Population analysis of the Giant Schnauzer breed Genetic analysis of the Kennel Club pedigree records of the UK Giant Schnauzer population has been carried out with the aim of estimating the rate of loss of genetic diversity within the breed and providing information to guide a future sustainable breeding strategy. The population statistics summarised provide a picture of trends in census size, the number of animals used for breeding, the rate of inbreeding and the estimated effective population size. The rate of inbreeding and estimated effective population size indicate the rate at which genetic diversity is being lost within the breed. The analysis also calculates the average relationship (kinship) among all individuals of the breed born per year and is used to determine the level of inbreeding that might be expected if matings were made among randomly selected dogs from the population (the expected rate of inbreeding). Summary of results The analysis utilises the complete computerised pedigree records for the current UK Kennel Club registered Giant Schnauzer population, and statistics were calculated for the period 1980-2014. 1
Figure 1: a plot of number of registrations by year of birth, indicative of any changing trend in popularity of the breed, followed by the yearly trend in number of animals registered (and 95% confidence interval). Breed: Giant Schnauzer Figure 1: Number of registrations by year of birth Trend of registrations over year of birth (1980-2014) = 3.10 per year (with a 95% confidence interval of 1.29 to 4.92). 2
Table 1: census statistics by year, including sire use statistics. Table 1: by year (1980-2014), the number of registered puppies born, by the number of unique dams and sires; maximum, median, mode, mean and standard deviation of number of puppies per sire; and the percentage of all puppies born to the most prolific 50%, 25%, 10% and 5% of sires. year #born #dams #sires puppies per sire %puppies sired by most prolific sires max median mode mean sd 50% sires 25% sires 10% sires 5% sires 1980 23 13 10 4 2 2 2.3 1.06 65.22 47.83 17.39 17.39 1981 90 22 16 17 5 1 5.63 4.33 77.78 51.11 31.11 18.89 1982 142 29 20 20 5.5 2 7.1 5.79 81.69 54.23 26.06 14.08 1983 156 29 20 31 4 2 7.8 9.17 85.9 68.59 37.82 19.87 1984 232 47 26 38 3.5 1 8.92 10.81 91.81 72.84 41.81 16.38 1985 206 55 21 65 5 1 9.81 15.18 89.81 68.93 50.49 31.55 1986 224 43 30 28 5.5 1 7.47 7.67 86.16 62.5 35.71 24.55 1987 198 35 24 29 6.5 4 8.25 7.34 79.8 56.57 26.26 14.65 1988 262 47 24 93 6.5 8 10.92 18.22 83.21 65.65 43.13 35.5 1989 241 40 24 47 8 1 10.04 10.9 86.72 61.41 31.54 19.5 1990 178 28 18 33 8 8 9.89 8.33 75.28 56.18 32.58 18.54 1991 230 33 18 31 13 6 12.78 7.6 72.61 46.96 23.91 13.48 1992 158 25 16 57 7 1 9.88 13.45 86.08 61.39 45.57 36.08 1993 276 38 22 57 8.5 1 12.55 13.98 84.42 65.22 35.51 20.65 1994 282 38 21 44 9 8 13.43 12 79.43 56.38 29.43 15.6 1995 238 39 27 52 7 1 8.81 10.18 84.03 57.56 38.24 21.85 1996 292 47 29 38 9 9 10.07 8.4 77.4 51.03 30.48 13.01 1997 265 41 25 44 7 1 10.6 11.48 86.79 63.02 40 16.6 1998 295 43 29 39 7 1 10.17 8.85 83.05 52.88 27.46 13.22 1999 294 43 27 24 9 1 10.89 7.23 78.57 49.66 23.13 8.16 2000 250 37 26 33 9 1 9.62 7.42 77.6 51.6 28.4 13.2 2001 206 33 23 26 6 5 8.96 7.62 80.1 59.22 24.76 12.62 2002 253 45 31 29 7 1 8.16 6.72 81.03 54.55 27.27 20.55 2003 279 45 27 38 7 1 10.33 9.81 84.23 59.86 35.13 13.62 2004 326 52 37 45 8 1 8.81 9.05 85.89 57.67 34.66 22.09 2005 283 47 33 35 8 1 8.58 7.9 84.1 54.06 29.33 21.2 2006 307 53 34 23 9 1 9.03 7.12 83.39 54.07 20.85 14.66 2007 233 40 33 23 7 1 7.06 6.55 86.7 55.36 29.18 19.74 2008 244 48 35 26 7 1 6.97 5.82 81.97 53.28 31.56 18.44 2009 224 50 30 49 4 1 7.47 9.63 87.95 66.96 39.29 32.14 2010 238 41 29 41 8 1 8.21 8.44 82.35 54.2 36.13 17.23 2011 219 38 29 30 8 1 7.55 6.49 83.56 50.68 28.31 13.7 2012 241 47 33 90 4 1 7.3 15.38 90.46 69.29 48.96 43.98 2013 202 37 26 30 4.5 1 7.77 9.14 89.6 68.81 42.08 14.85 2014 245 36 26 42 7.5 1 9.42 9.36 82.04 60.41 36.33 17.14 3
Generation interval: the mean average age (in years) of parents at the birth of offspring which themselves go on to reproduce. Mean generation interval (years) = 3.73 Figure 2: a plot of the annual mean observed inbreeding coefficient (showing loss of genetic diversity), and mean expected inbreeding coefficient (from random mating ) over the period 1980-2014. Expected inbreeding is staggered by the generation interval and, where >2000 animals are born in a single year, the 95% confidence interval is indicated. Figure 2: Annual mean observed and expected inbreeding coefficients 4
