Air, water, land, light: all affect cattle - December 15, 2002

Cattle environment influences not only animal health and welfare but, oftentimes, public health. Environment was a prominent program theme at the 2002 AABP conference in September in Madison, Wis.

Four speakers at a general session on the environmental challenges of bovine production addressed air pollution, feeding programs, rendering, and a model program for involvement in environmental issues.

Brent Auvermann, PhD, Department of Biological and Agricultural Engineering, Texas A&M University, talked about the control of air pollution from feed yards and dairies. Earlier this year, in a consent decree to resolve a lawsuit over dairy emissions, California adopted an emission factor for fugitive (ie, nonpoint source) particulate matter from dairies similar to the emission factor applied to cattle feed yards, despite the vast differences in dust-generating behavior between beef and dairy cattle. In Arizona and Washington, areas failing to attain federal air quality standards also regulate dust-emitting agricultural activities. Dr. Auvermann said that the health-effects data in the refereed literature are still inconclusive but that there were a few key areas that require closer research examination. Most environmental odor pollution involves exposures at subirritant levels. As an example, people detect the odor of hydrogen sulfide at about 2 ppb, recognize it at 4 ppb, and are annoyed by it at 100 ppb, but don't experience sensory irritation until around 2,000 ppb. Dr. Auvermann anticipates federal regulation of ammonia emissions in the next five years. He encouraged practitioners to impress the importance of environmental management systems on their producer clients.

In her presentation, Dr. Deanne M. Meyer, Department of Animal Science, University of California-Davis, talked about minimizing environmental impact of feeding programs. To reduce nitrogen and phosphorus excretions, for example, she said to monitor dietary requirements and feed additives only when they're of benefit to the cow. Federal regulations promulgated in December may, among other things, require large animal facilities such as dairies or feedlots to obtain a National Pollution Discharge Elimination System grant. Dr. Meyer urged veterinarians to help clients identify reliable information on permit requirements, legal responsibilities, and liabilities. Two sites she suggested are www.lpes.org and www.cals.ncsu.edu/waste_mgt/natlcenter/center.htm. Some state and federal assistance is available for improvements. It's also advisable to assemble a team of consultants to assist in developing appropriate comprehensive nutrient management plans.

According to David Kirsten, National By-Products LLC, Des Moines, Iowa, 137 million pounds of waste animal tissues are created daily. Rendering is a critical step in the food chain. Licensed renderers ensure biosecurity and traceability, to preserve groundwater, minimize nuisance odors, and reduce disease vectors. "Rendering protects the environment," he said. Because of bovine spongiform encephalopathy in the United Kingdom, renderers continue to lose markets here and abroad. He suggested some steps veterinarians can take to help stabilize cattle by-product value: don't damage the hide during necropsy (for a resource by Dr. D. Dee Griffin called "No Loose Parts," write dgriffingpvcc [dot] unl [dot] edutarget="_blank"); don't remove the head unless necessary; direct clients to make timely call for carcass removal; and communicate the cause of death, especially in multiple deaths, to avoid introducing chemical safety hazards into the food chain.

Dr. Roger G. Ellis described the New York State Cattle Health Assurance Program (www.nyschap.vet.cornell.edu). This is a voluntary program of the Division of Animal Industry of the New York State Department of Agriculture and Markets, where he is a field veterinarian. In NYSCHAP, environmental, biosecurity, and disease aspects are managed through a team approach. Producers, private and government veterinarians, university and extension staff, and agribusiness people develop a written herd plan using best management practices. The herd veterinarian and team review the plan for each NYSCHAP herd annually. As of August, 713 herds with 180,000 cows were enrolled. Maine used it as the model for its program. Dr. Ellis explained, "NYSCHAP is about creating multiple barriers to prevent problems."

At an AABP dairy session, Dr. Ken Nordlund, University of Wisconsin-Madison School of Veterinary Medicine, led off six speakers who addressed the interactions between housing and dairy cow health.

