Animal Science Abstract
The effect of natural zeolite on nutrient digestibility, carcass traits and performance of Holstein steers given a diet containing urea
A.A. Sadeghi1,A and P. Shawrang2
AE-mail: drsadeghi@sr.iau.ac.ir
1Department of Animal Science, Faculty of Agriculture, Science and Research Campus, Islamic Azad University, PO Box 14155, 4933 Tehran, Iran2Department of Animal Science, Faculty of Agriculture, Tehran University, PO Box 4111, Karaj, Iran
Abstract
The objective of this study was to evaluate effects of natural zeolite (clinoptilolite) on nutrient digestibility, carcass attributes and performance of Holstein steers given a diet containing urea. Forty-five Holstein steers (309 (s.d. 11.2) kg) were given diets as follows: control diet based on maize and soya-bean meal (SBM); treatment 2 (T2), control diet (without SBM) containing 20 g/kg urea; treatment 3 (T3), control diet (without SBM) containing 20 g/kg urea and 30 g/kg zeolite. Just before feeding, ruminal ammonia levels were low in all treatments. At 2.5 h post feeding, steers given T2 and T3 diets had higher (P<0.05) ruminal ammonia concentration than the control. At 5.5 h post feeding, steers on T3 diet had the highest ruminal ammonia concentration, which was higher (P<0.05) than the value for steers given T2 diet. Plasma urea nitrogen level increased post feeding for all treatments. At 3 h post feeding, the level for steers given T2 diet was higher (P<0.05) than those on control and T3 diets but at 6 h post feeding, the level was higher for steers on T3 diet. No differences (P>0.05) were observed in dry-matter intake among treatments. Live-weight gain and gain : food ratio were highest (P<0.05) for steers on the control diet, with no differences (P>0.05) between steers given T2 and T3 diets. Including zeolite in a diet containing urea had no effect (P>0.05) on total tract digestibility coefficients of dry matter, organic matter and crude protein but increased (P<0.05) digestibility of neutral-detergent fibre and acid-detergent fibre. Hot carcass weight and kidney, pelvic and heart fat weight of steers were highest in control, intermediate in T3 and least in T2 (P<0.05). No differences (P>0.05) were found in longissimus muscle area and fat thickness over longissimus muscle among treatments. Including 30 g/kg of zeolite in a diet containing 20 g/kg of urea decreased ruminal ammonia nitrogen concentration, plasma urea nitrogen level and increased fibre digestibility but its effect on feedlot performance was negligible.
Keywords: intensive husbandry, steers, urea, zeolites.
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