Forage Use and Evaluation in a Dairy Goat Ration

• An introduction to the growth, analysis and use of forages in the raising of dairy goats
  

TYPES OF FORAGES, HARVESTING AND SYSTEMS

The type of forage chosen on a farm is primarily based on the overall management and economics. Use forage that makes the best use of resources, including herd size, facilities, land, equipment, labor, finances, weather and management. In determining what forage system to use, one may consider the nutritional and health aspects as well .

Herd Size - How many animals are fed the forage on a daily basis? This will affect the bale size, silo type and size, and feeding methods.

Facilities - What type of storage facility is available? Can the storage facility hold a large quantity of forage? Would the forage be protected from outside elements in this storage facility?

Land - Is there enough land for pasturing or a forage crop? Is there a soil analysis for that land? How much fertilizer is necessary for the growing forage crop?

Equipment - What kind of equipment is available to this operation? What costs are involved in buying or leasing the necessary equipment for the particular forage system? Are there custom operators in the area and what is the cost?

Labor - Is the forage used on the farm, labor efficient? Does the producer have the time and resources to devote towards the managing and growing of the forage crop?

Finances - Does the producer have the finances to produce the forage crop or to purchase a forage crop?

Weather - Do you have 48 hours of good drying weather to make hay? Would you consider using drying or ensiling methods to get a good forage crop?

Management - Different forages systems require certain managerial styles? If using an ensiled product, a certain amount of that forage must be used every day to reduce air exposure and molding of the silage. Pastures require daily managerial decisions on forage availability in short and long term. Haymaking requires decisions based on weather predictions.

HARVESTING

The stage of maturity (Table 1) at which the forage is harvested influences the feeding quality of that forage. Most forage crops decline in nutritive value as they mature. Early cutting of the forage, improved the quality but reduces the harvest yield.

Table 1. Relationship of alfalfa maturity at harvest to crude protein (CP), acid detergent fiber (ADF),
neutral detergent fiber (NDF), and relative feed value (RFV), expressed on a dry-matter basis.

Maturity	CP %	ADF %	NDF %	RFVa
Late Vegetative	23	28	38	164
Bud	20	29	40	154
1/10 bloom	18	31	42	144
1/2 bloom	17	35	46	125
Full bloom	15	37	50	112
Seed pod	13	42	56	93

 
a. Relative feed value (RFV) calculated from (DDM x DMI) 1.29.
Reference RFV of 100 = 41% ADF and 53% NDF, Alfalfa hay.

FORAGE SYSTEMS

Ensiling - is a biological process involving the fermentation of the forage. Ensiling forages allows producers to harvest forages at a much higher moisture than dry hay. It is dependent upon several factors including microorganisms, moisture, packing and silo condition. Good ensiling practices are essential to make a quality forage. Several types ensiling additives (acids, enzymes and bacteria) are available to enhance the fermentation process. These are usually applied during the filling process and you need to know what type of product is appropriate. Each of the products has a different mode of action. A reputable silage additive, whether acid, enzyme or bacteria, can be profitable when used properly. This is because dry matter and nutrient losses will be reduced and silage stability may be increased. However, good silage can be made without additives by following good harvest and ensiling practices.

Using silage requires a special storage structure (upright, pit, or bunk silos or bagged silage systems) and the equipment to fill and pack that structure. In addition, once the silo is opened, silage must be fed at a high enough rate to remove 5” of material from the exposed face everyday during warm weather. Otherwise, yeasts and molds will grow rapidly and spoil the exposed silage.

Haymaking - involves the drying of the forage to the proper dry matter range (<14%) before baling. Hay may be baled as either round or square bales of varying sizes. Storage availability and ease of feeding should be considered when deciding on type and size of bale.

Hay which is baled at dry matters of lower than 14% may mold or spontaneously combust. Drying agents may be applied when plant is cut to expedite the drying process. Other stabilizers, such as propionic acid, may be used during baling to make hay at higher moisture content (< 25%) and prevent molding. Some producers make high moisture hay which is wrapped in plastic and allowed to ensile. This is known as balage.

