The effects of lysocellin and varying calcium levels on performance and ruminal and plasma characteristics of growing beef steers fed corn silage.

Twenty-four steers initially averaging 221 kg BW were used to evaluate the effects of lysocellin and calcium (Ca) level on performance and ruminal and plasma characteristics. Lysocellin at 0 or 22 mg/kg of diet and Ca at .3 or .6% were fed in a 2 X 2 factorial arrangement of treatments. Steers in individual pens had ad libitum access to a diet consisting of 80% corn silage and 20% (DM basis) of a protein, mineral and vitamin supplement. Ruminal fluid and blood samples were collected on d 42 and 85 of the 113-d trial. Steers fed the .6% Ca diet gained faster and required less feed/unit of gain than those fed the .3% Ca diet (P less than .05). There was a tendency for a lysocellin X Ca interaction for gain and feed efficiency (P less than .10). Lysocellin tended to depress performance when fed with .3% Ca, but it tended to improve gain and feed efficiency when fed with .6% Ca. Molar proportions of propionate were higher and those of acetate were lower (P less than .01) for steers fed lysocellin. Ruminal-soluble Zn, Fe and Cu levels were higher (P less than .01) in steers fed lysocellin. Ruminal-soluble Ca (P less than .01) was higher and ruminal-soluble P and Na were lower (P less than .01) in steers fed .6% Ca. Plasma K was higher (P less than .05) in steers fed .6% Ca but it was lower (P less than .05) in steers fed lysocellin. Results of this study indicate that dietary Ca affects certain metabolic responses to lysocellin in growing cattle.