A forgotten phase

To capitalize on the time and money invested early in a calf’s life, farmers must keep the momentum going after that animal is weaned.

Dr. Joe Armstrong, a technical service veterinarian at Zoetis based in southeast Minnesota, said there is a tendency for people to overlook the post-weaning phase, specifically calves between two and six months of age.

“You can’t afford to do that,” he said. “The highest risk period on a lot of dairies is now the post-weaning phase. There needs to be a mindset change, and everyone needs to be looking at those animals a little more. You can’t forget about them.”

Overlooking calves in the post-weaning phase can cause serious setbacks in the development of a heifer. This phase is a time of critical growth and can be the make-or-break period for achieving benchmarks.

Armstrong said heifers should weigh 55% of their mature body weight at breeding and 82%-85% of their mature body weight at first calving.

“That translates to more milk in the first and second lactations,” he said. “Studies show that heifers that reach their target mature body weight by first calving produce more milk in their first and second lactations compared to heifers that fall behind.”

A minimum of 2 pounds is the recommended average daily gain during the post-weaning phase. The biggest risk for impaired growth lies in the first 30-60 days post-weaning due to the high amount of stress during this time. To track and manage growth, Armstrong recommends that animals be weighed.

“I like tapes when calves are young,” he said. “They are a good measure of birth weights, weaning weights, and getting a snapshot of what’s going on from a performance basis pre-weaning. Post-weaning, I’d like a scale for safety reasons and ease of use. Scales are relatively inexpensive and give you a lot of information.”

A walkover scale or a scale attached to a chute is ideal for this age group. Armstrong prefers individual weights over pen weights to help improve accuracy in tracking progress.

“Weighing a trailer of calves gives you too much noise in the data,” he said. “Individual weights are preferred because the calf that isn’t doing well or gaining like it should, gets lost in the wash.”

Armstrong said bunk space, ventilation, pen space and water are important management components that can be easily overlooked in post-weaning care. Shortcomings within these categories can cause a heifer to fall behind, preventing her from reaching breeding and calving milestones and optimal first-lactation production.

When it comes to bunk space, a minimum of 18 inches per head is recommended.

“I want everybody to be able to eat at the same time,” Armstrong said. “When everyone cannot eat at the same time, you have two different rations being fed. Cattle are great at sorting. Therefore, your first group of heifers will eat what they are supposed to eat, and the second group gets a different ration because it’s already been sorted.”

This difference in diet is visible in the cattle, producing wide ranges in size and body condition.

Providing adequate ventilation year-round is another necessity.

“It’s a fine balance as we need good air movement without drafting calves,” Armstrong said. “In the summer, we need at least 60 air exchanges per hour.”

Air movement must continue in the winter as well, with four air exchanges per hour recommended.

“That usually means you cannot shut your curtain all the way,” Armstrong said. “There needs to be air moving into a building all the time, even in winter. The big thing is that you have to get the air exchanges; you can’t just bring air in and not have anywhere for it to go.”

Giving heifers enough space to grow is also important. Armstrong said heifers should have 40 square feet of pen space per head.

 “We start to see issues if we get lower than that,” he said.

From a water access perspective, best practice is to provide 1-2 linear inches of space per animal.

“That is a big ask, and it’s expensive to get,” Armstrong said. “Therefore, many times, water is not going to be up to the standard. If you don’t have enough water or water access, heifers won’t eat as much and won’t gain as much. Water is a driving factor for dry matter intake and is our most important nutrient, but producers must find that balance.”

When it comes to nutrition, the fewer changes made early on, the better. Considering the amount of stress the animal is already under, changing feed or starter as they transition from a pre-weaning to a post-weaning diet can be too much to bear, Armstrong said.

“I don’t like seeing pen moves and ration changes together,” he said. “When we transition to that post-weaning phase, I’m a big advocate for keeping the diet the same for a decent amount of time. There are a lot of people who want to get to a total mixed ration quickly. I don’t think that’s appropriate for that age of calf. We need to stay on that starter pellet and minimize the amount of stress on an animal by changing the fewest number of things.”

Minor adjustments can be made to protein content to save on cost, but for the most part, Armstrong said the post-weaned diet should remain the same until calves are at least 4 months old, but preferably 5 months or even 6 months of age.

“We can’t start stacking that stress,” he said. “We need to stay consistent so we don’t end up with a problem from a health standpoint. Whole shell corn is important, and it’s good to keep it in  the diet to continue rumen development. We can add hay at some point in small amounts, but I really don’t think we need to push that early. Lean on your nutritionist and make sure they’re involved with that period of a calf’s life.”

Producers must also be on the lookout for diseases that can attack this age group. Bovine respiratory disease is the No. 1 disease affecting calves in the post-weaning phase, and when it strikes, growth slows. Armstrong said calves that get respiratory disease can lose up to a quarter of a pound per day.

“BRD is complex and has a lot of moving parts with many pathogens involved,” Armstrong said. “The traditional model is what we worry about the most — a virus followed by a secondary bacterial infection, with the worst being BRSV (bovine respiratory syncytial virus). That one sets things up for disaster, wreaking havoc on operations and creating damage in the lungs while allowing other pathogens to become involved.”

Another disease pathogen that Armstrong has seen a lot of in the past year is Mycoplasma bovis. Stress and ventilation issues can trigger this bacterium. A calf’s environment can produce undue stress. For example, dirty, wet conditions and inadequate bunk space, pen space or water access are stressors that create competition in a group of calves, allowing BRD and mycoplasma bovis to become issues.

Gains made before weaning can be undone if a farm does not adhere to best management practices during the post-weaning period Armstrong said. Vulnerable to disease and other stressors that can impede growth, these animals cannot afford a hands-off approach.