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Results of a study by North Carolina State University showed that steers on a 14 percent protein finishing diet benefited from the inclusion of Availa-Zn zinc amino acid complex in their rations, according to the Zinpro Corporation. The purpose of the research was to determine (1) the effect of zinc source on performance and carcass quality of steers, and (2) if dietary protein level affects performance responses to a zinc source. The trial was conducted under the direction of Dr. Jerry Spears. Two protein levels were compared: 11 and 14 percent. The crude protein supplement was provided from soybean meal and urea. Zinc treatments included 30 PPM from a 50:50 combination of zinc sulfate and Availa-Zn, and 30 PPM Zn from Availa-Zn alone. These supplemental zinc levels were in addition to standard basal zinc levels coming from the feedstuffs. 
The cattle, 120 Angus and Simmental steers, were allocated by weight within a breed and randomly assigned to treatments. They were vaccinated, dewormed and identified with ear tags prior to beginning the study, which included a 56-day grower phase and 42-day finishing phase. All steers were implanted with Revalor at the beginning of the finishing phase. Key Findings During the growing phase, zinc source had no effect on any of the measurements due to limited stress on the cattle, which is typical of grower programs. Steers fed the 14 percent protein diet were 21.8 lbs. heavier than those on the 11 percent diet. Cattle on the higher protein ratio had average daily gain improvement of 0.41 lb., and dry matter intake that was 0.7 lb. better than those on the 11 percent ration. At the end of the finishing phase, steers fed the 14 percent protein diets were 22 lbs. heavier. Average daily gain was similar among groups, but Availa-Zn cattle showed the highest numerical response, primarily in the 14 percent protein treatment. Feed conversions showed a consistent positive downward trend by addition of Availa-Zn to both protein level diets, with the greatest responses in the 14 percent protein treated animal. This response suggested that as protein is increased in the diet and performance is increased with the use of implants, zinc requirements increase, the study's investigators said. The increased bioavailability of Availa-Zn increases the level of absorbed zinc to better meet the nutritional needs of the steers. (See chart). Zinc source also influenced both quality grade and marbling in the study. Quality grades were higher for steers receiving zinc from either straight Avail-Zn or from the 50:50 mix of Availa-Zn and zinc sulfate. Marbling also was increased in those carcasses. Numerically, rib eye area was greatest for the Availa-Zn fed cattle in the high protein group. The 14 percent protein level also resulted in heavier hot carcass weights and corresponding increased yield grade compared with the 11 percent protein group. |
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