Having a horse with a glossy coat, mane and tail comes from feeding the right feed, and proper grooming. Feeding metabolically unbalanced feeds causes ill health, as reflected by a dull coat. Overfeeding with high non structural carbohydrates (NSC) causes metabolic disorders, colic, and a dull, listless coat.

The coat, mane and tail are hairs that are composed mainly of the protein keratin. The hairs grow from the hair follicle, and the rate of hair growth depends on the blood supply to the follicle, and the nutrients supplied. Grooming stimulates blood flow to the follicles, and to removes dead skin cells, and old hair.

The keratin that forms hair is synthesised from specific amino acids in the dietary protein, called sulphur containing amino acids. These include methionine, cystine and cysteine, which also support wool growth in sheep, antler growth in deer, and hoof growth in horses. Not all feeds that contain sulphur containing amino acids.

Feeding oil also gives a glossy coat, mane and tail, by softening the hair cuticle.