Transfer efficiency of melamine from feed to milk in lactating dairy cows fed with different doses of melamine

This study was conducted to investigate the transfer efficiency of melamine (1,3,5-triazine-2,4,6-triamine) from feed to milk of lactating cows fed with different doses of melamine. Twenty-four China Holstein dairy cows were divided into 2 blocks according to milk yield (block 1 and block 2 for low- and high-producing cows). Cows of block 1 or block 2 each were randomly assigned to 1 of 4 treatments in a randomized complete block design and each treatment had 6 cows. The cows of treatments 1 to 4 were dosed with melamine at 0 (control), 90 (treatment 1), 270 (treatment 2), and 450 (treatment 3) mg/d per cow, respectively. The trial lasted 19 d. During the first 13 d, cows were fed melamine at the respective treatment levels, and the last 6 d was the clearance period after melamine was withdrawn. The results indicated that the levels of melamine used did not affect milk yield or composition. The mean milk melamine concentration increased during the initial 3 d after melamine feeding in all the melamine-supplemented groups, and then fluctuated slightly over the remaining 10 d of melamine feeding. No melamine was detected in the milk of any groups on d 4 of the clearance period. Milk melamine concentration measured between 3 to 13 d was significantly affected by melamine feeding doses, but was not influenced by milk yield. The transfer efficiency of melamine from feed to milk was not affected by melamine doses (0.95, 0.70, and 0.66% for treatments 1, 2, and 3, respectively), but was linearly related with milk yield (0.56% for block 1 and 0.95% for block 2, R2=0.80). The milk melamine concentration was linearly related with melamine intake (R2=0.84). The present study demonstrated that when the daily intake of melamine exceeds 312.7mg/cow, the milk should not be used to produce infant formula powder.