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Genetical-statistical analysis of traits in the German trotter
Livestock Production Science, 6 (1979)407--412
407
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
GENETICAL-STATISTICAL ANALYSIS OF TRAITS IN THE GERMAN TROTTER
O. KATONA Institut f~r Tierzucht und Tierhygiene der Universit~t M~nchen, Lehrstuhl fur Tierzucht, Munich (Federal Republic o f Germany)
(Accepted 13 December 1978)
ABSTRACT Katona, O., 1979. Genetical-statistical analysis of traits in the German trotter. Livest. Prod. Sci., 6: 407--412. Data on 331 321 racing performances of all competing trotters in the Federal Republic of Germany have been filed since 1973. After adjusting to environmental factors, repeatabilities and heritabilities of the most important traits (racing time, money earnings and perfect gait) have been estimated. The highest degrees for repeatability ( r b e t w e e n y e a r s = 0.55--0.79) and heritability (h ~ = 0.21--0.49) are found in the average racing time per year. Therefore, this trait should be the main selection criterion in a practical breeding programme.
INTRODUCTION T h e e c o n o m i c a l i m p o r t a n c e o f t r o t t i n g s p o r t s a n d b r e e d i n g is c o n t i n u a l l y increasing. P a r i m u t u e l t u r n o v e r a m o u n t e d in 1 9 7 6 to DM 5.5 milliards a n d t o t a l purses w e r e DM 285 millions in Western E u r o p e . Thus, research on possibilities o f s y s t e m a t i c a l i m p r o v e m e n t o f t h e racing ability o f t h e t r o t t e r is indicated. With this goal in m i n d , all racing p e r f o r m a n c e s in t h e F e d e r a l R e p u b l i c o f G e r m a n y h a v e b e e n filed since 1 9 7 3 f o r genetical-statistical analysis. This p a p e r describes t h e m o s t i m p o r t a n t results. MATERIAL AND METHODS F r o m e a c h h o r s e in e a c h race the t i m e is officially r e c o r d e d a n d c o n v e r t e d t o t h e average t i m e p e r 1 0 0 0 m {= racing t i m e ) , unless t h e h o r s e b r e a k s its gait and starts to gallop or p a c e and is going t o be disqualified. In m o s t races t h e r e are five m o n e y prizes a n d a l m o s t all races are issued o n t h e basis o f the a m o u n t o f m o n e y earnings w o n b y t h e horses u p t o this date. Thus, t h e t h r e e m o s t i m p o r t a n t traits o f t h e t r o t t e r are racing t i m e , m o n e y earnings and perf e c t gait. We have d e f i n e d p e r f e c t gait as t h e p e r c e n t a g e o f t h e c o r r e c t racing
408
performances of all racing performances (including disqualifications and other disorderly performances). All data on these racing performances have been filed (Table I). Racing performances are affected by several environmental influences. Thus, it is necessary to find adjusting factors. The systematic influences, for which we could find satisfactory adjusting factors are shown in Table II. All further analyses are carried out with linearly adjusted racing performances. Skew frequency distributions of m o n e y earnings and perfect gait were found. After adjusting the data by the squareroot-transformation for m o n e y earnings and the arcus-tangens-transformation for perfect gait, a normal distribution was found. Heritability estimates were analysed by the intra-classcorrelation (half-sib) method. TABLE I Material Racing year: Competing horses
1973
1974
4 138
1975
1976
1977 ~
Total
4 463
4 728
5 063
5 258
9 117
Racing performances Total Per h o r s e
50 9292 12.35
68 4 9 7 15.3
71 769 15.1
72 196 14.2
67 9 3 0 12.9
331 321 36.6
Racing times Total Per h o r s e
50 9 2 9 12.3
53 794 12.0
56 295 11.9
56 9 1 6 11.2
53 703 10.2
271 637 29.7
1J a n u a r y to N o v e m b e r . ~ Only racing times.
