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Implanting calves grazing native pasture is a good investment, according to research scientists at the Texas Agricultural Experiment Station at Bushland, Tex, in the Texas Panhandle, and there is no reason for feedyard operators to worry about such a practice. "One of the problems that we have is that feedlots and cattle feeders have the idea that if you implant a calf while he is grazing, you'll lose the benefit of that implant when he goes into the feedyard," said Dr. L. Wayne Green, who holds a dual position as an animal science and ruminant nutritionist at the experiment station and a professor of animal science at West Texas A&M University in nearby Canyon, Tex. Researchers took cattle over the last two years and implanted the cattle with Synovex S and Revalor G implants. A control group was not implanted. The researchers found the implanted calves fed just as well as the control calves. They maintained the gain improvement, and it did not affect their carcass characteristics, Green said. The first group consisted of 80 crossbred steers that averaged 554 pounds. "We put those cattle on native grass pasture," Green said. The steers grazed in a common pasture from Nov. 23, 1998 to May 21, 1999. They were provided a free-choice mineral supplement and fed about two pounds per head of canola meal three times a week. By putting implants into the calves, he said, they were able to increase gain by about a quarter pound a day above the control, or unimplanted calves. "When you look at the cost of that, about a dollar input versus a five dollar return, you really can't afford not to implant cattle on grass," Green said. The calves were taken to the feedlot after 179 days of grazing and divided into nine pens. Three pens had clay surfaces. Six pens had fly ash base surfaces. Green said the pens were designed to prevent cross contamination of pen surface nutrients during rain. All the steers were implanted with Synovex S at the beginning of the finishing period and reimplanted with Revalor S on day 91 of the finishing period. The steers were fed a receiving diet and changed to a finishing diet over a three week period. The finishing diet was 80 percent rolled corn, 10 percent cottonseed hulls and 10 percent protein and mineral supplements. Green said the cattle were killed after 137 days on feed and the carcass data gathered by the West Texas A&M University Cattlemen Carcass Data Survey Team. Pen manure was collected by scraping the pens with a skid loader. Green said the feed and excreta nitrogen and phosphorus were determined colorimetrically. During the growing period, the implanted steers had a greater final body weight and average daily gain than the control group. Implanting the steers during the growing period did not affect the average daily gain in the feedyard when compared to the control steers, nor did implanting them with Synovex S or Revalor G during the growing period affect the amount of nitrogen and phosphorus or total manure excreted in the feedyard. Feed intake during the finishing program was similar regardless of implant treatment. Pre-feedyard implant treatment did not affect hot carcass weight, marbling score, fat thickness or yield grade. Steers implanted with Revalor G during the grazing period had a greater rib eye area compared with the control and Synovex S steers. "Under the conditions of this trial implanting cattle during the growing period did not affect performance, carcass characteristics or nutrient excretion during the finishing period," Green said. The research was a cooperative effort between West Texas A&M University, the Texas Agricultural Extension Service and the USDA Agricultural Research Service. Participating scientists included Green, Damon R. George, Dr. Norbert K. Chirase, Dr. F. Ted McCollum and Dr. N. Andy Cole. |
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