From the University of Florida/IFAS:GAINESVILLE, Fla. — Geoff Dahl wants to know why heat makes cows less prone to produce milk, even when they are not lactating.
Dahl, a UF/IFAS animal sciences professor, has won a $450,000 grant from the National Institute of Food and Agriculture to study how to reduce mammary cell growth so he and his colleagues can develop strategies to limit the negative impact of heat stress on cows that are late in pregnancy and not producing milk, the so-called “dry cows.”
Dahl was one of two UF/IFAS animal sciences faculty members to win $450,000 NIFA grants last week. Cliff Lamb, a professor at the North Florida Research and Education Center in Marianna, Florida, will study the differences in fetal development of Bos Indicus cows compared to Bos Taurus cows.
Heat stress causes cows to eat less and reduces milk during lactation, Dahl said. But it also decreases mammary growth late in a cow’s pregnancy, when cows normally do not produce milk as they prepare for the next lactation.
“That depression of mammary growth translates to less milk throughout the next lactation, and thus reduced efficiency and profitability for dairy producers,” said Dahl, who’s also chair of the Department of Animal Sciences.
Dahl and his colleagues will go to the UF/IFAS Dairy Unit in Hague, Florida, to study the physiological mechanisms that reduce mammary cell growth. That way, they can develop ways to limit the negative impact of heat stress in “dry” cows.
Researchers will house these cows in heat-stress or cooled conditions, collect mammary biopsies during the dry period, track mammary growth impacts of heat stress early in the dry period and as calving time approaches, and try to connect those changes to milk yield in the next lactation.
They anticipate cooling during the cows’ early dry period will help mammary growth and thus production, Dahl said. This should lead to better cattle management methods to maximize milk production.Lamb plans to use his grant to study to determine if fetus and calf development differs between Bos indicus and Bos taurus cattle when faced with nutritional restrictions in early gestation (a cow’s pregnancy). He wants to see how that affects subsequent cattle performance.
“If feeding pregnant cows a higher energy diet in early gestation alters fetal development and enhances subsequent growth of calves, then altering the nutritional management of the herd would be prudent,” Lamb said.
Bos indicus cows live mostly in warmer climates — including Florida — as opposed to Bos taurus cows, which live in colder areas.
Research shows Bos indicus cattle fetuses grow slower in the uterus during early and mid-gestation. There are also indications in some studies that these fetuses grow faster in late gestation, thus leading to fetuses that are larger than their cows of the Bos taurus variety. This fetal growth pattern can produce lifelong changes to the cow’s metabolism, growth, immunology and reproduction, Lamb said.
“We propose that the poor postnatal growth performance of Bos-indicus-based genetics is programmed during early fetal development and this limits postnatal growth potential of these offspring,” Lamb said. “If this is the case, then modifying the environment could alter fetal development in ways that improve postnatal growth and production efficiency.”