Head Points: Selecting for Head Shape
Genetics Mini-Series Supplement #3
In the Genetics Mini-Series article #11, Breeding for Type, we discussed the importance of body shape for production characteristics such as egg laying and meat production. In this supplement, we will discuss the shape of the head and its role in breeding selection.
In Walter Hoagan’s 1921 Call of the Hen, he discusses a number of body shapes and what they mean for the egg-laying or meat-producing qualities of the chicken. He greatly emphasizes the importance of identifying individuals which tend more towards each of the types and breeding like to like to create more of the same. For example, a bird with a thin skeleton and a well-developed, deep abdomen with wide hips would make for an excellent laying-type where as a bird with a thick skeleton and deep abdomen is better suited for meat production. However, Hoagan found that putting chickens of the same type together was not enough: The chickens needed a quality he called prepotency or amativeness to be able to pass on their traits to their offspring.
Hogan proposed that if the brain was large, the nervous system was healthy and the chicken’s traits would be more apparent in its offspring than a chicken with a poorer nervous system. Borrowing heavily from the now mostly debunked theory of phrenology which was practiced on humans in the early 1900s, Hogan said that the development of the brain and nervous system that was the root of prepotency could be ascertained by looking at the size and shape of the skull. He placed one thumb at the back of the skull and his other thumb at the base of the ear: If the first thumb was to the rear of the second, the chicken was higher in prepotency. If his second thumb was equal to or behind the first, the chicken was lower in prepotency.
In his 1928 Breeding and Culling by Head Points, H. H. Steup, providing a history of chicken head-shape studies and often disagreeing with Hogan on selecting for body-type, instead emphasizes almost exclusively the proportions and shape of the head and identifies four desirable head characteristics. (1) When looking from the front of the head, the top line should be more flat and not curved (above). (2) The eyes should be towards the front of the comb, not around the side or behind. (3) The distance from the bottom of the comb to the top of the wattles should be equal to the distance from the front of the earlobe to the tip of the beak, called head balance (below). (4) From the side, the top of the head should be level and not sloping front or back.
The shape of the skull remains an important criterion of selection in modern improvement breeding. The American Livestock Breeds Conservancy (ALBC) recommends looking at the width of the skull because it indicates the development of the skeleton as a whole. A wide skull is indicative of a wide, sturdy skeleton which will grow well and have ample room for organs, digestion, and egg-making.
Skull width – A wide skull on a chicken is a strong indicator of good growth potential. If birds cannot be physically examined, often judging skull width visually can be a reliable indicator of young birds with good growth potential. If the skull is narrow, then the rest of the bird will be narrow. As a rule of thumb, medium to large skull width is good for egg layers, and large to extra wide skulls are better for meat birds. (Beranger & Schrider, 2007, p. 3) [emphasis added]
The American Poultry Association (APA) also places significant emphasis on head shape, although it only assigns three points out of 100 to head and face shape in a poultry show. The overall shape of the skull should be well-developed and long, flatter along the top, and full in the forehead. Thus, the depth of the skull is also important, as a shallow head is a serious defect because it indicates a lack of vitality. A crow head is defined by the APA as “a narrow, shallow, [sic] head and beak, (fig. 23); a serious defect,” (APA Standard of Perfection, 2010, p. 7).
The head is of great importance as it indicates the state of health and vitality. In all breeds where high egg production is characteristic, particular emphasis should be placed on the character of the head and eye. The head should be strong, moderately long, and well filled in forward of the eyes to avoid any appearance of crowheadedness, with the skill inclined to be somewhat flat on top rather than round. (APA Standard of Perfection, 2010, p. 28) [emphasis added]
Head shape, or head points, has been historically and consistently emphasized in the selection of breeding birds over at least the past century and a half because it correlates to the growth rate, vigor, skeletal strength, productivity, and prepotency of chickens. Select chickens with wide skulls, long towards the back with a slightly flattened top; good depth in the forehead; bright, forward eyes; and a level, non-sloping head.
“Chapter 9: Prepotency” in The Call of the Hen by Walter Hogan (1921); Available through Internet Archive
American Poultry Association. (2010). American Standard of Perfection. Burgettstown, Pennsylvania: American Poultry Association, Inc. The SOP is on sale on the APA website for only $59 until December 15th!
Breeding and Culling by Head Points by H. H. Steup (1928); Available through Internet Archive
Selecting for Meat Qualities and Rate of Growth by Jeannette Beranger and Don Schrider (2007), American Livestock Breeds Conservancy