Estimated effective population size: the rate of inbreeding (slope or steepness of the observed inbreeding in Figure 2) is used to estimate the effective population size of the breed. The effective population size is the number of breeding animals in an idealised, hypothetical population that would be expected to show the same rate of loss of genetic diversity (rate of inbreeding) as the breed in question. It may be thought of as the size of the gene pool of the breed. Below an effective population size of 100 (inbreeding rate of 0.50% per generation) the rate of loss of genetic diversity in a breed/population increases dramatically (Food & Agriculture Organisation of the United Nations, Monitoring animal genetic resources and criteria for prioritization of breeds, 1992). An effective population size of below 50 (inbreeding rate of 1.0% per generation) indicates the future of the breed many be considered to be at risk (Food & Agriculture Organisation of the United Nations, Breeding strategies for sustainable management of animal genetic resources, 2010). Where the rate of inbreeding is negative (implying increasing genetic diversity in the breed), effective population size is denoted n/a. Estimated effective population size = 100.0 NB - this estimate is made using the rate of inbreeding over the whole period 1980-2014 5
Table 2: a breakdown of census statistics, sire and dam usage and indicators of the rate of loss of genetic diversity over 5 year periods (1980-4, 1985-9, 1990-4, 1995-9, 2000-4, 2005-9, 2010-14). Rate of inbreeding and estimated effective population size for each 5-year block can be compared with the trend in observed inbreeding in Figure 2. Table 2: by 5-year blocks, the mean number of registrations; for sires the total number used, maximum, mean, median, mode, standard deviation and skewness (indicative of the size of the tail on the distribution) of number of progeny per sire; for dams the total number used, maximum, mean, median, mode, standard deviation and skewness of number of progeny per dam; rate of inbreeding per generation (as a decimal, multiply by 100 to obtain as a percentage); mean generation interval; and estimated effective population size. years 1980-1984 1985-1989 1990-1994 1995-1999 2000-2004 2005-2009 2010-2014 Mean #registrations 128.6 226.2 224.8 276.8 262.8 258.2 229 Total #sires 53 82 62 79 92 108 104 Max #progeny 69 163 174 101 103 59 132 Mean #progeny 12.057 13.768 18.081 17.481 14.272 11.935 11 Median #progeny 5 6 10 12 8 6 6 Mode #progeny 1 1 1 1 1 1 1 SD #progeny 15.917 24.547 25.316 19.636 20.324 14.682 17.65 Skew #progeny 1.8859 4.0196 4.1917 2.0788 2.5582 1.57 4.0404 Total #dams 98 166 113 153 155 181 148 Max #progeny 30 42 35 32 37 33 32 Mean #progeny 6.5204 6.8012 9.9204 9.0261 8.471 7.1271 7.7297 Median #progeny 5 4 8 8 8 6 7 Mode #progeny 1 1 6 9 1 1 1 SD #progeny 6.3785 7.5448 7.4608 6.4215 6.694 6.8199 6.7869 Skew #progeny 1.4531 2.0954 1.3064 1.0781 1.323 1.3825 1.3422 Rate of inbreeding 0.00886 0.037657 0.0031 0.004386-0.01083-0.01295-0.01672 Generation interval 3.6083 3.4505 3.597 3.6769 3.7759 3.6095 4.5457 Effective pop size 56.431 13.278 161.28 113.99 n/a n/a n/a 6
Figure 3: a histogram ( tally distribution) of number of progeny per sire and dam over each of the seven 5-year blocks above. A longer tail on the distribution of progeny per sire is indicative of popular sires (few sires with a very large number of offspring, known to be a major contributor to a high rate of inbreeding). Figure 3: Distribution of progeny per sire (blue) and per dam (red) over 5-year blocks (1980-4 top, 2010-14 bottom). Vertical axis is a logarithmic scale. 7
Comments As with most breeds, the rate of inbreeding was at its highest in this breed in the 1980s. This represents a genetic bottleneck, with genetic variation lost from the population. However, since 2000 the rate of inbreeding has been negative, implying moderate restoration of genetic diversity (possibly through the use of imported animals). There appears to be extensive use of popular dogs as sires in this breed (the tail of the blue distribution in figure 3). It should be noted that, while animals imported from overseas may appear completely unrelated, this is not always the case. Often the pedigree available to the Kennel Club is limited in the number of generations, hampering the ability to detect true, albeit distant, relationships. 8