A feeding trial was conducted to investigate the effect of supplemental levels of gelatinized starch-urea (GSU) on growth performance and plasma biochemical indices of growing-finishing beef cattle. Sixty Limousin crossbred bulls [(393.7±15.6) kg] were randomly allotted into six groups with 1 replicate each and 10 bulls in each replicate. The bulls in the six groups were fed diets with no supplemental GSU (control) or supplemented with nitrogen from GSU (GSU-N) at 8%, 16%, 24%, 32% or 40% of total dietary nitrogen, respectively. Results showed that dry matter intake (7.93 to 8.34 kg/d), average daily gain (1.13 to 1.27 kg/d) and feed conversion ratio (0.140 to 0.157) had no significant difference among all the treatments (P>0.10). Increasing supplemental level of GSU linearly increased plasma urea nitrogen concentration (L; P<0.01) and quadratically increased plasma total protein and plasma ammonia concentrations (Q; P<0.001). In addition, the plasma aspartate aminotransferase (AST) activity increased linearly with increasing GSU levels (L; P<0.01), whereas the GSU level had no significant effect on plasma alanine aminatransferaie (ALT) activity (P>0.05). In conclusion, it is considered that 25% GSU-N to diet total N ratio or less than 1.27% GSU-urea to diet dry matter ratio is a safe additive level for growing-finishing beef cattle.［Chinese Journal of Animal Nutrition, 2011, 23（10）：1710 -1715］
MA Wei,REN Liping,WANG Liwen,DING Jian,ZHAO Jinwei,MENG Qingxiang
. Effect of Supplemental Levels of Gelatinized Starch-urea on Growth Performance and Plasma Biochemical Indices of Growing-Finishing Beef Cattle[J]. Chinese Journal of Animal Nutrition, 2011
, 23(10)
: 1710
-1715
.
DOI: 10.3969/j.issn.1006-267x.2011.10.010
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