T A B L E II Adjusting possibilities for environmental factors Trait
Racing time
Money earnings
Perfect gait
Age Sex Race course Region of competing Track condition Racing distance Starting method Temperature Racing year
+ + + -+ + + + --
+ + -+ ----+
+ + + -+ -----
+: S a t i s f a c t o r y a d j u s t i n g f a c t o r .
409 RESULTS
Racing time The c o r r e l a t i o n c o e f f i c i e n t s b e t w e e n various t y p e s o f racing times on the one h a n d and t h e average o f all racing times per y e a r or lifetime on the o t h e r are given in Table III. These analyses are carried o u t with d a t a o f horses with at least twelve racing times per y e a r (= average n u m b e r o f racing times per horse and year). T h e repeatabilities increase with the n u m b e r o f racing times included. A n average o f at least three racing times seems t o be a s a t i s f a c t o r y p a r a m e t e r for the trait racing time. TABLE III Estimates of correlation of various racing times with average of all racing times per year, or per lifetime ~ Trait
/2
r
Best racing time of life Best racing time per year
5 005 13 859
0.68 ~ 0.85
Yearly means of racing times 1st 1st + 2 nd i st + 2nd + 3rd 1st + 2 n d + 3 rd + 4 t h l st + 2nd+ 3 rd + 4 t h + 5 t h l s t + 2 n d + 3 rd + 4 th
+
5 th + 6 th
7922 7922 7 922 7922 7 922 7 922
0.78 0.85 0.89 0.93 0.94 0.94
T h e c o r r e l a t i o n s b e t w e e n y e a r l y averages o f racing times are s h o w n in Table IV. The r e p e a t a b i l i t y o f the average racing time per y e a r exceeds the r e p e a t a b i l i t y o f t h e best racing time per y e a r in each age g r o u p and over all age groups. R e p e a t a b i l i t y increases with age f o r b o t h traits. Heritability estimates are also s h o w n in Table IV. T h e heritability c o e f f i c i e n t s are r a t h e r high as c o m p a r e d t o t h e repeatabilities, w h i c h are indicating t h e u p p e r b o r d e r o f heritability. Heritabilities f o r t h e average racing t i m e per y e a r e x c e e d the c o e f f i c i e n t s for the best racing t i m e per y e a r in each age g r o u p t o a c o n s i d e r a b l e degree. Considering estimates over all age groups, heritability o f the average racing time per y e a r is 50% higher t h a n t h e heritability o f t h e best racing t i m e (h 2 = 0.20, sh2 = 0.03). The highest h e r i t a b i l i t y estimate is f o u n d in the average racing t i m e o f the t h r e e y e a r old t r o t t e r .
410
TABLEIV R e p e a t a b i l i t i e s b e t w e e n yearly averages and heritabilities for various t y p e s o f racing t i m e s Age g r o u p
2--33--44--55--66--7-
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age groups (2--12year-old)
Best racing t i m e per year
Average racing time per year j
r
h2
Sh2
r
h2
Sh2
0.44 0.57 0.64 0.64 0.66 --
0.15 0.31 0.20 0.16 0.15 0.14
0.07 0.06 0.04 0.04 0.04 0.05
0.55 0.68 0.76 0.76 0.79 --
0.26 0.49 0.38 0.30 0.26 0.21
0.10 0.09 0.08 0.06 0.06 0.06
0.61
--
--
0.75
0.30
0.03
r: P < 0.001 for each coefficient. ' C o m p u t e d w i t h data o n horses w i t h at least f o u r racing t i m e s per year (2-year-old t r o t t e r s at least t w o racing t i m e s per year).
