My horse has a thin mane! And now he barely has a forelock. smh. Is there a supplement? That actually works?

I've had the best luck just running coconut oil through it weekly. Works better than anything I've tried to feed, like BioMane 

May sound strange, but a hoof supplement that contains lysine, methionine and zinc will do more for mane growth than they usually do for feet. Don’t worry about biotin in this application. 

Win

I tried biomane for my horse for a month and I think it worked. He had shorter pieces that would stick up and a month on biomane it doesn't stick up anymore. I think it grew around an inch. I don't think biomane will be like a miracle worker and make your horses mane super thick like the pictures, but I can't say for sure because I only did it for a month. I would like to do it again when I have extra money. 

Many moons ago I was given a 50lb bag of omega horseshine. When I bought my grey horse, he had no tail. It had been chewed off clear up to the end of the tail bone. It was ugly... I hated it but he was so nice, I overlooked it and got on a mission to get that thing to grow. Anyway.. I went thru the whole bag.. I cant say for sure it was the OHS or just time, I kept it clean, bagged it all that jazz.. but his tail grew, now it's all the way down to the ground, I trim it often. I'm not currently feeding OHS but I'm contemplating on getting my boys on it again. It's got more benefits in one that just hair coat, mane and tail support. 

May sound strange, but a hoof supplement that contains lysine, methionine and zinc will do more for mane growth than they usually do for feet. Don’t worry about biotin in this application. 

Win

I've also had good luck with this! 

When I had mine on BioMane their hair or coat didn't change but they started growing 3/4-1" of foot in 4-5 weeks, it was stupid. My farrier was always at my place. I have one on the Tough as Nails & it does seem like his mane is better, it's not so afro like. Its smoothed out a lot. He's got a 4' mane and its thick as heck but its natural, no supplement necessary. But interesting how sometimes a supplement for one thing can provide unexpected results, even better results, on something else 

Omega Horseshine.  My mare lost her whole mane and it grew about 6 inches in 6 months.  

Ive had the best luck just feeding 1 cup of flax seed daily. I also have used coconut oil in the past on the mane/tail with good results.