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Feedlot Performance, Blood Metabolic Profile and Calcium Status of Steers Fed High Concentrate Diets Containing Several Levels of Calcium

US Department of Agriculture, Beltsville, MD 20705^,2

Abstract

Two feeding trials with Hereford x Angus steers were conducted to evaluate effects of dietary Ca level in high concentrate diets on feedlot performance, carcass traits, blood metabolic profile and Ca status. Dietary treatments of .3, .6, .9 and 1.2% Ca (10 steers*treatment^-1,trial^-1) were fed for 90 (Trial 1) and 114 d (Trial 2). Ground limestone was the source of supplemental Ca. Blood samples were collected weekly throughout Trial 1 and for the first 7 wk of Trial 2. In both trials .3% Ca resulted in lighter weight (P<.10) carcasses and lower (P<.05) blood pH and HCO^-₃ than the rest of die Ca levels during the first 7 wk of feeding the high concentrate diets. Average daily gain increased linearly (P<.10) in response to increased dietary Ca level in Trial 1, but not in Trial 2. There were no significant differences among treatments in feed intake, carcass quality traits, bone ash, bone Ca, or overall characteristics in the blood metabolic profile including total serum or plasma Ca and plasma ionizable Ca. Increasing dietary Ca to .6% or more resulted in improved blood acid-base status during die initial weeks of feeding high concentrate diets, which is associated with heavier carcasses and a trend towards more rapid weight gain. I interpret these data to suggest that the Ca requirement for steers fed high concentrate diets is greater than .3%, but no greater than .6% for maximal feedlot performance.

¹ The author thanks Dr. B. Stroud and his staff for help in blood collection, Mr. Beall and Mr. H. Johnson for care and feeding of the steers, and Ms. B. Hartzell, Ms. M. Bell, Ms. E. Zetina, Ms. J. Whitt and Mr. A. Kozak for their able laboratory work.

² Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.