Development and Growth Rates of a Horse

Growth Rates

Understanding of the normal parameters of the development of the young horse so anything outside the norm can be easily flagged and deal with issues before they arise. From my time in Japan good management is monitoring the rate of this growth for each individual horse by measuring their weight, height and cannon circumference weekly can identify even the slightest chance. This data gathered each year allows us to track our stock on an accurate curve based on the same farm. This proved very useful at detecting problems before they become issues. Prudent management of young stock is rarely acknowledged without poor management practices i.e. people expect good management and it’s not until they have bad management of their stock that they acknowledge good management. Importance of monitoring growth rate in foals, weanlings and young horses is all linked but we will watch out for different problems at different stages.

Foals, Weanlings and young stock

While in-utero and particularly during the last trimester we feed the pregnant mare increased grain but not to excess. Feeding to excess can result in nutritional imbalances and a foal that is already behind. Circulating growth hormones are responsible for the ossification of the joint and bone development and for these growth hormones to be present enough amounts of protein needs to be available in the young horse’s diet. In the early stages of the foal’s life the foals get all their nutrition from the mare’s milk which has soluble milk solids/proteins that are easily digested and utilized by the infant. The volume of milk solid in the milk will depend on the body condition and nutrient levels the mare has access to. This highlights the importance adequately feeding the lactating mare. A foal is 10% of its mature body weight at birth. Excessive growth in young foals can result in flexural deformities (upright or lax in fetlocks/ pasterns) and improper ossification of bones and joints resulting in OCD lesions, Epiphysitis and sometimes bone cysts.  As the infant matures their digestive tracts develops and they start to be able to gain nutrients for solid feed no longer reliant on soluble proteins.

It’s common for foals that are foaled over 365 days post cover to have big foals at birth and its also common for some foals that are born early to suffer a ‘bounce’ or spurt of compensatory growth that results in conformational issues such as going upright on heir forelimbs.  With foals we need to not just monitor the foal but also monitor the mare’s milk. Not enough milk will result in the foal having a poor weight gain below the growth curve. On the other hand, too much milk will result in a fast-growing foal that will be susceptible to things like OCD and epiphysitis. In weanlings we need to carefully manage the transition from milk and grass to hard feed. Use of creep feeders can help in managing this stress and nutritionally transformational period. We can again see epiphysitis in the knee or fetlock at this period. In winter horses tend to have slightly slower growth rates. Yearlings and Young horses outwintered tend to grow less in winter and suffer a ‘bounce’ or spurt of compensatory growth that results in conformational issues in the spring. This can be particularly telling in places like Kentucky or Japan where the ground is covered by snow and is followed by incredibly lush spring grass within a short period. If young horses get too top heavy, they can also develop issue such as splints, this can also become more prevalent when the ground is hard.

The premise of little and often is always best when feeding horses, it’s also beneficial if they eat slowly so that the full nutritional benefit of the feed can be absorbed by the from gut. Lysine and amino acids are also incredibly important that as the young horse has a much higher need for lysine that at a later stage.  It is the total energy intake that will largely determine how fast the horse will grow. For all young stock its essential to supply them with a balanced diet of minerals but protein, lysine are the two key considerations for balanced growth and this must be in conjunction with adequate energy but not excess energy in the diet. Too much protein in any horse for a period can cause liver damage and, in the racehorse, it can cause bleeding through breathing in urea from the stable floor. While every diet depends somewhat upon the use that we wish to make of the horse or the primary objective at least. When feeding young horses, I usually feed 32% Gain balancer to all my young stock– this ensures optimum supply of nutrients for young stock, 32% protein with elevated levels of vitamins and minerals. .6 of a kg is recommended for weanlings and 1kg for yearlings. It is branded for optimum development and a ‘low starch balancer’. This feed is fed at a very small volume making it easy to eat for the horse. This feed gives all the nutritional benefits the young horse needs without the starch and helps avoid an excessively heavy topline. I outwinter all young stock. When forage is of low quality in winter this balancer needs to be fed with some oats and good quality hay or haylage to keep growth rates on track. If feeding for the sale ring it can be advisable to feed a stud cube as a top line in early spring helps in getting into a sale, but it makes the horse more susceptible to developmental disorders.

