Pasture Forages for Small Ruminants
Dr. Kimberly Cassida, research agronomist, USDA-ARS, Appalachian Farming Systems Research Center
Dr. Kimberly Cassida, research agronomist, USDA-ARS, Appalachian Farming Systems Research Center (AFSRC), was the first speaker of this session. Her presentation was Pasture Forages for Small Ruminants. She started her presentation by asking the question, “Do sheep and goats need different pastures than cattle?” To start this analysis, she listed two rules of pasture forages as it pertains to goats and sheep. First rule is: “Quantity and nutritive value of forage are inversely related.” Rule number two: “As grazing height decreases, gastrointestinal nematode (GIN) infection risk increases.”
A corollary to this rule is: “Goats are more susceptible to GIN than sheep.” The reason for goats being more susceptible to GIN is that they are browsers. They typically eat plant parts that are more elevated off the ground than sheep, who are grazers. This sets up the paradox that taller forage that is eaten is less nutritious and also has less worms than shorter forage. Shorter forage is more nutritious but is also laden with more worms than tall forage (browse). AFSRC research emphasizes intensively-managed, high quality pasture using two strategies:
Strategy #1 – Enhance protein nutrition through use of legumes, because greater CP intake helps animals tolerate worms.
Strategy #2 – Grow bioactive forages, which contain compounds that may assist animals in developing resistance or resilience to GIN.
Under strategy #1, several legumes have been studied. Alfalfa, often called the Queen of Forages, is a cool season legume that grows well throughout the growing season. Its forage quality is excellent and the varieties tested at AFSRC are persistent to grazing, having a life expectancy of 2-5 years. However, it is a high maintenance forage requiring:
- soil pH above 6.5
- phosphorus (P), potassium (K), and boron (B) fertilizer
- a deep, fertile soil
- good soil drainage
Along with the drawbacks of:
- limited stand life
- hard to establish into existing pastures
Red clover is a good legume with these good and bad traits:
- short-lived cool-season perennial – 2 year stand life unless allowed to reseed
- excellent forage quality including low protein degradability
- adapted varieties available for all parts of USA
- easily established and renovated by frost-seeding yearly into existing sod
- difficult to maintain as a pure stand if desired
The legume, birds-foot trefoil, has some real potential to decrease GIN in small ruminants. Its traits are:
- Cool-season, self-reseeding perennial
- Tolerates wetter and more acid soils than many legumes
- Slow to establish – best sown in mixtures
- Can be frost-seeded
- Contains condensed tannins that
- Prevent pasture bloat
- Improve protein nutrition
- Provide anthelmintic activity
- Reduced adult worm burden (Marley et al., 2003)
- Improved tolerance of high worm burdens (Ramirez-Restrepo et al., 2005)
- Less anemia (Burke et al., 2009)
- Inconsistent effect on ruminant fecal egg counts (FEC) and egg hatch
Meanwhile, a non-leguminous forb, chicory (Editor note: Considered a noxious weed in some states), has some GIN activity. Its traits are:
- Short-lived perennial forb (2 to 3 year stand life)
- Yield up to 6000 lb DM/acre/year
- Good forage quality, but has palatability issues in that it is bitter tasting
- Establish by clean tillage, can be frost-seeded
- Has helped reduce GIN problems as it contains compounds called sesquiterpene lactones , but these compounds’ concentration is reduced under high P soil fertility
- Reduced adult worms (Marley et al., 2003)
- Reduced numbers of larvae on forage
- Reduced anemia (Burke et al., 2009)
An experiment trial of pasture-finished Boer goats on MIG using a 40-day grazing cycle, 4-day grazing period and 36-day rest on 3 different pastures, orchardgrass, alfalfa, and red clover-grass, found that alfalfa and red clover produced a significantly better average daily gain (ADG) than orchardgrass. Alfalfa produced the most gain per acre (177 lbs/acre), while orchardgrass and red clover-grass pastures produced approximately 150 lbs./acre of live-weight gain per acre. As with other experiments witnessed in the first session, crude protein in these pastures were high. As a result TDN:CP ratios calculated here were low, too low in fact. TDN:CP ratios for the orchardgrass and red clover grass pastures were 3.8 and 3.9 respectively, while the alfalfa pasture had an even lower ratio of 3.2. These values are considerably lower than the recommended range of 5-7.
