# How much food value is a horse to a cavalryman?

Suppose you have a group of say, 1,000 cavalry, that were besieged on a fortress awaiting relief. As such, they are dismounted and fight like infantry.

Suppose they are short on food, but they can kill their 1,000 horses for such. How many days could a cavalryman survive eating his horse?

Suppose further, that the horses have "fodder" for ten days. At least half of that (five days' worth) is in the form of grain edible by humans. The remaining half would be in the form of grass that may or may not be accessible in the area between the fortress and the besiegers. How many days' worth of grain for himself would the soldier save by killing his horse?

This question would be for the ancient times, in the pre-stirrup era

-
To get a useful answer, you need to factor in ability top preserve meat from spoilage (unless you kill a few horses each day and feed many people from one horse); AND maybe also the possibility to get disease from eating horsemeat that will decrease army's effectiveness. – DVK Jan 10 '14 at 17:04
@DVK: I'd be thinking terms of killing a few horses a day. that's why I introduced the idea of fodder (grass) for the surviving ones. Horsemeat can give disease, but so could other items. The main objection was that horsemeat was NOT as nutritious as beef, so you could starve soldiers by giving them as much as you would beef. I'm assuming there would be salt or other preservatives. – Tom Au Jan 10 '14 at 17:23
tell that to Tesco – DVK Jan 10 '14 at 17:27
@DVK: Tesco. THAT's where I got the idea that horsemeat was inferior to beef. – Tom Au Jan 10 '14 at 17:29

One pound of horse meat has about 603 calories. warhorses weigh between 800 and 2000 pounds, so the amount of calories would be anywhere between 482.400 and 1.206.000 calories. Since a grown man needs about 2500 calories a day, he can eat for another 192,6 to 482,4 days.

|Edit As has been remarked in the comments only part of the horse is edible. Apparently this could be about two-thirds of the meat in case of cows. I couldn't find any numbers for horses but since we're talking about warhorses who where not bred for eating the percentage would probably be lower. Keep in mind though that supposedly non-edible parts become very attractive as you get hungrier.|

Of course, provided he can keep the food good for so long. Since in ancient times the only place a 1000 man horse army trapped in a siege seems likely is the east, it is probably too hot for that. The only ways to keep food good in the warmer regions of the ancient world would be smoking or salting, but it's doubtful a besieged army has enough access to any of these to preserve a 1000 horses.

A horse should eat about 0,3 to 0,4 percent of it's body weight in grain, which is about 24 to 80 pounds per day, so 5 days of grain makes for 120 to 400 pounds. A male Roman citizen would eat about 4 modii of grain per month (source: my prof), making 36 liters of grain. 1 liter of (chicken*) grain weighs 690 grams, so 24,84 kilos or 54,763 pounds per month or 1,8254333 pounds per day. Thus the grain for his horse would keep him fed for 2-7 months.

I'd like to add that a desperate sally by heavy cavalry could be a much better option, and has proven succesfull in the past. An example:

"Eucratides led many wars with great courage, and, while weakened by them, was put under siege by Demetrius, king of the Indians. He made numerous sorties, and managed to vanquish 60,000 enemies with 300 soldiers, and thus liberated after four months, he put India under his rule" Justin XLI,6

*I had to weigh it myself, and i don't have any grain for horses. If anyone knows a better weight i'd be happy to recalculate (not really).

-
This link addresses the percentage of an animal's weight that is actually rendered as meat. Of course, it refers to cows, not horses, but at least you have a ballpark estimate. – Avner Shahar-Kashtan Jan 10 '14 at 18:55
@AvnerShahar-Kashtan Good point. I'll edit accordingly. – Jeroen K Jan 10 '14 at 19:14
A sally is good. Normally, most cavalry would be sent away before the siege for many of these reasons. They could harry the defenders from the outside better than inside. – Oldcat Jan 10 '14 at 19:26
@Oldcat: Which is what Vercingetorix did at Alesia. Which was the battle I had in mind. – Tom Au Jan 10 '14 at 19:30
Also, if the besiegers can force the defenders to remain active via probing attacks or by forcing them to work on their fortifications (repair, creating fall back positions inside the outer line, etc) they can force the defenders to burn though at lot more than 2-2.5k Calories/day. – Dan Neely Jan 10 '14 at 21:27

re At least half of that (five days' worth) is in the form of grain edible by humans.

This is incorrect - Horses cannot safely eat grain unless it is mixed with high-cellulose forage which is completely inedible to humans.

But, when grain or other concentrates are fed [to horses], quantities must be carefully monitored.
...
It is safe to feed a ration that is 100% forage5 (along with water and supplemental salt), and any feed ration should be at least 50% forage.

Access to water is much more likely to be a problem, for the horses as well as the soldiers:

Horses normally require free access to all the fresh, clean water they want, and to avoid dehydration, should not be kept from water longer than four hours at any one time.
...
Even a slightly dehydrated horse is at higher risk of developing impaction colic. Additionally, dehydration can lead to weight loss because the horse cannot produce adequate amounts of saliva, thus decreasing the amount of feed and dry forage consumed.

How much drinking water does a horse need?

The average horse will intake 5 to 10 gallons of fresh water per day. Just like humans different horses crave or need different water amount intakes. A horse deprived of feed, but supplied drinking water, is capable of surviving 20 to 25 days. A horse deprived of water may only live up to 3 or 6 days. After lacking water intake for two days a horse may refuse to eat and exhibit signs of colic and other life-threatening ailments.

Even the health fiends who advocate large water consumption for humans only recommend about half a gallon per day; certainly humans can survive on half that or less. That means each horse is drinking water for 10 to 40 soldiers - simply unacceptable in a siege.

All in all, no sane commander ever kept his cavalry cooped up during a siege with constricted food or water supplies, given other options. A horse's food value is simply inadequate relative to the care involved under the trying conditions of a siege.

Update:
According to this Canadian Government report the average carcass weight of horses slaughtered in Canada from 1994 to 2012 was about 300kg with a live-to-carcass weight conversion factor of about 55%. The Carcass Weight to Retail Weight conversion factor decreases for larger animals with 75% being typical for beef. This would mean 300kg * 75% = ~ 225 kg of usable meat per animal at best.

-
Not to mention the replacement value of said warhorse is high in any society. – Oldcat Jan 11 '14 at 1:22

Less than you think, because each man would have to kill his horse at about the same time. Then given spoilage, most of it would be lost. There isn't time or room or materials for every man to cure his horsemeat for sausages and the like

-
Exactly why would each man have to kill his horse at about the same time? That simply maximizes food waste, when food is scarce. – Pieter Geerkens Jan 11 '14 at 4:26
If you keep horses alive, they eat grain and cut into the food supplies more than their flesh can give you back. If you starve them, they die. – Oldcat Jan 13 '14 at 20:35