Late gestational nutrition impacts dam, calf
“Late gestation is a time period many ranchers are very familiar with, and this is the time we often start to say, ‘That cow might be a little thin. We might get her bumped up before calving,’” says Janna Kincheloe of South Dakota State University.
During late gestation, 75 percent or more of calf growth occurs.
At the same time, muscle fibers continue to grow, as well.
“Because they are lower priority, we can see an impact on fiber growth during late-gestation when we implement a nutrient restriction,” Kincheloe comments. “In addition, this is when most of our fat cells form and fill with lipid. There are lots of implications in this.”
Nutrition restriction during late gestation may result in intramuscular fat.
Several classic energy restriction studies have looked at impacts from nutrient restriction dropping to 65 percent of requirements.
Work from the University of Wyoming laid the groundwork for systemic impacts.
“Cora and others evaluated a 65 percent nutrient restriction in a group of first-calf heifers, again versus the 100 percent,” Kincheloe says. “There was a slight decrease in calf birthweight, but no different in dystocia, so providing 100 percent of energy requirements did not increase dystocia.”
The research showed an increase in death loss related to energy restriction, and a decreased weaning weight was seen. However, no impact was seen on milk production as a result of restriction.
“There is some type of impact on weaning weights, and it’s not due to milk production,” Kincheloe explains. “Some mechanism causes this change not due to milk production.”
She adds, “There have been other studies since this time that have evaluated milk production and found differences in that production, largely in quantity of milk produced and quality and quantity of colostrum. There have been impacts seen, just not in this study.”
Another study from Purdue used mature cows fed at 100 percent and 70 percent of energy requirements.
“I’m not focused on the calf response in this study but wanted to look at the influence in the cow,” Kincheloe comments. “This study laid the groundwork for body condition score at calving and subsequent reproductive performance.”
When looking at post-partum interval, cows with a body condition score of three or less took nearly 90 days to return to estrus. Those cows in moderate or high condition score took less than 60 days.
Kincheloe says, “These studies indicate to me that we could have a lot of potential impacts, not only on the calf but also on the dam’s ability to go on and be productive in the herd.”
Kincheloe explains protein supplementation in late gestation is a common management practice across the country, and many studies have highlighted the impacts of additional protein.
A study on dormant range in the Sandhills of Nebraska compared cows fed no supplement to those fed a pound of 42 percent crude protein supplement daily.
“There were no differences in calf birthweight, but we did see an increase in percentage of calves weaned and a weaning weight advantage for calves from dams who were supplemented,” Kincheloe says.
Heifer calves were followed through their reproductive cycle.
“There was no difference in age of puberty, but there was a higher percentage of heifers that calved in the first 21 days and an increased pregnancy weight,” Kincheloe explains.
For steer performance, no differences were seen in hot carcass weights, dressing percentage, marbling score or Choice grading.
“Research shows there might be differences based on the sex of the calf and the metabolic environment,” Kincheloe says.
“There’s a lot of data that has found different results,” Kincheloe comments. “Long-term research at the Fort Keough Research Center in Miles City, Mont. has looked at seven-plus generations.”
Currently, Fort Keough research suggests heifers from supplemented dams are more efficient and tend to stay longer in the herd.
“Research is definitely conflicting, but these are some things to keep in mind,” Kincheloe says. “We haven’t landed on any definitive about what will work in every situation.”
Kincheloe presented during the 2019 National Cattlemen’s Beef Association Cattlemen’s College in late January.
Saige Albert is managing editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.