Every cattle producer knows that forage production is typically the single expenditure in most livestock operations. Since forage is the foundation of most cattle diets, an understanding of forage quality can be a very important management tool.
Production of quality forages can play a very profound effect on performance and profits. Production of high quality forages is, unfortunately, illusive. It is much easier to produce large amounts of poor quality roughage than moderate or even low amounts of that which is of high quality.
In general, a reduction in forage quality can have a very significant effect on the overall nutritional plane of the animal. As forage quality decreases (in other words the total percentage of fiber increases), forage digestibility is reduced and feed intake (especially in ruminants) will also decrease. The following data as reported by Mertens (1985) shows the effect that decreasing forage quality has on forage intake.
|
Forage Quality
Excellent
*
*
*
*
*
*
*
Poor |
% Forage NDF
Dry Matter Basis
38
40
42
44
46
48
50
52
54 |
Dry Matter Intake as a % of Body Weight
3.16
3.00
2.86
2.73
2.61
2.50
2.40
2.37
2.22 |
|
As you can see, as the NDF (Neutral Detergent Fiber) content of the forage source increases, the ability for the animal to consume adequate amounts decreases. Thus in a situation where the animal truly NEEDS to consume more forage to access the nutrients it needs, it is unable to do so. In these cases it is very important to supplement with protein, energy or other sources as needed to compensate for this short-coming. Of course this is expensive and needs to be minimized. It's best to promote the production of good quality forages upon which a solid foundation can be built. Let's take a look at some ways to assess forage quality.
Determining Forage Quality
A number of steps can be followed to determine forage quality. Here are some of the more important ones:
1) Visual Appraisal
The primary as well as the easiest and fastest means of evaluating forage is by visual inspection. Color, leaf content, texture, and maturity, as well as the presence of weeds, dirt, mold or other contaminants can all be determined by a thorough visual appraisal. Observing the texture and odor of the forage sample can also assess forage palatability.
2) Laboratory Analysis
a. Conventional Chemical Analysis (Wet Chemistry). Traditional laboratory methods involve various chemical drying and burning procedures to determine the major chemical components within the forage. These procedures are based on sound chemical and biochemical principles. This is the most �tried and true� method of determining nutrient components such as crude protein, ADF and NDF, minerals, etc.
b. Near Infrared Reflectance Spectroscopy Analysis (NIRS). NIRS is a rapid and low cost computerized method used to analyze forage and grain crops for their nutritive value. Instead of using chemicals to determine protein, fiber, energy, and mineral content, NIRS uses near-infrared light.
3. In Vitro and In Vivo Disappearance Evaluation.
These procedures are seldom used for farm forage analysis. They are however, commonly used by scientists to evaluate forage quality. Most often, dry matter disappearance in a specific period of time is measured and this value will indicate the digestibility of the forage.
a. In Vitro (in glass or in test tube). In vitro is usually a two-step procedure. First the forage sample is digested using rumen fluid from a donor animal, to simulate digestion in the rumen. The sample is then digested in an enzyme solution to simulate digestion in the small intestine.
b. In Vivo (In animal). The term "in situ" describes a procedure that involves placing small nylon bags containing forage samples into the rumen of live animals. This is done through a sealed external opening (fistula) into the rumen of an animal.
Steps to Putting up Quality Forages
The first principle in making good-quality hay for winter feeding is to harvest early. Rain damage will reduce hay yields and cause bleaching. However, rain does relatively little damage to hay quality as measured by forage digestibility, crude protein, and intake. Hay can provide a low-cost, homegrown winter feed. It can provide all the energy and protein needed by beef cattle and sheep. Even in rations for high producing dairy cattle, hay can provide over half the feed requirements. When we talk about forage quality, we want to know the hay digestible energy content, crude protein, and the potential dry matter intake of the forage as discussed above.
