Generation Time in English Shepherd Breeding Programs

The average generation time, also known as the mean interval between generations, can be calculated by breeders to understand and manage the genetic diversity of their breeding program. Here’s a general way to calculate it:

Create a List of Breeding Dogs: First, list all the dogs that have been used for breeding in your program over the time period you’re interested in. Include both males and females.

Calculate Age at Breeding: For each dog on the list, calculate the age at which they first produced offspring that were also used in the breeding program. It’s important to only consider dogs whose offspring were used for breeding, as they’re the ones passing on their genes to the next generation.

Calculate Average Age at Breeding: Add up all the ages at first breeding, then divide by the total number of dogs on your list. This gives you the average age at first breeding, or the average generation time, for your breeding program.

For example, let’s say you have 5 dogs that were used for breeding and their ages at first breeding were 2 years, 3 years, 2.5 years, 3.5 years, and 4 years. Add these together to get a total of 15 years, then divide by 5 (the total number of dogs), and you get an average generation time of 3 years.

A shorter generation time increases the speed at which genetic diversity is lost in a population. This is due to several factors, including genetic drift (the change in frequency of a gene variant in a population due to random sampling), inbreeding (mating between close relatives, which can increase the frequency of harmful genetic variants), and artificial selection (selective breeding for specific traits, which can limit genetic diversity). As generations progress from the founding event (the initial establishment of the population), genetic diversity declines. This loss of diversity can make a breed more susceptible to diseases, reduce adaptability, and compromise the overall health and vitality of the population.

A longer generation time generally means a slower rate of genetic diversity loss. It offers more time to screen for potential health issues, ensuring only the healthiest individuals contribute to the next generation. It also provides more opportunities for a wider range of individuals to breed, enhancing the gene pool’s diversity. This approach requires patience and a commitment to the long-term health and stability of the breed, and may not be feasible in all circumstances, but it’s a goal worth striving for in dog breeding.

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Tony Bierman, "Generation Time in English Shepherd Breeding Programs," OBTESA, Accessed February 28, 2024,