Horse -keeping in the winter presents a few challenges. Horses have to rely on us in order to maintain their health and body condition. Less time riding and exercising your horse and more time spent in the stall means that your horse will be utilizing less calories. However, as temperatures drop, horses will actually burn calories in order to keep warm. In a normal horse caloric needs may rise 10-20%. Blanketing your horse can help reduce caloric use in maintaining body temperature. Blanketing must done correctly, or it can actually hinder and harm your horse. I layer and blanket according to the temperature. You should not just throw a blanket on and never take it off. Horses can overheat very easily.
It is now early November, and grass has been going into its dormant state. You might still see some grass in the fields, but there is no nutritional quality left in the grass. I see a lot of horses still grazing solely on grass. You want to begin feeding hay around mid-October before the grass loses its nutritional quality. You need to make sure that you are feeding a high quality and clean hay. A lot of horse owners board their horses, and don't check the quality of the hay provided. There are even some people who don't know how to tell what good quality hay looks like. (That will be another post.) I send off hay samples and have my hay tested for nutritional content. Additional high-quality forage is essential in the winter months in order to maintain a healthy weight and body condition.
A horse's diet should be first based off a high-quality forage and then a feed concentrate. At minimum a horse should receive 1.5% of their body weight in hay. A 1,100lb horse would need at least 16.5lbs of hay per day. A horse can consume up to 3% (33lbs) of hay per day if the hay is high quality. Horses generate more heat in their hindgut from the fermentation of forage than from feeding concentrated feeds. Just by replacing feed with hay will help your horse maintain their bodyweight easier. For every 1lb of grain you reduce from your horse's diet, you should add in 2lbs of hay. If you are noticing that your horse is dropping weight, it would be most likely from poor quality hay or not enough hay.
I like to use a benchmark temperature of 40 degrees farenheit to calculate winter diets. For every degree below the critical temperature I increase the caloric intake by 1%. So if I had a 1,000lb horse that was receiving 18.6Mcal (18,600 calories per day) I would increase his diet by 1,860 calories when the temperature drops to 30 degrees farenheit (10x186). If my hay has tested at 1Mcal (1,000 calories) per pound, an additional 2lbs of hay would help my horse maintain his body conditional at that temperature. I like to look ahead at the weather and plan ahead. It is a good practice to increase the dry-matter content of their diet 24 hours prior to the forcasted cold conditions.
Some other concerns with winter horse-keeping are impaction colic due to dehydration from decreased water intake. Horses should drink between 10-12 gallons of water per day. Horses will tend to not drink water if it is too cold. They prefer to drink water when the temperature is between 40-65 degrees farenheit. Insulated or heated buckets can help keep their water warm. Does your farm have automatic waterers? If they do, are there gauges that show how much water your horses have drank? I personally do not like automatic waterers for a few reasons, but the main reason is that I am not able to monitor water intake.
Some ways to help prevent impaction colic in the winter is to add loose salt to their feed. (I prefer loose salt over blocks, as horses prefer not to lick a cold salt block in the winter.) Exercise improves gut motility. You can also soak their feed in the winter. Hay only contains 10% water whereas grass contains 80% water. Horses should always have unlimited access to water.
Another good tip is that you want to make sure that your barn has good ventilation. A lot of barns will close their doors in order to keep the horses warm. Good ventilation is always more important than warmth. Do not store hay in haylofts over the stalls, as this increases the chances of respiratory illness. (It also increases fire hazard. That will be another post.) Also, do not feed hay in hay racks or in hay nets set over their heads. Hang them low enough for their respiratory tracts to drain down (but not so low where they might get tangled). I prefer to feed hay on the ground. If you have a dirt hallway, it is a good idea to lightly spray it down throughout the day with water to minimize dust.