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By Hybrid Turkeys, Kitchener, ON, Canada
Feathers are replaced several times during a bird’s life and follow consistent, predictable patterns. Since certain nutrients are required for feather growth and replacement, the quality of feathers and their rate of growth can be affected by factors such as nutrient intake, body composition, day length, age and sexual maturity. Highlighted here are feathers in the domestic turkey and how monitoring their status may be used as a management tool for welfare and production.Feather growth
Historically, feathers have been categorised into six different classes: contour; down; semi-plume; filo-plume; bristle, and powder-down. Contour feathers are the vaned feathers that cover the bird’s body. The largest of the contour feathers are the flight feathers that extend beyond the body (wings and tail) and function in flight (Welty, 1975).
Historically, feathers have been categorised into six different classes: contour; down; semi-plume; filo-plume; bristle, and powder-down. Contour feathers are the vaned feathers that cover the bird’s body. The largest of the contour feathers are the flight feathers that extend beyond the body (wings and tail) and function in flight (Welty, 1975).
Feathers are attached to the bird’s skin in the dermal and epidermal layers. All feathers are anchored within a feather follicle that appears (in the turkey embryo) around Day 10 of incubation. All follicles develop during incubation and serve the bird for life. Feathers appear on Day 11 of incubation and contain keratin that is distinct for feathers, scales, beaks and claws. A typical feather grows until it reaches a definite size, then it stops and the cells in the feather follicle become dormant until the feather is molted. Normally, at the proper time for molting, reactivated cells in the follicle grow a new feather that pushes out the old feather above it. Consequently, feathers grow from the base, not the tip. If a feather is accidentally removed, the germ cells in the follicle can reactivate to replace it.
Feather replacement
Feathers grow at different rates, depending upon the species, the bird’s age, its diet and health. Other factors in the rate of feather growth include the part of the body where the feather is located, time of year and day length (night-time growth is slowest). For birds that nest on the ground, including turkeys with precocial young (parents bring no food), feather growth is the most rapid and the soonest completed.
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| Replacement of feathers #4 and #5 in a 10 week old bird. |
In most birds, feathers are distributed in scattered patches on the body, called “feather tracts”. Within a tract, feathers are arranged in definite patterns, often in rows. Though species vary, most birds have eight different feather tracts. The wing and tail tracts carry the contour feathers responsible for flight. The largest and most distal feathers are clustered together on the wing flipper (hand) and are called the primary wing feathers. Most turkeys have 10 primaries and they have been assigned the Roman Numerals one to ten (I-X) from innermost to the wing tip. The secondary wing feathers are large quill feathers along the forearm (ulna). They vary in number by species. Turkeys normally have 18 and (numbered 1-18) from the wrist to the elbow.
Molting of feathers
As feathers become worn, they loosen in their follicles and drop out, pushed out by the already growing new feather underneath. The prime function of a molt is the replacement of worn feathers. Adult birds normally molt and renew their feathers once a year, usually after the natural breeding season. In young birds plumage is regularly replaced as they reach adult size.
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| Replacement of feather #7 in a 15 week old bird. |
The natural functions of feathers, protection and flight, are indispensible. Therefore, the replacement of feathers is arranged in such a pattern to preserve both functions. The energy demand of feather growth is heavy and usually does not occur during times of reproduction (or in wild birds, during migration). Feathers are not replaced all at once, but with a definite, bilaterally symmetrical pattern. The most common molting pattern of a primary wing feather molt is called “descending” in which feathers drop out beginning with number one (I) at the wrist joint, proceeding in sequence outward and is complete when the 10th (X) feather is replaced.
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Source: World Poultry, Vol. 27, No. 6
