Goats on Forage: An Overview of Nutrition
Updated: Sep 16
Written and compiled by Kendra Shatswell of Hefty Goat Holler Farm
Author's note: In an effort to keep this from becoming a novella, I share MANY sources. It is not intended to be a definitive answer to all your questions about goats on forage but a jumping off point; my goal is to hit broad topics and make them easier to understand and understand enough to start asking more questions. I've included a table of contents so you can quickly jump to each section but it will make the most sense to read the post in order, in its entirety, as the topics build off one another. I will be writing more blog posts that branch off from this one, about hay, parasites on pasture, toxic plants, and more. I will continue to write blog posts on individual vitamins and minerals, as well.
Introduction
By design, goats are ruminant browsers, meaning their ideal diet consists of more browse than grass. But goats do eat browse (leaves and small twiggy bits), grass and legumes, and forbs (weeds). Goats are highly selective eaters, but they eat a host of plants unpalatable to other livestock.
Did you know:
Inheritance of foraging skills or diet preferences in goats has been documented (Ellis et al.2005; Waldron et al.2009). Findings of several researchers indicate an effect of breed of goats on diet selection (Bryant et al.1979; Aharon et al.2007; Bakare and Chimonyo 2011; Glasser et al.2012), which suggest a genetic basis for foraging ability and forage selection. “Dietary Selection by Goats and the Implications for Range Management in the Chihuahuan Desert: A Review”
In large part due to their foraging skills, goats adapted to various climates around the world. This series is all about raising goats that forage and this specific installment will focus on pasture and forage nutrition which encompasses many topics including important terms to know, soil health, forage and soil testing, and nutritional requirements.
What’s In Your Pasture?
All pastures are not created equal and a pasture will change with the seasons. New plants are brought in naturally by heavy rains, hay, animal waste, even the wind; seed might lay dormant for quite some time until the ground is disturbed or until conditions are favorable. Of course, producers can also sow seed or plant sprigs.
Simply observing and identifying species is a great way to better understand the pasture. Are there times of year with little growth, even in optimal conditions? Are there an abundance of plants that the goats simply won’t eat or plants they love? As mentioned earlier, goats are highly selective, meaning that they usually try to eat the most nutritious plants first (and the least harmful compounds - more on that in the upcoming Plant Toxicity post).
In temperate climates, producers often see a mixture of cool season and warm season plants. For example, our pasture here in the Ozarks consists of legumes like hairy vetch, clovers, and cool season grasses like Kentucky bluegrass, orchard, and/or rye grass in late winter and early spring. Some of these, like vetch and low hop clover, go dormant as the average temperature increases, making way for warmer weather grasses and more forbs and browse - young wild rose leaves are a particular favorite during this period. By the hottest months of the year, warm season grasses like crabgrass, bermuda, Johnsongrass, and lespedeza (including sericea lespedeza) are in high production. Warm season natives include big and little bluestem, switchgrass, gamagrass, and purpletop grass. Fall provides persimmons and acorns and drops deciduous leaves. We also see a lot of broomsedge, which is still technically a grass but isn’t considered desirable because of its low palatability. A mild fall and winter will see a re-emergence or reinvigoration of some cool weather plants. Winter is a time of dormancy until the earliest cool weather grasses and legumes begin again - usually late February, here (22, 24).
Toxic plants are often seasonal as well, but more of those will be covered in upcoming installments. Currently, these posts about potentially harmful plants are available:
Oak Toxicity in Goats - Uncommon But Not Impossible
Pasture Quality
Pasture quality fluctuates depending on a myriad of factors including growth stage, moisture, and soil health aspects like fertilization, water infiltration, compaction, and pH etc.
Soil Health
Soil is alive and good soil is a thriving biome - you do not have a good pasture without healthy soil. Soil health is a dense subject so here are some good starting resources, in my opinion. Many of these are specific to beef cattle production but the principles are worth understanding no matter what species you graze.
Soil Organic Matter
Many of the sources above will mention “soil organic matter” when talking about soil health. What is this? According to Cornell University, it is “the fraction of the soil that consists of plant or animal tissue in various stages of breakdown (decomposition)” (27). Think of it like naturally occurring compost. It is often the best indicator of overall soil health - you can read more about it here - Soil Organic Matter.
Soil Nutrients - Macronutrients
These are just the simplest of definitions. There are some great resources listed below that go into greater detail.
