If you can measure something in cattle, you can either manage or select for it. We can now measure individual animal water intake. So, it shouldn’t come as any surprise that researchers are looking into the heritability of water intake in cattle.
Dr. Megan Rolf, assistant professor of animal science at Kansas State University, presented recent findings in a webinar held Tuesday, Feb. 19 that asked the question: “Is water intake a heritable trait?”
The answer is “Yes.”
“It is a moderately heritable trait,” said Rolf, summarizing the findings of a study she led into individual animal water intake during the webinar. “[It is] pretty on par with what you typically see in the literature for growth traits and things like dry matter intake.”
“I think it’s a first step in getting us to the point where we could have an EPD for water,” Dr. Sara Place—senior director of sustainable beef production research at the National Cattlemen’s Beef Association and also a principal investigator on the study—told WLJ. She added that the potential to select for water efficiency in cattle is on the horizon with this research.
“I think that could be a real advantage for producers in the future.”
The research, then and now
“One of the surprising things when I started thinking about this idea was, I thought there would be quite extensive literature already existing on the issue,” Rolf explained during the webinar.
“There’s maybe not as much as you might think, and there certainly wasn’t as much as I thought.”
Before Rolf’s study, the existing research on water intake in cattle was limited to pen-level data. This is too general to answer heritability questions accurately or well. By comparison, Rolf’s study looked at individual animal variation in water intake, making it unique—a first step into a new field of investigation.
Though the finding that water intake is heritable has the potential to have important practical effects for ranchers down the road, that was not the purpose of the study. Its stated goal was to “determine the test duration necessary for collection of accurate [water intake] phenotypes.”
Establishing a proper protocol for measuring a trait is an important first step when pursuing a new field of genetic investigation.
“Water is an essential nutrient, but the effect it has on performance generally receives little attention,” the study’s report read. “There are few systems and guidelines for collection of water intake (WI) phenotypes in beef cattle, which makes large-scale research on WI a challenge.”
Rolf’s study—reported on in the academic article, “Test duration for water intake, ADG, and DMI in beef cattle,” and published in the July 28, 2018 issue of the Journal of Animal Science—tried to tackle this challenge. Over the three-year study, researchers collected individual water intake data on 578 crossbred steers in feedlot settings using the Insentec system. The Insentec system, much like the GrowSafe systems for feed, collects individual animal water intake data.
After controlling for numerous environmental parameters—temperature, wind speed, humidity, and solar radiation—and things like individual cattle size and dry matter intake, the researchers found that only about 40 percent of the variation in individual water intake could be explained by the environment.
“As a geneticist, what’s really interesting to me is that we have a lot of individual animal variation that we are not accounting for when we are looking at differences in dry matter intake, weight, and weather factor,” Rolf said.
The study also looked at genetic correlations of water intake to some carcass traits, such as hot carcass weight, backfat, ribeye area, and marbling.
“Genetic correlations will basically tell us, ‘if we select for water intake, what changes are we likely to see in other traits that are genetically correlated?’” Rolf explained.
From the dataset gathered in the study—which Rolf repeatedly stressed was relatively small—it does not appear that water intake negatively affects economically-important carcass traits.
“We didn’t note any strong antagonistic relationships between water intake and any of our feed intake traits, and really no relationship with average daily gain. The big question now is, there are certainly more economically-relevant traits than just dry matter intake, as an example, so we need to expand this analysis to other traits.”
Why measure water intake?
“Water is not necessarily an unlimited resource, even though sometimes we tend to think of it that way,” Rolf explained in the webinar about why she thought to pursue this research in the first place.
“Of course, in certain parts of the country, water is not really limited within the environment and may not be as big of a concern in those areas. But we do have a lot of cattle in pretty large portions of the country where we do have less rainfall and of course we do have, in many of those areas, issues surrounding use of that water or water rights.”
Some of those issues include drought. According to the U.S. Drought Monitor, 6 percent of the U.S. cattle herd is in an area experiencing drought as of Feb. 19. This is quite small, but the same time last year, that population was 38 percent due to the extensive drought in the Southern and Central Plains.
“Regardless of whether we’re in an area where there may be water challenges or not, we do sometimes have to deal with the impact of competition,” Rolf went on.
[inline_image file=”0be4ca03a90e005752309f491b035ca5.jpg” caption=”Empty water holes caused by the drought in California.”]
“Certainly, competition from humans and municipalities that need to use water resources that are available. Competition from wildlife in the area. And also competition from other agricultural enterprises, like irrigation used in crop production.”
Additionally, though this was not brought up in the webinar, there is increasing consumer attention on water use as part of the sustainability discussion.
In asking Place about the role of water use in the sustainability discussion, she told WLJ that, “From a macro level, the water use in the industry really comes down to feed and how it’s produced. But to the individual producer, this idea of ‘how much does the animal really need, and can I select for water use efficiency?’ That’s where [this research] really comes into play.”
Ranchers already select for feed efficiency because it just makes business sense, regardless of the sustainability factor. The same could be true of water efficiency in cattle.
“Just like the research we’ve seen with feed efficiency and things like residual feed intake, I think we’re going to probably have a similar potential to exploit that genetic variation when it comes to water,” Place said.
“Look for this to be something else—especially if you’re in the western U.S.—to get animals that are hopefully feed efficient and fit their environment in terms of feed and water. I think that could be a real advantage for producers in the future.” — Kerry Halladay, WLJ editor
