Following microbes' path through cattle

Following microbes' path through cattle

*Krissa Welshans holds a bachelor's degree in animal science from Michigan State University and a master's degree in public policy from New England College. Welshans has long been involved in agriculture and has worked with numerous agricultural groups, including the Animal Agriculture Alliance.

RESEARCH from the U.S. Department of Agriculture is shedding some light on the microbes that dwell in cattle manure: what they are, where they thrive, where they struggle and where they can end up.

The research, being conducted by Agricultural Research Service (ARS) scientists at the agency's Agroecosystems Management Research Unit in Lincoln, Neb., supports the USDA priority of ensuring food safety.

"When we look at potential pathogens that can cause foodborne illness, we need to look at the whole bacterial ecosystem," ARS microbiologist Lisa Durso said. "For instance, some people used to think all cattle have the same bacteria in their gastrointestinal (GI) tracts, but we've found some big differences. So, if we say, 'Oh, it's just manure,' we could miss important factors in pathogen control."

In one project, Durso used fecal samples from six beef cattle to identify a core set of bovine GI bacterial groups common to both beef and dairy cattle.

She also observed a number of bacteria in the beef cattle that had not been reported in dairy cows and identified a diverse assortment of bacteria from the six individual animals, even though all six consumed the same diet and were the same breed, gender and age.

Durso used pyrosequencing, a relatively new method of rapidly analyzing bacterial DNA markers to classify the bacteria into different taxonomic groups.

"People hadn't looked at doing this type of bacterial census before because some bacteria could be cultured, but other types didn't grow well," said Durso, who conducted this investigation while she was working at the ARS U.S. Meat Animal Research Center in Clay Center, Neb. "Pyrosequencing lets us give every bacterium a name tag ID."

According to Durso, the strategy for controlling pathogens needs to be approached differently.

"The focus on food safety is fecal contamination, and pre-harvest pathogen control has often been animal-centric -- for instance, how to 'fix' the problem of (Escherichia coli) in a cow's GI tract -- but a bacterium has a different pathway once it's outside of the gut," Durso said. "So, we need to start thinking strategically about how to control pathogens when they are at their weakest -- outside the animal rather than inside it."

In another study, Durso collaborated with ARS agricultural engineer John Gilley and others to study how livestock diets affected the transport of pathogens in field runoff from manure-amended soils.

The scientists added two types of manure to experimental conventional-till and no-till fields at application rates of one, two or four years. The manure was collected from livestock that had consumed either corn or feed containing wet distillers grains.

After a series of simulated rain events, the team collected and analyzed samples of field runoff and determined that neither diet nor tillage management significantly affected the transport of fecal indicator bacteria, but they did note that diet affected the transport of bacteriophages -- viruses that invade bacteria -- in field runoff.

Gilley also conducted an investigation into how standing wheat residues affected water quality in runoff from fields amended with manure at application rates of one, two or four years.

The scientists found that runoff loads of dissolved phosphorus, total phosphorus, nitrates, nitrogen and total nitrogen were much higher from plots with residue cover. The team also observed that runoff from fields amended with manure at the four-year application rate had significantly higher levels of total phosphorus and dissolved phosphorus than fields amended at rates of one year or two years.

"Our study -- which is one of the first studies on this question -- indicates that there is a significant difference in how manure application rates affect runoff loads, and even though crop residues can be effective in controlling soil erosion, the residues also slow the movement of water across fields, so there's more time for water to pick up nutrients from the soil," Gilley said.

In a follow-up study, Gilley's team found that narrow grass hedges planted at the edge of manure-amended plots reduced mean runoff loads of dissolved phosphorus from 0.69 to 0.08 kg per hectare and total phosphorus from 1.05 to 0.13 kg per hectare -- similar to levels from plots that had not been amended with manure.

"This study shows that if you have hedges, you can substantially reduce nutrient loads in runoff," Gilley said. "Planting grass hedges is a practice that isn't expensive and can have a substantial impact."


