Research evaluates impacts of respiratory disease on calves

UNIVERSITY PARK, Pa. — Newborn beef on dairy calves are highly dependent on maternal antibodies much like Holstein calves.

“Passive transfer immunity really only helps that calf out for the first week of life and then it starts to really taper off,” said Melissa Cantor, assistant professor of precision dairy science at Penn State University.

“Half of the beef on dairy calves are sick before they are transported on the truck,” said Cantor during a webinar hosted by Hoard’s Dairyman. “Fourteen days after the calves arrived at the facility they are going to be reared at, 77% were showing outward signs of respiratory disease.”

Beef on dairy calves, Cantor said, are put through even more stress than purebred Holstein calves because they are moved multiple times.

“We often transport them at a few days of age and they might get transported again around weaning time,” she said. “They come off milk, go on a high-grain diet that is oftentimes low on forage and we ask them to become a ruminant.”

Respiratory disease is complicated, Cantor said.

“We theorize that stressors and external factors are why some of these natural microflora go down into the upper lung and cause infection,” she said. “There are also viruses that can cause disease and we can have multiple coinfections.”

Research has shown that lung consolidation in dairy calves affects future performance of the animals.

“Up to two months of age, these calves are going to grow about 0.12 to 0.13 kilograms less per day, which is a pretty substantial amount of growth,” Cantor said.

“When we identify lung consolidation during the pre-weaning period, we see decreased milk production, as well, up to about 500 kilos,” she said. “That is a substantial amount of milk when we think about decreased performance in the first lactation from a very early life insult.”

Cantor discussed a study that was designed to investigate the association of lung consolidation at weaning on the growth performance of beef on dairy calves up to 238 days, since calves are often transitioned to feedlots at 238 days of age.

The researchers were also interested in learning about the impact of breeds, so they followed Holstein crossed with Simmental, Angus, Red Angus or Charolais.

“The calves had to have passive transfer immunity, so all these calves started off with a good set of colostrum,” Cantor said. “We transported them to a calf ranch where the calves were fed by bottle, offered free choice grain and water by bucket.”

The calves were fed up to 6 liters of milk per day and then weaned.

Calves were raised in a hoop barn for the study, which is called the grower ranch phase, and they were fed a total mixed ration. To monitor growth, the calves were weighed at birth, four days after weaning, two weeks after arrival at the facility and at 238 days of age.

“We did a lung ultrasound at weaning because we know weaning is a high-risk period for respiratory disease,” Cantor said. “We followed up at day 83 to see if they cured or not or if they got worse.”

Average daily gain was calculated for three separate periods. Period one was from birth to four days after weaning. Period two is the high-risk phase from day 61 to 83 days old.

“This is when the calves got transported and they are commingled,” Cantor said.

Period three is from day 83 to 238 days. Calves are typically sold to a feedlot for finishing at the end of this period.

“We found that healthy calves that did not have any lung consolidation grew better in that 61- to 83-day period than the BRD calves, which is what you would expect,” Cantor said. “But what I find fascinating is that by period three, the calves were very similar.”

The study included 145 animals, 37 of them had respiratory disease and 10 of those calves had lung consolidation in the 3-centimeter category.

Researchers did nasal swabs on the calves at weaning and they were sent to the University of Wisconsin diagnostic laboratory.

“We found 35 of the 37 calves had Pasteurella multocida, there was one case of Bibersteinia trehalosi and one came back with nothing,” Cantor said. “We found one dominant pathogen in the environment that was associated with the lung consolidation we were seeing in our calves.”

Some of the healthy calves were shedding the Pasteurella multocida, she said, but most were not.

“The healthy calves were 79% less likely to be shedding this pathogen compared to calves that had 1 to 2 centimeters of lung consolidation,” the assistant professor said.

“We found that lung consolidation early in life is not associated with feedlot performance like you would expect,” Cantor said.

“When we have an early life insult with respiratory disease, it affected growth for 61 to 83 days,” she said. “But it no longer affected growth at the feedlot where the calves had similar gain to feed ratio and similar dry matter intake.”

However, the researchers found an association between lung consolidation and carcass characteristics.

“Calves with lung consolidation at weaning tended to have 3.05 increased odds of scoring Select versus a better grade of Choice or Prime, compared to the healthy calves,” Cantor said.

“So, I think this study needs to be repeated to see if researchers continue to find this,” she said.