Money earnings As m o n e y earnings may be affected b y the number of racing performances, repeatability and heritability estimates were carried o u t both for m o n e y earnings per racing performance and year and total m o n e y earnings per year. The results are given in Table V. Repeatabilities and heritabilities of m o n e y earnings per racing performance exceed the referring coefficients for total earnings in each case. The heritability estimate over all age groups for m o n e y TABLE V E s t i m a t e s o f r e p e a t a b i l i t y b e t w e e n years and heritability e s t i m a t e s for m o n e y earnings per year Age g r o u p
2--3 3--4 4--5 5--6 6--7
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age g r o u p s (2--12year-old)
Total m o n e y earnings
M o n e y earnings per racing p e r f o r m a n c e
r
h2
Sh~
r
h2
Sh2
0.38 0.44 0.49 0.49 0.50
0.26 0.15 0.18 0.09 0.08 0.07
0.12 0.06 0.06 0.06 0.08 0.09
0.41 0.55 0.59 0.61 0.58 --
0.34 0.13 0.11 0.11 0.13 --0.08
0.13 0.06 0.05 0.07 0.09 0.07
0.45
0.11
0.02
0.58
0.25
0.04
r: P < 0.001 for each c o e f f i c i e n t .
411
earnings per racing performance is more than twice as high as the corresponding estimate for total m o n e y earnings per year but is lower than the heritability of the average racing time per year over all age groups.
Perfect gait The correlation coefficients between perfect gait analysed on the basis of a certain number of consecutive racing performances on the one hand and on the basis of all racing performances per year on the other, are given in Table VI. Only horses having at least 20 racing performances per year (= average number of racing performances per year and horse excluding the 2-year-old trotters) are included in these analyses. The correlation coefficients for the percentage of perfect gait between racing years are shown in Table VI. The repeatabilities are increasing with age, however h 2- estimates are very low at older age. The standard deviations of heritability estimates are rather high. Thus, it is doubtful if it is worthwhile to consider this trait in a breeding programme. DISCUSSION
The heritabilities found are in rather good agreement with those found by Minkema (1975), RSnningen {1975) and Katona and Osterkorn (1977). The highest heritability estimates are found for the average racing time per year. Although rather different numbers of racing performances per year are required for analysing breeding values for the three discussed traits, the averT A B L E VI E s t i m a t e s o f r e p e a t a b i l i t y w i t h i n or b e t w e e n years ~ and h e r i t a b i l i t y ~ for p e r f e c t gait Number of registered racing performances
rwithin years
1 5 10 15 20
0.20** 0.20** 0.36*** 0.58*** 0.76***
Age g r o u p
rbetween years
h:
Sh2
2--33--44--55--66--7-
0.16" 0.17" 0.23** 0.24*** 0.27*** --
0.12 0.07 0.16 0.02 0.02 0.00
0.11 0.06 0.06 0.05 0.06 0.06
0.25***
0.17
0.04
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age groups (2--12year-old)
*P < 0.05; * * P < 0.01; * * * P < 0.001. C o m p u t e d w i t h data o n horses w i t h at least t h e average n u m b e r o f racing p e r f o r m a n c e s per year.
412 age r a c i n g t i m e p e r y e a r s e e m s t o p r o m i s e t h e h i g h e s t s e l e c t i o n r e s p o n s e . T h u s , t h i s t r a i t s h o u l d b e e s t a b l i s h e d as t h e m a i n s e l e c t i o n c r i t e r i o n i n a p r a c t i c a l breeding programme. ACKNOWLEDGEMENT T h e a u t h o r is i n d e b t e d t o t h e H a u p t v e r b a n d fiSr T r a b e r - Z u c h t u n d - R e n n e n e.V. ( H V T ) f o r t h e g e n e r o u s s u b s i d y .
