Feeding practice of grazing ruminants

Dr. Éva Cenkvári, Ph.D.

University of Veterinary Medicine, Budapest

Department of Animal Breeding,

Animal Nutrition and Laboratory Animal Sciences

Herbage, Forage and Roughage. Pasture Definitions and Terms

All of herbage, forage and roughage are bulky feeds

that have a low weight per unit of volume.

Herbage may be best defined as the total plant material available. It is a term used more or less interchangeably with forage.

Forages are that which can be consumed by an animal.

Roughages would include herbage, forage and all fibrous plant materials (e.g. straw, corn stem, peanut hull). Coarse, indigestible

plant food relatively low in nutrients.

PASTURE AND GRAZED FORAGES

Forages:a) nativeb) cultivated

Pasture, forages for pasture- Native species used by grazing animals- Grasses - members of the family Gramineae- Legumes - members of the family Leguminosae- Forbs - broadleaf, non-woody plants (diff. species)- Browse - woody plants

Forages may be- annuals (1 year),- biennials (2 years)- or perennials (3 years or more).

Pasture: utilization of forages by grazing

animals.

Temporary pastures: utilization of forages before

or after harvesting of crops.

Permanent pastures: utilization of green forages

exclusively by grazing.

Grazing systems

- traditional grazing: continuous grazing

- intermittent grazing

- rotational grazing

- strip grazing

Harvested forage production 1

Cultivated cereal grains utilized as green forage after cutting.

Grasses as green forage - cultivated cereal grains

(e.g. corn, wheat, barley, oats, sorghum, etc.)

Corn as green forage: 15-20 t/ha,

40-60 kg/cow/day.

Corn as silage crop: see silages.

Rye as green forage: the first green forage in spring, 7-10 t/ha.

Harvested forage production 2

• Legumes as green forage

• - cultivated species (alfalfa, clovers, lupines, etc.)

• Green alfalfa: perennial

(3-5 years),

20-25 t/year (high protein production, saponin)

• Red clover: biennial, 8-10 t/ha, bloat hazard

• White clover: perennial (3-4 years), less bloat hazard, trifoliosis (photosensitivity – inflammation on the pigment free surfaces of the animal)

Nutrient content of pasture forages

Quite variable, being affected by many different factors, mainly by the maturity and the plant species.The water content of green herbage may range from

60 to 85 percent.

The vegetation water content is related to the stage of plant growth, namely younger plants contain more water than older plants. Due to the low dry matter

content, the result is that animals may get diarrhoea.

Nutrient content of pasture forages

•Protein content may be highly variable both within and among forages. Grasses contain 15% crude protein on dry matter basis. In comparison with grasses, legumes tend to be higher in crude protein (25%), although a third or more of it may be in the form of non-protein nitrogen (NPN) such as amino acids, amides and nitrate.

•Grasses, in general, contain fewer non-protein amino acids than legumes. Ruminants are adapted well to dietary non-proteins because rumen micro-organisms are capable of reducing NPN to ammonia, which is well utilized. For monogastric animals, the NPN has a lower nutritive value than the protein amino acids.

Nutrient content of pasture forages

• Most green forages have high crude fibre content, ranging from 15 to 35% (dry basis)

• Appreciable amounts of cell wall material such as hemicellulose, cellulose, pectin, lignin and silica. The amount of lignin appears to be a critical factor with respect to digestibility; lignin greatly reduces the digestibility of nutrients

• High negative correlation between lignin content and digestibility. Juvenile plant tissues contain relatively little lignin and it gradually increases with the maturity of the plant.

Nutrient content of pasture forages

• Forages are generally low in readily available carbohydrates (NFE), particularly for legumes, although much higher for the whole plant of sorghum and corn.

• Mineral content may also be exceedingly variable; forages are relatively good sources of Ca and Mg. In pasture grasses, the proximate content of Ca is 5-6 g/kg DM. Legumes generally contain rather high levels of Ca (16-17 g/kg DM). Phosphorus content of green crops is moderate to low, usually below Ca level

• (2-3 g/kg DM).

Nutrient content of pasture forages

•Forages are excellent sources of beta-carotene but are poor in vitamin D.

