How you feed impacts AI success; gaining diets improve results

Mar 14, 2014

Despite the perceptions of the mainstream population, those in agriculture are a technologically advanced lot. Cutting-edge? Try bleeding edge. Technological advancement and adoption of the most recent science—particularly in the pursuit of the best genetics—is par for the course on many ranching operations.

But the benefit of technology is dependent upon proper use and technique. Deal improperly with a vehicle and you get a poorly- or nonfunctional vehicle at best or a big, deadly mess at worse. Similarly, certain management choices with artificial insemination (AI) can turn a great opportunity into an expense that doesn’t produce the desired results.

How you feed your AI-bred replacement heifers can be the difference between conception and a costly task.

According to a recent study, what and how much beef heifers are fed immediately after being AIed has a large impact on their conception rate and the quality of those early-stage embryos. The report—“Nutritional management post-AI to enhanced pregnancy outcomes”—was compiled following an experiment conducted cooperatively between researchers at the University of Wyoming, the University of Minnesota, Purdue University, and South Dakota State University.

The researchers noted that common practice among beef producers utilizing estrus synchronization and AI is to keep heifers on a feedlotlike system to get up to the proper breeding weight. Once inseminated, heifers are then immediately moved from this setting to pasture, as transport at a later date can compromise conception rates. But the nutritional change from gain-focused feedlot feeding to pasture in those early days post-insemination may cause similar problems as later transport.

“We sometimes forget that high-concentrate diets can put heifers at a disadvantage when they go back to an allforage diet. Heifers bred in the spring may be turned out on grass that is washy, too. They can’t get the calories they are used to,” Scott Lake, Beef Cattle Extension Specialist at the University of Wyoming and the primary author listed on the report, told audiences at the Range Beef Cow Symposium where the paper was first presented.

“A drop to a maintenance diet can put them on a negative plane of nutrition immediately after AI, and it can result in lower pregnancy rates.”

The researchers hypothesized that maintaining the same plane of gain-focused nutrition used before insemination through to at least day 25 post-insemination would result in an increase to first service conception rates. The results of their experiment seem to support their hypothesis.

The experiment took several groups of heifers in a couple different locations and fed them on a gaining diet on drylot. Following insemination, the original groups were broken into groups of three based on different nutritional planes.

One group at each location was kept on the gaining diet used pre-breeding, or 125 percent of maintenance requirements. A second group was put on a maintenance diet of 100 percent maintenance requirements, and the third was put on a losing diet of 80 percent maintenance requirements. At the end of the experiment, the 21-day post-insemination data for the heifers according to feed groups was combined due to small sample numbers at the two different test locations: University of Wyoming and Purdue University.

The results of the study, which was supported by past similar studies, showed a notable increase in conception rates for the heifers on a gaining diet. The gaining heifers, which gained between 1.44-2.09 pounds of gain per day on average, had a combined AI pregnancy rate of 77.4 percent. The maintenance diet heifers had a combined AI pregnancy rate of 56.3 percent, and the losing heifers had a combined AI pregnancy rate of 60.8 percent.

Lake noted at the symposium when presenting the data that the diets had an impact on second service conception rates, as well.

“To me, what’s even just as telling, if we didn’t get them bred in that first cycle, our second service conception rates were terrible.”

According to the data Lake presented, combined second service conception rates were 58.3 percent for the gain-fed group, 23.8 percent for the maintenance-fed group, and 35 percent for the loss-fed group.

“So that means whatever physiologically we’re affecting them so they wouldn’t breed the first time, we’re not getting them bred the second time either. So it could have tremendous impact in setting us back. When we talk about AI programs, that’s an investment.”

The experiment also included an embryo quality portion with a different, though similarly treated, group of heifers. At South Dakota State University and the University of Minnesota, heifers were similarly fed a gaining diet before being AIed, then switched to one of two feeding groups: gain or lose. At six days post-insemination, the embryos were flushed using non-surgical methods and examined for quality.

The examination of the recovered embryos showed that embryos from the gainfed heifers were larger, higher quality, at a more advanced state of development, and had fewer dead cells than did the embryos of lossfed heifers.

“These results suggest that the early embryo, oviduct, and uterus are sensitive to immediate changes in nutrition,” the researchers concluded. “It is proposed that the immediate retardation of embryonic development observed is likely responsible for reduced pregnancy rates due to an inability of the embryo to successfully signal maternal recognition of pregnancy at later stages of development.”

“We’re having a huge impact in how we feed these cattle. If we go from a feedlot diet to grass, that change is huge and metabolically speaking, we’re causing a huge train wreck,” said Lake to the symposium audience in closing. “Unquestionably, nutrition impacts reproduction. We know that we’re affecting those embryos in as little as six days of diet change.” — Kerry Halladay, WLJ Editor