Storey's Guide to Raising Chickens (67 page)

A good way to find out about lethals and other problem genes in your chosen breed is to chat with experienced breeders at poultry shows. Even if you don’t intend to show your chickens, you can glean a wealth of genetic information about your breed from people who do. Other ways to obtain information are by joining a breed club and by participating in discussion groups on the Web. Some breeds have entire books written about them. You can find out if a book has been written about your chosen breed through the breed club, poultry suppliers, experienced breeders, or an online search.

By concentrating genes, inbreeding not only creates uniformity of size, color, and type, but it also brings out weaknesses such as reduced rate of lay, low fertility, poor hatchability, and slow growth — a phenomenon called
inbreeding depression
. Inbreeding doesn’t cause these problems but does accentuate any tendency toward them.

To minimize inbreeding depression, avoid brother-sister and offspring-parent matings and instead mate birds to their grandsires or granddams. Retain as future breeders those with the best fertility, hatchability, chick viability, disease resistance, and body size. Never breed birds with any tendency toward infertility. By inbreeding gradually and choosing your breeder cocks and hens carefully, you can improve such traits as laying ability and disease resistance.

Some strains are less susceptible than others to the effects of inbreeding depression. And popular breeds with lots of varieties offer more opportunities for avoiding inbreeding depression than less popular breeds with fewer numbers, and breeds with few varieties.

Outcrossing
means increasing heterozygosity by introducing a bird that is not directly related to your bloodlines. In an inbreeding program, red flags indicating that an outcross is needed include the following:

Unexpected appearance of an undesirable trait

Rapid or drastic reduction in fertility, hatchability, chick viability, or general health

Continuing lack of improvement, indicating that your birds simply do not carry the right genes

When you bring in new blood, you may not see the changes you desire until the second generation. Meantime, you run the risk of introducing new weaknesses, a hazard you can minimize by crossing your strain with distantly related birds, called a
semi-outcross
. A semi-outcross is essential if you’re trying to improve type, since conformation cannot be improved by crossbreeding.

To further reduce the risks of outcrossing, select new blood from a strain that is not deficient in any of the properties you have been working to establish and that has been properly inbred. A properly inbred sire or dam is likely to be
prepotent
, or able to pass on its attributes to the majority of its offspring. Prepotency can result only from homozygosity.

If you work with a breed or variety that has few distinct bloodlines, the time may come when you have no choice but to outcross to a different breed or variety. If you’re breeding show birds, you’ll then have to work to bring them back to type. To avoid, or at least delay, the need for such an outcross, retain as future breeders the best offspring from each mating rather than the best offspring overall.

Outcrossing results in
hybrid vigor
, the opposite of inbreeding depression. Hybrid vigor is a phenomenon whereby a chick is better than either of its parents. Traits with low heritability that show the greatest degree of inbreeding depression — such as reproductive performance and chick viability — react the most favorably to hybrid vigor.

To realize the greatest benefits of hybrid vigor, you must maintain a high degree of heterozygosity by continually outcrossing or semi-outcrossing, which entails a constant search for new blood. If your goal is to preserve genetic diversity, not only shouldn’t you cross different breeds but you shouldn’t mix established strains within a breed.

In deciding whether to create homozygosity through inbreeding or heterozygosity through crossbreeding, consider these two points:

How important is predictability to your breeding program?

Do you prefer to hide your birds’ genetic weaknesses and hope they never surface or force them to the surface so you can eliminate them?

A breeding flock can degenerate rapidly if you make no effort to select in favor of health, vigor, hardiness, and good reproduction. Birds that don’t measure up should not be used to produce future generations and should be culled. Some backyard poultry keepers use culling as an opportunity to fill the freezer. Others sell their culls to people with less demanding needs, such as those who keep chickens as pets or wish to produce eggs for eating rather than for hatching.

Problem birds, especially those with health issues or a mean streak, should be humanely killed rather than being passed along — together with their problems — to someone else. In pursuit of your breeding goals, keep only your best offspring or, if you’re working with limited genetics, the best from each mating. Get rid of the rest, even though they may be a large percentage of each hatch. A good rule of thumb for developing a critical eye is to retain for future breeding only about 10 percent of each year’s progeny.

To ensure that your initial breeders, or
foundation stock
, are worth devoting years of work to, acquire birds from someone who specializes in the strain you’re interested in, has worked with it for a long time, freely offers details about its background, and has a good reputation among fellow poultry breeders. Once you acquire your foundation stock, improving the stock to meet your goals is a matter of mating and culling.

Culling is an ongoing process. It starts when chicks hatch, and any deformed chick or runt is removed. As the birds grow, cull in favor of good health and resistance to disease. If you choose to nurse a sick chicken back to health, do not include that bird in your breeder flock, as it will pass its weak immunity to future generations. Since evidence shows cannibalism is heritable, all other things being equal, cull birds that feather pick or otherwise exhibit cannibalistic behavior.

Cull birds that develop slower than is normal for your breed, are not energetic, or might otherwise be described as unthrifty. The keepers are the ones that show some improvement over their parents. Don’t just visually inspect the birds, but handle each individual to check for skeletal irregularities or outright deformities. Any bird that does not measure up should not be retained as a breeder.

Aside from removing obviously ill, deformed, or other undesirable individuals, double check your decisions by noting which ones you plan to keep and which ones you plan to cull. Then revisit your decisions later to make sure you still feel the same way. I make my first pass when my chicks are about 8 weeks of age and continue reviewing my decisions as the birds mature.

At 8 to 12 weeks, depending on how rapidly your breed matures, cull any chickens that don’t grow at the same rate as the majority, or that have poor conformation for the breed. If you’re breeding for egg production or for show, the first heavy culling should occur when your flock reaches about 30 weeks of age. The pullets will be reaching peak production and the cockerels will look their best at that age.

A second culling time for layers is toward the end of the first year of production, since a good hen lays for at least 12 months, while a poor layer takes an early break. If you’re raising exhibition birds, select your future breeders according to the
Standard
, culling more heavily against disqualifications than defects.

Regardless of your purpose, cull in favor of good temperament — it’s no fun raising chickens that are wild, aggressive, or downright mean. Although you’ll hear all manner of advice on how to cure meanness, the only sure cure is to breed for good disposition.

After the first generation, you can start identifying and culling problem breeders so your flock will include not only good birds but also birds that transmit their good qualities to their offspring. The older your breeder flock, the better the chances they will pass along to future generations such essential qualities as vigor and disease resistance.

Assuming your breeder flock is healthy and free of both internal and external parasites, good nutrition is the greatest factor in promoting fertility and hatch-ability. Poor breeder-flock nutrition can arise because rations are:

Poorly balanced