Repeatability of subjective grading in fur animals I. Grading of live foxes (Vulpes vulpes) Hilkka Kenttämies and Harri Käyhkö Kenttämies, H. & Käyhkö, H. 1992. Repeatability of subjective grading in fur animals. I. Grading of live foxes (Vulpes vulpes). Agric. Sei. Finl. 1: 303-307. (Univ. Helsinki, Dept. Anim. Breed., SF-00710 Helsinki, Finland and Turkis-Sampo, SF- -83900 Juuka,Finland.) Repeatabilities of subjective grading were studied for colour and body size in silver foxes, and for general appearance in various colour types of the fox. Statistically sig- nificant differences between scoring times were found for each trait. However, the judge factor had the greatest effect on scores for colour and body size in silver foxes. There were differences between the mean scores in general appearance given for the various colour types. Colour tended to be easier to judge than body size or general appearance. The coefficients of repeatability were 0.74 for colour, 0.55 for body size and 0.57 for general appearance. The repeatabilities among the various judges were 0.68-0.82 for colour and 0.51-0.59 for body size. Among the various colour types the ”silver types” seemed to be easier to judge than the ”golden types”. The repeat- abilities were 0.57 to 0.59 vs, 0.50 to 0.55 for general appearance. Key words: silver fox, body size, colour, repeated grading Introduction Body size and fur characteristics of live fur animals are usually subjectively graded. A lack of objective methods to estimate colour and fur quality in farm conditions has led to subjective judging. In addi- tion, scoring may be quickly conducted. The high reliability of evaluation for body size and fur cha- racteristics is important for the selection of the breeding animals. However, grading may be affected by species and colour types, skill of the judge, circumstances of the farm and variations in lighting conditions (Jonsson 1970, Jezewska and Maciejowski 1982). In order to study the accuracy of evaluation, the coefficient of repeatability can be estimated from the repeated scorings. Repeated judging of exterior traits in fur bearing animals has been previously studied mainly in minks (Jonsson 1970, Macie- jowski and Slawon 1973, Reiten 1977, Jezewska et al. 1981, Jezewska and Maciejowski 1982, Borsting and Clausen 1986, Kenttämies and Vilva 1988). In addition, Jezewska and Macie- jowski (1982) performed repeatability studies in silver foxes and blue foxes. The purpose of the present investigation was to study the repeatability of grading scores for body size, colour and general appearance in foxes, and the factors affecting the scores. Material and methods Repeated grading in live foxes was studied in a pri- vate farm Turkis-Sampo. In two samples the an- 303 Agric. Sei. Finl. 1 (1992) imals were graded three times by each judge. In October 1986 five persons judged the colour and body size of 248 live purebred silver foxes (Sample 1). The animals were males and females in a 1:1 ratio. In December 1989 one person judged the general appearance of 2063 foxes (Sample 2). The animals were males of several colour types of fox. In the both samples the animals were graded in individual cages on a scale from 1 to 5 (Table 1). An automatic recorder was utilized in the recording of the scores. The materials were edited and analysed using the statistical program WSYS (Vilva 1987). Factors affecting the traits were studied by the analysis of variance using models, where all the effects were considered fixed. In Sample 1 the following model was applied: Model 1: Y..., =u+a. + b. + c.