Everyone knows that dam nutrition influences how a calf comes into this world and survives early on. In fact, at least three decades ago, research showed that underfeeding pregnant cows -- relative to their energy requirements -- during the last trimester of gestation resulted in calves with higher morbidity and mortality rates.
Colostrum quality and quantity is part of it. Adequate Body Condition Score (BCS, e.g., 5 at calving) is tied to immunoglobulin levels. The more immunoglobulin, the more disease protection in calves.
"Since most fetal growth occurs in the latter part of pregnancy, the traditional hypothesis has been that the effect of variation in nutrient intake by the dam would have more effect during early pregnancy," says Kim Vonnahme, a beef cattle reproductive physiologist at North Dakota State University. She points out 75% of the growth of the ruminant fetus occurs during the last two months of gestation.
Though it is logical to focus on the last trimester, Vonnahme says recent studies indicate dam nutrition does more than affect growth and development of the fetus throughout gestation.
"While maternal nutrient delivery during pregnancy has been shown to program the growth and development of the fetus, both during pregnancy and later into adult life, it appears that maternal nutrition also programs the development of the placenta," Vonnahme says. "Not only is neonatal health compromised, but subsequent health may be programmed, as offspring from undernourished dams have been shown to exhibit poor growth and productivity, and also to develop significant diseases later in life."
Vonnahme explains fetal programming is the concept that a maternal stimulus or insult at a critical period of fetal development has a long-term impact on the offspring.
Knowledge surrounding this concept is still in its infancy, but Rick Funston, a beef cattle reproductive physiologist at the University of Nebraska, is already proving the impact.
Funston and his colleagues conducted a three-year study evaluating the effect of dam nutrition on the growth and reproduction of those dams' heifer calves. Briefly, 93% of the heifer calves from cows supplemented with protein during the last trimester became pregnant overall, compared with 80% of the heifers out of dams receiving no supplementation.
All told, 77% of heifers from supplemented cows calved in the first 21 days of the season, compared to 49% of those from un-supplemented dams. Those from supplemented dams also calved four days earlier on average. Heifers from dams receiving supplement also had fewer calving problems (78% unassisted vs. 64%), though the average birth weight was identical for both groups. Actual and adjusted weaning weights and weights at pregnancy were higher for the calves out of supplemented cows.
"Our work was the first to demonstrate that late-gestation nutrition can impact the calf for its life," Funston says. "And all our data indicates this is independent of health."
In an associated three-year study -- examining the effect of prepartum and postpartum nutrition on reproduction in spring-calving cows and calf feedlot performance -- cows receiving protein supplementation weaned 5-9% more calves than cows not receiving supplementation.
"It doesn't appear to be a passive immunity challenge," Funston emphasizes. "Though we don't know all the metabolic signals involved, it seems to be more an effect of neonatal programming."
So, dam nutrition affects calf health, but also the fetal programming for performance independent of calf health.
"It is during this early phase of fetal development that maximal placental growth, differentiation and vascularization occurs, as well as fetal organogenesis (development of internal organs), all of which are critical events for normal conceptus development (any point between conception and birth)," Vonnahme says.
Consequently, dam nutrition exists as a critical control point for calf health across the entire gestation period because of its impact on fetal and placental growth and development.
As this new knowledge emerges, though, if you had to pick the most critical period of dam nutrition, it would still be during the last trimester, says Funston. Not only is that when the greatest fetal growth occurs, but that's also when dam nutrition helps determine the ability of the dam to breed back in timely fashion.
Although Funston believes having cows at BCS 5 by calving is a solid benchmark, he's convinced breed-back performance has more to do with the transition to an increasing plane of nutrition at early lactation than it does with cows being a particular BCS at calving.
Likewise, recent research conducted by Vonnahme underscores the fact that over-feeding can be as detrimental to fetal growth as under-feeding.
"We always talk about how the environment affects genetic expression and phenotypic performance," Vonnahme says. "Now, we must also include the uterine environment in that discussion."