I don't have a ready supply of grass-fed beef, but I can get grass-fed beef tallow.
Could I fry hamburger, drain the fat and add back some grass-fed beef tallow to make the meal healthier? Will this significantly change the ratios of fat?
Why don't you just use the tallow in other cooking? I render lots of grass fed beef fat and use the tallow in refried beans. If you're not into beans add the tallow to beef stews. I do that in a crock pot and it adds great flavor.
Yes, it will make the meal healthier, but as for how much that would depend on how fatty the grain-fed meat was that you were using in the first place. I render my own grass-finished tallow and use it for everything (or, at least I try it with everything and decide whether I like it). Even if you left the fat from the hamburger in and added the grass-finished tallow you'd be getting more fat and that is a bonus! The 6-3 ratio would be somewhat better, but I have no idea how much. In the end, how your body feels will be the best judge. You can at least feel better for trying!
Uh ... I really don't think you should go to this much trouble.
Here is a good paleo hack resource on conventional meats.
If you are concerned about offsetting 'optimal' omega 3/6 ratios, take some fish oil or be sure to consume some fish every week.
most grass "fed" beef is still fed corn feed before slaughter. corn is toxic to beef. look for grass FINISHED beef. there are now a good selection of ranches/butchers online you can order grass FINISHED meats from.
Grass AND Grain fed cows 7 Answers
Fatty or lean meat 4 Answers
Grassfed Beef Tallow 2 Answers