Nitrogen (N) - responsible for leafy growth and essential to photosynthesis. Grasses cannot pull nitrogen from the air but legumes can. Legumes are terrific nitrogen fixers, using a symbiotic relationship with bacteria - "Rhizobia bacteria provide the legume plant with nitrogen in the form of ammonium and the legume plant provides the bacteria with carbohydrates as an energy source" (34). Grasses can utilize some of the nitrogen compounds released by legume roots but actually receives more when the legume plants decompose. Pasture grasses also pull nitrogen from animal waste; basically grasses rely on soil organic matter, which is defined down below, for nitrogen. Of course, nitrogen and other nutrients can be provided by fertilizers. Nitrogen deficiency is likely to lead to deficiencies in micronutrients like molybdenum and boron. Nitrogen is one of the fastest moving nutrients, depending on the type of nitrogen, the soil composition, and even soil temperature (33). Read more about the nitrogen cycle here - Nitrogen Cycling in Pastures - Cornell Small Farms and here Nutrient Cycling in Pastures – NCAT
Phosphorus (P) - responsible for a variety of processes essential to energy including photosynthesis and sugar synthesis. It is necessary for root growth and helps the plant deal with stress. P is important for seed, flower, and fruit growth. "Phosphorus is supplied to soils through various avenues including atmospheric deposition, mineral fertilizer application, plant residue, and animal manure/biosolids" (35). Read more here - Phosphorus Plays Key Roles in Regulating Plants’ Physiological Responses to Abiotic Stresses - PMC and here The Phosphorus Cycle (this was the clearest illustration I found of this complicated cycle - it does a great job - don’t forget to click where it says “more” on each section.)
Potassium (K) - responsible for water regulation, air uptake, and protein synthesis. Potassium plays an important role in winter survival and surviving pests and diseases. As someone with acidic soils and plenty of broomsedge, getting ready to do some major pasture rejuvenation, I found this article on the importance of potassium very interesting - to summarize, correcting low potassium levels on a hayfield reduced the amount of broomsedge, increase overall production, increased the rate of volunteer red clover and made the applied nitrogen more available (36).
Read more here The Potassium Cycle
Sources to learn more about these macronutrients: A Brief Overview of Nutrient Cycling in Pastures and Essential Plant Micronutrients for Crop Yield | Sound Agriculture
Micronutrients
There are many micronutrients in the soil but *some* important to plant growth are listed below.
Copper (Cu)
Zinc (Zn)
Boron (B)
Manganese (Mn)
Molybdenum (Mo)
Nickel (Ni)
These may only be necessary in small amounts (parts per million or ppm) but that doesn’t diminish their importance. Some of these have a very small window between deficiency and toxicity. The amount of micronutrient in the plant does not mean that the entire amount is necessarily bioavailable to the plant or the animal that consumes it. Ideal ppm can vary quite a bit depending on what crop (including pasture) is being grown so I think it is best to avoid hard numbers in this blog post and instead encourage you to consult with whatever professional performs a soil or forage test in your area.
If you’ve read the Hefty Goat Holler blog posts on copper, then you’re familiar with the roles copper and molybdenum ratios can play in goat health, and that includes the levels of those minerals in the soil and thus forage. As is illustrated in that article, a major source of molybdenum in the diet is often alfalfa; molybdenum is less available to plants in acidic soils so liming is often a quick fix when molybdenum levels are too low. Boron is especially important to legumes because it aids in nitrogen fixation by improving the necessary root nodule formation (26). As stated in the Hefty Goat Holler blog post on zinc, zinc is usually low or even deficient in forages in many states and it will be even lower in hays - interesting fact, there is an abandoned zinc mine just over 20 miles away as the crow flies, but our soil is radically different and zinc is something I must be vigilant about supplementing. Again, minerals and vitamins will each get their own posts as time permits.
Acidity or Alkalinity
The ideal PH is considered to be close to neutral for pasture grasses to slightly acidic for legumes or about 6.0 - 6.5 to 7.0, respectively. PH is very important to nutrient uptake, because nitrogen is affected by the pH extremes and without optimal nitrogen, the plants do not receive optimal nutrients (21). The chart "Plant Nutrient Availability According to Soil pH" is a modern reproduction of the 1935 "Truog Nutrient Availability Diagram," thought to originally be first widely published in the Virginia Agricultural Extension Bulletin. (I believe this graph is from the University of Connecticut but the source link was broken).
