CSU hay test explained

For starters horses need a minimum of 1% forage but in reality a horse will want to, and naturally, consume 1.5-2% of their diet in forage to meet their energy needs. Hay is your forage.  So if your horse weights 1200 lbs you should not give them less than 12lbs of forage a day with 18-24lbs/day being more realistic to their natural and desired consumption.

If you have a horse that is susceptible to obesity do not reduce the volume of hay, reduce the quality of hay. By that I do not mean get moldy cow hay. I mean get lower energy, lower protein hay that the horse can eat all day long without gaining. A full gut round the clock is a happy gut.

The below information is based on the factors tested by Colorado State University standard forage test. In 2016 it was a $35 test. There are more tests for minerals available but the below information is just for the basic test that they provide for the hay test. The test from Colorado State University was selected for this post because they are well known. Other institutions may give other reports with other components.

 

Moisture -  Ideal is 10-17%, when it reaches 18% it’s at high risk of mold. Hay over 25% poses a huge heat and fire risk.

 

Crude protein (CP) --  Is actually an estimation of total protein based on the amount of nitrogen in the hay. So areas with high nitrogen may falsely read high protein.  It does not tell you anything about the amino acid composition or the protein quality.

High quality proteins are usually found in legumes, like Alfalfa. Combining the two makes a more balanced protein diet for the horse.
Ideally a horse needs around 10% protein (Lactating, Pregnant and Growing foals need more)
Grain hays (oat, rye) generally have a lower CP than grass hay
grass hay contains 8 to 10%
legumes  (alfalfa, clover, perennial peanut) can range from 17-20+%.

 

Neutral Detergent fiber (NDF) – Measures insoluble fibers. Since fibers are digested by the microbes living in the hindgut (cecum and large colon), a healthy microbial population is important for your horse to derive calories from fiber. This figure is a good indicator of Net Energy (NEL, NEM, NEG see below) they are inversely related so when NDF goes down NE_ increases. This measurement is also the best indicator of how much forage a horse will eat. The lower the # the more the horse will eat. Legumes (alfalfa) are lower in NDF so horse will want to eat more legume than grass. But as most people know high alfalfa diets can risk founder, bloating and other issues. So just because they like Legumes doesn’t mean that is what they should eat 24/7.

40-50% are good
65% the horses may not want to consume them
 

Acid detergent fiber (ADF) ADF is composed of cellulose, lignin (not digestable), and other poorly digested components. The lower the ADF value, the more digestible the nutrients in the hay. Lignin increases in mature plants and more hay will end up in the manure.

30-35% is desirable
45% and above you will have to feed more hay

 

Equine Total Digestible Nutrients (Equine TDN): This is a measure of the hays energy value, TDN is rarely used in evaluating horse hay, which is ironic because it’s the digestible nutrients. TDN is very closely related to Net Energy (NE) below. As TDN (DM% increases so does the NE for Lactation, Growth and Maintenance. It is a measurement that is also directly correlated to Digestible Energy (DE) and Metabolizable Energy (ME) below.
 40 to 55% is desired.
 

Equine Digestible energy (DE): Measure of the digestible energy in the hay. Horses in light work should get about 20 Mcal/day. So if hay is DE 1 Mcal/lb you need to feed 20lbs to that horse. Horses usually have a loss of 35-40% DE in feces, so don’t be stingy on feeding hay to your horses.

Most hays are 0.76 to 0.94 Mcal/lb of DE.
The DE requirements for a 1,102 lb  horse (500kg) can range from 15.2 Mcals to 34.5 Mcals

Net Energy (NE):  There are 3 types of Net Energy

Maintenance (NEm) –maintenance of the animal
Gain (NEg) – Growth and gain for that animal
Lactation (NEL) – Lactation (mainly dairy cattle)
This is highly dependent on the animals actual intake of the forage.
 
Estimated Net Energy (ENE) A term expressing available energy in a forage. The higher the number, the greater the energy to the animal.
 

Net Energy Lactation (NEL) this is usually used for cattle to help determine if the forage will meet the needs for lactation. Mostly used for the dairy industry but it can also be helpful for horses.

An average NE Lactation is 0.5-0.95
When TDN is 50 (DM%) NEL is around 0.5
When TDN is 90 (DM%) NEL is around 0.95
So very closely related

Net Energy Maintenance (NEm)

This is the energy available for maintaining the animal
An average alfalfa maintenance is around 0.4-1.02
When TDN is about 50 (DM%) NEm is around 0.44
When TDN is about 90 (DM%) NEm is around 1.02

Net Energy Gain (NEg)

This is the energy available for the horse to gain.
An average around 0.19-0.7
When TDN is about 50 (DM%) NEg is around 0.19
When TDN is about 90 (DM%) NEg is around 0.7

Metabolizable Energy (ME)

Range from 0.82 – 1.48
when TND (DM%) is around 50 ME will be around 0.82,
when TND (DM%) is around 90 ME will be around 1.48

 

Relative Feed Value (RFV)- Combines ADF and NDF to estimate consumption of the hay. So in theory it’s the expected consumption, or the animals want to consume the hay . As ADF and NDF increase, RFV decreases.  It’s mostly used for Cattle. There is no formula for horses yet for RFV because this formula is based on fiber and cattle have a better fiber conversion because of the rumen digestive system. But it’s a number CSU gives for their hay evaluation so it’s one that we are going to explain.  

Average RFV for alfalfa is 100 (ADF 41, NDF 53). The higher the # the better the quality

Alfalfa can be up above 150, 185+ is considered Supreme quality. Low quality alfalfa will be around 70.

 

Keep in mind that horses do not need the higher quality forages that a dairy or meat cattle need. And horses digestive systems are not equipped to handle the higher levels of RFV and CP. Feeding strait Alfalfa with a  100 RFV could risk obesity, founder and other health issues, So please consider other values that are more tailored for horse feed to base your feed choice on. If you pick a lower TDN grass hay you could supplement with Alfalfa to meet your horse’s needs, or free choice the grass hay so the horse has a full gut (much more healthy for them than sporadic feeding)

 

But when in doubt test your hay, soil and water. Take those results with your current grains and supplements to an equine nutritionist to balance your ration. You may find that a few simple changes could reduce your feed cost and ultimately have a healthier horse. Do not grain your horses blindly, know what they are eating so you don’t throw them off balance.