Grass and health

Question 1

What are endoparasites?

Answer 1

Small redworms that are present in all grazing horses. The infection intensity is linked to pasture management, age, and the use of anthelmintics.

Question 2

How can endoparasite burden be reduced?

Answer 2

Through good pasture management -
1. Cross grazing horses and sheep - they act as biological vacuum cleaners for each other and remove each’s worms
2. Sustainable parasite control - diagnostic monitoring including blood samples, FECs, saliva tests and only worming when necessary
3. Removal of droppings - breaks the life cycle of the parasite.
New horses must be quarantined and wormed as a precaution as well.

Question 3

What is the benefit of removing droppings from pasture?

Answer 3

It breaks the parasite life cycle and removes its ability to get to the stage of its life where it sheds eggs.

Question 4

What are examples of noxious weeds?

Answer 4

Sycamore, St Johns wort, acorns, buttercup, ragwort, giant hogweed, yew, nightshade, bracken

Good pasture management involves the removal of these plants.

Question 5

What is photosensitivity? How is it caused?

Answer 5

A manifestation of pigment which causes intoxication. Typically affects horses without pigment in their skin (greys and coloureds; those with lots of white areas). When some plants, such as St johns wort, the pigment is floressed and this causes photosensitivity

Question 6

What are some bacterial diseases associated with grassland?

Answer 6

Tetanus, botulism, mudfever,

Question 7

Define BOTULISM

Answer 7

Botulism is a fatal nerological disease caused by sporeforming, soil dwelling bacteria. Caused by eating contaminated forage (rat urine, dead animals).

Question 8

What is equine grass sickness?

Answer 8

There are two types: acute and chronic
Acute is worse: symptoms present as colic, as well as nasal reflux, tachycardia, SI distension, sweating and increased salivation.
These horses are often put down quickly.

Chronic: Weight loss, tachycardia, dysphagia, patchy sweating, muscle tremors, greyhound look.
These horses may or may not survive, it depends on the individual case.

Question 9

What are the risk factors for EGS?

Answer 9

• sandy, loamy soil (found in the East of England mostly)
• once one horse is infected, other horses in close proximity at high risk - there is a 10 mile impact range
• young horses have higher risk
• early summer/late spring is higher risk time
• change in diet
• ivermectin treatment
• mechanical poo picking

Question 10

What are the causes of laminitis (aside from the diet)?

Answer 10

• disturbance of blood flow to the foot (e.g. due to lameness in one foot that causes excessive weight bearing in the others)
• underlying endocrine condition - leads to disruption of the lamella which starves them of glucose

Question 11

What are the 3 phases of laminitis onset caused by a horse ingesting high sugar grass?

Answer 11

Phase 1 - horse eats grass that contains WSC, fructan and starch. Too much starch and fructan ends up in the large intestine, because it cannot be digested by the SI
Then occurs rapid fermentation in the hindgut causing a drop in pH and more lactate is produced. Amines and endotoxins are produced caused by the death of bacteria. There is increased oermeability of the gut wall and these are released into the bloodstream.

Phase 2 - Circulation of amines in the bloodstream. These mimic normal body function such as the release of serotonin. Alters the blood flow to the foot.

Phase 3 - The lamella in the foot are deprived of glucose. The lamella have glute 1 receptors, which means they are always open for accepting glucose. Glucose is needed to stick the lamella together and with lower levels of glucose, the lamella comes unstuck. This causes a higher laminitis risk.

Question 12

What is starch?

Answer 12

Repeating glucose units. A storage molecule

Question 13

What is fructan?

Answer 13

A storage molecule. In is produced during the plants stress response (i.e. when it is cut). Made of glucose and repeating fructose units (may be up to 200). Has to be fermented in the hindgut which is a problem as it increases the laminitis risk.

Question 14

What is the fructan content of grass?

Answer 14

Hugely variable -

may be 32-439g/kg DM

Question 15

What may increase the fructan content of grass?

Answer 15

• drought or frost (stress)
• cool growing conditions (in comparison to warm)
• perennial ryegrass has high levels of fructans (220g/kg DM) in comparison to other species like Timothy or cocksfoot

Question 16

Which species of grass have the highest fructan levels?

Answer 16

Perennial ryegrass *******

Question 17

How does fructan level change?

Answer 17

Can change daily and seasonally -

• 3 hours of daylight can double WSC content
• lowest in the morning as the plant has been respiring overnight
• highest in the afternoon
• changes as plant gets older

Question 18

When are fructan levels highest and lowest throughout the year?

Answer 18

Highest in May and lowest in August

Question 19

What is insulin resistance?

Answer 19

When the cells in the body ignore the signals given out by insulin, which is to get glucose out of the bloodstream and into the cells. The body fights back by producing more insulin as blood sugar rises (because glucose has not been removed).

In horses, high fructan content causes rapid fermentation in the LI. Causes weight gain and excess fat deposits around the body, as glucose is stored as fat. This fat can affect the other messages sent by the body/

Question 20

Is laminitis a seasonal condition?

Answer 20

No, it can happen all year round - just different types at different times of the year

Question 21

Which types of horses are most at risk of laminitis?

Answer 21

• obese ponies, some may be prone
• insulin resistant horses
• those with metabolic syndromes (e.g. EMS)
• those who have had laminitis before
• mares
• those with PPID

Question 22

How can the onset of laminitis be avoided?

Answer 22

• the greatest risk is during spring/early summer when the grass is young and full of sugar as it still growing. During this time it would be beneficial for the horses most at risk to be turned out over night.
• don’t turn out on stemmy grass/stubble
• avoid feeding flowering hay
• control parasites