In the delicate dance that is dairy nutrition, it’s not all about just getting more milk.
How and what we feed pregnant cows also matters for the development of the calf she is carrying. Researchers have just begun to scratch the surface of the influence of dairy dam nutrition on the lifetime productivity of their calves, according to Billy Brown, assistant professor in the Department of Animal Sciences and Industry at Kansas State University.
In a presentation at the 2024 Cornell Nutrition Conference, Brown explored recent knowledge that can help dairy cows not just deliver healthy calves, but calves that perform better throughout their lifetimes, whether their career destination is the feedlot or the milking parlor.
Creating those successful calves is dependent on events through a number of biological touchpoints throughout their embryonic and fetal development, many of which are not completely understood. Brown says factors such as placental mass, blood flow and nutrient transport to the fetus can be critical.
Other effects may happen at the cellular level. Brown says “epigenetics” refers to DNA alterations that influence genomic material that ultimately activate cellular functions. By pulling the nutritional levers in dams that activate these changes, traits like growth, marbling and mammary gland productivity in their calves might be influenced for the better.
This type of research has been conducted for decades in the beef industry. A number of studies have shown cows that were supplemented with either energy or protein while pregnant produced calves with greater body weight from birth through slaughter, and heifers from supplemented dams reached puberty earlier.
Less-extensive beef research has also shown calves from supplemented dams showed statistical improvements in marbling, quality grades and ribeye area – an interesting finding considering the ever-growing proportion of calves from dairy dams that now are channeled into beef production.
But to date, dairy cattle research has not pursued this topic as extensively.
“There has been a flurry of recent and convincing research evaluating the negative impact of gestational heat stress on calf performance,” Brown says. “But comparatively fewer investigations have focused on effects of dam nutritional interventions.”
From the dam nutrition research that has been conducted in the dairy arena, one thing we have learned is simply feeding dams more is not a simple solution at all. While research has shown dairy calf birth weight increases about 4.5 lb. with each half-point increase in body condition (5-point scale), over-fat cows and first-calf heifers can experience calving difficulties and metabolic challenges in lactation.
“Data from other species indicate dams with excessive energy intake during gestation have deleterious effects for the neonate’s long-term ability to regulate feed intake and body composition,” Brown says. Those long-term effects, including over conditioning, higher metabolic disease incidence and reduced milk yield, have been shown to surface even more in the second generation from overfed dams.
Researchers have also learned high milk production does not guarantee dams will pass that genetic potential to their offspring. In fact, those calves might be hindered by their mothers’ milk production, as several studies have shown.
“Intuitively, the dams with greater milk production might have greater genetic merit for milk production, which could be passed along to their offspring,” Brown hypothesizes. “However, if epigenetic changes are occurring from reduced nutrient supply to the fetus while competing with the mammary gland, then this could limit the progeny milk supply potential.”
So, while hitting the sweet spot between too little and too much energy and protein is one challenge, Brown believes more knowledge could be drawn from the finer details of dairy rations.
Feeding rumen-protected choline to dairy dams has been shown to improve offspring performance in terms of birthweight; preweaning weight gain; feed efficiency; marbling; kidney, pelvic and heart fat; and insulin sensitivity. Rumen-protected methionine and lysine have been shown to positively affect offspring growth and weight gain, as have omega-3 fatty acid supplements.
Brown believes these, and other supplements, could help fine-tune lactating dairy rations to deliver the best possible nutrition package for both the lactating cow and her developing calf.
He says more research is needed, noting: “As this body of research grows, the future of the dairy industry may involve more deliberately setting up calves for success through the use of dam nutritional management during gestation.”
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