VI. Intensity of oestrous behaviour and errors in diagnosis of oestrus

Abstract

During the 1970 season, 90 members of the Taranaki Livestock Improvement Association used a simple scoring system to record the intensity of oestrous behaviour observed in each cow at the morning milking before insemination. The maximum score of 5 was for cows that stood when ridden by other cows. Among the 8094 cows scored before their first insemination, only 7.4% scored 3 or less. The conception rate for these cows with lower scores was 52.6% compared with 66.7% for cows receiving scores of 4 or 5, and 65.7% for all cows. Some of the cows which received these higher scores would not have been in oestrus. Six hundred and eighty-seven cows received a score of 4 or 5 before their first insemination but returned to service 20 or 21 days later. The conception rate to second insemination for this group, which would have included very few cows incorrectly diagnosed in oestrus, was 78.9%. The results suggest that most errors in diagnosis occurred because herd owners liberally interpreted behavioural symptoms of oestrus. This tendency may be caused by herd owners striving to obtain a seasonally concentrated breeding programme to produce a concentrated calving pattern.