By Dagan Montgomery, UW Extension Educator
Interpreting Results of Hay Analysis Reports
More and more beef producers nationwide are having their hay sampled to analyze its nutrient content. This relatively simple and affordable exercise allows cattlemen an in-depth look at the actual nutrient profile their herd will receive from hay, allowing them to plan supplemental feed programs accordingly.
However, before a hay analysis can be effectively put to use, it has to be understood.
Depending on the lab performing the analysis, one may receive a simple list of nutrients next to the corresponding measured value, with no indication of whether the value is high, average or low compared to similar feeds.
The nutrients themselves may only appear as abbreviations and could include a long list of measured components, some of which are more important than others.
This article will go through a basic breakdown of the key nutrient components found in most routine hay analyses, as well as the relative values to look for in each.
Typically, the first values one will find on a hay analysis report are moisture and dry matter (DM), a means of comparing the amount of water within different feeds. This is determined by drying the hay in an oven and then weighing all non-water components.
Nutrient values will often be reported as both dry matter (DM) and “as-fed” (AF) or “as received.” Hay should be compared to other feeds using the DM value for nutrients. For the rest of this article, values for other nutrient measurements will be discussed on a DM basis.
Moisture level also greatly influences the stability of harvested forage during storage.
The target for hay is around 85 percent DM or 15 percent moisture. Baleage is usually 40 to 60 percent DM and silage is 30 to 40 percent DM for proper fermentation. Producers will notice some moisture should remain, as being 100 percent water-free decreases palatability and leads to leaf shatter.
Protein in ruminant feeds is usually expressed as crude protein (CP) – as a percentage of DM. This is based on the total nitrogen in the plant matter multiplied by 6.25 as plant protein is typically 16 percent nitrogen.
CP level is critical for a productive beef herd. Protein is required for growth, lactation, reproduction and muscle development. This is why protein is the one of the most commonly supplemented nutrients for grazing or hayed cattle. It is also the most expensive.
Dry gestating cows need at least seven percent CP on a daily basis – seven percent value is also considered the bare minimum for wintering cattle, as this is lowest level needed to support rumen function.
For at least the first 60 days after calving, a cow’s needs increase to 11 percent CP. Throughout the rest of lactation cows need at least nine percent CP. Growing rations for calves typically contain 14 to 16 percent CP.
CP can vary based on forage species, maturity, soil and storage stability.
The fiber content of the forage is made up of the structural components in the grasses’ cell wall and is usually broken into neutral detergent fiber (NDF) and acid detergent fiber (ADF), both expressed as a percentage of DM.
NDF contains the components cellulose, hemicellulose and lignin and is what remains after the digestible material is removed with a neutral detergent. Forage intake will decrease as NDF increases, and the formula 120 divided by NDF can help determine how much the animal will eat as a percentage of body weight.
For example, if NDF is 50 percent, DM intake will be 2.4 percent of the animal’s weight. NDF can range from 40 to 65 percent DM, and at 60 percent and higher, it begins to noticeably affect feed intake.
Lower values are typically desired for NDF.
ADF is what remains after remaining NDF has been removed with acid detergent. Forage digestibility decreases with increased ADF.
Average ranges for ADF in hay are anywhere from 30 to 45 percent DM. Values above 40 percent ADF usually indicate a lower-quality hay. Both forms of fiber increase with plant maturity and are typically lower in legumes than grasses.
Energy in a feed can be measured in several ways.
The most common and practical way to evaluate energy content of a forage is total digestible nutrients (TDN). TDN is also expressed as a percentage of DM and is the sum of digestible carbohydrates, protein and fat the animal will receive.
In general, hay with less than 52 percent TDN would be considered lower quality, hay with 52 to 58 percent TDN would be medium or average quality and hay exceeding 58 percent would be high quality.
Based on the 2016 “Nutrient Requirements of Beef Cattle, Eighth Revised Edition,” mature cows nursing calves need a minimum of 58 to 61 percent TDN in their diet, whereas a dry pregnant cow should be getting at least 50 to 54 percent TDN, depending on stage of pregnancy.
These values can easily be converted to pounds by multiplying the percentage of TDN by the total pounds of dry matter the animal eats per day.
Both macrominerals and trace minerals are critical for cattle growth and performance, and several will show up on a good hay analysis.
Two of the key minerals one should look for are calcium (Ca) and phosphorous (P), both usually reported as a percentage of total DM. These are both needed for skeletal growth in growing cattle and are crucial for lactation.
Dry cows need 0.25 to 0.28 percent Ca and 0.16 to 0.19 percent P a day in their diets. Cows at peak lactation need at least 0.31 percent Ca and 0.21 percent P per day. The ratio of Ca to P should remain between 1.5:1 and 4:1, because too much P can impede Ca absorption.
Most common complete mineral mixes are sufficient to provide cattle with enough Ca and P.
Several values can be calculated based on other results from a hay sample. Relative feed value (RFV) and relative forage quality (RFQ) are calculated values and meant to combine energy content and DM intake into a single value, which is measured against full bloom alfalfa as a standard – full bloom alfalfa is assumed to have a RFV of 100.
These are meant to provide an idea of how well a forage would provide for a ruminant animal if it was all that was being fed. Both may appear on a hay sample analysis. However, depending on the lab, these may need to be specifically requested.
RFV was developed first, calculated using the measured values for ADF and NDF in the sample. The problem is RFV isn’t accurate across forage types, such as when comparing good grass hay to legumes, so RFQ was developed using TDN as part of the calculation and is considered a better judge of true potential for a forage to predict animal performance.
In most cases, RFQ will range from 50 to 250. In hay, an RFQ of less than 90 is low quality, 90 to 110 is fair quality, 111 to 140 is good quality, 141 to 200 is premium hay and over 200 is outstandingly high-quality hay.
Dry cows can get by on hay in the 100 to 115 range, whereas growing cattle and lactating cows really need hay in the 115 to 140 range.
A good hay analysis can provide a tremendous amount of information about the actual nutrition a herd is receiving. But the data producers get back can be difficult to sort through, especially without a good frame of reference for what the values and nutrient components mean.
Some values are extremely important to pay attention to and can go a long way in formulating a good supplementation program for a herd. Others may not be as crucial.
Dagan Montgomery is University of Wyoming Agriculture and Natural Resources Extension educator. He can be reached at firstname.lastname@example.org.