reproduction vaccines. That will typically be an IBR/ BVD combination and a lepto/vibrio combination.” Then the next step will be boosters, at least 2 weeks
away from the start of the breeding season. Spire says they recommend a 30-day span between the boosters and breeding, which places the heifers around 13 to 14 months of age at the time of booster vaccination. Spire explains a replacement heifer at the yearling
age is not under the same level of stress as weaned calves. “Those yearlings are generally on a positive plane of nutrition. Their immune system is developing into a more mature setup, so they can respond to the vaccines very well.” The boosters, as the name implies, boost the base immune level in the heifers.
Pay attention to timing Timing is important when it comes to preventing
reproductive disorders. “Lepto and vibrio vaccines need a good booster in replacement heifers,” Spire says, “so a month apart is a good time to do that.” He says vaccination
has helped reduce the prevalence of vibrio in the national cow herd, but producers still need to be vigilant. Vibrio is not routinely tested for and there are no clinical signs in infected bulls or in females until they abort or recycle. Lepto, Spire says, is
diffi cult to prevent. He explains, “While we can look at controlling IBR and BVD in the cows themselves, lepto can be easily brought in by fe- ral hogs, dogs, cats, rac- coons, possums, squir- rels…. We see species of lepto, which can affect reproduction, in a lot of different carriers that can accidentally intro- duce it into a herd.” L e p t os p i r os i s i s
causes late-term abor- tions and can also in- duce infertility.
Another prebreeding vaccine that has received a
lot of attention in recent years is for the prevention of trichomoniasis. Texas requires that all bulls be tested when they change possession for the 1-celled protozoan organism that causes the disease, unless they are cer- tifi ed as virgins or are moving directly to slaughter. While infected bulls cannot be cured and are typi-
cally sent to slaughter, there is treatment and a preven- tive vaccine for females.
Viruses can be passed on through the mother Viruses remain a concern because an infected cow
will pass the pathogen on to her calf. “IBR virus can attack the developing embryo or
fetus,” says Spire. “It can actually attack the ovaries. It’s a vicious disease that can cause infertility, early embryonic death or abortion at any time and it has a predilection to go to fetal tissue. When it does, it attacks the brain and the liver of the fetus and it aggressively at- tacks the placenta. This causes abortion.” BVD, particularly the
noncytopathic strain, is more subtle. Although the cow will eventually shut off the pathogenic effects of the virus, it may not be before the bug circulates through her body and infects the calf. An infected cow, he
says, will spread it to the fetus “in an effi cient manner. If she’s between 45 and 120 days of ges- tation, that fetus picks up the virus and recog- nizes it as just another protein that it’s building into its own tissue, so it becomes incorporated into the calf.” This leads to a persis-
tently infected (PI) calf, which will carry the virus for the rest of its life and shed it in great quantities, infecting oth-
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