Bone Growth

The flat bones use intramembranous ossification while long bones grow using endochondral ossification. Issues with long bone development are more common and development of long bones is where poor nutrition usually tends to show with the development of DOD’s. Bones grow in both diameter and length. Most DOD’s tend to be associated with the growth plates at the end of the long bones. The epiphyseal plates are where the bones grow in length. These close or fuse at different points the pastern/fetlock fuses within the first 3 months whereas the knee epiphyseal plates doesn’t close until between 12 and 15 months. These times vary slightly depending upon each horse’s bat are visible on x-ray. When thing go wrong from an angular, flexural or radiographic point of view we quickly become aware of these fusing windows as we tend to try to correct them using various forms of manipulation such as management techniques such as box rest, corrective trimming or veterinary intervention such as screws before it is too late. Although some of this is genetic most and probibly all can be prevented with good nutritional management. The main 4 DODs are OCD, ephiphifisitis, wobbler syndrome and angular, flexural limb deformities. They are usually caused by overfeeding sugars and starch in the diet, causing spikes in insulin levels, usually the animal has lots of excess energy and they either over do things in the paddock or they are in an intensive prep for a sale. There is also an aspect of genetic heritability which makes certain animals more likely to suffer from the condition, but a different nutrition plan should be applied to these cases. Deficiency in cooper, calcium, phosphorus and zinc can affect bone growth and cause DODS. Zinc oversupply or toxicity can also be a negative. The Calcium /phosphorus ration should be 2:1. Protein daily intake is recommended at no more than 16% or no less than 12% but remember this is on the overall daily intake. The 32% balancer is only fed in very small amounts that balance the much larger quantity of hay which have much lower levels of protein that are fed to a higher level. Overweight horses can also suffer from these disorders due to the extra strain on the limbs.

Process involved in healthy hoof growth and horn growth

The horse needs Phospholipids, omega 3 fatty acids, zinc, b7 (biotin) vitamins, minerals and amino acids and importantly lysine and methionine to grow healthy and strong hoof. Horses hoof grow from the coronary band to toe. The horn of the hoof is made up of a tough protein called keratin. This is layered in horizontal sheets for extra durability. Hoof growth is believed to be highly correlated with heart rate and so young horses with a naturally higher heart rate have faster growing hooves. It takes 1 year for a hoof to fully grow out. It grows slower in winter than in summer. Hooves grow between ¼ – ½ and inch every month the laminae forms a tight bond between the inner hoof wall and the pedal bone. This bond causes the pedal bone to be suspended within the hoof cavity. Any damage to the laminae as a result of physical trauma or toxicity in the bloodstream can cause this bond to weaken and so the pedal bone can lower in the hoof cavity due to a stronger pull from the deep digital tendon than the extensor and this will cause pain and laminitis.

Supplement 1: Horse first Hoof First

The Manufacturers description of the product is “The strongest hoof product on the market today. 400mg of Biotin per 25g dose. All essential vitamins and minerals to produce a healthy hoof. 2kg provides 80 days’ supply”. We can see this is primarily a biotin supplement but from the picture below in also supply’s Lysine and Methionine. Biotin a water-soluble vitamin from the B family helps in a range of metabolic processes its primarily used in utilization of carbohydrates, fats and amino acids. Methionine is essential amino acid and is very important in the development of strong hoof tissue. Lysine is often very short in horse grass and hay. It is an essential amino acid that plays a major role in the generation of hoof tissue.

Supplement 2: Biotin Plus

We can see this is primarily a biotin supplement but from the picture below. Biotin needs to be used for up to 60 days before the horse will start to show improved signs of hoof health. It’s the most common supplement used to see improvement in hoof quality. It really acts as a contributor to allowing the horse to utilize the feed better so the hoof can avail of the nutrients within the diet. Biotin is a water-soluble vitamin from the B family helps in a range of metabolic processes its primarily used in utilization of carbohydrates, fats and amino acids.

References

• https://stanceequineusa.com/wp-content/uploads/2016/04/Developmental-Orthopedic-Disease-DOD.pdf
• https://www.rideawaystore.com/en-IE/Horse-First-Hoof-First-Hoof-Supplement/r5055947.htm?colour=White+Red&sku=428494&productid=125371&utm_source=google&utm_medium=cpc&utm_campaign=Shopping%20API&_$ja=tsid:|cid:912779750|agid:48213161000|tid:pla-415050482605|crid:216771581220|nw:g|rnd:629704599484800427|dvc:c|adp:1o1&gclid=CjwKCAiA9efgBRAYEiwAUT-jtExSw0iZe2dEstD4mjbXIHuzRZB9OpGUjqVM9sLkLx7hAlYE8bp1JBoCyKEQAvD_BwE
• https://ker.com/equinews/protein-energy-ratio-young-horse-diets/
• https://www.google.com/search?q=biotin+plus+for+horses&rlz=1C1EJFA_enIE780IE780&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiG0rH45avfAhWtURUIHc_0BU4Q_AUIDigB&biw=1152&bih=753#imgrc=dC3tmRWbOiS3CM: