Effect of rapeseed meal as a protein supplement in feedlot lamb diets on excretion of urinary purine derivates and microbial protein synthesis
2014
Yossifov, M. R. (Institute of Animal Science, Kostinbrod (Bulgaria). Department of Animal Nutrition and Feed Technologies)
The objectives of our work were to establish the feeding effects of rapeseed meal (RSM) on urinary purine derivatives (PD) excretion as an indicator of ruminal synthesized and yielded microbial crude protein (MCP), and nitrogen (N) balance. Experimental animals (n=5, Tsigai breed wethers, 4-y aged, 65±2kg BW) averaging 1.1±0.1kg digestible organic matter intake (DOMI) randomly assigned to dietary treatments (n=2) in the two-stage 21–d periods– preliminary (14-d) and collection (7-d). Diets were consisted of 36% meadow hay, 34% cereal (corn, tritikle), 3% vitamin–mineral premix, 27% protein supplement. Diets were either control (with sunflower meal=SFD) or experimental (with rapeseed meal=RSD). They’re isonitrogenous (crude protein, CP=16%), iso-caloric (net energy as feed units for gain, FUG=1.0/kg DM), equal in protein digestible in small intestines (PDI=86g/kg dry matter) and Ca:P ratio (2:1). The results have revealed that RSD gained (p=0.2) in higher DOMI (1.1 vs. 1.0kg) and tended to improve N balance (p=0.4) compared with SFD. PD-s value (24.0 vs. 22.3Mm), as allantoin (14.8 vs. 11.7Mm), xanthine+hypoxanthine (7.2 vs. 8.6Mm) and uric acid (1.9 vs. 2.0), respectively weren’t affected (p=1.0, 0.9, 0.5 ?nd 0.7, respectively) among the dietary treatments (SFD vs. RSD). Similarly, established ratios, as allantoin (2.1 vs. 1.9) and PD to creatinine (2.4 vs. 2.1, respectively), were not differ (p=0.3, respectively) between diets (SFD vs. RSD). Evaluated microbial N yield (20.7 vs. 19.3g, respectively) wasn’t affected (p=0.9), and gained 19.3 vs. 17.1 microbial protein synthesis efficiency, respectively (p=0.8). Observed relationship between DOMI level and allantoin value (R2=0.62), and between PD value and MCP level (R2=0.99) suggested good parity among the treatments. In conclusion, the usage of high level RSM (27% of total ration), as a protein source in feedloot lamb diets tended to improve DOMI and dietary N utilization, but didn’t affect PD excretion and microbial N yield.
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