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Culling Rates of United States and Canadian Artificial Insemination Dairy Sires for Type and Production of Daughters1
C u l l i n g Rates o f U n i t e d States a n d C a n a d i a n A r t i f i c i a l I n s e m i n a t i o n D a i r y Sires f o r T y p e a n d P r o d u c t i o n o f D a u g h t e r s I J. L. KRATZ 2, C. J. WILCOX 3, F. G. MARTIN 4, and R. B. BECKER 3 Dairy Science3 and Statistics4 Departments Institute of Food and Agricultural Sciences University of Florida, Gainesville 32611 ABSTRACT
Reasons for disposal of 9883 United States and 692 Canadian artificial insemination sires were evaluated to compare frequencies of culling for undesirable type (2.3 and 7.9%) of offspring and for low milk yield (15.3 and 16.3%). Frequencies by country-reason were heterogeneous. Selection pressure apparently has been greater on Canadian artificial insemination sires for desirable type of daughters than on United States sires. INTRODUCTION
Reasons for disposal of dairy animals provide crude estimates of selection pressure for important traits as well as aiding in management decisions by permitting estimates of economic loss due to various diseases and infirmities. Roman et al. (3) tabulated frequencies of reasons for disposal of 8887 US and Canadian artificial insemination (AI) sires which left service during 1939 to 1964. Low milk yield of daughters accounted for 9.7% of total sire disposals; an additional 2.5% left because of undesirable type of daughters. Variation among breeds in these two causes was small except for markedly lower frequencies for both with Milking Shorthorns. Kratz et al. (2) subsequently evaluated these and additional data, totaling 11,704 disposals from 1939 to 1974. They reported distinct increases in disposals for low milk yield from 7.6% for 1939 to 1949, to 11.8% for 1950 to 1964, to 30.9% for 1965 to 1974. There is considerable evidence on genetic interrelationships of dairy type and production.
Received June 25, 1975. 1Florida Agricultural Experiment Station Journal Series No. 5966. 2Lakeshore Technical Institute, Cleveland, WI 53015.
White (5) suggested that the relative emphasis on milk yield and type in a selection program should be about 3:1. Objectives of the present investigation were to compare culling rates of AI dairy sires in US and Canada for undesirable type and low milk yield of daughters. MATERIALS AND METHODS
Vital statistics of sires were provided by cooperating AI studs and breed registry associations. Data included information on identification, dates of birth, and first and last AI collection, reason(s) for disposal, and ultimate fate. Data from 1939 to 1974 were available for US sires but only from 1956 to 1974 for Canadian sires. Though time trends in causes of loss were real (2, 3), they were not considered in statistical tests of independence of country and reason. The major statistical technique was Chi-square test of independence. RESULTS AND DISCUSSION
Data from four dairy breeds were represented and included 10,575 sires (Table 1). To date 326 different reasons have been listed as causes of loss. Losses due to cuUing for undesirable type of daughters were 2.3% for US and 7.9% for Canadian sires; losses for low milk yield were 15.3 and 16.3%. Analysis of all data in Table 1 for independence (no interaction) of breed-country-reason resulted in X2 = 11.58 (P<.10). Interaction arose primarily from lack of a significant difference in frequencies of reasons for the two countries for Guernseys. If breeds were ignored, country-reason lack of independence was apparent (X2 = 82.59, P<.01). There being little difference in culling rates for low milk yield between the two countries, the analysis then was restricted to the narrower question of differences due to poor type by pooling low milk yield with all other reasons. Chi-squares for the two-way and three-way interactions 767
768
KRATZ ET AL. were 80.70 (P<.01) and 4.12 (P<.25). Statistical analysis s h o w e d t h a t a higher f r e q u e n c y of culling of dairy sires for undesirable t y p e of daughters had o c c u r r e d in Canadian studs. Frequencies for each breed were higher (range of 1.5 to 2.5% for US, and 2.5 to 8.8% for Canada). Such differences m a y reflect true differences in selection pressure for t y p e and overall goals of breeders in the two countries. R e c e n t surveys of reasons for culling of registered females in Canada (1), and registered and grade females in N e w Y o r k (4), do not show appreciable or clearly defined differences in culling rates for undesirable type, however. ACKNOWLEDGMENTS
Support and c o o p e r a t i o n of the National Association of Animal Breeders, US and Canadian AI studs, and breed registry associations are gratefully acknowledged. REFERENCES Ox
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Journal of Dairy Science Vol. 59, No. 4
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1 Burnside, E. B., S. B. Kowalchuk, D. B. Lambroughton, and N. M. Macleod. 1970. Canadian dairy cow disposals. I. Differences between breeds, lactation numbers and seasons. Can. J. Anim. Sci. 51:75. 2 Kratz, J. L., C. J. Wilcox, F. G. Martin, and R. B. Becker. 1975~ Dairy artificial insemination sire vital statistics. J. Dairy Sci. 58:141. (Abstr.) 3 Roman, J., C. J. Wilcox, R. B. Becker, and M. Koger. 1969. Tenure and reasons for disposal of artificial insemination dairy sires. J. Dairy Sci. 52:1063. 4 Van Vleck, L. D., and H. D. Norman. 1972. Association of type traits with reasons for disposal. J. Dairy Sci. 55:1698. 5 White, J. M. 1974. Generic parameters of conformational and managemental traits. J. Dairy Sci. 57:1267.
