Hot Stuff, Fall 1998
- Prescribed burning not always the cure (Fall 1998)
- No bull about it, this is a heavy test (Fall 1998)
- Sorghum ergot: A sticky situation (Fall 1998)
- Breathing easy in eastern New Mexico (Fall 1998)
Prescribed burning not always the cure
Fire may be a good way to get rid of weeds on Texas and Oklahoma rangelands, but the control method is not so hot for dealing with broom snakeweed in New Mexico.
"Burning should only be done under prescribed conditions, and in New Mexico the ideal weather conditions rarely occur," says Kirk McDaniel, a range scientist with NMSU's Agricultural Experiment Station.
Ranchers lament poisonous broom snakeweed, common on rangelands throughout New Mexico, because it chokes out grasses desirable for grazing cattle. "One of its common names is turpentine weed, and if you take a bite of it, it tastes like gasoline," McDaniel says. "Cows have the same reaction to it, so it's a plant that the animals won't eat unless they absolutely have to."
The goal of a prescribed burn is not only to reduce the amount of broom snakeweed but also to get increased growth of grasses for grazing, McDaniel says. That means rainfall is needed following a burn to promote the regrowth.
"Prescribed burning is a tool that is usually used in areas with higher rainfall, such as Texas or Oklahoma, and there's a greater fuel source availableto carry the fire," he says. "New Mexico's really marginal in terms of having enough fuel and the ideal weather conditions in order to burn."
McDaniel and his graduate students conducted seven years of research at NMSU's Corona Range and Livestock Research Center, located 15 miles east of Corona, on whether prescribed burning is an effective way to control snakeweed in the state.
"We've conducted more than 100 burns," McDaniel says. "We've tried to conduct our fires in a way that we burn under a variety of weather conditions to determine the ideal air temperature, relative humidity and wind conditions necessary to control snakeweed with fire on blue grama grasslands."
The fires were started with small torches in research plots that were cleared around the edges to create fire breaks. "It's exciting research in that you never quite know what the fire is going to look like as it carries across the plot," he says.
For a prescribed burn to be successful, weather conditions must be optimum before, during and after the fire. "Landowners can control the before and during conditions, but the after conditions are obviously out of their hands," McDaniel says.
Results of the research showed that when conditions are right, prescribed burns do kill the snakeweed. "But we don't necessarily get good enough grass growth after to justify the burning expense," he says.
Part of the problem is that a year or two can go by before conditions are optimal to start a prescribed fire. For example, during the seven years of research at Corona, McDaniel says the scientists only had three years in which there was a suitable window of opportunity to burn. Even then, the window was only a few days in either the spring or summer.
"There's a lot of risk associated with this practice, because a rancher may rest a pasture a year in advance in order to get enough fuel to conduct the fire," McDaniel says. "Then the next year when they hope to burn, the air temperatures may be wrong, or the windy conditions may prevent safe conditions for starting the fire."
The rancher must then wait another year to see if conditions are right. If the fire is conducted, then the land needs to be rested a minimum of one and ideally two growing seasons after to allow grasses to come back to support grazing again.
"The rancher is looking at a big economic investment to keep the cattle off the land," McDaniel says.
Ranchers have other options for controlling snakeweed. "There are some situations in which a stand of snakeweed is too dense to burn, and the only option for removal is chemical control," he says. "In other situations, when there is minimal snakeweed, it is possible to reduce the plants' impact through grazing managment."
Sometimes snakeweed becomes infested with insects like the round-headed root borer. "In this case, you want the insects to do their business and eliminate the snakeweed. You don't have to go in there with chemical control or burning," McDaniel says.
Results of the research, funded by the state and a special grant from the U.S. Department of Agriculture's Cooperative State Research Education and Extension Service, were published recently in the Journal of Range Management.
No bull about it, this is a heavy test
While most of us dislike the idea of gaining weight, each year 130 to 140 young bulls at the Tucumcari Bull Test put on the pounds, competing for top dollar at the final auction.
The test measures each animal's ability to convert feed into weight gain.
"Breeding potential also is determined," says Ron Parker, test supervisor and livestock specialist with NMSU's Cooperative Extension Service. "After the test, area ranchers can purchase these performance-tested bulls to improve their herds."
Only purebred bull calves are eligible for the test. Each October, livestock breeders from New Mexico and surrounding states place their finest bulls in the care of test staff at NMSU's Agricultural Science Center at Tucumcari. For 112 days, the bulls receive identical feed and treatments.
"We try to keep the environmental conditions the same for each pen, so the data will be as accurate as possible," Parker says.
The bulls are weighed several times to calculate their average daily gain. During the most recent test, the bulls gained an averarge of more than three pounds per day.
"Weight gain is an important factor because it predicts how the bull's offspring will perform in a feedlot setting," says Rex Kirksey, science center superintendent. "Livestock producers want calves to put on weight quickly and efficiently to reduce their feed costs."
Through the test, breeders can identify their better-performing bulls and either keep them for their own herds or sell them to other ranchers, says Don Fields, a rancher from Dora who tested eight Saler bulls this year. "It also gives cattle producers good exposure to potential buyers."
At the end of the test, the top 80 percent of the bulls are eligible for the auction.
