Just a quick chemistry note...
When you first mentioned asparagus, I had no idea what it might be. But if you say its more like canned asparagus, it could be a few things, all very similar chemically:
There's DMS: CH3-S-CH3
Commonly described as cooked or canned corn. Pilsner malts naturally have a lot of the precursor.
In high concentrations, it smells more like rotting cabbage or sewerage. It shouldn't be so strong as to be offensive!
There's methyl mercaptan: CH3SH
This is the smelly ingredient in asparagus pee (not in asparagus in great proportions). Smells similar to DMS,
and again in large quantities can smell like rotting vegetables. In fact its one of the main chemicals in bad breath.
There's Prenyl mercaptan: <something complicated>-SH
This is the all important molecule that is the result of UV light cleaving hop iso-acids apart. Same chemical in a skunk's stink, but since we don't have them here, its hard to describe. But in any case, very similar to DMS and methyl mercaptan. Its typically the result of leaving a beer in sunlight. If you ever want to find out what its like, just buy a bottle of Corona and leave it in the sun for an hour. Open it up and you won't forget the smell!
Bottom line is that its either a result of skunking of your beer or a badly made/handled beer.
My suggestion is if it is that bad, take it back to the bottlo and get the guy behind the counter to drink it.
Berp.