It is all about our horses. Like we all have ups and downs, horses or even all animals can have ups and downs, bad days, good days etc. The important part is to realize which behaviour is permanent which behaviour is temporary. Because if you have time to get to know your horse enough, you can understand which situation or behaviour is normal which is not.
Let's see a little bit about feeding and drinking (FEI) :
Free-living horses are constantly on the move, foraging and moving from one grazing area to another. Feeding takes place during two main periods of 5-6 hours each:
from dawn to approx. 10 a.m.; and
from 7 p.m. to midnight.
Horses are highly selective feeders, cropping the grass closely with their teeth. Competition for food does not occur among horses ranging freely over large areas.
Satiation (the feeling of having eaten enough) depends on the amount of food eaten and on the number of chewing movements.
If the horses doesn't spend enough time chewing, this may lead to behavioural problems such as chewing on woodwork, crib-biting, or wind-sucking (McGreevy 2004), even if the amount of food it receives is adequate.
If allowed free access to water, the volume of water a horse drinks and the drinking frequency depends on:
The nature and consistency of the feed
Amount and type of exercise
Loss of fluid due to sweating
Increase exercise caused by the breeding period, hierarchic fights or fear (Schäfer 1993)
Pregnant mares drink more frequently, taking in smaller amounts of water.
Horses prefer to drink with their necks extended, from watering holes or water troughs close to the ground. If horses have free access to water, they will drink according to their rank within the herd or group.
Even though some of us have the privalage to have grooms, I always prefer taking care of my horse on my own. Watch carefully what your horse likes to eat, how often it drinks water or these kind of details and do not hesitate to change the amount of the food (especially special foods) if necessary. For example if you are not working in summer days, you can give less food than the jumping season.
The more you take care of your horse, the more your horse will take care of you back:)