"We keep excellent records so the buyer has a great deal of information about each bull," Parker says. "That's something you can't get in the sale ring."
This year's top seller at $6,500 was a year-old Charolais bull weighing 1,280 pounds from DuVall Ranches in Colorado.
Since 1961, more than 4,600 bulls have been tested at the science center. The test is sponsored jointly by the New Mexico Beef Cattle Performance Association and NMSU's Extension Service and Agricultural Experiment Station.
Sorghum ergot: A sticky situation
Last year, a sticky fungus that infects sorghum made its way into the country, infecting crops in several states, including New Mexico. Researchers now have more information that could help growers manage sorghum ergot.
Earlier reports from Africa and Asia, where the disease originated, indicated that sorghum ergot was a cool-temperature pathogen that requires temperatures below 60 degrees and high humidity for infection.
"We now know that the fungus isn't restricted to low temperatures," says Natalie Goldberg, plant pathologist with NMSU's Cooperative Extension Service. "The occurrence of the disease in the Rio Grande Valley of Texas in May and June indicates that the fungus is somewhat adaptable to our environmental conditions. It has a much wider temperature range, provided there's adequate humidity."
Optimum conditions for infection are temperatures between 66 and 70 degrees with high relative humidity, Goldberg says. The fungus grows between 57 and 82 degrees with humidity between 67 and 100 percent.
"Sorghum ergot is a potentially damaging disease," she says. "It lowers grain and seed quality, reduces germination and seedling emergence and makes seedlings susceptible to other diseases."
Curry, Roosevelt and Quay counties lead the state in sorghum production. In 1996, more than 220,000 acres of sorghum were harvested at a value of $18.5 million.
The fungus can infect unfertilized flowers even when daytime conditions are hot and dry, provided nighttime conditions are conducive, Goldberg says. These findings indicate a greater potential for the disease even in traditionally hot and dry climates such as New Mexico's.
Infected flowers produce a sticky substance-a honeydew-that clogs equipment and makes harvesting difficult. The honeydew, which contains masses of fungal spores (conidia), is sweet and attractive to insects and animals. In severe infections, excessive amounts of honeydew drip over leaves and soil.
"Secondary spores produced in the honeydew are spread by splashing water and wind currents," she says. "Conidia spread by wind can infect fields long distances from the initial infection sites. The fungus also can be moved in dried honeydew attached to animals, clothing, shoes and farm equipment."
To help manage sorghum ergot, growers should plant only high quality seed treated with a fungicide, and use protective fungicides (approved by special exemption) in hybrid seed fields only. Sorghum producers also should harvest forage sorghum prior to flowering, use good pollen management techniques for seed and grain production and disc fields after harvest.
The rapid dissemination of sorghum ergot has allowed it to spread around the world in just three years. The disease first moved from Africa and Asia to Brazil, where it caused an economic epidemic in 1995. Then it moved to other South American countries and to Australia in 1996 and Mexico and the United States in 1997. During the 1997 growing season, the fungus spread from Texas to Kansas, Nebraska, Georgia, Mississippi and New Mexico.
"While we have learned a lot in a short period of time, we still have much to learn," Goldberg says. "Research continues in all areas, including identifying and breeding for disease resistance.
One thing we've learned already in 1998 is that drought is a very effective management tool."
Breathing easy in eastern New Mexico
Each year, groups of newcomers to the High Plains face a variety of stresses: being away from their families, adjusting to a new location and recovering from their journeys. Glenn Duff is helping them breathe easier in spite of these anxieties.
The "newcomers" are weaned calves from the southeastern United States, and Duff is the superintendent at NMSU's Clayton Livestock Research Center. He's researching the best methods for preventing shipping fever, or bovine respiratory disease.
"We're evaluating different nutritional programs and antibiotic treatments that may help lower the risk of disease," Duff says. "When animals are stressed during transportation, organisms that occur naturally in the nasal passages can proliferate and pass into the lungs, causing severe breathing problems."
Currently, 40 to 60 percent of transported cattle contract some type of illness. Duff is discovering that certain feed ingredients like the protein supplement urea may improve feed intake and reduce the risk of disease. "We've found that a level of about 0.5 percent urea in a dry matter diet optimizes the animals' performance," he says.
The research center simulates a feedlot setting, housing approximately 480 cattle. "Like many of the state's livestock producers, we receive cattle from the Southeast."
A small-scale feed mill at the center is used to mix feed and minerals, including corn, milo, alfalfa, urea, calcium and limestone. A truck with six separate feed bins distributes the mixture to each pen. "We're fortunate to have these facilities," Duff says. "We flake our own grain and we're able to mix and feed the same diet to six different pens at a time."
In addition to making sure the cattle eat a nutritious diet, Duff is researching current vaccines for shipping fever. "Few studies have tracked the performance of vaccines administered in different locations on the animal's body," he says.
These vaccines typically are given either as a spray in the animal's nose or an injection in the muscle tissue. Duff's initial findings suggest that an internasal injection given when the animal arrives at the facility is the most successful. He is planning further studies to evaluate a combination of the two methods-internasal followed by intermuscular.
Proper diet and vaccinations to stay healthy-sounds like something pediatricians would prescribe. With more research, Duff's patients will be living, breathing success stories.