Describing some diseases and conditions that take root in dairy facilities, Dr. Nordlund cited examples of underlying causes. Barns with three-row configurations provide fewer square feet of alley space, leading to more manure depth, which is a factor in the prevalence of digital dermatitis. Postparturient cows run a greater risk of infectious disease and metabolic problems such as ketosis when mixed in pens with sick cows in special-needs barns. He summarized his ongoing research trial with Dr. Nigel Cook that relates increased surface cushion with reduced lameness, improved udder hygiene scores, and lower incidence of new mastitis cases. In the past 25 years, milk production has increased dramatically, Dr. Nordlund said, but most measures of health have deteriorated. Many housing/health interactions aren't yet clear, but veterinarians must take a major role in improving the quality of on-farm diagnostics and recording systems.

Ventilation and facility solutions to heat stress were addressed by Dr. John F. Smith, Department of Animal Sciences and Industry, Kansas State University, which has a cow comfort consortium. Why is heat stress important in production? If you don't alleviate it, the result will be a drop in peak milk production in the fall, he noted. Heat stress begins at >72 F. There are two ways to cool a cow—cool the animal or cool the air. High humidity limits the ability to use evaporative cooling for the air. Dr. Smith described eight treatments his team experimented with to cool cows. Soaking the cows every five minutes and using fans reduced their respiratory rates and body temperatures the most. He also offered recommendations on ventilation in free-stall barns, north-south vs. east-west barns, and row configurations.

Looking at microbiologic water quality, Dr. John M. Gay, Department of Veterinary Clinical Sciences, Washington State University, noted that many enteric agents survive well if not better in aqueous than other environments, and lactating cows drink large quantities of water. Water systems are a complex web of agents, protozoal predators, nutrients, and other factors, he said. Human drinking water can contain up to 0.3 rotaviruses per 100 mL and 0.2 Giardia lambia cysts, but Escherichia coli is not allowable. Nevertheless, a fourth to a third of rural water wells are contaminated by E coli. A dairy water trough survey revealed a count of 1,000 E coli per 100 mL. Microbial contamination originates from the environment, animal feces, and the oral cavities of cattle. One study found 35 percent of human gastrointestinal diseases were water related and preventable. Dr. Gay said that more research is needed to quantify the risks from these agents in livestock drinking water.

Bedding management can reduce the risk of mastitis and hock injuries, and Dr. Jeffrey K. Reneau, University of Minnesota, noted a linear correlation between contamination of bedding and bacteria in milk. Environmental pathogens found in bedding material are frequently the same as those found in bulk tank milk and clinical mastitis. Research shows that the best bedding material is properly managed clean sand that is free of organic matter, Dr. Reneau reported. Carefully managed organic bedding will also work well. For organic bedding, particle size is important. Fine, dusty bedding can be a problem because the rate of bacterial growth is faster.

Geoffrey E. Dahl, PhD, Department of Animal Sciences, University of Illinois, spoke on "lighting the way to optimal cow performance" through photoperiod manipulation. Dr. Dahl summarized 10 studies showing that cows exposed to long days produced more milk than those exposed to a natural photoperiod. Recent evidence suggests that photoperiod manipulation can also enhance disease resistance. Dr. Dahl directed those interested in photoperiod manipulation of lactation in dairy cattle to http://il-traill.outreach.uiuc.edu/photoperiod.

Dr. Nigel B. Cook, University of Wisconsin-Madison School of Veterinary Medicine, wound up the session with a look at the influence of barn design on hygiene, lameness, and udder health. Dr. Cook described a system of scoring hygiene, developed to measure manure contamination on the udder, lower rear limb, and upper limb and flank (viewable at http://www.vetmed.wisc.edu/). The degree of contamination on each of the three zones may be compared with established benchmarks from other farms or with the hygiene of different groups of cows on the same farm. Using this quantitative approach is more useful to veterinarians working with farmers, he explained, and zone scoring offers more meaningful advice on how they can keep their cows cleaner. The motivational message to farmers is that poor hygiene poses an increased risk of mastitis and lameness.