Drought or Moisture Surfeit
Both moisture extremes cause major, sometimes surprising impacts to forage. Plants struck by drought will use energy in the roots and crowns, sacrificing the leaves, resulting in overall less production. Interestingly, there’s evidence that some plants are actually more nutritious under drought conditions, accumulating higher crude protein levels in part due to depressed maturation and thus smaller amounts of leaves and stems. However, certain neutral detergent fibers can also increase, making the plant less digestible (3). Weeds are more likely to take advantage of the poor growing conditions during drought, and legumes are all but certain to disappear. In a wet year, plants grow robustly but the fast growth usually means lower crude protein and so much moisture means that the animals cannot consume enough to meet their dry matter requirements. Additionally, both the increased growth and/or rain usually means reduced palatability due to higher fiber content thanks to increased stem to leaf ratio or sugars (carbs) being leached, respectively. The pasture’s health is not determined by a single season or year. This study conducted in the semiarid rangelands of the US illustrates these “legacy effects” but found they can be surprisingly variable - “Multi-year drought has persistent forage quality and quantity effects that can be intensified by heavy grazing in semiarid rangelands.”
Undesirables might need to be managed for herd and pasture health, whether that’s by bringing in a species that does eat those plants, improving the other desirable plant species until they overtake the undesirable ones, often through soil improvement, or manually or chemically removing the offending plants - more on this is in the upcoming Plant Toxicity post.
Rotation
Rotation is considered the best tool to preserve or increase pasture quality and quantity. There’s a plethora of information out there on various ways to manage pasture growth via rotation - too much to get into in this piece, but most methods do agree to be flexible. Rotate as the pasture needs it, not necessarily on a set schedule. Many of the soil health examples above implement the Adaptive Multipaddock Pasture management system or AMP, which focuses on soil and thus pasture and animal health through frequent rotation and long rest periods after aggressive grazing, which increases water infiltration, carbon sequestration, and nitrogen fixation especially (25).
Since goats do not willingly graze as low as cattle or sheep, AMP rotation might not be so simple for most producers. Arguably the best examples using goats for a similar purpose isn’t rotation at all but “goatscaping” where goats are brought to clear brush or other forages in a specific area, usually using very high stocking rates to ensure the goats are not too selective and to clear the area in a short time before moving on to the next job. For those interested in this, there's a website where you can Find a goat herd for hire.
For those just rotating their herds on their own properties - observe rumen fill at the end of the day and see what’s left in the pasture - have all the forbs and browse been nipped? How much grass is left? How high and thick is the forage? A very general rule of thumb is to let the pasture rest when a third or half of the grass has been eaten or to leave 4-6 inches of grass. Goats naturally do NOT want to graze close to the ground and only do so when there’s no alternative.
Overgrazing, especially continuously, will negatively affect the nutritional value of plants as well as expose goats to more parasite larvae (more on that in the Parasites on Pasture installment). The general rule of thumb for minimizing parasite larvae ingestion is to leave at least 6 inches of forage.
When continuously grazed short, forage will not grow well above or below the soil. Overgrazing also inhibits the plant’s ability to utilize water. Some roots die off naturally each year and must be regrown. In general, especially with grass, if more than half the plant above the soil is gone, the roots cannot regrow, much less spread. Over time or in a particularly poor season, this can lead to the plant dying out entirely - though these scenarios are more likely with grazing species and not goats unless incredibly overstocked (3).
If you can’t rotate, pasture health can be maintained by a low stocking density or periodically dry-lotting to allow for regrowth.
Testing Soil and Forage
Soil testing is a relatively simple process. Samples are collected using probes - drills or augers can make the work easier if the ground is rocky or hard. You need about 4 inches of soil and should remove any rocks or plant debris from the sample. Pastures should be divided into specific areas and testing in those areas should be random - a zigzag pattern is often recommended.
Check out the videos and links below for more details. The University of Arkansas does offer free soil testing to Arkansans - again, take advantage of the local extension offices for testing and result interpretation. Not all labs will test for organic matter or for all micronutrients - sometimes additional testing can be requested. Additionally, there are multiple methods of testing for soil organic matter and many nutrients - do a bit of research to decide which works for your situation, as they often differ in price and availability. At the time of this blog post, there is an additional fee if you’d like soil organic matter testing done at Arkansas State University.
I think Heifer USA has a very helpful, easy to understand video on soil testing and interpreting results, including a download you can sign up for, though it is geared specifically towards gardening. Soil Testing Made Easy: Report Explained
Hay is tested by sampling bales with a special tool called a hay probe - some extension offices will either do this for the producer or rent out the probes.
The University of Arkansas provides details on how to correctly sample round bales here -
The University of Missouri Extension says how to collect samples from large or small square bales here -
Here are a couple good videos on understanding results- Interpreting a Forage Analysis Understanding and Using a Forage Test Report. The second video compares three bermuda hay samples and a real life example using those samples.
