Document Type : Research Paper
Authors
1 Animal Science Group, Faculty of Agriculture, Lorestan University, Khorramabad, Iran.
2 Department of Animal Science, School of Agriculture, Lorestan University
3 Department of Animal Processing, Animal Science Research Institute of Iran (ASRI), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
Abstract
The present study was conducted to investigate the effects of substituting different levels of urea with biuret on growth performance, rumen fermentation parameters, microbial hydrolytic enzyme activity, and rumen microbial protein synthesis in Afshari fattening male lambs. Twenty-eight lambs with average age of 135±15 days and average live weight of 34±3.45 kg were used with 4 treatments and 7 replications in a completely randomized design. Four experimental diets were used, including substitution of 0 (control), 34, 67 and 100% levels of biuret instead of urea on dty matter (DM) basis during a 70-day fattening period. Results showed that with increasing the level of biuret in the diet, total weight gain, average daily weight gain and feed conversion ratio significantly improved linearly compared to the control treatment (P<0.05). But, the average final weight and DM and organic matter intake were not affected by the experimental diets (P>0.05). With increasing dietary biuret level, rumen ammonia-N concentration and rumen protease activity decreased linearly (P<0.05). Ruminal acetate concentration and microcrystalline cellulase enzyme activity increased linearly with increasing dietary biuret level compared to the urea-containing treatment (P<0.05). The urinary allantoin concentration, total urinary purine derivatives excreted, total absorbed purine derivatives and microbial protein synthesis increased linearly with increasing biuret levels in the diet (P<0.05). The concentration of uric acid and xanthine+hypoxanthine were not affected by the experimental diets (P<0.05). Overall, replacing biuret with urea up to 100% in fattening lambs diet improved growth performance, fermentation parameters, and rumen microbial protein synthesis.
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