REFERENCES Katona, 6. and Osterkorn, K., 1977. Genetisch-statistische Auswertung des Leistungsmerkmals Rennzeit in der deutschen Traberpopulation. Ziichtungskunde, 49: 185--192. Minkema, D., 1975. Genetic studies on performance in Dutch trotters. Proceedings of the International Symposium on Genetics and Horse-Breeding, Dublin, pp. 24--32. RSnningen, K., 1975. Genetic and environmental factors for traits in the North-Swedish trotter. Z. Tierz. Ziichtungsbiol., 92: 164--175. RESUMI~ Katona, C)., 1979. Analyse g~n~tique des performances des chevaux trotteurs allemands. Livest. Prod. Sci., 6 : 4 0 7 - - 4 1 2 (en anglais). Les r~sultats (331 321 )des courses de trotteurs ont ~t~ enregistr~s en totalit~ en RFA depuis 1973. Apr~s correction des influences de l'environnement, on a estim~ la r~p~tabilit~ et l'h~ritabilit~ des caract~res les plus importants (temps kilom~triques, gains, allures). Les valeurs les plus ~lev~es de la r~p~tabilit~ (rentre armies = 0.55--0.79) et de l'h~ritabilit~ (h 2 = 0.21--0.49) ont ~t~ trouv~es pour le temps kilom~trique moyen par annie. Cette performance devrait donc ~tre le principal crit~re de s~lection. KURZFASSUNG Katona, ()., 1979. Genetisch-statistische Auswertung yon Leistungsmerkmalen beim deutschen Traber. Livest. Prod. Sci., 6 : 4 0 7 - - 4 1 2 (in Englisch). Die Renndaten der 331 321 Starts aller Traber in der Bundesrepublik Deutschland wurden seit 1973 erfasst. Nach der Korrektur auf Umwelteinfliisse wurde die Wiederholbarkeit und Heritabilit~t der wichtigsten Leistungsmerkmale (Rennzeit, Gewinnsumme, Trabsicherheit) gesch~itzt. Die hSchsten Werte ftir die Wiederholbarkeit (rzwischen Jahren = 0.55--0.79 ) und Heritabilit~it (h 2 = 0.21--0.49 ) wurden bei der Jahresdurchschnittsrennzeit gefunden. Dieses Merkmal sollte demnach als entscheidendes Selektionskriterium in einem praktischen Zuchtprogramm dienen.
407
© Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
GENETICAL-STATISTICAL ANALYSIS OF TRAITS IN THE GERMAN TROTTER
O. KATONA Institut f~r Tierzucht und Tierhygiene der Universit~t M~nchen, Lehrstuhl fur Tierzucht, Munich (Federal Republic o f Germany)
(Accepted 13 December 1978)
ABSTRACT Katona, O., 1979. Genetical-statistical analysis of traits in the German trotter. Livest. Prod. Sci., 6: 407--412. Data on 331 321 racing performances of all competing trotters in the Federal Republic of Germany have been filed since 1973. After adjusting to environmental factors, repeatabilities and heritabilities of the most important traits (racing time, money earnings and perfect gait) have been estimated. The highest degrees for repeatability ( r b e t w e e n y e a r s = 0.55--0.79) and heritability (h ~ = 0.21--0.49) are found in the average racing time per year. Therefore, this trait should be the main selection criterion in a practical breeding programme.
