McLennan Equine

Big Head Syndrome - Part 4

Here is a full list of symptoms:

Swollen face
Swollen jaw
Loose teeth
Tooth root infection
Pain during eating
Difficulty chewing
Separation of upper and lower incisors
Nasal collapse
Watery nasal discharge
Breathing noise
Upper airway obstruction
Difficult or labored breathing
Loss of appetite
Weight loss
Poor condition
Dullness
Depression
Coarse, stark coat
Difficulty breathing
Pica involving dirt
Distal pastern swelling
Stiff gait
Shortened stride
Staggering gait
Muscle tremors
Tenderness or pain in joints
Tendon ruptures
Spontaneous fractures
Lethargy
Lying down
Difficulty rising
Shifting, intermittent lameness
Paralysis of hind limbs
Decreased height in younger horses

Big Head Syndrome - Part 3

If the low calcium intake continues, the bones are leeched to provide more and more of their calcium to maintain the blood levels, subsequently weakening the bones. Without having any available calcium the bone cannot regenerate and so the bone matter is replaced by fibrous tissue. This is usually where outward, physical signs are seen on the facial bones, appearing as swelling. Other long bones and joints are often affected, bringing lameness as another symptom.

At this point horses usually become deficient in phosphorus, as well as calcium, due to the loss of phosphorus in the urine under the direction of the PTH.

Treatment Plan
First and foremost the horse needs removing from the high oxalate pasture and if this is not possible, every length must be taken for the offending grasses be removed or the horse’s access be limited. Grasses with more than 0.5% oxalate are capable of inducing Bighead and some high oxalate grasses in the right conditions can have concentrations as high as 6% (Stewart, J), so removal of it is key for there to be a chance of recovery.

Secondly the balance of calcium and phosphorus needs to be corrected through supplementation. It can take up to a year to remineralise the bones, but the reversal of the Bighead appearance is not always possible at all.

The presence of calcium-oxaltes means that although the horse has the correct intake amount of calcium to meet their requirements, the calcium cannot be absorbed and is passed straight through the horse into the manure. As a result, the body calcium levels begin to fall and once the low level is detected, the parathyroid gland releases parathyroid hormone (PTH).

The main function of the PTH is to prevent blood calcium becoming dangerously low. Dr Jennifer Stewart explains that the hormone does this by;

1. Increasing the phosphorus excretion and reabsorbing the calcium from the urine.
2. Instructing the gut to increase the uptake of calcium from the feed, but unfortunately for unsupplemented horses grazing high oxalate pastures, there is no available calcium in the diet.
3. PTH stimulates the release of small but continuous amounts of calcium from the bones, which it uses to increase the blood levels back to the normal healthy range.

Tomorrow we will see what symptoms this presents in the horse.

Big Head Syndrome - Part 1

Big Head Syndrome is a fairly common syndrome that affects any horse, no matter of breed or size. It is caused by the horse having inadequate absorption of calcium, leading to a gradual leeching of calcium from the bones so that it can balance the blood calcium levels. There are a series of events that take place that lead to the horse’s decline in calcium, but first lets look at what causes it.

More commonly found in Australia than anywhere else, sub-tropical grasses contain oxalate, which is “a chemical that significantly interferes with mineral utilisation in horses.” (Stewart, J). When a horse ingests these high oxalate grasses, such as Buffel, Setaria, Pangola, Kikuyu, Green Panic, Guinea and Signal Grass, the oxalate binds to the calcium in the gut, forming calcium-oxalate. The calcium-oxalate is insoluble which prevents the horse from absorbing the calcium.

Tomorrow we will look at what problems this triggers for the horse.

Lectins - Part 3

The horse’s body has somewhat adapted to processing the higher number of lectins in their modern grain-based diet. The saliva in their mouths and the mucous in their nose contain sugars that lectin proteins naturally bind to and these sugars work to trap the lectins before they reach the digestive system. An increase in mucous production is one of the symptoms of lectin poisoning, triggered by excessive ingestion of lectins. If the lectins are able to pass the first lines of defence and enter the system, another symptom is caused in the gut by an over production of mucous created to try to es**rt the lectins out of the body. This, to the owners, appears to be a symptom of mucous coated droppings. General malaise, loss of appetite, soreness of the abdomen and irritability are also common symptoms to be expected, but the most concerning symptom is malnourishment due to the lessened ability to absorb nutrients.

It is important to note however that lectins are not always the villain as they can actually be useful, but the key is in the quantity. If consumed in moderation, lectins provide a manageable strain onto the horse’s immune system and cells, which actually stimulates it to work to combat the toxin, strengthening it in the process. However, in larger quantities, lectins are associated with obesity, chronic inflammation, digestive issues and autoimmune disease.

Lectins - Part 2

Because of lectins size they cannot fit through the spaces between cells in the mucosal wall of the gut lining, so they create holes and break down the wall instead to enter. They do this by binding with certain cell receptors to create a chemical compound that opens spaces between the cells, which not only lets them through but also bacteria and other toxins. This is known as leaky gut syndrome. Once lectins get through the intestinal wall, they have access to the horse’s tissues, lymph nodes, glands and bloodstream. This is where it is detected as a foreign protein by the immune system, which launches an attack on them, and it is in that attack that the symptoms of inflammation begin to be felt.

A secondary problem occurs at this point, caused by lectins ability to mimic other proteins. The immune system is unable to tell the difference between the lectin proteins and the natural proteins, causing it to attack its own proteins. As different proteins are what directs the cells to do different bodily actions, like store fat, speed metabolism etc, this can cause the body to follow the wrong instructions, not in its own best interests, such as chronically storing fat.

Tomorrow we will look at how the horse tries to combat lectin poisoning and what symptoms to look out for.

Lectins - Part 1

Lectins are known ‘anti-nutrients’ and as the name suggests, they block the absorption of nutrients. Lectins are found in many plants and although deemed as the enemy of horses and their humans alike, they serve a good purpose to the plant, as they are responsible for protecting plants against bacterial infections and being eaten by insects. Lectins form in the outer shell or covering of plants, seeds, fruits, stems and leaves and are a fairly large protein, in comparison to vitamins, minerals, fats, sugars and simple proteins that the intestinal cells regularly absorb. Because of their size they cannot fit through the spaces between cells in the mucosal wall of the gut lining, so they create holes and break down the wall instead to enter.

Tomorrow we will explore how they damage your horse's digestive system and what symptoms of lectin poisoning to watch out for.

What are the w**ds in your paddock telling you?

Weeds do not necessarily indicate that the soil is poor, but they certainly can give us clues to the health of the soil in our pasture paddocks. Most w**ds are in fact showing symptoms of the paddock, or in other words indicating that the paddock soil is favouring the growing conditions of the w**d rather than the wanted grasses. This is why the w**ds that are growing are often referred to by Agronomists as indicator species, because they can indicate soil related problems that disadvantage good pasture species but are viable for the w**d’s growth and dominance.

Pyrrolizidine Alkaloid Poisoning is also known as Ragwort Poisoning, as it is most commonly caused by the Ragwort plant. This w**d is highly toxic to horses and the subsequent poisoning results in liver failure that causes long-term damage. Ragwort is not the only w**d that causes it, the list includes Senecio (ragwort), Crotalaria (woolly groundsel), Heliotropium (monkey tail), Amsinckia (yellow tarw**d), Echium (blue thistle), Cynoglossum (hounds tongue), and Trichodesma (borage forget-me-not) families, but they all have in common that they like to grow in temperate climates, though some require tropical or subtropical conditions to thrive. Horses, alongside cattle and pigs, are very susceptible to their toxins, but thankfully most of these w**ds, especially ragwort, have a very bitter taste which puts most horses off of grazing them.

The poisonous pyrrolizidine alkaloids present in ragwort cannot be processed by the liver and so they accumulate and over time, this compromised the healthy liver cells. As the function of the liver cells become compromised their numbers reduce, subsequently reducing the live function. The danger comes from the fact that there is most likely to not be any physical signs to alert the horse owner that this is happening, until it is already at a very dangerous level and quite often untreatable. In fact, sadly Pyrrolizidine Alkaloid Poisoning is often not diagnosed until after sudden death from liver damage. If the owner is fortunate enough to notice a change in their horse, the symptoms would include loss of condition, loss of appetite, dullness, malaise, constipation or diarrhea but likely to contain bloodstained faeces. There may be a build-up of fluid in the abdomen and jaundice may be seen in the whites of the eyes. Weakness progresses and the last symptoms would likely be of lessens coordination and wandering. Immediate veterinary care must be sort and any further intake of the toxic w**ds stopped, but horses at this stage of liver failure due to accumulative poising rarely recover.

Did you know that Australian Stringhalt is a condition that is caused by the horse consuming Flatw**d, known to be toxic to horses. Flatw**d (Hypochoeris Radicata) is also known by the name False Dandelion or Cat’s Ear and all efforts should be taken to remove from your horse paddocks.

The main symptoms of Stringhalt are:

• An altered hind leg gait
• A ‘hitch’ in their stride, describing a momentary pause within the movement
• Difficulty in lifting hind feet for trimming or hoof care
• Upward fixation/sticking of the Patella
• Difficulty to back up or turn in small circle
• Shivers
• Difficulty in breathing (usually under exercise)
• Roaring sound when breathing (usually under exercise)
• Laryngeal paralysis to varying degrees

The use of B1 has had great success in the recovery of Stringhalt in horses and its relevant research is ongoing. Vitamin E (tocopherol) and Vitamin C (ascorbic acid) have also proven to aid in the repair of nerve cells caused by ingested toxins, so they also help pave the road to recovery.

Spent the morning doing a f***l egg count on my mare. Now to identify the little suckers!