Transition Trials - Environment Impacts Cows More Than We Think
During the dog days of summer, it’s easy to grasp the role stress plays in harming milk production in lactating cows, but have you ever considered what stress does to transition cows?
“The transition period is one of the most critical time frames in a cow’s production cycle,” says Virginia Ishler, a dairy Extension specialist with Penn State University. “Setting her up to succeed requires attention the few weeks prior to freshening and the weeks post calving.”
Many issues that can arise during the postpartum period have to do with stress. These include decreased immune function, ketosis, metritis, mastitis and displaced abomasum, according to Jennifer Roberts, DVM, Boehringer Ingelheim. Health events such as these can lead to poor milk production and often result in financial loss.
“A well-laid transition plan that includes diligent management practices to ensure a stress-free environment can help your herd through this period seamlessly,” explained Dr. Roberts. “Providing a calm environment with adequate space and relief from potential causes of stress seem like small actions but can have lasting impacts.”
Managing heat stress in lactating cows is a no-brainer. But high temperatures can cause extreme stress in transition cows, too.
“We need to make sure that we're cooling those cows,” says John Lee, with Zoetis dairy technical services. “We think a lot about cooling lactating cows, but it's just as important to cool close up and fresh cows.”
It’s easy to assume heat stress causes a decrease in feed intake leading to poor transition or poor milk production during summer, Lee says. Heat stress cows do produce less milk, but it’s not all related to feed consumption, he warns.
“It really has to do with metabolic changes as they start to shut nutrition away from milk production, to cooling, and controlling body temperature,” he says. “So, it's not it's not just about feed intake.”
The environment the cow is in during the transition period is tremendously impactful, Lee says.
“We’re talking about setting the lactation curve for the next lactation,” he explains. “If we do anything that erodes that lactation curve, there’s tremendous financial loss associated with that.”
Lee also recommends providing cows with shade over their feed bunk to encourage consumption in addition to good air flow and proper ventilation.
Transition cows are particularly sensitive to stocking density and appropriate grouping, Lee says.
“We know that first lactation cows are particularly sensitive to being introduced to mature cows for the first time in close up or in the fresh pens,” he says. “We need to avoid that, so they're not under additional stress.”
Cows with appropriate bunk space who are housed in pens that aren’t overcrowded have a better chance of doing well, he says.
“We sometimes underestimate the significance of overcrowding,” Lee says.
Feed availability & nutrition
Transition cows in close-up or even far-off pens should have access to feed at all times, but availability becomes a crucial factor at about three weeks prior to calving, Lee says.
“Close-up cows need access to feed 24-7,” he says.
Paying attention to changes in nutrition is also critical, according to Roberts.
“There are three different rations: one that’s formulated on paper, one that gets mixed and fed, and one that the cows actually eat,” Roberts says. “In a perfect world, these would all be the same, but in reality, cows can be picky eaters. Particular care needs to be given to ensure her ration is balanced for the cow’s metabolic needs and [that the feed] is properly mixed with the correct components at the proper particle length to minimize sorting.”
1) Dry period. Managing calcium levels through a negative dietary cation-anion difference (DCAD) diet is recommended throughout this phase, Roberts says. “Studies have shown a well-formulated negative DCAD ration results in increased dry-matter intake in early lactation, increased milk production, decreased disease incidence, fewer displaced abomasa and improved reproductive performance,” she adds.
2) Calving. Nutrition is critical in supporting energy demands, calcium needs and immune function for the transition cow, particularly around the time of calving, Roberts says. “Low blood calcium can contribute to dystocia, or delays in the calving process, by decreasing muscle tone and uterine contractions,” she says. “Uterine contractions after calving also aid in expulsion of any contaminants in the reproductive tract that may have resulted from calving.”
3) Postpartum. After calving, cows must adjust to the high calcium demands of colostrum and subsequent milk production, Roberts says.