+ e....ijkl ~ i j k ijkl where Y. k| = body size or colour of the Ith scoring (i = general mean a ( = effect of the ith judge; i=l-5 b = effect of the jth time of grading; j=l-3 c. = effect of the kth sex; k=l ,2k e... = random errorijkl In Sample 2 the Y-variable was general appear- ance and the model included colour type of foxes and time of grading. The repeatability coefficients of the traits were analysed using random and mixed models. In the completely random model the effects of the judges were ignored, and the data were analysed using the following random model: Model 2: Y =u+d+e ij f- , ,j where d = effect of the /th animal with all other fac- I tors as described in Model 1. Model 2 was also used in analysing repeatabil- ities separately by judges (Sample 1) and colour types (Sample 2). In addition, for Sample 1 the effects of animal were analysed separately by males and females. In order to eliminate the effects of the judge on the coefficients in Sample 1, the following hier- archic model was used: Model 3: Y... =u+a. + d + e...ijk " i ij ijk where d(j = random effect of the /th animal within ith judge with all other effects as described in Model 1. In Sample 2 the Y-variable was general appear- ance and the model included colour type of foxes and animal. Results and discussion Means and standard deviations The data consisted of a total of 3720 observations in Sample 1,and of 6189 ones in Sample 2. Slightly higher scores were given for general appearance than for colour and body size. There existed plenty of variation in the traits. Standard deviations for general appearance tended to be lower than for the other traits (Table 2). Similar means were found for the general appearance of different colour types. However, larger variation appeared for silver fox type and the cross foxes as compared to those with a gene for platina or arctic marble colour type. Table I. Number (N) and colour type of foxes and scoring of the traits graded in Samples 1 and 2. Sample N Colour type Trait Scores Number of judges I 248 Silver fox Body size I (small)-5 (large) 5 1 248 Silver fox Colour 1 (dark)-5 (light) 5 2 2063 Various General appearance I (poor)-5 (excellent) 1 304 Agric. Sei. Finl. 1 (1992) Table 2. Total number of observations (N), means and stand- ard deviations (SD) for the traits graded in Samples 1 and 2. Trait N Mean SD Body size 3720 3.17 0.76 Colour 3720 3.01 0.83 General appearance 6189 3.43 0.66 Factors affecting the traits In Sample 1 there were statistically significant dif- ferences between judges and scoring times for colour and body size, as well as differences between males and females for colour (Table 3). The judge had the greatest effect on the scores. There was a tendency for graders to perceive body size as getting larger on subsequent gradings. In Sample 2, statistically significant differences between colour types and times of grading were found in scores for general appearance (Table 4). Lower scores for general appearance were given to the golden cross foxes and the silver cross foxes as compared with the other colour types. The scale of grading tended to get stricter on the third time of scoring. Repeatability ofevaluation The repeatabilities of grading scores analysed within animals were 0.30 for colour, 0.40 for body size and 0.57 for general appearance (Table 5). A slightly higher repeatability coefficient was found for colour of females (0.69) as compared with males (0.66), in line with Reiten (1977). In previ- ous studies with live minks and silver foxes, colour has appeared to be easier to judge as compared with the fur quality traits and total evaluation (Jonsson 1970, Reiten 1977, Jezewska and Maciejowski 1982). The fairly low repeatabilities for body size in the present study could be due to the fact that the animals were in cages during the grading. Average repeatabilities after eliminating the effects of the judge on scores were 0.74 for colour and 0.55 for body size (Table 5). Differences Table 3. Effect of the judge, time for scoring and sex of an animal on scores forbody size and colour in Sample 1. Factor N LS-means Body size Colour Judge 1 744 3.11 3.12 2 744 2.91 2.99 3 744 2.91 2.78 4 744 3.48 2.98 5 744 3.45 3.17 F-statistics *** *** Time of scoring 1 1240 3.13 3.05 2 1240 3.17 2.97 3 1240 3.21 3.00 F-statistics * * Sex of animal Males 1860 3.15 3.04 Females 1860 3.20 2.97 F-statistics NS ** *** (P<0.001), * (P<0.05), NS = not significant Table 4. Effect of the colour type of an animal and time for scoring on scores for general appearance in Sample 2. Factor N LS-mean General appearance Colour type Silver fox 5208 3.45 Gold fox 372 3.35 Gold/silver cross fox 207 3.15 Platinum, arctic marble 336 3.43 Platinum/sun glow gold/ cross fox 60 3.50 F-statistics *** Time ofscoring 1 2061 3.44 2 2061 3.44 3 2061 3.25 F-statistics *** ***(P