Dairy farmers who have good calf care protocol are likely to raise more heifer calves to maturity that go on to become productive herd members. But raising calves can be tricky, and they often become ill without warning.
Dr. Michael Ballou, nutritional biologist at Texas Tech University, states a fact that every dairy farmer knows: calves are the future of the herd. “What you do for calves will have a long-term impact on that animal’s productivity later in life.”
According to the Dairy Calf and Heifer Association (DCHA), mortality goals should be less than five percent death rate in calves between 24 hours and 60 days of age; less than two percent from 61 to 120 days and less than one percent from 121 to 180 days. Why do so many calves get sick and die within the first several weeks of life? Ballou says there are numerous ‘holes’ in the gastrointestinal immune system of the calf that keep it susceptible to enteric issues.
About 60 percent of calf deaths are due to gastrointestinal (GI) disease. “There are two reasons calves die from GI disease,” said Ballou. “A lot of calves become septic and they die really fast.” Septicemia occurs when bacteria enters the bloodstream and spreads throughout the body. In most cases, that bacteria entered the calf through the GI tract.
Failure of passive transfer, or FPT, is an issue that calf raisers should watch for. Ballou says about 15 to 20 percent of newborn calves are at risk for FPT. Colostrum is the key to preventing FPT, but the colostrum must be good quality and fed within the first two hours of life. Calves should receive 10 percent of their body weight in good colostrum within the first two hours of life.
“At good dairies, Holsteins are getting four quarts and Jerseys are getting three quarts,” said Ballou. “Jerseys will typically have higher total serum protein levels, probably because many are getting four quarts and they’re smaller. It also appears that Jerseys have better absorption, but that also makes them more susceptible to certain gastrointestinal diseases.” Ballou added that on large dairy farms where numerous calves are born each day, tube feeding is probably a good option for the initial colostrum feeding to ensure each calf receives adequate colostrum.
Colostrum should be collected from tested, disease-free cows. Ideally, the standard plate count (SPC; for bacteria) should be under 100,000 CFUs/ml. “There’s some bacteria, but we want to minimize the amount that we’re feeding the calf,” said Ballou. “The calf’s gastrointestinal tract is immature so we don’t want to throw a lot of bacteria in there.” Ballou noted most farmers probably don’t test colostrum for bacteria, but it’s something to consider if calves are performing poorly. It’s important to note there is more variation in colostrum quality within a herd than between any two herds.
Ballou says when it comes to respiratory disease, a stressor predisposes the animal to a virus, which predisposes the animal to a secondary bacterial infection. In his research work, Ballou has found if he exposes an animal to a virus followed by bacteria, the animal becomes ill. However, if the animal is exposed to bacteria without first having been exposed to a virus, it doesn’t become ill. “The virus plays an important role,” he said. “The virus can alter the immune system, which means the animal is more likely to become ill.”
Studies show that calves with lung lesions at 90 days are more likely to be culled before first calving. “A lot of calves will have some degree of respiratory disease that is subclinical or isn’t severe enough to be treated,” said Ballou. “We necropsied a lot of calves and found that many had severe lung damage but only had minor nasal discharge that I wouldn’t have treated.”
White blood cells, or leucocytes, are an important part of the calf’s immune system. These cells are present in blood and body fluids, and their role is to help fight disease. Certain leucocyte populations develop during the first six months of age. “Calves and heifers must develop their own active immunity to viral and bacterial pathogens,” said Ballou. “Active immunity is the animal getting sick and developing immunity, or we can vaccinate and expose them to the disease so they develop antibodies.”
Ballou points out the difference between infection and disease. “Infection is the presence of a pathogen in tissue that shouldn’t be there,” he said. “Disease is the animal’s immune response to that infection. Animals are good at hiding disease. Once an animal is showing clinical signs of disease, we are already behind in terms of treating that animal. The sooner treatment is given, the more likely it is the animal will recover.”
No matter what system is used for raising calves, eliminating stressors goes a long way in reducing disease. “In a more stressful environment, disease occurs more frequently,” said Ballou. “If they’re stressed, and also exposed to a lot of pathogens, they are more likely to get sick. If the environment is improved and the animals are properly vaccinated, susceptibility is decreased.”
Although scours is a serious issue on some dairy farms, good colostrum is the first line of defense when it comes to preventing the problem. “The Dairy Calf and Heifer Association suggests that less than 25 percent of calves should be treated for scours during the pre-weaning period,” said Ballou. “If you have to think about whether or not to treat a calf for scours, you should probably treat.”
Record keeping is a key factor in calf health and disease prevention. “We don’t do a good job with record keeping,” said Ballou. “It’s important to record data and use that data to track what’s going on rather than simply observing calves.”