• In plants major changes take place as the plant matures and blooms; namely the protein content decreases, structural carbohydrates increase along with lignin (lignification),

•Readily carbohydrates decrease as well as the digestibility of both protein and energy

DM CP EE CF NfE Ca P NEm NEl NEg

g/kg g/kg DM MJ/kg DM

Meadow

Grass

267 155 45 261 459 5.6 3.2 5.86 5.64 3.42

Green

Alfalfa

228 204 29 279 371 16.8 3.5 5.58 5.78 3.17

Corn

Silage

329 92 42 201 612 4.9 1.9 6.88 6.49 4.33

Nutrient contents of some forages

Grasses

- The grass family includes not only all of the wild and cultivated species used by grazing animals but also the cereal grains, including corn and

sorghum species.

- As a food for grazing animals, the grass has many advantages. Most grass species are quite palatable and only a few are highly toxic (e.g.

Sudan grass). However, the palatability usually declines as the plant matures.

Grasses

Several sorghum species are used for pasture or harvested forage. Sudan grass (Sorghum vulgare sudanense) and its

hybrids are one of the more common ones.

They are prone to contain high level of glycosides

(i.e. dhurrin) which can be converted to prussic acid (hydrocyanic acid). This is highly toxic, particularly following

frost or drought damage. Graze or green chop only when forage is greater than 45 to 65 cm in height. Prussic acid will break

down in one to two weeks.

Grasses

Cultivated grasses as follows are of great importance:

- perennial ryegrass (Lolium perenne),

- Italian ryegrass (L. multiflorum),

- orchard grass (Dactylis glomerta),

- bluegrass (Poa spp),

- smooth brome-grass (Bromus inermis) and various members of the wheat grass family (Agropyron spp).

Others considered less desirable include for example - Bermuda grass (Cynodon dactylon) and

tall fescue (Festuca arundinacea).

Grasses

Cultivated grasses as follows are of great importance: - perennial ryegrass (Lolium perenne),

- Italian ryegrass (L. multiflorum), - orchard grass (Dactylis glomerta),

-bluegrass (Poa spp),- smooth brome-grass (Bromus inermis)

- various members of the wheatgrass family (Agropyronspp).

Others considered less desirable include for example -bermuda grass (Cynodon dactylon) and

- tall fescue (Festuca arundinacea).

Legumes

Many different legumes are utilized by grazing animals, although the cultivated legumes comprise a much smaller group than do

cultivated grasses. Nutritionally the legumes are frequently superior to grasses in protein and mineral content, particularly Ca,

Mg, K, Cu and Co.

Alfalfa or lucerne (Medicago sativa) is the most common legume used for pasture and green crop. Other legumes that find

extensive usage for pasture include clovers such as red clover (Trifolium pratense), white or Ladino clover (T. repens), Alsike clover (T. hybridum), crimson clover as the annual clover (T. incarnatum), and other legumes such as bird’s-foot trefoil (Lotus corniculatus),

honey or sweet clover (Melilotus spp), sainfoin (Onobrychis Lupinusspp).

spp), vetches (Vicia spp) and lupines (Lupinus spp).

Legumes

Alfalfa or lucerne (Medicago sativa) is the most common legume used for pasture and green crop.

Other legumes that find extensive usage for pasture include

- clovers such as red clover (Trifolium pratense),

- white or Ladino clover (T. repens),

- Alsike clover (T. hybridum),

- crimson clover as the annual clover (T. incarnatum), and other legumes such as

- bird’s-foot trefoil (Lotus corniculatus),

- honey or sweet clover (Melilotus spp),

- sainfoin (Onobrychis Lupinus spp).

- vetches (Vicia spp) and

- lupines (Lupinus spp).

Legumes

- Legumes, particularly alfalfa, red and white clover, are considerably hazardous for bloat in grazing ruminants,

especially cattle. Bloat is caused by a number of different factors (e.g. soluble leaf proteins, readily available cell

content). - In pasture bloat, gas is retained in the rumen because of the extensive foam produced, which inhibits eructation of

the gas.

- Plants include lucerne, red clover, white/Ladino clover; sweet clover and bird’s-foot trefoil are known to contain

oestrogenic substances. - Although the potency of these plant oestrogens is low compared to sex hormones, excessive intake may affect

reproduction adversely in female animals.

