Japanese Journal of Veterinary Research;Volume 29, Number 3-4

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STATISTICAL CONSIDERATIONS CONCERNING THE DISPOSAL OF DAIRY BULLS USED FOR ARTIFICIAL INSEMINATION IN HOKKAIDO FROM 1958 to 1979

ISHIKAWA, Tsune;KANAGAWA, Hiroshi

Permalink : http://hdl.handle.net/2115/2235
JaLCDOI : 10.14943/jjvr.29.3-4.53

Abstract

A survey was conducted on Holstein bulls kept for service at artificial insemination centers in Hokkaido from 1958-1979. Analysis was made of the reasons for discharge of 312 bulls considered to be no longer serviceable. The following results were obtained : 1) It was revealed that the main reason for disposal was not sexual trouble or seminal vesiculitis but impotentia coeundi followed by undesirable factors, which were the reasons given for more than 60% of the discharged bulls. It was shown that 10-15% of the bulls used at the beginning of the year were slaughtered for some reason or other within that year. 2) The lowest age for semen collection was 10 months and the highest age was 12 years and 8 months. Analysis of the bulls entered for service under 24 months revealed that one half of the bulls were a full 17 months of age and that 90% were entered before 20 months of age. 3) It was shown that approximately one half of the total number of bulls were used for service for 6 years, and those used for 8 years accounted for a quarter of the number. The longest period of service was 16 years. 4) The maximum number of years of survival was 16 years and 10 months. One half of the bulls used for service were discharged at 7-8 years while three quarters of them were discharged until 10 years old. 5) A comparison was made between the bulls employed for service during the period 1958-1965 and 1966-1979,and it was shown that the latter period group entered service later than the former period group. The reason for the delay remains unknown.

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