N ‐stearoyl‐D, L‐methionine, a protected methionine source for ruminants

The effect of intraruminal doses (16.8, 33.5 and 50.3 mmol day −1 ) of D.L‐methionine, methionine hydroxy analogue (2‐hydroxy‐4‐(methylthio)‐butanoic acid calcium salt) and N ‐stearoyl‐D, L‐methionine on the flow of methionine (free and protein bound) and its derivatives into the proximal duodenum of the sheep was investigated. Methionine hydroxy analogue was assayed using the reaction of the S‐methyl group with nitroprusside after ion exchange chromatography. On the basal diet the daily flow of methipnine was 20.5 mmol and with the 16.8 mmol treatment N ‐stearoyl methionine, methionine and methionine hydroxy analogue, values of 29.4, 22.1 and 22.5 mmol, total methionine or its equivalent were obtained respectively. With the 33.5 treatment the corresponding flows were 39.6, 22.4 and 22.5 mmol day −1 . During the 50.3 mmol treatments complete feed refusal, probably due to methionine toxicity was noted with N ‐stearoyl‐D,L‐methionine while with methionine and methionine hydroxy analogue the total flow of methionine equivalents was only 20.5 mmol day −1 . Thus, N ‐stearoyl‐D,L‐methionine was the only material to increase the flow of methionine or its equivalent to the duodenum.