Population analysis of the Miniature Schnauzer breed Genetic analysis of the Kennel Club pedigree records of the UK Miniature 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 Miniature 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: Miniature Schnauzer Figure 1: Number of registrations by year of birth Trend of registrations over year of birth (1980-2014) = 158.53 per year (with a 95% confidence interval of 140.23 to 176.83). 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 174 112 69 11 2 1 2.52 2.37 80.46 57.47 33.91 17.24 1981 619 239 97 38 4 1 6.38 7.16 83.36 60.74 38.93 24.72 1982 834 300 153 49 3 1 5.45 7.4 83.93 64.03 41.61 30.34 1983 925 299 123 61 5 2 7.52 8.41 83.46 60.43 34.27 22.38 1984 1041 354 141 72 5 2 7.38 8.75 82.23 59.56 37.08 24.98 1985 1239 409 156 76 5 1 7.94 9.58 85.15 64.41 39.06 23.57 1986 1242 413 162 58 5 3 7.67 8.18 83.01 62 35.1 21.26 1987 1209 416 168 52 4 2 7.2 8.08 83.29 61.54 36.89 23.16 1988 1423 444 173 67 5 1 8.23 10.34 84.68 63.04 39.49 27.41 1989 2081 482 181 63 6 4 11.5 12.13 84.14 61.85 35.32 21.67 1990 2044 440 179 72 7 6 11.42 11.86 81.16 59.83 35.08 22.36 1991 1929 419 176 61 6 5 10.96 11.02 82.06 60.55 35.2 21.05 1992 2036 425 179 80 7 4 11.37 12.12 81.63 59.72 36.84 22.94 1993 2001 437 183 80 7 5 10.93 11.27 82.11 60.07 34.23 20.89 1994 2208 456 197 100 7 5 11.21 11.62 80.93 58.92 34.1 20.79 1995 2403 520 205 131 7 4 11.72 15.03 84.39 63.13 38.29 25.72 1996 2521 543 218 77 6 6 11.56 12 83.42 61.52 34.39 21.18 1997 2483 532 206 83 7 5 12.05 13.35 82.96 62.02 36.85 23.28 1998 2537 535 218 115 7 5 11.64 14.09 82.34 61.81 38.98 26.61 1999 2224 463 214 76 7 6 10.39 10.48 80.71 59.35 34.13 21.31 2000 2313 508 210 67 7 5 11.01 11.62 82.71 61.31 36.66 22.83 2001 2390 503 220 71 6 5 10.86 11.11 81.92 60.96 34.69 20.92 2002 2654 583 231 93 6 5 11.49 13.46 84.33 64.09 38.06 24.42 2003 2928 657 249 135 7 1 11.76 15.71 85.48 65.54 42.14 27.7 2004 3410 725 286 76 6 4 11.92 13.48 84.52 63.49 38.33 23.28 2005 4252 884 310 76 9 1 13.72 13.64 83.7 60.49 33.61 20.37 2006 4434 912 373 89 7 5 11.89 12 82.5 59.16 34.39 21.36 2007 5225 1058 402 91 8 5 13 13.72 82.97 60.46 34.97 22.18 2008 5291 1085 441 70 7 5 12 11.41 82.9 58.99 32.68 18.81 2009 5388 1082 454 71 7 5 11.87 11.84 82.35 60.97 33.65 20.29 2010 5501 1113 463 70 7 4 11.88 12.26 83.13 61.35 35.12 21.01 2011 5993 1212 526 127 7 5 11.39 12.82 82.88 61.49 37.19 23.13 2012 5664 1120 518 99 7 5 10.93 11.28 81.18 59.07 34.55 21.75 2013 5583 1108 499 123 7 5 11.19 12.5 82 60.02 35.81 23.45 2014 5234 1010 447 62 8 6 11.71 10.22 79.31 56.19 30.89 17.94 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) = 3.57 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 = 158.9 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 718.6 1438.8 2043.6 2433.6 2739 4918 5595 Total #sires 316 413 452 513 610 958 1249 Max #progeny 182 278 359 328 369 248 458 Mean #progeny 11.351 17.407 22.584 23.717 22.449 25.666 22.393 Median #progeny 5 7 10 10 10 11 10 Mode #progeny 1 1 5 6 1 1 1 SD #progeny 19.241 28.173 35.636 37.194 36.155 35.676 32.422 Skew #progeny 4.416 4.1502 4.212 3.8335 4.198 2.6787 4.1281 Total #dams 867 1363 1406 1593 1954 3076 3560 Max #progeny 25 36 33 35 32 37 33 Mean #progeny 4.1373 5.2759 7.2667 7.6378 7.0082 7.9938 7.8565 Median #progeny 3 4 6 6 6 6 6 Mode #progeny 1 4 4 4 5 5 5 SD #progeny 3.4209 3.9546 5.1634 5.4783 4.8059 5.5697 5.3676 Skew #progeny 1.7563 1.6278 1.5482 1.4245 1.2728 1.3482 1.2213 Rate of inbreeding 0.01264 0.018859 0.005284 0.015108-0.00986-0.00753-0.01073 Generation interval 3.0902 3.214 3.7785 3.8861 3.7193 3.4777 3.8415 Effective pop size 39.558 26.512 94.62 33.096 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 and 1990s. This represents a genetic bottleneck, with genetic variation lost from the population. However, since 2000 the rate of inbreeding has been negative, implying moderate replenishment of genetic diversity (possibly through the use of imported animals). It appears that the extensive use of popular dogs as sires has increased (the tail of the blue distribution increasing 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