In a second experiment trial, forages with bio-activity towards GIN, birds-foot trefoil and chicory, were compared to red clover. All three species were seeded with prairiegrass to form a grass-forb pasture. The red clover-prairiegrass pasture had the best ADG over the 2 years of the experiment (but not significantly better than birds-foot trefoil-prairiegrass) and had the lowest FEC even though it was only statistically significantly lower to chicory-prairiegrass only in 2009.
One disadvantage of alfalfa as a forage for goats is that goats do not like stems so the alfalfa must be clipped after grazing since alfalfa does not like tall stubble. Potato leaf hopper is also a problem seasonally as well and can cause the loss of leaves for grazing when they strike.
Birdsfoot trefoil cultivars vary in tannin concentration and seed availability inconsistent as there are few growers. The development of a good stand requires patience. However, goats like it!
Grazing chicory with goats requires that bolting be managed by grazing it often and hard. It also requires rotational stocking, small N applications after each grazing, and top-clipping after grazing. Goats and sheep have issues with chicory palatability. They sometimes refuse to eat it. The sesquiterpene lactones (SL) found in it are bitter. Their concentrations in chicory can be elevated when soil P is low. SL profile differs across chicory cultivars. Sheep preferred Puna over Forage Feast (Foster et al., 2002), while goats had no preferences (Cassida et al., 2010).
Prairiegrass was used as the companion species in the bioactive pasture trial, and as summer emergency pasture for goat kids. It is:
- A cool-season perennial bunchgrass
- Very palatable, in vitro true digestibility (IVTD) up to 78%
- Lambs gained 0.48-0.58 lb/day, 172-216 lb/acre on fall stockpiled prairiegrass
And then… winter of 2008/09, almost complete die-off across two research farms. (Editor’s note: Prairiegrass is most adapted to areas with moderate winters. An unusually cold winter, or a late harvest that weakens plants going into winter, can cause substantial winterkill.)
Sericea lespedeza also contains condensed tannins with anthelmintic activity. However, it has poor cold tolerance, a very short growing season, and is not suitable for pasture in Northeast. Feeding sericea hay has same anthlemintic benefits as fresh forage for goats (Shaik et al., 2004, 2006) and lambs (Lange et al., 2006). An optimal ration is 50-75% sericea hay in their diet (Dykes et al., 2006). Pelleted hay is more effective than long hay (Terrill et al., 2007).
Another set of forages for goats and sheep are the brassicas. They are annual forbs (turnips, tyfon, rape, kale, swedes). They have outstanding cold tolerance so they are excellent for fall stockpiling. They can be no-tilled or planted in prepared seedbed and yield up to 6000 lb DM/acre. They have outstanding forage quality (“high moisture concentrate”). Pasture finishing lamb ADG of 0.24 to 0.55 lb/day were observed. Historically, they were used as forage for dairy goats in Europe. They may have a potential to be forage for meat goats. Always provide trace minerals with iodine to animals grazing brassicas.
Sheep and goats grazing brassicas also need a source of roughage to provide adequate dietary fiber. When they are on brassicas, feed hay or provide access to a grass pasture so that they can mix their diet on their own. Another way would be inter-plant grass or legumes into brassicas, or no till brassicas into a grass pasture that has had its growth suppressed. Brassicas should be strip grazed to prevent waste. Crop management of forage brassicas requires good soil drainage, a soil pH at least 6.0, heavy fertilizer requirement for NPK, prepared seedbed establishment for greater yields, and sod suppression for no-till establishment (HEAVY grazing or herbicides).
Remember, know your local environment when selecting forages to seed. Only select those that are adapted to your soils and climate and can grow well with the other forages in the pasture.