Raising the bar on passive transfer

by Katie Navarra

The first few hours of a calf’s life are critical. Calves are essentially born without immune systems. They rely on antibodies from colostrum to provide protection from bacteria and other pathogens. Colostrum, provided through the mother’s milk, jumpstarts the calf’s immune system through a process called passive transfer.

“Passive transfer is when the antibodies are passed from the colostrum through the young animal’s digestive tract to the bloodstream,” explained David L. Cook, Ph.D., technical services manager for Milk Products.

Adam Geiger, Ph.D., a research nutritionist at Zinpro Corporation, described passive transfer as a once in a lifetime opportunity for the calf. Without passive transfer, mortality rates increase, a cow is more likely to be culled from the herd and it never achieves its maximum production potential.

“As an industry, we have grown complacent with passive transfer a little bit,” Geiger said. “We never really asked if we could do better, but it is clear now we can. If more calves get passive transfer it will help the industry a great deal – that’s both the beef and dairy industry.”

Leaving it up to nature simply isn’t enough to ensure a calf ingests enough antibodies. During a Dairy Calf & Heifer Association webinar, Cook and Geiger offered insight into how farms can achieve higher passive transfer goals.

The first feeding

The calf’s first feeding is the most critical because shortly after calving, the maternal colostrum is at its highest IgG concentration and the efficacy at which the calf can passively absorb the IgGs is at its highest point. The efficiency at which calves absorb the antibodies decreases in time after the calf is born.

“Left to their own devices, newborn calves will rarely drink the full amount of colostrum they need for successful passive transfer,” Cook said.

Data show that if calves are allowed to suckle directly from the cow, passive transfer decreases dramatically, according to Geiger. To counteract that deficit, farms must actively manage calves’ first feedings. At most dairies, the calf is immediately removed from its mother to avoid injury, reduce risk for disease and ensure adequate amounts of colostrum are consumed.

“When calves suckle directly, we don’t have the ability to prepare the cow’s udder so there can be a large transfer of bacteria along with those IgGs,” Geiger said. “We just can’t control intake and this is a time sensitive process. There’s plenty of data that show that if we can pull that calf away, her likelihood of being a successful animal in the herd and having a long life is significantly improved.”

Typically, farms collect colostrum and process it – some freeze it to create a larger supply, others use a milder pasteurization process to reduce bacterial growth. Supplementing maternal colostrum with another source of antibodies is often necessary.

Benchmarking for success

Much of a cow’s health or production problems later in life can be traced back to the amount of colostrum it received at birth, according to Geiger. Calves that achieve passive transfer are more likely to make it into their first lactation, survive longer and produce more milk. Those that don’t have higher mortality and cull rates and never achieve maximum production levels. However, without data it’s difficult to know how to fix the problem.

“If we don’t have an idea of what our passive transfer rate is on farm it’s hard to go back and fix anything,” Geiger said, “so we need people to benchmark their passive transfer rates.”

Measuring the colostrum in the blood can be done through centrifuged blood that separates the serum. Traditionally, the ideal result has been 10 (IgG) grams of antibody per liter. Generally, IgGs are not measured on farm. Instead, farmers use refractometers, which measure total serum protein. The total protein is an estimator for IgG or antibody content in grams per deciliter. The goal is for calves to measure in the 5.2 to 5.5 range.

“Everybody’s rule is a little bit different, but my general rule of thumb is I want 95% of the calves to be a 5.2 for serum total protein and want 85% of those calves above 5.5,” Geiger said. “But what’s most important is that we’re measuring that serum at about 24 to 48 hours of age.”

Raising the bar on passive transfer

New research suggests that what was considered “good” – 10 IgG or 5.2 to 5.5 (for serum protein) – is likely closer to “fair.” A group of 20 industry experts have research that indicates the new “excellent” category is 25 grams per liter of IgG, which equals 6.2 (serum protein).

“If we can get a larger percentage of calves above that new bar set by academia (researchers), it will bring herd health up,” Cook said. “And you have to accept that there is a cost in achieving that.”

Farms with calves consistently falling below the standards should first look at their sanitation process to confirm that equipment is clean and pathogen-free. Once a farm’s cleaning process is evaluated and altered as necessary, calves that are not getting enough antibodies need to receive more IgG from maternal colostrum. When this is not feasible, supplementation of maternal colostrum with a quality colostrum replacer should be considered.

“Even for our best achievers, this is not going to be a walk in the park to achieve the new standards,” Geiger said. “It doesn’t mean it has to be intimidating. There are tools and resources that can help.”

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