Pasturing or Green Chop - involves measuring the amount of forage available in the short and long term. In pastures, rotation of animals based on forage availability is important. Green Chop utilization involves daily equipment and time investment to provide a fresh forage to the animal.

FORAGE QUALITY

The value of high quality forage for milk production cannot be overemphasized. Diets based on high quality forages support high levels of milk production with a moderate amount of concentrate. Digestion problems are minimized and feeding less concentrate generally reduces feed costs. The quality of forage relates to forage intake and how efficient the nutrients in the forage are converted into animal products.

Legume and mixed (mostly legume) hays average slightly over 60% Total Digestible Nutrients (TDN) on a dry matter basis. However, mixed (mostly grass) or grass hays average about 58% TDN. This is 5% under a goal value of 63% for lactating animals. Silages and haylages are lower in estimated digestible protein and TDN content than the same type of forage harvested as hay. This may be due to heat damage caused by poor ensiling or the overall fermentation of the silage.

Both visual appraisal and a forage test are necessary to determine the quality of a forage. Forages should be inspected for absence of mold and have a good green color. Forage quality information is important for: 1) formulating nutritionally balanced rations, 2) developing and allocating forage inventories, 3) evaluating forage management practices and 4) marketing and pricing forages. However, a forage test does not show the moldiness of a hay and may not indicate heat damage.

FORAGE TEST

An accurate forage test can provide a good estimate of forage quality. The tests are: dry matter (DM), crude protein (CP), adjusted crude protein (ACP), acid detergent fiber (ADF), neutral detergent fiber (NDF), energy values (TDN or net energy) and relative feed values (RFV). Table 2 shows the differences in forage quality.

Dry Matter - the moisture has been removed and the nutrients concentrated in the DM portion of the feed.

Crude Protein - is a mixture of available and unavailable protein. It is determined by measuring the total nitrogen and multiplying this number by 6.25.

Adjusted crude protein (ACP) - the amount of CP available to an animal for utilization after being corrected for the unavailable protein. Some true proteins become tied up with carbohydrates during the heating process especially in dry silages and wet hays, which makes them unavailable to the animal. Heat-damaged forages are characterized by being brown to black in color and having a sweet caramel-tobacco aroma.

Acid Detergent Fiber (ADF) - is the percentage of highly indigestible and slowly digestible material in a forage or feed. This fraction includes cellulose, lignin, and ash. Lower ADF indicates a more digestible forage and is more desirable.

Neutral Detergent Fiber (NDF) - is the percentage of cell walls or fiber in a feed. It includes ADF as well as hemicellulose. NDF is inversely related to animal intake potential. For example, a lower NDF percent indicates a greater potential consumption. Therefore, a lower percentage is desirable as long as a certain minimum fiber level in the ration is met.

Relative Feed Value (RFV) - is an index used to rank forages by the potential intake of digestible dry matter. This index should be used in evaluation of the quality of hay or haylage made from legumes, grass or legume-grass mixtures. This does not include CP because CP in influenced by factors unrelated to those affecting RFV, but CP should be considered in pricing forages.

Table 2. Forage quality standards for legume, grass and grass legume mixture.

Quality Standarda	RFVb	ADF	NDF	DDMc	DMId (% of body weight  % of DM)
Prime	>151	<31	<40	>65	>3.0
1	151-125	31-35	40-46	62-65	3.0-2.6
2	124-103	36-40	47-53	58-61	2.5-2.3
3	102-87	41-42	54-60	56-57	2.2-2.0
4	86-75	43-45	61-65	53-55	1.9-1.8
5	<75	>45	>65	<53	<1.8

SAMPLING FORAGES FOR LABORATORY ANALYSIS

Baled Hay - use a forage sampler that takes a core sample (i.e. Penn State forage sampler). Sample at least 15 to 20 bales from each lot or cutting of hay. For square bales, sample from the end of the bale to the full length of the corer. Place each core in a plastic bag. For round bales, sample across the bale at the center.

Loose Hay - if a forage sampler is not available, remove a handful of hay from 15 to 20 sites for each lot or cutting of hay. Be careful to save all leafy material belonging to the sample. Cut into three-inch lengths, mix and send a representative sample to the laboratory.

Pasture - Sample by choosing 8 to 10 locations. Remove the forage from a square foot area at grazing height. Mix all the collected forage and take a representative sample for analysis and place in a plastic bag. The plastic bag should be packed tightly and sealed with air excluded. Green pastures samples should be immediately dried or frozen to prevent changes in the composition and send to the laboratory immediately .

Green Chopped Forages - take random grab samples from the blower, cutter or several locations in the wagon or truck and place in a plastic bag. The plastic bag should be packed tightly and sealed with air excluded and sent to the laboratory immediately.

Silage - samples should represent several locations within the silo to ensure a representative sample if not sampled while filling the silo. The sample must be packed tightly into a plastic bag with all air excluded and send to the lab immediately. A silo should be sampled more than once during the feedout period of the silo. Make sure to reseal the sample sites to avoid spoilage.

Balage - a hay probe should be used to core a sample from the ensiled bale if not cored before wrapping. A representative sample from 15 to 20 randomly selected from the lot or cutting will work. Seal the sample in a plastic bag with air excluded and send to the laboratory immediately. Make sure the plastic around the bales is resealed with tape to avoid any spoilage.

FORAGES USED IN FORMULATING RATIONS

The use of forages in rations will differ in regions of the U.S. This is mainly due to the growing season and the amount of rainfall in those regions. If buying a forage source, always ask for a laboratory analysis on the forage before purchasing in order to judge the
quality of the forage. If utilizing home grown forages, be sure to use a forage analysis in balancing the ration.

Traditional US Forages - these are the typical forages found in US dairy rations. Corn silage, alfalfa or grass hay, haylage and balage, and sorghum. These are usually the best choice for long term production of high quality, high tonnage harvested forages.

Alternative Forages - are usually used in emergency situations. Small grain crops such as rye, wheat, triticale, barley, oats and peas should be harvested in the boot stage (head beginning to emerge from leaf whirl. Other alternatives may include rape, turnips, peanuts, beets or mangles.

MATCHING ALFALFA FORAGE QUALITY TO ANIMAL NEEDS

The nutrient needs of a dairy animal depends on its age, body size, reproductive status and level of milk production. Maximum profit results from matching forage quality to the animal needs. The most efficient use of alfalfa is to be included at maximum amounts in balanced rations to meet animal requirements.

Kids from 2 weeks to three months old benefit from a high quality forage such as a 1 or prime standard hay with an RFV >150, >18% CP and <42%NDF. Alfalfa consumption usually begins at two weeks of age and will increase until it is a significant amount of the kid’s diet at over eight weeks of age. The rumen is not fully developed and there is limited rumen capacity so, fiber should be limited: however, alfalfa is a good source of protein, minerals and soluble carbohydrates.

Doelings, 3 to 12 months old, have sufficient rumen function and capacity to utilize fiber to meet some of their requirements. Feeding alfalfa that contains 16 to 18 % crude protein, 41 to 46% NDF, and 135 to 151 RFV will provide optimal growth with minimum concentrate supplementation. Milking does in the first third of lactation period will benefit from this hay quality, due to a high leaf content in the alfalfa. This would be considered a hay quality standard of 1.

Yearling does, 12 to 18 months of age, have larger digestive tracts and can utilize more forage. Alfalfa containing 14 to 16% CP, 45 to 48% NDF, and 124 to 103 RFV. Milking does in the last third to two-thirds of lactation period can benefit from this hay quality also. This would be considered a hay quality standard of 2.

Dry does are able to utilize alfalfa, grass or grassy alfalfa of a lower quality that the other classes of dairy animals. Forage that is 12 to 14% CP , 48 to 52% NDF and 80 to 102 RFV is adequate. This would be considered a hay quality standard of 3 to 4. Feeding large quantities of a higher quality hay could lead to metabolic problems (i.e. milk fever) at freshening.

Related Links:

National Goat Handbook from the University of Maryland

Maryland Small Ruminant Page