Reasons for disposal of 9883 United States and 692 Canadian artificial insemination sires were evaluated to compare frequencies of culling for undesirable type (2.3 and 7.9%) of offspring and for low milk yield (15.3 and 16.3%). Frequencies by country-reason were heterogeneous. Selection pressure apparently has been greater on Canadian artificial insemination sires for desirable type of daughters than on United States sires. INTRODUCTION
Reasons for disposal of dairy animals provide crude estimates of selection pressure for important traits as well as aiding in management decisions by permitting estimates of economic loss due to various diseases and infirmities. Roman et al. (3) tabulated frequencies of reasons for disposal of 8887 US and Canadian artificial insemination (AI) sires which left service during 1939 to 1964. Low milk yield of daughters accounted for 9.7% of total sire disposals; an additional 2.5% left because of undesirable type of daughters. Variation among breeds in these two causes was small except for markedly lower frequencies for both with Milking Shorthorns. Kratz et al. (2) subsequently evaluated these and additional data, totaling 11,704 disposals from 1939 to 1974. They reported distinct increases in disposals for low milk yield from 7.6% for 1939 to 1949, to 11.8% for 1950 to 1964, to 30.9% for 1965 to 1974. There is considerable evidence on genetic interrelationships of dairy type and production.
Received June 25, 1975. 1Florida Agricultural Experiment Station Journal Series No. 5966. 2Lakeshore Technical Institute, Cleveland, WI 53015.
White (5) suggested that the relative emphasis on milk yield and type in a selection program should be about 3:1. Objectives of the present investigation were to compare culling rates of AI dairy sires in US and Canada for undesirable type and low milk yield of daughters. MATERIALS AND METHODS
Vital statistics of sires were provided by cooperating AI studs and breed registry associations. Data included information on identification, dates of birth, and first and last AI collection, reason(s) for disposal, and ultimate fate. Data from 1939 to 1974 were available for US sires but only from 1956 to 1974 for Canadian sires. Though time trends in causes of loss were real (2, 3), they were not considered in statistical tests of independence of country and reason. The major statistical technique was Chi-square test of independence. RESULTS AND DISCUSSION
Data from four dairy breeds were represented and included 10,575 sires (Table 1). To date 326 different reasons have been listed as causes of loss. Losses due to cuUing for undesirable type of daughters were 2.3% for US and 7.9% for Canadian sires; losses for low milk yield were 15.3 and 16.3%. Analysis of all data in Table 1 for independence (no interaction) of breed-country-reason resulted in X2 = 11.58 (P<.10). Interaction arose primarily from lack of a significant difference in frequencies of reasons for the two countries for Guernseys. If breeds were ignored, country-reason lack of independence was apparent (X2 = 82.59, P<.01). There being little difference in culling rates for low milk yield between the two countries, the analysis then was restricted to the narrower question of differences due to poor type by pooling low milk yield with all other reasons. Chi-squares for the two-way and three-way interactions 767
768
KRATZ ET AL. were 80.70 (P<.01) and 4.12 (P<.25). Statistical analysis s h o w e d t h a t a higher f r e q u e n c y of culling of dairy sires for undesirable t y p e of daughters had o c c u r r e d in Canadian studs. Frequencies for each breed were higher (range of 1.5 to 2.5% for US, and 2.5 to 8.8% for Canada). Such differences m a y reflect true differences in selection pressure for t y p e and overall goals of breeders in the two countries. R e c e n t surveys of reasons for culling of registered females in Canada (1), and registered and grade females in N e w Y o r k (4), do not show appreciable or clearly defined differences in culling rates for undesirable type, however. ACKNOWLEDGMENTS
Support and c o o p e r a t i o n of the National Association of Animal Breeders, US and Canadian AI studs, and breed registry associations are gratefully acknowledged. REFERENCES Ox
r-~
t'q
e,
E ~
~
e~
Journal of Dairy Science Vol. 59, No. 4
=
1 Burnside, E. B., S. B. Kowalchuk, D. B. Lambroughton, and N. M. Macleod. 1970. Canadian dairy cow disposals. I. Differences between breeds, lactation numbers and seasons. Can. J. Anim. Sci. 51:75. 2 Kratz, J. L., C. J. Wilcox, F. G. Martin, and R. B. Becker. 1975~ Dairy artificial insemination sire vital statistics. J. Dairy Sci. 58:141. (Abstr.) 3 Roman, J., C. J. Wilcox, R. B. Becker, and M. Koger. 1969. Tenure and reasons for disposal of artificial insemination dairy sires. J. Dairy Sci. 52:1063. 4 Van Vleck, L. D., and H. D. Norman. 1972. Association of type traits with reasons for disposal. J. Dairy Sci. 55:1698. 5 White, J. M. 1974. Generic parameters of conformational and managemental traits. J. Dairy Sci. 57:1267.