Cattle temperament

USDA and university scientists have found that cattle temperament influences how animals should be handled, how they perform and how they respond to disease.

The team of researchers looked at stressful events -- such as weaning, transportation and vaccination -- that beef cattle experience during routine management practices. The researchers examined the interrelationships of stress and cattle temperament with transportation, immune challenges and production traits.

Studies were conducted by: animal scientist and research leader Jeff Carroll at the ARS Livestock Issues Research Unit in Lubbock, Texas; associate research professor Rhonda Vann at Mississippi State University's Brown Loam Branch Experiment Station; animal physiologist Ron Randel at Texas AgriLife Research, The Texas A&M University System in Overton, Texas, and endocrinologist Tom Welsh with Texas AgriLife Research and the Texas A&M department of animal science in College Station, Texas.

Between 24 and 36 calves were used for each study, depending on the trial. An exit velocity system, which measures the rate at which an animal exits a squeeze chute and crosses a certain distance, was used to select for temperament. A pen scoring system was used in conjunction with exit velocity to calculate an overall temperament score for cattle selected as the calmest, the most temperamental or intermediate.

When challenged with a bacterial toxin, cattle showed dramatic differences in sickness behavior, depending on their temperament. The more temperamental animals failed to show behaviors that allow caretakers to detect sick animals, whereas calm animals immediately displayed visual signs and became ill.

The studies also revealed that temperamental cattle did not have the same vigorous immunological response to a vaccine as less temperamental cattle in the same herd.

"We're not talking about one breed compared to another breed," Carroll said. "We're talking about animals within the same breed type, and the only difference is their temperament."

Results showed that the endotoxin increased the animals' body temperature and induced secretion of epinephrine and cortisol, hormones associated with coping with stress, Welsh said.

When animals are transported, they become stressed, contributing to the incidence of disease, Randel said. Therefore, identifying cattle that are more susceptible to stressors and, subsequently, have altered immune responses may help to reduce the impact of sickness after transport.

In related research, the team found that the main cause of stress for cattle was not transportation itself but being handled and loaded into a trailer.

Previous studies have indicated that human/animal interactions are probably the most stressful events for the majority of cattle.

"The duration of transportation is not the problem," Randel said. "It's the action of being handled and loaded into the trailer that is producing the stress."

If cattle are handled in an appropriate manner and given water and feed at a minimum of 12-hour intervals, then getting on and off the trailer is the major stressor, he said.

The study did find, however, that transportation duration and conditions do have negative effects on intramuscular fat or marbling, which is used for fast sources of energy by cattle in transport. Marbling determines the quality grade of the beef. Lower levels of marbling reduce the quality grade. Temperamental cattle have fewer fat stores, indicating that temperament makes a difference in the final quality grade.

"From a production standpoint, temperament of animals does make a difference in the ultimate quality grade, for example, Choice versus Select," Vann said. "As stressors and transportation times increase, temperamental animals could potentially have lower quality grades, and that could mean lower profits."


IPB buys land

Iowa Premium Beef (IPB) is one step closer to completing its new packing plant in Tama, Iowa, after purchasing $1 million worth of land surrounding the former Tama Pack plant on Tama's east side.

According to the Marshalltown Times-Republic, the company purchased 120 acres of land from the Iowa Economic Development Authority, which took ownership of the land from the previous owner when it went bankrupt.

The new IPB facility will focus on custom processing and more specialty brands.

The first phase of operation will allow for an 800-head-per-day kill and will employ 650 people. After phase 1, the plan is to then advance to the second phase of a 2,000-head kill operation, which could require up to 1,000 jobs.

"Certainly, we're about the creation of jobs, and that's what they are moving forward to do," Tina Hoffman, communications director of the Iowa Economic Development Authority, said.

A completion date for the packing facility has not been set.

Volume:85 Issue:11

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