er cattle with which they’re in con- tact. If the BVD infection occurs be- tween 120 to 160 days of gestation, it can lead to fetal abnormalities, including skin and eye problems and improper brain development. After 160 days of gestation,
there’s yet another condition, “con- genital infection.” Spire says, “This means the calf saw the virus, but was able to respond to it. We fi nd those calves don’t gain as well, have a higher illness level in the long run, and there are some other con- ditions like birth weights that may be affected by it.”
Bacterial effects via the mother The bacterial and protozoal dis-
eases have different effects when they attack the calf through its mother. “If a cow picks up lepto,” Spire says, “it will go to the fetus, particularly a late-term fetus, and can cause some very ugly lesions.” Vibrio and trich affect the uterus
rather than the calf. They lead to abortions or, in the case of trich, stillbirths. “You can go in and feel her uterus and tell she was preg- nant — the calf withers away and becomes mummifi ed,” he says. There are a couple of other or-
ganisms to worry about that can in- terfere with reproduction. Neospora caninum, a coccidian parasite that can also cause spontaneous abor- tion, is carried by dogs and other canine species. Spire says there’s no effective vaccine on the market for it. “It’s a protozoal disease that will go into the fetal tissue and cause disruption and death,” he says. “If it’s a late-term event, the calf may survive and just not grow well.” Brucellosis was once the scourge
of the U.S. cattle industry. A con- certed effort in the 1980s virtually eliminated it from herds, but it still
110 The Cattleman October 2013
emerges from time to time, spread by wild ruminants or by the im- port of infected animals from other countries. “The traditional method of con-
trolling brucellosis, besides test- ing, was to use heifer vaccinations. There’s an age restriction on heifer vaccinations,” Spire says, “therefore, often the fi rst shot the heifer re- ceived shortly after she was through the stress of weaning was a brucella vaccination.” A lot of herd owners have
stopped calfhood vaccination of heifers, but Spire says producers might keep their future needs in mind. “If they’re planning on mov- ing cattle interstate, if they want to have show heifers or if they want to sell replacement heifers, some states still require that they’re calfhood vaccinated. It’s a nice insurance policy to have, and it cuts down on the regulatory headache,” he says.
Right weight for the right response An underweight heifer will not
respond as well to vaccines as one with a strong body condition score. Spire says, “Look at your heifers’ weaning weights, then look at what your adult cows weigh. Are the adult cows 1,100, 1,200 or 1,300 pounds? Are your replacement heifers at about 65 percent of the adult cows’ weight at the start of the breeding season?” If the herd owner maintains
1,200-pound cows, then the replace- ment heifers need to weigh about 780 pounds when breeding season begins. Calculate the heifers’ nu- tritional needs to meet the target weight. “When you do that you’re keeping the heifers on a positive plane of nutrition and your vaccines are going to work well,” Spire says. The problem comes, he says,
when a producer decides that feed is tight and expensive, so he’ll get the heifer through her fi rst calf with a lot of grass and a little preseason supplement. “We’ll see heifers that don’t hit
the target weights that we want before the start of the breeding sea- son,” Spire says. “So she’s not going to gain her full reproductive poten- tial at the start of the breeding sea- son, which costs the producers lost weight of her calves and lost time because she doesn’t breed back on time as a 2-year-old. It also makes her a candidate to not respond to vaccines. If she doesn’t have the calories in her to respond to vac- cines well, then your vaccines are a waste of money.”
Viruses
remain a concern
because an
infected cow will pass the pathogen on to her calf.
thecattlemanmagazine.com
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