Breeding Plan and DNA testing
One of our breeding goals is to create identified homozygous Pure Polled dairy cows and stud bulls with a polled gene inherited from a polled Dam and a polled Sire with DNA testing to show this inheritance by which the animal is called "homozygous polled" and generally indicated as Homo P in the breed name, or PP. A horned animal is homozygous horned, but because the polled trait is dominant, like brown eyes in humans, a polled dam or sire may be heterozygous polled. In our discussions we use P to indicate a polled gene and H (equivalent to p used by some writers) to indicate a horned gene. To obtain a PP homozygous polled animal, both parents MUST be polled, and normally it is assumed that both parents are PH heterozygous polled when DNA testing is employed. http://skyway.usask.ca/~schmutz/polled.html For this Test, read DNA Test Preparation and the Bova-Can Laboratories order form.
Here are the possibilities:
PP to PP always results in 100% PP homozygous polled offspring.
PP to HH always results in 100% PH heterozygous polled offspring.
PP to PH always results in 100% polled offspring, but with 50% of the offspring PP, 50% offspring PH.
PH to PH results in 25% offspring PP, 50% offspring PH, and 25% HH.
PH to HH results in 50% offspring PH and 50% horned.
DNA testing is used in the event PH to PH breeding is employed. Without DNA testing you have to wait until a sufficient number of offspring is identified as having no horns when one of the breeding pair is horned. As noted above, if ANY offspring of a polled animal when bred to another produces a horned calf the horned calf’s polled parent is heterozygous polled PH. The use of DNA testing determines homozygosity at a confidence rate in excess of 90% for calves at the age of 60-90 days. To reach the same confidence level without DNA testing, the following offspring results must be shown.
1. A bull with polled parents would need a minimum of:
10 polled calves from horned cows; or
25 polled calves from a known heterozygous PH polled cows; or
38 polled calves from polled cows of unknown genotype, PH or PP.
2. A female with polled parents would need either from ET flushes or individual births a minimum of:
10 polled calves from horned bulls, or
25 polled calves from known heterozygous PH bulls.
While some polled bulls have top predicted proofs, it is important to increase the number of top polled bulls. To do this owners breed the best to the best of elite cows to produced even better polled bulls. If both parents are polled, the DNA testing will be used to pick future AI sire candidates which are designated HOMO P. Polled bull calves can be used for natural service of the breeder or of neighbors, or sold to heifer raisers. The greater number of polled animals created will be a greater poll of elite polled cows. So, use PP bulls to create a pool of polled heifers, then chose the highest predicted proof bulls whether PP or PH on these polled heifers to produce the bulls of the next generation, and DNA test the offspring for PP polled homozygosity.
Scurs may be present over a polled head. For a primer on scurs (which is recessive while polled is dominant) see: http://www.telusplanet.net/public/salers/Gen.html. Don't use a scured bull.
Service Resources are provided for you to locate the Studs through the Stud
Code, for places to find
embryologists, for heifer raisers who will inseminate their heifers to polled bulls and provide recipients. Transportation resources are also there as well as USDA sites. We need contributing participants in this area.