INTRODUCTION T h e e c o n o m i c a l i m p o r t a n c e o f t r o t t i n g s p o r t s a n d b r e e d i n g is c o n t i n u a l l y increasing. P a r i m u t u e l t u r n o v e r a m o u n t e d in 1 9 7 6 to DM 5.5 milliards a n d t o t a l purses w e r e DM 285 millions in Western E u r o p e . Thus, research on possibilities o f s y s t e m a t i c a l i m p r o v e m e n t o f t h e racing ability o f t h e t r o t t e r is indicated. With this goal in m i n d , all racing p e r f o r m a n c e s in t h e F e d e r a l R e p u b l i c o f G e r m a n y h a v e b e e n filed since 1 9 7 3 f o r genetical-statistical analysis. This p a p e r describes t h e m o s t i m p o r t a n t results. MATERIAL AND METHODS F r o m e a c h h o r s e in e a c h race the t i m e is officially r e c o r d e d a n d c o n v e r t e d t o t h e average t i m e p e r 1 0 0 0 m {= racing t i m e ) , unless t h e h o r s e b r e a k s its gait and starts to gallop or p a c e and is going t o be disqualified. In m o s t races t h e r e are five m o n e y prizes a n d a l m o s t all races are issued o n t h e basis o f the a m o u n t o f m o n e y earnings w o n b y t h e horses u p t o this date. Thus, t h e t h r e e m o s t i m p o r t a n t traits o f t h e t r o t t e r are racing t i m e , m o n e y earnings and perf e c t gait. We have d e f i n e d p e r f e c t gait as t h e p e r c e n t a g e o f t h e c o r r e c t racing
408
performances of all racing performances (including disqualifications and other disorderly performances). All data on these racing performances have been filed (Table I). Racing performances are affected by several environmental influences. Thus, it is necessary to find adjusting factors. The systematic influences, for which we could find satisfactory adjusting factors are shown in Table II. All further analyses are carried out with linearly adjusted racing performances. Skew frequency distributions of m o n e y earnings and perfect gait were found. After adjusting the data by the squareroot-transformation for m o n e y earnings and the arcus-tangens-transformation for perfect gait, a normal distribution was found. Heritability estimates were analysed by the intra-classcorrelation (half-sib) method. TABLE I Material Racing year: Competing horses
1973
1974
4 138
1975
1976
1977 ~
Total
4 463
4 728
5 063
5 258
9 117
Racing performances Total Per h o r s e
50 9292 12.35
68 4 9 7 15.3
71 769 15.1
72 196 14.2
67 9 3 0 12.9
331 321 36.6
Racing times Total Per h o r s e
50 9 2 9 12.3
53 794 12.0
56 295 11.9
56 9 1 6 11.2
53 703 10.2
271 637 29.7
1J a n u a r y to N o v e m b e r . ~ Only racing times.
T A B L E II Adjusting possibilities for environmental factors Trait
Racing time
Money earnings
Perfect gait
Age Sex Race course Region of competing Track condition Racing distance Starting method Temperature Racing year
+ + + -+ + + + --
+ + -+ ----+
+ + + -+ -----
+: S a t i s f a c t o r y a d j u s t i n g f a c t o r .
409 RESULTS
Racing time The c o r r e l a t i o n c o e f f i c i e n t s b e t w e e n various t y p e s o f racing times on the one h a n d and t h e average o f all racing times per y e a r or lifetime on the o t h e r are given in Table III. These analyses are carried o u t with d a t a o f horses with at least twelve racing times per y e a r (= average n u m b e r o f racing times per horse and year). T h e repeatabilities increase with the n u m b e r o f racing times included. A n average o f at least three racing times seems t o be a s a t i s f a c t o r y p a r a m e t e r for the trait racing time. TABLE III Estimates of correlation of various racing times with average of all racing times per year, or per lifetime ~ Trait
/2
r
Best racing time of life Best racing time per year
5 005 13 859
0.68 ~ 0.85
Yearly means of racing times 1st 1st + 2 nd i st + 2nd + 3rd 1st + 2 n d + 3 rd + 4 t h l st + 2nd+ 3 rd + 4 t h + 5 t h l s t + 2 n d + 3 rd + 4 th
+
5 th + 6 th
7922 7922 7 922 7922 7 922 7 922
0.78 0.85 0.89 0.93 0.94 0.94
T h e c o r r e l a t i o n s b e t w e e n y e a r l y averages o f racing times are s h o w n in Table IV. The r e p e a t a b i l i t y o f the average racing time per y e a r exceeds the r e p e a t a b i l i t y o f t h e best racing time per y e a r in each age g r o u p and over all age groups. R e p e a t a b i l i t y increases with age f o r b o t h traits. Heritability estimates are also s h o w n in Table IV. T h e heritability c o e f f i c i e n t s are r a t h e r high as c o m p a r e d t o t h e repeatabilities, w h i c h are indicating t h e u p p e r b o r d e r o f heritability. Heritabilities f o r t h e average racing t i m e per y e a r e x c e e d the c o e f f i c i e n t s for the best racing t i m e per y e a r in each age g r o u p t o a c o n s i d e r a b l e degree. Considering estimates over all age groups, heritability o f the average racing time per y e a r is 50% higher t h a n t h e heritability o f t h e best racing t i m e (h 2 = 0.20, sh2 = 0.03). The highest h e r i t a b i l i t y estimate is f o u n d in the average racing t i m e o f the t h r e e y e a r old t r o t t e r .
