An exhaust gas treatment system includes a SCR device and a DOC converter disposed upstream of the SCR device. A DEF dosing system includes an injector disposed upstream of the DOC converter for injecting ammonia reductant into the flow of exhaust gas upstream of the DOC converter. The DOC converter includes a corrugated metallic substrate having an ammonia-neutral oxidation catalyst compound that is operable to oxidize hydrocarbons and carbon monoxide in the flow of exhaust gas, while not reacting with the ammonia reductant in the flow of exhaust gas. The ammonia-neutral oxidation catalyst compound allows the ammonia reductant in the flow of exhaust gas to pass through the DOC converter, for reaction with a selective catalytic reduction composition in the SCR device.