Lack of topline affects strength, stamina, stride length and the power:weight ratio.Horses may lose topline due to low quality feeds, amino acid deficiencies, dental problems, metabolic disturbances and diseases. Lack of energy can be secondary to poor muscling, below optimum lean muscle mass and/or a simpleenergy deficiency in the daily diet – regardless of the cause, the bottom line isreduced work tolerance. Whilst oats provide energy, there are more advanced ways, in terms of safety, efficiency and delaying fatigue, of meeting energy requirements. Topline can be fat or muscle. Increasing ‘fat’ or‘cover can usually be achieved by increasing calorie intake; increasing muscle mass requires correctly profiled protein. Increasing ‘cover’ just requires an increase in calories. But it is important to determine what type of ‘weight’ you wish to increase – muscle, fat or both? To build muscle and cover, the glycaemic index and the amino acid composition of the feed are important – by reducing carbohydrate intake (grains, pollard, rice-bran etc) and fine-tuning protein (soybean meal, cottonseed meal, lucerne) intake we can reduce fat and build muscle mass. When assessing the ‘muscle building’ power of a feed, there are 3 factors to consider: 1.Digestibility in the small intestine. Highly digestible feeds are rapidly cleavedby digestive enzymes to yield amino acids. Feeds not easily digested in the small intestine pass to the caecum where they are degraded to ammonia -increasing urea and ammonia levels and wasting amino acids. 2.Percent protein is meaningless when assessing and comparing feeds. Horses require a certain number of grams of protein a day, not a percent. For example if a horse eats 1kg of a 20% protein feed – it obtains 200g of protein.If it eats 2kg of a 10% protein feed it again receives 200g of protein. 3. Lysine and other essential amino acids must be present in the correct amounts to make muscle protein. If one is deficient, the ‘recipe’ cannot be made. A useful way to picture this is with an old-fashioned wooden water (or wine or beer) barrel. The shortest slat sets the amount of water the barrel canhold. Similarly, if each slat represents an amino acid, the amount of bone andmuscle a horse can build is set by essential amino acid deficiencies Physical strength comes primarily from the muscles, and to build muscles a high quality protein intake is essential. Protein-rich feeds, and exercise, are known to cause a muscle-building effect by stimulating the release of the hormones concerned with the uptake of amino acids by the body's cells. Potentially, the more amino acids are taken up, the more protein is produced - and the more protein is produced, the more muscle is laid down.