Justin Waggoner, KSU Extension Beef Cattle Specialist, Garden City, KS
Cattle operations typically produce or have access to several different types and qualities of hay. Strategically managing hay inventories requires an accurate assessment of the nutrient content of the forage(s) and a basic of understanding of cow nutrient requirements. Our objective is to match the forage resources to the nutrient demands of the cowherd and avoid under/over-supplying nutrients (i.e., energy and protein).
The first step in managing a hay inventory is to sort hay into “Lots”. This is essentially sorting hay into groups that will become the “units” of hay that will be sampled and submitted to a laboratory for analysis. Hay “Lots” are generally based on forage type (grass, alfalfa, forage sorghum) and then by cutting, field or source. Hay should be stacked by “Lot” and labelled in manner that can easily be identified. Larger operations or hay brokerages will commonly use spray paint to identified individual “Lots” of hay. Additionally, any “high risk” forages that may contain weeds or elevated concentrations of anti-nutritional components (nitrates, mold etc.), should also be segregated into “Lots” as well. I generally recommend that any potentially “high risk” forages be stacked in a pre-determined area away from other hay so they may easily be identified.
Once hay has been grouped into “Lots” the next step is to obtain a representative sample of the bales. Obtaining a representative sample is essential and sampling is an often-overlooked source of error. Commercial labs use less than a gram of sample for an individual analysis. Thus, it is imperative that the grams of sample used in those analytical procedures represent the tons of hay on the farm. A general rule of thumb is that 20% of the bales in the “Lot” should be sampled using a forage probe, which takes a core or cross-section of the bale. Using a forage probe ensures a consistent sample with the same leaf-to-stem ratio. There are many different types of forage probes available from commercial retailers. Once the appropriate amount of hay cores has been obtained; samples should be stored in a plastic zipper bag and appropriately labelled. Samples may be stored in the refrigerator or frozen prior to shipping to a commercial laboratory for testing.
Analytical laboratories often have a standardized sample submission form that will ask the type of forage and the specific analyses requested. The type of forage is a key piece of information that allows the lab to apply the appropriate reference standards and equations. Producers’ will also need to select the type of analysis; most commercial labs offer Near Infrared Reflectance Spectroscopy (N.I.R.S. or N.I.R) or wet chemistry procedures. Wet chemistry analysis is often more expensive and is considered the “gold standard” as it offers a direct measurement of the chemical composition of the forage. Whereas, N.I.R.S. is an indirect measurement of the composition of the forage and are less expensive as they require less preparation and can be performed more rapidly in the laboratory. Most labs will offer a number of different analysis packages which encompass the most common procedures. These packages will typically include the basic procedures (dry matter (DM), crude protein (CP), total digestible nutrients (TDN) and then add on specific analyses such as Macro-minerals (Ca,P, Mg, K, Na, Cl, S). Some laboratories may also group analysis packages by the type of sample (Forage, vs. mixed ration) or production purposes (dairy vs. beef).
When submitting a forage sample for testing, the basic components of a forage analysis are dry matter (moisture), crude protein, an estimate of the energy content of the feedstuff (Total Digestible Nutrients (TDN), Net Energy for Maintenance (NEm), Net Energy for gain (NEg), and the macro minerals, Calcium and Phosphorous. These are the most basic analytical procedures that are required to evaluate forages and balance rations. If the forage will be fed in combination with a byproduct feedstuff such as wet distiller’s grain or corn gluten feed including an analysis for sulfur can be beneficial. There are also additional analyses that are not essential but can offer insight into the quality of the forage or improve our ability to predict animal performance. I recommend that the report include acid detergent fiber (ADF) and neutral detergent fiber (NDF).
The amount of NDF in forage reflects the amount of cell wall contents (hemicellulose, cellulose, and lignin) within the sample. The NDF fraction is often associated with the respective bulkiness of forage and is correlated with dry matter intake of the forage or feedstuff. Therefore, the amount of NDF may be used to estimate the expected dry matter intake associated with the forage. The ADF number represents the amount of cellulose and lignin within the forage and is correlated with the respective digestibility of the forage. In general, a higher ADF value is associated with forage that has a greater proportion of cellulose and lignin and would likely be more mature. Additionally, the ADF fraction is used to calculate the energy estimates TDN, NEm, and NEg. As forages mature, ADF increases and energy content decreases.
If the hay was put up under less-than-ideal harvest conditions or contains a large proportion of weeds, mold may be a concern. A generic mold count may be requested. This analysis does not identify specific molds but simply reports the concentration of mold within the forage sample. In addition, if the forage is a known nitrate accumulator (forage sorghums, crop residues, cereal hay), contains weeds that accumulate nitrates (kochia, pigweed, Johnsongrass) or was stressed (i.e. drought, hail damage) prior to harvesting, a nitrate analysis is recommended. Nitrates and mold can be managed by blending forages to dilute out the mold or nitrates. However, the concentrations must be known to accurately dilute the mold and nitrates to safe concentrations. Mold counts or nitrate analyses are usually offered as separate analytical procedures and must be requested separately for additional fees. In addition, some labs may not offer all services in-house and may send samples to other laboratories for analysis, which can require additional time.
Once we have the results of the forage analysis, producers should consider managing hay on their operations by placing hay in 4 management/feeding categories based on forage quality and the approximate nutrient requirements of beef cows. These 4-hay management categories are I recommend are outlined below.
1). Low Quality Hay. Forage contains less than 7% crude protein and an ADF value greater than 45%. Mature grass hays, and crop residues would be common forages in this category. These forages are often used to replace dormant native range and in some cases are capable of meeting the nutrient requirements of dry, bred, cows post weaning. Energy supplementation may be required, especially if forage NDF content limits intake.
2). Moderate Quality Hay. Forage contains 8-15% crude protein and approximate ADF values of 40-45%. Cool season grass hays, cereal grain hay, and forage sorghum fit into this category if harvested at the appropriately. These forages match the nutrient requirements of Gestating cows (2nd and 3rd Trimester).
3). High Quality Hay. Forage contains more than 16% crude protein and approximate ADF values from 31-40%. Alfalfa and most legume hays would be represented in this category. The nutrient content of forages in this category are sufficient to meet or exceed the nutrient requirements of cows during most production phases. These forages are often used supplement grazed forages or fed in combination with lower quality forages to meet cow requirements. These forages are often best utilized post-calving when cow nutrient requirements are greatest.
4). High Risk Hay. Forages contain potentially dangerous or toxic levels of nitrate, molds etc. The concentrations of these compounds in these bales are high enough that they must be diluted to safe levels. These forages may be fed in combination with other feedstuffs or intake must be limited. Consulting with an Extension specialist or nutritionist is advised when working with hay in this category.
Strategically managing hay quality comes down to the old adage “don’t guess…test”. A forage nutrient analysis is essential. It is imperative to know the dry matter, crude protein, energy, calcium and phosphorous content forages. The fiber fractions (ADF, NDF) are used to estimate forage intake and digestibility. Although not essential ADF and NDF values allow us to more accurately predict animal performance and avoid under/over-supplying nutrients.
