Written by Stefani Millman June 2009; Revised February 2013

Below is a great comprehensive definition of a Dexter.  We have copied this from Stephani with her permission.  Further information is available in the new book by Stephani Millman and Gabriella Nanci.  You can also read more at Stephani's website:   

A dual-purpose animal is bred to serve two functions: milk and beef. The Dexter is to be compactly built, shorter in length than that of a true dairy breed but thicker in the thighs, hips, loin and shoulders. Its disposition should be easy to handle and docile as its main purpose is to be a family cow. It should not be overly large and tall, nor should it be excessively small. 
Balance: The size of bone, depth and fullness of all parts, low-setness, and length of leg and neck should reveal a consistently uniform harmony throughout. A balanced animal reveals equality in all parts. The animal should appear smoothly blended in such proportions as to give even and uniform appearance.
Quality:  Indicated by smooth, neat, clean-cut features throughout which contribute to the beauty and general ability of the animal to economically perform the function of production. Neat joints, general refined condition of bone, a pliable softness to the hair and hide, a clean cut appearance of the head and smoothness of body lines and finish are necessary attributes.
Style:  Associated with harmonious development in all body characteristics. It involves the general beauty and the degree of grace which it displays while moving or at rest. The animal should have an attractive, graceful carriage, with enough nervous response versus stability that keeps muscles in proper tone to hold the body together to impress his or her true value. Style is often responsible for the animal catching the eye of a judge or prospective buyer and selling at a premium.
Constitution:  Characteristics that determine the feeding ability, reproductive capacity, health, vigor and longevity: Broad mouth and large nostrils; wide and deep chest capacity, as determined by length and fullness of the fore ribs and width of chest floor; deep heart girth and well-sprung ribs encase the diaphragm, heart and lungs, which are vital to longevity and reproductive ability.
Locomotion:  Gait should be free and smooth with long, fluid strides not choppy or rough. The hind hoof should be placed in line with the front with no twisting or crossing of legs, with a long reach as to cover ground efficiently. 
Head:  A desirable head displays breed character and refinement without frailty. Proportionate to the body, medium in length, clean-cut and tapering down into a broad muzzle that is strong and powerful with wide, open nostrils; a lean, strong lower jaw showing good muscling with teeth matching pad correctly, as to avoid an over or under bite. Desirable proportions of the following:
Eyes:  Placed well in sockets. Large, alert, bright and lively showing interest in their surroundings. They range in colors from dark brown to light amber.  
Forehead:  Wide between the eyes, bridge of nose straight.  
Ears:  Relative to size of head, neatly paced and alertly carried.  
Neck:  Should be of good length and blend smoothly into shoulders and brisket. Clean throat and dewlap without excessive loose flesh or surplus skin underneath.
Shoulders:  Set smoothly against chest wall and withers with an adequate cover of flesh.  
           Note: Winged shoulder is the term used to describe the condition caused by the failure of the connective tissues to hold the shoulder blade firmly to the rib structure. The point of the shoulder will be pulled away from the ribs. Winged shoulder is and undesirable trait.
Brisket and Chest:  Deep and wide between the front legs with plenty of capacity for heart and lungs. Neat and trim with little dewlap.
Withers:  Sharpness of withers and thickness at the top of the shoulders coincides with condition. A cow in heavy flow of milk and relatively thin flesh will usually be sharp at the withers, whereas the same cow in high condition just prior to calving may show a thickness of 5 – 6 inches (or possibly more) at this region. Only a cow in peak lactation may show some sign of withers.
Ribs:  A massive housing for the vital organs. The barrel should be deep and strongly supported with ribs wide apart, well sprung, and covered with firm flesh. Depth and width tending to increase toward the rear of the barrel with little space between the ribs and hips.
Heart Girth: Large and deep filled both out and down; contributing its part in a straight bottom line and side line. 
Foreribs: Long and well sprung with a wide chest floor between the front legs and fullness at the point of the elbow.  
