.

Data suggests that calves born in the cold of December, January and February suffer, but a look at individual Central Texas ranches that are fall and winter calvers suggests that as calving progresses from the cold of December and January to the relatively warmer months of February and March, there is a slight but not significant improvement in calf performance. Sprott said this implies that it usually does not get cold enough in Central Texas to dramatically affect calf performance.

"This is completely contrary to what happens to performance in winter-born calves in northern states where temperatures are more severe and high death loss and the potential for low growth rate in calves are a major concern," Sprott said.

As calving progresses from the warmth of October to the relative cool of November, calf performance in Central Texas improves, but only slightly.

Sprott said if producers can stay away from extreme cold or extreme heat, it should benefit calf performance.

"Maybe the most important thing to conclude from the data is that stressful temperatures of both cold and heat will affect calf performance," Sprott offered, "and for calves in the central and Gulf Coast regions of Texas, summer calving is not recommended."

Research does not clearly identify a specific month to calve and breed cows in Texas, Sprott reiterated, but there is no question that summer calving, May through September, in Central and South Texas will result in significantly reduced calf performance.

It is also highly questionable, he said, that a drop in calf performance ranging from 57 to 124 pounds in summer-born calves is economically acceptable. In six Texas trials, management steps to eliminate summer-born calves and concentrate the calving season in the cooler months of spring or fall resulted in a 74 percent increase in production and a 20 percent reduction in breakeven prices.

It is clear that fertility drops in cows being bred after June and though September. Depending on location, cows bred in May and June in the Gulf Coast region had pregnancy rates about 30 points below those bred in cooler months, while cows in the central and Gulf Coast regions bred from July through September had pregnancy rates from 60 to 65 points below cows bred in cooler months.

"Summer breeding and summer calving in Central and South Texas is not recommended," Sprott concluded.