Does your horse have a topline that has been showing deterioration while on winter hay? Perhaps you have been working him/her through the winter and still the topline looks shallow and sunken? Maybe your saddle isn't fitting your horse quite as well as it should be? Or perhaps when you do ride, your horse is expressing behaviour issues, or has difficulty in changing leads?
These could all be indicative of a poor topline and a low quality protein diet. Even though you may be feeding adequate amounts of protein (expressed as Crude Protein content), it is the quality of the protein and balance of Amino Acids (AA) that affect the topline. If there is a problem with the topline, usually there is a problem with the nutrition program your horse is on. Let's dig a little deeper on this subject, and hopefully it will make more sense to you...
So what is "Topline"? Topline refers to the muscle groups that run along the horse's spine: from the end of the neck at the withers, down the back and loin, and over the hip into the croup. The three main muscle groups are the longissimus dorsi (pelvis-thoracic vertebrae-last four cervical vertebrae), the latissimus dorsi (upper and mid back vertebrae-lower lumbar vertebrae), and the thoracic trapezius (neck- midback vertebrae-shoulder blade).
Topline can be affected to a certain degree by conformation, age, training and intensity, and injury, but mostly by nutrition. Exercise will condition muscle but it really needs to be fuelled by the right types of amino acids in sufficient quantities. If the diet lacks sufficient amino acids and calories, existing muscle mass can actually shrink even with the exercise. A poor topline (withers, back, loin, croup) is the result of little or no fat due to inadequate calories, poor muscling caused by AA deficiency or imbalance, and in severe cases muscle atrophy. A superior amino acid profile is needed to repair, build and recover muscle especially along the topline.
Just as we use Body Condition Scoring to monitor fat deposits on horses and to identify if caloric intake should be adjusted, the Topline Evaluation Score (TES) helps us to grade the topline musculature and amino acid status. It is very easy to do - more information about the TES can be found at http://toplinebalance.com/topline-resources/
Keep in mind that the topline of a horse is mostly muscle - if the horse has a BCS of 8 or more, fat layers over the topline musculature then become more visible. The goal of a good topline is to increase muscle mass not fat. By doing both the BCS and the TES, it will tell a more complete story of the caloric status and the amino acid status - two very different types of scoring systems and results! Can horses be overweight and still have a poor topline? YES! (see the example below).
More about Amino Acids: Did you know that muscle is made up of about 73% Protein, which is comprised of amino acid chains? There are 22 natural amino acids identified, and 10 of these are essential to the diet of the horse: Methionine, Histidine, Arginine, Leucine, Lysine, Phenylalanine, Valine, Threonine, Tryptophan and Isoleucine. If feed lacks balanced amounts of any of the essential amino acids, topline development and other tissues in the body may be compromised.
Limiting Amino Acids include Lysine followed by Methionine. If they are not present in the diet at the right levels, they will “limit” the extent of protein being built in the body by the other eight essential AA. They are considered to be the weakest link of the chain so protein quality is only as high as the level of the lysine and methionine in the diet. Most feed products will give lysine, methionine, threonine and tryptophan levels on the bag, indicating that the feed is a high quality source of protein. Contact the manufacturer for more information and check the ingredients on the label too for sources of high quality protein.
How do you know if you are feeding a diet deficient in Amino Acids? Signs of AA deficiencies will show up in your horse's topline, skin, hair, hooves and overall muscle condition. But to make sure, it is best to do some calculations to see what is going on with the diet. Remember, even though you may be meeting the "amount of protein" requirements (Crude Protein) for your horse, it is the quality of protein that you may need to focus on and the amino acid profile.
Did you know that most grass hays and/ or cereal grains cannot come close to meeting the required AA intake to support optimal growth, development and performance? The NRC* suggests that a 500 kg horse, average temperament and at maintenance requires 27.1 g Lysine per day. Methionine requirement is generally 1/3 of Lysine so that would be 9 grams per day.
If you were feeding 2% BW of good quality Grass Hay, that would be 10 kg of hay delivering 3 g lysine and 1.0 g methionine, far below the requirements!. In this case you would have to feed 9X the amount of hay to achieve the requirements - which is impossible to do! Right off, you will know that you need to seek other sources of AA to provide your horse with the high quality of protein needed to avoid loss of topline, protect tissue integrity and to increase performance.
Here is a list of common feedstuffs for horses with values for %Lysine and %Methionine (L/M) from NRC* : Grass Hay (cool season) 0.03 / 0.01; Alfalfa Hay 0.21 / 0.06; Soybean Meal 3.08 / 0.67; Oats 0.44 / 0.24; Beet Pulp 0.55 / 0.08; Flaxseed Meal 1.32 / 0.65
Soybean Meal is considered to be the closest to being the perfect protein source because it has all the AAs in the right proportions. A complete listing of forages, grains and feedstuffs and their AA profiles can be found in the *National Research Council's Nutrient Requirements of Horses, 6th ed.
If your horse has a less than perfect topline, always turn to the diet first to make improvements. After you make the necessary adjustments, you should be seeing good results in 30-90 days. If you are not sure of the Amino Acid profile and amounts in a commercial feed, it is best to contact the company to get the answers you need. The Amino Acid profile is part of a complete nutrition plan: always analyze your hay, balance minerals, and supplement vitamins and minerals to your horse’s needs to achieve peak health and performance for your horse.
Do you have a horse that requires a specialized diet? Do you need help in determining the best combination? Send an email to firstname.lastname@example.org and share your story!
Jean Klosowicz, Equine Nutrition Consultant & Educator
Superior Equine Health and Nutrition Inc.
Bruce Mines, ON
Reference: National Research Council Nutrient Requirements of Horses, 6th ed. 2007
Photo Credits: Hygain.com.au and www.baileyshorsefeeds.co.uk
Healthy Horses. Happy Owners. Superior Results!
Superior Equine Health and Nutrition Inc.
www.SuperiorEquineNutrition.com ~ www.FeedMyHorse.ca ~ SuperiorEquine@gmail.com
The articles contained in this column are for the purpose of education and are not intended to take the place of proper veterinary care. They may be used in conjunction with such care to facilitate healing and maintain health of the horse.