An Overview of the Nutritional Value of Forages
Just a note - I am only going to cover the basics and this will not include minerals or vitamins - minerals and vitamins are each getting their own posts as time permits, as well as a post on hay specifically. I will also do posts with basic nutrional information on specific plants. Do check out the sources I list at the end of the blog post.
Generally speaking, plants are more nutritious when young. The more mature the grass or legume, the lower the protein value and the higher the fiber, making the grass both less palatable and less nutritious. A grass reaches the boot stage when the seed head is present but still encased in the stem - this stage in reproduction is usually the tipping point between most nutritious and palatable to least. Legumes are most nutritious just before fully blooming (7, 24).
Shrubs and forbs generally maintain higher protein levels throughout growth than legumes or grasses. Unfortunately, shrubbery typically grows back slower than grass and is more likely to be killed by heavy or continuous browsing - this is a big reason why goats are so useful for killing brush or even saplings and small trees.
Terms to Know
Total Digestible Nutrients - essentially the estimated measurement of energy value. A formula is used to calculate the energy values of digestible proteins, fats, carbohydrates, and fibers. TDN is expressed as a percentage, and the higher the percentage, the more energy the animal receives from that particular forage or feed.
Net Energy - a more specific value of energy than TDN. The primary difference is it allows for energy lost during digestion. The specific formula accounts for losses from urine, feces, gas, metabolizable energy, and body heat (8).
Dry Matter - very simply, dry matter is the material left if all the moisture in a feed or forage is removed. Dietary recommendations are often made on a “dry matter basis” and what the animal will eat in a certain period of time is called “dry matter intake.” By taking moisture out of the equation, forages or hays or feeds with differing moisture levels are essentially made equal, making it accurate to compare the actual nutritional value since it is no longer being diluted by water. Dry matter requirements are usually calculated as a percentage of the animal’s bodyweight. Langston University has a fantastic Nutrient Requirement Calculator and Ration Balancer but the producer does need to know some parameters, including the estimated TDN (13). A very general rule of thumb is a goat requires 2-5% of body weight in dry matter per day.
Crude Protein - a measurement of all proteins in a feed or forage. It includes true protein and non-protein nitrogen. Examples of non-protein nitrogen are urea or ammonia (9). Crude protein is expressed as a percentage, usually a percentage of the dry matter. It can be further divided into the following categories: degradable protein, undegradable protein, and microbial crude protein. However, most literature and feed and forage evaluations etc. will not make the aforementioned distinctions (10). Excess protein is NOT stored in the body and too much protein can actually be as much of an issue just as too little protein - a real world example of this is under OR over-conditioned does experiencing ketosis which is detailed in Hefty Goat Holler blog post on Pregnancy Toxemia.
Acid Detergent Fiber - a measurement of cellulose, cutin, and lignin in plant material. Acid detergent fiber is the least digestible type of fiber. ADF is defined in relation to digestibility. The lower the ADF number, the better. It should be noted that grass fibers are typically easier to digest than legume fibers (stemmy grass is easier to digest than stemmy alfalfa though neither are ideal).
Neutral Detergent Fiber - a measurement of cellulose, lignin, hemicellulose, and cutin - the entire plant cell wall. NDF is a good estimate of voluntary intake of the plant (palatability) and the higher the NDF number, the less palatable. It is a good indication of how “bulky” a forage or hay or feed is and thus how much space it will take up in the rumen.
Relative Feed Value - most associated with alfalfa, RFV is used to compare the palatability and digestibility and thus intake of similar forages - you don’t compare the RFV of alfalfa to the RFV of brome, for example. It isn’t a flawless method as indicated by the sources below (16,18), but it can be useful (17). It is not a test but a calculation derived from ADF and NDF values, where ADF is used to predict the digestible dry matter and NDF is used to predict the dry matter intake.
Relative Feed Quality - A modern update to RFV. The Relative Feed Quality value builds upon the RVF but includes the Total Digestible Nutrients formula to increase accuracy. Instead of just measuring fibers and their palatability or digestibility like the RFV formula, the RFQ also includes crude protein, fatty acids, non-fiber carbohydrates, and all fibers. RFQ can be used accurately on forages and grass hays in addition to legumes. The University of Georgia Extension also provided this webinar, covering many of the topics I’ve written about in this blog post, as well as a section focusing on condensed tannins, which I will write about in an upcoming installment: Forage and Pasture Management for Small Ruminants.
What Do Goats Need? Nutritional Requirements
Much of the nutritional information that we “know” about goats is from "Nutrient Requirements of Goats: An Update and Reevaluation" which is a competitive grant that was awarded to the E (Kika) de la Garza American Institute for Goat Research of Langston University. Their findings were published in a scientific journal called Small Ruminant Research, in 2004. Langston continues to study, host webinars and clinics, and offer online learning for small ruminant producers.
“The Nutrient Requirements of Small Ruminants” was published in 2007, by the National Research Council, combining previous books on sheep and goats independently and adding information about cervids (deer, elk, caribou) and New World camelids (alpacas and llamas). Of course, research specific to small ruminants is perpetually ongoing and the current recommendations are not gospel, so to speak. From Langston:
There are different means of determining expressions of nutrient requirements of livestock. Ones described in the reports of this project and used in these calculators were thought logical given the information available. There was an intent to develop expressions that would be useful in the field. However, goats like other ruminants are not simple animals and, likewise, in some cases most accurate descriptions of requirements may be more complex than desired. It should also be mentioned that, when thought beneficial, there was an attempt to put forward frameworks for expressing some requirements based on limited data or with extrapolation from data with other ruminant species, in order to facilitate future enhancements for greater accuracy.
In other words, take it all with a grain of salt. Research is still ongoing. But we do know needs vary greatly among different animals i.e. sex, growing versus mature, dry versus lactating, production, body condition, activity level, climate, parity, season, number of kids etc.
Energy (TDN)
Without getting my hands on a copy of Nutritional Requirements of Small Ruminants, I am reliant on other sources graciously offering up that information. In this article from Merck Vet Manual online, written by Signe G. Balch, DVM, the recommended TDN is 50% for maintenance and 70% for the highest demanding groups (late gestation, milkers, and growing kids). The Maryland Small Ruminant website offers two goat ration evaluator calculators that lists various parameters for different classes and includes TDN values. Spreadsheets | Maryland Small Ruminant Page.
The absolute simplest way to ascertain if a goat’s energy demands are being met is by judging its body condition. An animal in good body condition (3-4BCS in most cases) has its energy needs met, exceeded in higher body condition scores, and not met in lower. For much more detail about body condition scoring, please check out the Hefty Goat Holler blog post on body condition scoring and its sources. It is important to understand that a diet otherwise adequate in energy cannot overcome outside factors such as parasitism or disease or even physical issues such as worn teeth; intake can be adequate but utilization can be hampered.
Fiber
Though goats rely on roughage for proper rumen function, this is one of the murkiest areas I’ve found while writing this piece - very few studies actually pinpoint suggested parameters for NDF or ADF. One paper suggests “8–20% ADF or 41% NDF is nutritionally adequate for high producing lactating dairy goats. For growing goats between 4 and 8 months of age, 23% ADF is recommended” but cautions that “the bulk of information is still far too small to draw reliable and precise conclusions” (29).
Crude Protein
These values come from the Merck Vet Manual.
Minimum - 7%
Kids - 10-16%
Pregnant does - 12-16%
Lactating does - 12-20% lactating does*
*highest values being for very high production does in early lactation.
Note that the above recommendations for TDN, Fiber, Crude Protein are listed as a percentage of the dry matter intake.
I hope you've enjoyed the first installment in this series about forage!
Sources
Plant structural and nutritional responses to drought differ among common pasture species
Quality of Forage and Impacts on Intake and Animal Performance | UNL Beef
Nutritional value of pasture forages changes through the growing season | OSU Extension Service
ASAS CENTENNIAL PAPER: Net Energy Systems for Beef Cattle – Cattles, Application, and Future Models
Rain Impacts Forage Quality — Extension and Ag Research News
Neutral Detergent Fiber (NDF) and its Role in Alfalfa Analysis COOPERATIVE EXTENSION
Relative Feed Value: The #1 Most User Friendly Number for Feeding Horses
Understanding Relative Feed Value (RFV) and Relative Forage Quality (RFQ)
Comparison of Relative Forage Quality (RFQ) to Relative Feed Value (RFV)
Why is my RFV so different from my RFQ? - Progressive Forage | Ag Proud
Soil Testing and Fertilizer Management Strategies for Warm-Season Forage in Missouri | MU Extension
Forage Nutritive Value and Herbage Mass Relationship of Four Warm-Season Grasses
Runoff reduced, water retention increased by multipaddock grazing - AgriLife Today
Nutritional Requirements of Goats - Management and Nutrition - Merck Veterinary Manual
Nutrition of Goats - Management and Nutrition - Merck Veterinary Manual
Nitrogen Changes in the Soil, and it Changes Fast | Topics in Subtropics
Nitrogen Fixation - Texas A&M AgriLife Research & Extension Center at Overton
Potassium Helped Turn this Hayfield Around | Master Grazer