Back:  The topline should be strong and straight from the withers to the end of the tail head with adequate flesh. The topline is determined by the position and strength of the backbone (vertebral column). Much of the roughness or lack of symmetry and smoothness in an animal is due to irregularity of the spinal column. This roughness may or may not impair the function of the animal, but it does reduce eye appeal and thus reduces the value of registered, purebred animals.
Loin:  Broad, deep, thick, strong, smoothly fleshed at maturity. This is the most expensive cut on a beef animal. A young animal my roach (curve upward) at the loin but may level out with maturity. This is only permissible at the loin; if the back roaches midway, the prospect for improvement with maturity is not likely. A dipped or sagging, weak loin is an undesirable trait.
Hips:  Wide, approximately level laterally with the back, with adequate flesh. Females will tend to be more prominent in the hips than males.
Pin Bones:  Wide apart and slightly lower than the hip; contributing to calving ease.
Rump:  Long and wide, it should carry out the same width that prevails on the loin and ribs. Straight, level from loin and square at the tail head extending down deep towards the hock. Pelvic bone shape, slope from hook to pin, and distance between hook and pin all contribute to rump conformation. Sloping, angular or narrow are not ideal. A high tail head also detracts from the overall appearance of the rump.
Flank:  Deep and smooth allowing for capacity. It should be an extension of a deep barrel, not cutting at an upward angle.
Thigh:  Wide apart when viewed from the rear, providing sufficient room for udder and its attachments. The fullness should carry well down to the hock, tying in the rump.
Legs:  Set in all four corners of the animal, clean-cut and strong. When viewed from behind, legs set wide apart and straight. Toes pointed forward with feet short, balanced, well rounded with deep heel and level sole. Bones of the legs must be firm and dense, pasterns relatively straight, of medium length, strong and springy. Tendons well defined. Hocks cleanly molded with an adequate amount of bend. Hind legs nearly perpendicular from hock to pastern. Poor bone quality, puffy joints, weak or excessively short pasterns, and long toes with under-slung heels are all extremely undesirable traits.  
Udder:  Long along the underline, wide and of moderate depth with a smooth floor. Full and balanced in all four quarters of even symmetry. Front quarters extending well forward and strongly attached. Rear attachment high and wide. Teats place squarely and evenly in all four corners and are a uniform, convenient size. Cylindrical in shape, free from obstructions, well apart and plumb. Texture soft, pliable and elastic. Rudimentary teats should be removed at birth. Well collapsed after milking. May or may not show excessive veination on either or both, udder and body.  
Scrotum and Sheath:  Testicles balanced and symmetrical. Rudimentary teats set wide apart, squarely placed in front of scrotum. Sheath clean-cut to belly without extra sagging skin.
Tail:  Fine, hanging straight. Tail head level and neatly placed between pin bones.
Color:  Black, Red or Dun. White is permissible if confined to the rear part of the underline behind the naval. It is often found on the udder or in the tail switch. White on the scrotum, or forward of the naval is unfavorable. Black has a black or “smutty” nose, teats and hooves. Red has various shades of pink, or a black “smutty” nose and teats, hooves are black or brown. Dun has a tan colored nose and teats and brown hooves. Teats may be pink on any udder that is white. Both red and dun coat colors range in several shades.
Size:  Frame score should be 1 or below for both males and females. Cattle must be of diminutive stature compared to that of a standard breed but still capable of producing a carcass of reasonable market value, and a reasonable quantity and quality of milk production. They should be of proper size for their age and sex. An animal should be sufficiently developed for his or her age. They should have proper form and equivalent body proportions.
Horns:  Inclining up and forwards on females, more forward on males, moderately small at base, medium in length, tapering toward black tips, or brown in the case of red and dun animals. They should contribute to the attractiveness of the head by being neat, symmetrical and properly placed. Dehorned animals are allowed without penalty.
Polled:  Polled animals are characterized by a well-defined poll.

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