Marty Caldwell, DVM, says heat can be a major stressor to southeastern calves.
Caldwell says calves are weaned in pens for two weeks and bunk-broke at the same time, then moved to grass traps. “High-stress weaning can lead to immune stress and respiratory disease,” he says. “Environmental factors, such as heat stress, also affect this.” To offset problems, Caldwell’s clients try to eliminate heat stress with shade and fresh water, along with boostering the previous vaccines and adding antibiotics to the feed if needed.
Hawaiian producers handle weaning in different ways. Fenceline weaning isn’t common, mainly because it doesn’t fit most ranchers’ management or pasture configurations. The most common method is to wean and confine to a small area immediately after separation from the cow. A combination of prepared feed, hay cubes or pellets, in conjunction with plenty of fresh water, is kept in front of the calves. Loose mineral is also available, and some ranchers use molasses or protein blocks for energy.
This small confinement restricts the calves from walking too far while also bunk-breaking them, which in their case is important as during the upcoming trip to Canada and the continental United States, their only source of feed will be the cubes or pellets while on board the ship. How long they are kept in pens after being separated from their dams depends on how quickly they settle and go on feed, usually five to seven days. It’s decided on a case-by-case evaluation if they need longer confinement.
Laurin cautions against weaning and immediately shipping calves. “It increases the stress burden to the calf, especially when commingling is included. Not only is the calf learning a new feedstuff and adjusting the rumen microbes to that new feed source, but it is having to learn both a new environment and pecking order among unfamiliar cohorts.”
Both stress and exposure to disease have an effect on the immune system, and both can be mitigated by human interaction. “We know that severe stress for an extended period of time can have far-reaching effects such as poor response to vaccinations, thus more unhealthy calves, and poor performance on pasture and in the feedyards,” says Richards. “We recognize this and try to minimize its effects by adhering to principles that lessen stress.”
Once calves are separated from their mothers, Richards says the target goal between weaning and shipping is 30 days minimum. “During this time, we do the best job we can managing the stress levels, keeping the nutrition in front of the animals while watching for any illness,” he explains. “The nutrition plane ties into the level of stress, which ties into immune function, which relates back to the animal’s overall performance.” Like many places with volcanic origins, Hawaii is notoriously low in copper and often selenium, and zinc often is in question, as well, and recently they have found a calcium deficiency that appears to be related to the type of grasses available.
Calves are turned out to pasture for the balance of time between weaning and shipping, for about three weeks. They again are offered mineral and sometimes molasses and/or protein blocks. The calves are monitored and checked for illness. Sick cattle are uncommon, and daily treatments are few and far between.
For backgrounded calves, once they are weaned, bunk-broke and showing an increased intake and gain, Laurin says they typically have a decreased incident of disease. However, many smaller producers can’t get paid enough for these calves at the sale barn to justify the feed and facilities of backgrounding them. “But, systems like Missouri Verified Beef can help those producers receive more money back because they own those calves for a longer period of time and are fed with other calves to create the numbers needed to reduce the per-head cost of backgrounding,” states Laurin.
Laurin likes to see a minimum of 30 days of weaning before calves go into a drylot and prefers 45 days. “We can reduce the days-weaning requirement for stocker operations dependent upon management ability of the operation, size/age of the calf, length of haul and time of the year in comparison to type of grass available.”
In Mississippi, calves are shipped to feedlots within 45 to 60 days of weaning. “If a calf is unhealthy, it is not shipped because it will not gain like its penmates,” explains Caldwell. “The stress at weaning can impact this from poor immunity and low-grade infections that show up in the initial feeding period to poor weight gains throughout the feeding period.”
Approximately 30 days after weaning, all of the health aspects of the Hawaiian calves come into play when they are ready to be shipped. Cattle are gathered and sorted into like-sized groups to fit into the “cowtainers” that will be placed on the ships. “All sick and any questionable animals are removed from the group,” says Richards. “Every effort is made to only ship animals that are completely healthy and free from any discernible disease.”
Realizing that the animals are going to be confined in close proximitiy for the next week or so, the concern for the individual animal’s health is also tempered with the concern for exposing the rest of the group to an infectious problem. “Remembering that the goal,” says Richards, “is to deliver a group of healthy cattle to the mainland, and decisions regarding the health of the group are always kept on point.”
Start with the cows
Keeping calves healthy during these challenging times goes back to having them healthy when they are born. And that goes straight back to the cow. Laurin has been working with her clients to develop good cow-herd vaccination programs. “I discuss how immunity works in a calf and the impact of the cow’s immune status prior to calving, colostral immunity and whether vaccinating calves at a younger age makes sense to that particular herd. Most of these producers are smaller, and by showing a large reduction in sickness from one year to the next through their records affirms their belief in the need to continue a vaccination program.”
Caldwell notes that outside of nutrition, cow immunity is the most important thing producers can do to ensure calf health. “New vaccine technology for fetal protection is instrumental in helping solidify herd immunity,” he says.
It is Richards’ firm belief that the entire herd’s health must be considered. “We have learned over the years that the more intensive we become with our grazing management, the more we need to put into our herd-health programs,” he says. “The healthier the cow, the healthier the calf. The chance of success for that calf increases, and the long-term yield is a healthier, more productive and, accordingly, more efficient herd.”
You may wonder why calves get shipped from Hawaii to Canada and then transported back into the U.S. over the border. The Jones Act prohibits the transportation of U.S. commodities or passengers between U.S. ports on anything but U.S. ships. Unfortunately, there are no livestock transport vessels flagged as U.S. ships. Consequently, cattle from Hawaii cannot go directly to the west coast of the United States when using a foreign-flagged ship. Instead, they must be taken to a port in Canada to be offloaded and then trucked down to their destination.
Hawaiian cattle are tagged with a USDA silver tag prior to boarding the ship, and therefore are identified as U.S. cattle, so they are allowed to cross back in- to the United States from Canada.
Immunology of the weaning calf
Mother Nature does an excellent job of passing down immunity to calves from their dams, provided that the dam’s colostrum is rich in antibodies, the calf gets it at the critical early hours after birth, and the calf gets sufficient volume. Jim Roth, DVM, PhD, Iowa State University, says the length of time a calf is protected depends on those factors. “The protection might last for six to eight months,” he says. “However, if the cow did not have antibody or the calf did not get colostrum, there won’t be any protection after birth.”
Getting good colostrum in the first place can be enhanced with good cow vaccination. Vaccinating the cow is very important for increasing her antibody titer. That results in more antibody in the colostrum, higher antibody titer in the calf and longer duration of immunity in the calf.
Some practitioners and producers have seen illness in calves within a couple of weeks of vaccinations and some place the blame on the vaccines, but it’s important to understand immunologically what’s going on during those times. “Illness within two weeks of vaccination may be a coincidence,” says Roth. “Illness could also be brought on by stressors that occur at the time of vaccination, like weaning, castrating or dehorning. Stress can suppress the immune system and allow subclinical infections to become clinical. Vaccination itself is a stress on the animal’s immune system. Giving multiple vaccines at the same time, along with pour-on, implanting and parasite treatment, adds to the stress.”
In addition, he notes, exposure to infected animals when the calves are rounded up and confined for vaccination can result in clinical disease. “The incubation period for many diseases would result in illness within two weeks of vaccination. Vaccines take a couple of weeks to induce immunity, so they have not had time to protect the calf that is stressed and exposed to disease at the time of vaccination.”
Because of this, the timing of calf vaccinations is important. The immune response takes at least two weeks to protect the animal. If the vaccine is a two-dose product, you can’t expect protection until two weeks after the second dose. In order to protect the animal at the time of weaning when it is most vulnerable, it needs to be well-vaccinated at least two weeks before weaning. “Vaccines are tested and shown to be effective in non-stressed animals,” says Roth. “Vaccination at the time of stress can reduce their effectiveness.”
Vaccines and stress aren’t the only factors that influence the immune system for the good or bad. Vitamins and trace-minerals are very important for immune function. Often, the immune system is the first system impacted when an animal has vitamin deficiency or trace-mineral imbalance. “Their immune system can be suppressed, resulting in increased susceptibility to infection before other symptoms of deficiency occur,” adds Roth.
Roth sums up the most important points for optimizing the calf’s immune system at preweaning and weaning times:
Vaccinate at least two weeks before weaning.
Minimize stress at the time of vaccination and at weaning. Some stress is inevitable, but it should not all be piled on at once.
Avoid exposure to infectious agents from mixing and crowding animals.