410
TABLEIV R e p e a t a b i l i t i e s b e t w e e n yearly averages and heritabilities for various t y p e s o f racing t i m e s Age g r o u p
2--33--44--55--66--7-
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age groups (2--12year-old)
Best racing t i m e per year
Average racing time per year j
r
h2
Sh2
r
h2
Sh2
0.44 0.57 0.64 0.64 0.66 --
0.15 0.31 0.20 0.16 0.15 0.14
0.07 0.06 0.04 0.04 0.04 0.05
0.55 0.68 0.76 0.76 0.79 --
0.26 0.49 0.38 0.30 0.26 0.21
0.10 0.09 0.08 0.06 0.06 0.06
0.61
--
--
0.75
0.30
0.03
r: P < 0.001 for each coefficient. ' C o m p u t e d w i t h data o n horses w i t h at least f o u r racing t i m e s per year (2-year-old t r o t t e r s at least t w o racing t i m e s per year).
Money earnings As m o n e y earnings may be affected b y the number of racing performances, repeatability and heritability estimates were carried o u t both for m o n e y earnings per racing performance and year and total m o n e y earnings per year. The results are given in Table V. Repeatabilities and heritabilities of m o n e y earnings per racing performance exceed the referring coefficients for total earnings in each case. The heritability estimate over all age groups for m o n e y TABLE V E s t i m a t e s o f r e p e a t a b i l i t y b e t w e e n years and heritability e s t i m a t e s for m o n e y earnings per year Age g r o u p
2--3 3--4 4--5 5--6 6--7
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age g r o u p s (2--12year-old)
Total m o n e y earnings
M o n e y earnings per racing p e r f o r m a n c e
r
h2
Sh~
r
h2
Sh2
0.38 0.44 0.49 0.49 0.50
0.26 0.15 0.18 0.09 0.08 0.07
0.12 0.06 0.06 0.06 0.08 0.09
0.41 0.55 0.59 0.61 0.58 --
0.34 0.13 0.11 0.11 0.13 --0.08
0.13 0.06 0.05 0.07 0.09 0.07
0.45
0.11
0.02
0.58
0.25
0.04
r: P < 0.001 for each c o e f f i c i e n t .
411
earnings per racing performance is more than twice as high as the corresponding estimate for total m o n e y earnings per year but is lower than the heritability of the average racing time per year over all age groups.
Perfect gait The correlation coefficients between perfect gait analysed on the basis of a certain number of consecutive racing performances on the one hand and on the basis of all racing performances per year on the other, are given in Table VI. Only horses having at least 20 racing performances per year (= average number of racing performances per year and horse excluding the 2-year-old trotters) are included in these analyses. The correlation coefficients for the percentage of perfect gait between racing years are shown in Table VI. The repeatabilities are increasing with age, however h 2- estimates are very low at older age. The standard deviations of heritability estimates are rather high. Thus, it is doubtful if it is worthwhile to consider this trait in a breeding programme. DISCUSSION
The heritabilities found are in rather good agreement with those found by Minkema (1975), RSnningen {1975) and Katona and Osterkorn (1977). The highest heritability estimates are found for the average racing time per year. Although rather different numbers of racing performances per year are required for analysing breeding values for the three discussed traits, the averT A B L E VI E s t i m a t e s o f r e p e a t a b i l i t y w i t h i n or b e t w e e n years ~ and h e r i t a b i l i t y ~ for p e r f e c t gait Number of registered racing performances
rwithin years
1 5 10 15 20
0.20** 0.20** 0.36*** 0.58*** 0.76***
Age g r o u p
rbetween years
h:
Sh2
2--33--44--55--66--7-
0.16" 0.17" 0.23** 0.24*** 0.27*** --
0.12 0.07 0.16 0.02 0.02 0.00
0.11 0.06 0.06 0.05 0.06 0.06
0.25***
0.17
0.04
or or or or or
2-year-old 3-year-old 4-year-old 5-year-old 6-year-old 7-year-old All age groups (2--12year-old)
*P < 0.05; * * P < 0.01; * * * P < 0.001. C o m p u t e d w i t h data o n horses w i t h at least t h e average n u m b e r o f racing p e r f o r m a n c e s per year.