Legumes

- Sweet clover is quite coarse and stemmed, has an attractive vanilla-like fragrance but it is somewhat unpalatable. The odour is

due to the coumarin present in the plant.

- Coumarin reaches its highest levels in the late bud or early flower stage of growth. Most of the material is concentrated in the leaves

and flower buds.

- Responsible for sweet clover or bleeding disease, which is

- Caused by a chemical compound called dicoumarol, produced from coumarin by the metabolism of moulds

- Dicoumarol is an inhibitor of vitamin K and leads to impaired formation of protrombin,

- Resulting in spontaneous internal haemorrhage and uncontrollable bleeding to death.

Broad leaved forage plants

Brassica spp.: they are planted in the autumn and provide pasture (for sheep, cattle) over the winter

months.

Forage brassica: 50-90 t/ha,

seeding in mid-July after crops are harvested, grazing from October till December.

Sugarbeet-top with leaves: 10 t/ha,

oxalates, easy fermentable sugars, 10-15 kg/cow/day.

Toxic properties of grasses-Two nutritional problems that are mainly associated with grasses are nitrate

poisoning and grass tetany.

- Nitrate poisoning can occur when grasses are frequently fertilized with nitrogen. Nitrogen in excess of the plant’s requirement for protein synthesis is accumulated as

nitrate ion.

- Toxic effect on ruminants is caused by the reduction of nitrate to nitrite (NO2). (In the rumen, nitrate is reduced to nitrite.) Nitrite is actually toxic;

- It is absorbed and reacts with haemoglobin, forming methaemoglobin, which is incapable of transporting oxygen to the body tissues.

- Symptoms of toxicity include laboured breathing, bluish mucous

membranes, convulsion, trembling, staggering, dark brown blood and death.

-Toxic symptoms may occur in animals grazing herbage containing

0.5 percent nitrate in the dry matter.

(Levels of 0.5% or more in forage are potentially dangerous.)

Toxic properties of grasses

- Grass tetany is a metabolic disorder mainly associated with consumption of grasses by ruminants. The disease is caused by very low

blood levels of magnesium (<17 mg Mg/l).

- Mg level in blood: in horse:0.8-1.2 mmol/l, in cattle 0.7-1.1 mmol/l, in sheep 0.8-1.5 mmol/l, in goat 0.9-1.9 mmol/l)

- Signs of grass tetany include inco-ordination, convulsion, especially when animals are disturbed and high mortality in affected individuals.

Grasses in the spring tend to have a low

Mg content and a high content of organic acids that tie up

Mg in the rumen in an unavailable form.

- Positive relationship between tetany and dressings of nitrogenous and potassic fertilisers.

Toxic properties of grasses

- Fescue foot or fescue toxicosis, is apparent in animals grazing tall fescue.

- Fescue foot is a serious condition and should not be allowed to run its course. Animals with this condition have swelling in the legs and restricted blood flow to the feet, which causes

tissue to die and hooves to detach from the feet.

- Fescue foot is a non-infectious disease caused by endophytes.

- Endophyte (Neotyphodium coenophialum, formerly called Acremonium coenophialum) is a fungus that lives inside the

grass plant. The relationship between grass and endophyte is symbiotic.

- Plant tissues remain entire and functional, endophytes or endophytic fungi produce toxins (i.e. ergot alkaloids) that are

harmful to livestock.

Alcaloids of ergot

Claviceps purpurea, C. paspali

Occurance:cereals

Effects: bleeding,

disturbances of central nervous system,

fertility↓

milk production↓

Toxic properties of grasses

-The effects on cattle include elevated body temperature (hyperthermia), lower feed intake and weight loss, lower pregnancy

rates and decreased milk production.

-Tissue death because of restricted blood flow also can occur at the tip of the tail and ears. These clinical signs, although more apparent

during hot weather, can occur any time of the year

- Sheep appear to be less affected by the endophyte in tall fescue, possibly because they are inherently hardy. However, sheep are prone to fescue foot, hyperthermia, poor wool production and reproductive problems as well as lowered feed intake and the

resulting poor weight gain.

Maximum daily intake of green forages (kg)

Feedstuffs Dairy

cows

Sheep Goats

Grasses ad lib. ad lib.

(up to 7)

ad lib.

Lucerne,

red clover

45-50 5 3-4