Carry-over And Depletion Of Dietary Melamine In Beef Cattle

Three experiments were conducted to explore carry-over of dietary melamine in beef cattle and its residue and depletion in the cattle’s tissues and organs. A feeding trial with beef cattle on diets containing different doses of melamine was conducted to determine the residue of melamine in their tissues and organs at different intervals during a56d period. Depletion of melamine in the tissue and organ of beef cattle was determined when melamine was withdrawn for1,3and7d. The effect of melamine on ruminal fermentation parameters was evaluated in vitro.Trial1:This trial was conducted to determine carry-over and residue of melamine in beef cattle on diets containing melamine.75Simmental or charolaisxlocal yellow beef crossbreed weighed about500kg were randomly allotted to5treatments which were fed a basal diet supplemented with0,2,10,30and100mg melamine/kg of diet, respectively. On days7,14,21,28and56,3cattle from the treatment were slaughtered. The melamine concentration in the M. Longissimus dorsi, leg muscle, rumen and kidney was determined. The melamine concentration of urine and plasma was determined on days7,14,21,28,42and56. The results showed that performance of beef cattle was not affected by supplemental melamine (P>0.05). The residue of melamine in urine, plasma, M. Longissimus dorsi, leg muscle, rumen and kidney was dose independent. The concentration of melamine decreased in the order of urine, plasma, kidney, leg muscle, M. Longissimus dorsi, and rumen. Melamine was excreted mainly through urine. The concentrations of melamine in the kidney, leg muscle, M. Longissimus dorsi, and rumen of cattle on the diet with100mg melamine/kg were137.67,79.33,65.67, and79.00μg/kg, respectively.Trial2:This trial was conducted to determine the residue depletion of melamine in beef cattle.60Simmental or charolaisxlocal yellow beef crossbreed weighed about500kg were randomly allotted to the same5treatments as in Trial1. On day56, melamine was withdrawn. After1,3and7d of withdrawl,3cattle from each treatment were slaughtered. The melamine concentration in the M. Longissimus dorsi, leg muscle, kidney, urine and plasma was determined. The results showed that the half-time of melamine in urine, plasma, M. Longissimus dorsi, and kidney were5.34,16.03,41.78and19.16h for cattle on the diet containing100mg melamine/kg. The melamine content in urine, plasma, M. Longissimus dorsi, and kidney decreased to less than20μg/kg in43.65,39.8,24.14, and22.96h.Trial3:This trial was conducted to investigate the effects of melamine on ruminal fermentation parameters in vitro. Melamine was supplemented in graded levels:0,2,10,50,250,1250mg/L, respectively. Incubation mediums were taken after incubation of0,1,2,4,6,8,12,24and48h, respectively. Melamine, total volatile fatty acid, acetic acid, propionic acid, butyric acid, valeric acid, isobutyric acid, isovaleric acid, and ammonia nitrogen concentration were determined. The result showed that melamine supplementation resulted in no change in melamine degradation during48h incubation (P>0.05) but decreased dry matter degradability (DMD)(P<0.05). With melamine supplementation at the level of1250mg/L, molar proportion of propionic acid decreased (P<0.05) while ratio of acetic acid to propionic acid increased (P<0.05). Molar proportion of butyric acid increased (P<0.05) with melamine supplementation. Melamine showed an inhibitory effect on ruminal microbial fermentation.