J. Anim Sci.
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J. Anim Sci. 1976. 42:434-438.
© 1976 American Society of Animal Science
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Effect of Season and Year of Measurement on Testicular Growth and Consistency of Holstein Bulls1

G. H. Coulter2 and R. H. Foote

Cornell University3, Ithaca, New York 14853

Abstract

Seasonal effects were found for 635 testicular size and consistency measurements taken in early spring and 644 in late summer on Holstein bulls 6 to 180 months of age. Regression equations were calculated for each season to best describe the data. The equation for early spring measurements of scrotal circumference was Y = –9.54 + 53.93 log X – 13.63 (log X)2 where Y is scrotal circumference in centimeters and X is bull age in months. The corresponding equation for late summer was Y = .54 + 39.86 log X – 9.29 (log X)2.

Tonometry measurements made in the early spring were described by the equation Y = 25.10 – 14.63 log X + 4.24 (log X)2, where Y is the average deflection in millimeters of weak and strong spring tonometers and X is bull age in months. The corresponding equation for late summer was Y = 22.53 – 10.33 log X + 2.81 (log X)2.

Bulls 6 to 48 months of age were analyzed more extensively. An effect of season and/or artificial insemination center on both testicular characteristics were found. Also, there was a significant year effect. Regression equations fitted to data for each of the 5 years were more accurate (P<.01) in describing the distribution of data than was a common equation for pooled data.

These results emphasized that selection of bulls for these traits can best be made within the same age group, bull stud and year-season. As more data become available correction factors could be developed and indexes computed to make more general comparisons possible.

Footnotes

1 The authors gratefully acknowledge Dr. L. L. Larson, Dr. J. Hahn, Dr. G. B. Anderson, Dr. P. J. H. Ball, Mr. R. Cole, Mr. M. Simkin, Mrs. Harriette Polan and Ms. J. Schiavo for their assistance, and the National Association of Animal Breeders, Eastern A. I. Coop., Inc., American Breeders Service, Inc. the North Central Biological Research Committee and its member studs for their cooperation and financial assistance.

2 Present address: Agriculture Canada Research Station, Lethbridge, Alberta, Canada T1J 4B1.

3 Department of Animal Science.






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Copyright © 1976 by the American Society of Animal Science.