Digestible Energy
High levels of digestible energy in hay mean that a pound of feed will provide more energy for growth, milk production, or body maintenance. Digestible energy is measured as total digestible nutrients (TDN), or as net energy lactation (NEL), or as net energy maintenance (NEM) and net energy gain (NEG). Digestible energy is a measure of the solar energy captured by the plant which can be digested by the animal for use in maintenance and in making products useful to humans. In studies from central West Virginia, it was shown that as the harvest date for first-cut hay extends past early June, the digestibility of the hay decreases.
Crude Protein
Crude protein is estimated by measuring hay's nitrogen content and multiplying that by 6.25. Much of the protein in feeds for ruminants (cattle, sheep, and goats) is broken down by rumen bacteria and used by them in digestion of carbohydrates (cellulose, sugars, and starches) in the forage and supplemental grains in the ration. This produces more bacteria which are digested in the true stomach of the animal. Once again, based on the WV data showed as the date of harvesting first cut hay extended past early June the crude protein content decreased.
Dry Matter Intake
When looking at animal performance on forage based diets 85 percent of the difference in performance is due to forage dry matter intake (DMI). One reason that this is so is that as forage digestibility increases, forage DMI also increases. As more highly digestible forage is eaten, more energy is available to the animal for growth and milk production. Therefore, hay quality is best described as how much the animal can eat. Again, as the harvest date extends past early June, the predicted DMI of the hay decreases.
Relative Feed Value
Relative Feed Value (RFV) is reported on many forage test reports. It is a combination of the forage's digestibility and DMI. Hay with an RFV of 115 will provide about 15 percent more digestible energy than a feed with an RFV of 100.
The optimum cutting date for any location will depend to a large degree on your land's elevation. Watch the growth stage of the grasses to determine when to start making first cut hay. When grass is in the late-boot to early-head growth stage, it will provide the best compromise between yield and forage quality.
The Value of Legumes
Legumes are of major value in hay production. Legumes fix nitrogen from the air and eliminate the need to purchase expensive nitrogen fertilizers. In hay production, a good legume-grass stand having about 25 percent to 50 percent legume, will have a hay yield over the growing season comparable to grass fertilized with 150 lb. of actual nitrogen. With nitrogen fertilizers costing $0.33/lb. N this is a savings of $50/a year.
Livestock will eat more legume forage than grass forage. This obviously allows the animal to grow faster or produce more milk. Also, mixed grass-legume hays are higher in crude protein at the same date than most straight grass hays. This allows for their use as a protein supplement with low-protein hays or for feeding with energy supplements such as corn.
Challenges Making Hay Early
There are several challenges in making early-cut hay. The main one is that the drying conditions in late May are poor compared to late June. Fortunately, for beef cattle not all of our hay needs to be top quality. For them, however, the key is to make some hay early, to have some high quality forage for growing replacements, for cows after calving, and for use as a protein supplement to be fed with low quality late cut hay.
Be ready to make early-cut hay by having all equipment and storage preparations in place in early May. If the weather turns favorable you will be ready to go. Also, hay wrappers allow baleage to be made out of early-cut hay without drying it down as far as necessary as for hay. If you have a large herd, this can be a cost effective option. For smaller herds, renting the needed machinery is possible in some areas. Before deciding baleage, however, make sure to count all your costs, including disposal of the used plastic.
How much early-cut, high quality hay you need depends on your livestock management system and your goals. If your cattle are in poor body condition or are not breeding back as soon or as evenly as they should or if your supplemental feed costs are high, you should evaluate your system and see if you need to be managing your hay and forage program differently.
Conclusions
The foundation of your cattle operation is your forage program. Cattle producers need to be as proficient in their management of forages as in their management of cattle. Development of a high quality forage program will dramatically reduce your production costs and improve operational profits.
Dr. Steve Blezinger is a nutrition and management consultant with an office in Sulphur Springs, TX. He can be reached at P. O. Box 653 Sulphur Springs, TX 75483, by phone at (903) 885-7992, or by e-mail at [email protected].
