Effects of Dietary Calcium Levels on Growth-performance and Digestive Function in Cattle Fed a High-fat Finishing Diet

Abstract

A growth performance and digestion trial was conducted to evaluate the Influence of dietary calcium level on the feeding value of a high-fat (11\%) finishing diet. Treatments consisted of three levels of dietary Ca: 0.50, 0.70 and 0.90\% (DM basis). Ca source was limestone and yellow grease was included as supplemental fat. There were no treatment effects (P>0.20) on DMI. Increasing dietary Ca level enhanced ADG (P<0.10) and feed conversion (F:G, P<0.05). There were both linear (P<0.05) and quadratic (P<0.10) effects on dietary NE. Increasing Ca level from 0.7 to 0.9\% increased dietary NEg by 8.0\%. Carcass dressing percentage and LM area increased (P<0.10) with increasing dietary Ca level. There were no treatment effects (P>0.10) on total tract digestion of OM, ADF, lipid., starch or N. However, increasing Ca level from 0.7 to 0.9\% decreased ruminal digestion of OM (P<0.05), ADF (P<0.10) and feed N (P<0.05), but enhanced (P<0.10) ruminal microbial efficiency and (P<0.01) ruminal N efficiency. Postruminal Ca disappearance tended to be greater (P<0.10) with 0.9\% dietary Ca. Increasing dietary calcium level did not affect (P>0.20) either ruminal pH or,ruminal soluble Ca. It is concluded that dietary Ca levels greater than 0.7\% (DMB) are necessary to achieve optimal performance of feedlot steers fed a high-fat finishing diet.