Water intake can be heritable
Published on Jan. 4, 2020
“Water is one of the six essential nutrients, but producers often overlook it,” says Dr. Megan Rolf of Kansas State University. “We are tempted to think of water as an unlimited resource and neglect it when balancing for rations because we are usually more concerned with protein and carbohydrate content.”
Despite this, Rolf stresses the importance of water intake (WI) in beef cattle.
Rolf, alongside a team of colleagues, conducted a study to better understand WI, including heritability estimates, genetic correlation to other economically important traits and prediction estimates of WI.
“In terms of the amount of water cattle drink, there is a lot of previous research out there based on large pens of animals in confined settings and feedlot type conditions,” Rolf states.
Rolf explains this data was collected by placing a water meter on the line feeding into the pens, measuring what the entire pen drank during the day, then calculating an average for individual animals.
According to Rolf, the results of these studies found average water intake of cattle is around 7.93 to 10.57 gallons per head per day during summer months and only 4.5 gallons per head per day during winter months.
She points out these results are general values spread across a large number of animals, and there isn’t much data looking at individual animal variation.
“There is a lot less published data looking at individual animal WI, but the technology to collect large numbers of WI records on individual animals exists,” explains Rolf.
She continues, “At this point in time, there is also not a lot of research on individual WI data from a genetics or selection perspective. There are no heritability estimates or genomic studies of WI in beef cattle that I have been able to find, although there is some work showing it is a heritable trait in mice.”
“In our study, we set out to see if water intake is a heritable trait in beef cattle and if it is something we might be able to target through genetic selection,” Rolf explains.
“We looked at 579 crossbred steers over a baseline period of 70 days,” she says. “Over those 70 days, we collected data on all feed and water intake and had body weights taken every two weeks to calculate average daily gain.”
Rolf notes although there were a few management differences in terms of feed intake data, all of the heifers in the study were fed a growing diet and had ad libitum access to water over both summer and winter months.
“We found average WI ranged from about 7.3 gallons per head per day up to just under 13 gallons per head per day. Keep in mind, there were some differences in the size of animals,” Rolf states.
A heritable trait
The main goal behind the Kansas State University research was to understand if WI is a heritable trait.
“It was interesting to me, as a geneticist, that even after accounting for differences in dry matter intake, weight and other factors, we still had a lot of individual variation in WI, which made me think it is a heritable trait,” says Rolf.
Rolf’s prediction was accurate as the research found WI is a moderately heritable trait of 0.39.
After gathering data to understand heritability estimates, Rolf and her colleagues also looked at the relationships between WI and other economically relevant traits so they could understand if selecting for WI would have negative impacts on these traits.
“When looking at the correlation between WI and feed associated traits, we found the highest relationship is between WI and dry matter intake, with a moderate relationship between the two. The relationship between WI and residual feed intake and feed-to-gain ratio is much lower,” explains Rolf.
“As one might imagine, the correlation between WI and other water related traits, such as residual water intake and water-to-gain ration are quite high,” she adds. “The genetic correlation between WI and residual feed intake is fairly small but positive.”
Rolf also notes there was no relationship between WI and average daily gain.
The researchers also collected carcass data on all animals including hot carcass weight, rib eye area, back fat, marbling, yield grade and final body weight.
“There is uniformly weak phenotypic relationships between WI and carcass traits. Genetic correlations between water intake and carcass traits were zero to slightly positive, although there were large standard deviations. There were some slight antagonisms with hot carcass weight, marbling and final body weight, but we need more data to get precise estimates on these,” Rolf states.
Rolf and her team also developed some prediction equations.
“We found the main drivers of predicting WI in the summer are dry matter intake and average ambient temperature, while predicting WI in the winter is solely driven by dry matter intake,” Rolf states. “When combining all data together, the biggest drivers are dry matter intake, ambient temperature and weight of the animal.”
She continues, “Therefore, we have concluded from our findings WI is a moderately heritable trait with weak phenotypic relationships between feed associated traits and carcass traits and predictions can be made on water intake if weather factors and dry matter intake data are present.”
Hannah Bugas is the assistant editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.