412 age r a c i n g t i m e p e r y e a r s e e m s t o p r o m i s e t h e h i g h e s t s e l e c t i o n r e s p o n s e . T h u s , t h i s t r a i t s h o u l d b e e s t a b l i s h e d as t h e m a i n s e l e c t i o n c r i t e r i o n i n a p r a c t i c a l breeding programme. ACKNOWLEDGEMENT T h e a u t h o r is i n d e b t e d t o t h e H a u p t v e r b a n d fiSr T r a b e r - Z u c h t u n d - R e n n e n e.V. ( H V T ) f o r t h e g e n e r o u s s u b s i d y .
REFERENCES Katona, 6. and Osterkorn, K., 1977. Genetisch-statistische Auswertung des Leistungsmerkmals Rennzeit in der deutschen Traberpopulation. Ziichtungskunde, 49: 185--192. Minkema, D., 1975. Genetic studies on performance in Dutch trotters. Proceedings of the International Symposium on Genetics and Horse-Breeding, Dublin, pp. 24--32. RSnningen, K., 1975. Genetic and environmental factors for traits in the North-Swedish trotter. Z. Tierz. Ziichtungsbiol., 92: 164--175. RESUMI~ Katona, C)., 1979. Analyse g~n~tique des performances des chevaux trotteurs allemands. Livest. Prod. Sci., 6 : 4 0 7 - - 4 1 2 (en anglais). Les r~sultats (331 321 )des courses de trotteurs ont ~t~ enregistr~s en totalit~ en RFA depuis 1973. Apr~s correction des influences de l'environnement, on a estim~ la r~p~tabilit~ et l'h~ritabilit~ des caract~res les plus importants (temps kilom~triques, gains, allures). Les valeurs les plus ~lev~es de la r~p~tabilit~ (rentre armies = 0.55--0.79) et de l'h~ritabilit~ (h 2 = 0.21--0.49) ont ~t~ trouv~es pour le temps kilom~trique moyen par annie. Cette performance devrait donc ~tre le principal crit~re de s~lection. KURZFASSUNG Katona, ()., 1979. Genetisch-statistische Auswertung yon Leistungsmerkmalen beim deutschen Traber. Livest. Prod. Sci., 6 : 4 0 7 - - 4 1 2 (in Englisch). Die Renndaten der 331 321 Starts aller Traber in der Bundesrepublik Deutschland wurden seit 1973 erfasst. Nach der Korrektur auf Umwelteinfliisse wurde die Wiederholbarkeit und Heritabilit~t der wichtigsten Leistungsmerkmale (Rennzeit, Gewinnsumme, Trabsicherheit) gesch~itzt. Die hSchsten Werte ftir die Wiederholbarkeit (rzwischen Jahren = 0.55--0.79 ) und Heritabilit~it (h 2 = 0.21--0.49 ) wurden bei der Jahresdurchschnittsrennzeit gefunden. Dieses Merkmal sollte demnach als entscheidendes Selektionskriterium in einem praktischen Zuchtprogramm dienen.