The World Horse Welfare has a large amount of information available to horse owners in their Horse Advice Library.  

If you have concerns about the welfare of a horse; want further information on specific diseases such as Laminitis; want to learn more on disease prevention or winter welfare, to name but a few topics, then please visit their website.

For more on general well-being including physical and environmental needs for your horse, please see the horse owners booklet on General Well-Being in the 'Health Horses' series by MSD Animal Health. There is also a booklet on general nutrition which is very helpful.