Emerging Health Research, Issues

Schmallenberg virus, low-stress weaning and pulmonary disease are three of the issues discussed.

by Kasey Miller, Angus Productions Inc.

DENVER, Colo. (July 26, 2012) —New viruses, alternate weaning strategies and new thoughts on pulmonary hypertension in cattle were all topics of discussion at the National Cattlemen’s Beef Association (NCBA) Emerging Health Research and Issues Working Group.

Schmallenberg virus. Julia Ridpath, research microbiologist at USDA Agricultural Research Services’ Ruminant Diseases and Immunology Research Unit National Animal Disease Center, described the new Schmallenberg virus (SBV) and how it was discovered.

In August to October 2011, there was an outbreak of disease in adult cattle, mostly dairy, reported in the Netherlands and Germany. The cattle exhibited signs of mild to moderate fever, reduced milk yield, loss of appetite, loss of body condition and diarrhea.

 

In November and December 2011, abortion and stillbirths were associated with fetal central nervous system abnormalities. The disease was affecting mainly sheep, but it was present in cattle and goats. It was in the Netherlands, Germany and Belgium at this point.

In January 2012, abortion and stillbirths associated with fetal abnormalities in cattle were reported in the same countries.

 

The virus was identified by a metagenomics approach, Ridpath explained. Researchers compared DNA and RNA isolated from clinically ill dairy cattle to normal cattle in the German outbreak. The virus, she explained, is carried by insects and presents in adult cattle with symptoms similar to heat stress, but with added diarrhea. Newborns are delivered at or near term, but are malformed and have symptoms similar to central nervous system abnormalities. The virus spread to 4,000 farms within six months.

 

The virus is known to now exist only in Europe, but knowledge of the disease is important, Ridpath warned

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Weaning performance. Terry Swecker, associate department head and professor at Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech, explained that by looking at behavior, some stressors could be reduced to improve performance of calves at weaning. Swecker reported on differences observed between groups of calves weaned “cold-turkey” (the control), weaned with fence line weaning and weaned using nose clips.

 

The research showed that calves weaned with nose clips didn’t eat as much the week before separation, while the fence line calves started grazing because they couldn’t suck.

 

Once separated, all three groups didn’t eat much, but the control group spent less time eating and more than double the time walking, which uses energy and calories. By Day 42, all the growth had evened out. When looking at non-esterified fatty acids (NEFAs), metabolic parameters (which look at the negative energy balance), the nose-clip calves exhibited more NEFA, which means they didn’t gain as well. The immune function of the calves, measured by oxidative enzymes, did not differ by weaning method. To avoid added stress of taking blood, cortisol levels were measured in the feces, and fence-line-weaned calves were the least stressed.

 

Pulmonary hypertension. Professor Frank Garry, and doctoral candidate Joe Neary, both at Colorado State University, presented some new thoughts on pulmonary hypertension and high-altitude, or brisket, disease. High-altitude disease typically causes increased stress on the lungs and heart, and thus calves have an increase in pulmonary arterial pressure (PAP). Essentially, reduced vessel diameter and increased pressure cause the issues.

 

Garry says that many feedlot cattle are experiencing issues similar to high-altitude disease, even at lower elevations. This is potentially because cattle have been bred to be too large for their heart and lung capacity. Cattle do not use air as efficiently as horses or other athletes, so they need larger lungs. Calves that do not get enough air are essentially hyperventilating, thus they are more prone to disease.

 

Other risk factors include oxygen demand, altitude, fluctuating temperatures, sex, stress and unknown breed effects. Therefore, greater demand on the cardiopulmonary system results in pulmonary disease, cardiac failure and limited growth.

 

He says he hopes to show that lower-altitude cattle can be improved by crossing with adapted high-altitude cattle to increased lung capacity. Ultimately, “animals that can deliver more oxygen grow better,” Garry concluded.