|Edwards, Jana - STUDENT, VPI|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2001
Publication Date: N/A
Interpretive Summary: Obtaining high data accuracy is dependent upon prudent record keeping. Correct birth dates are essential because they are carried with animals throughout their lives and impact genetic evaluations for yield and fitness traits. A study of information from Dairy Herd Improvement (DHI) were compared to pedigree records reported earlier by DHI and the breed associations. Frequency of birth dates recorded for dairy animals since 1987 were compared to frequency of recorded calving dates. Of particular interest was the percentage of birth dates on each day of the month. Subsets examined were year, herd size, and registry status. Since birth dates are to a large extent a random event, each day within any month should have an equal percentage of births. However, this was not the case. Birth dates recorded on d 1, d 2, d 10, d 15, and d 20 had higher percentages; sometimes double the average percentage on the remaining days. The frequency of birth dates on the first day of the month was highest. Some of this increase is apparently due to estimated birth dates that are not being coded as such. The first day of a show class for registered cows (cows enrolled in a breed association herd book) had a higher recorded frequency of birth dates than any other days. Matching birth dates with dams' calving date on individual animals confirmed these results. Calving dates appear to be more accurate than recorded birth dates for both registered and grade cows. A general knowledge of the accuracy of birth dates could be helpful to breed association in managing their recording programs, and could contribute to a revision at AIPL in weighting information received from the industry.
Technical Abstract: Frequency of births that were recorded on specific days of the month were documented by birth year, herd size, and registry status for US dairy cattle that had been born since 1987 and compared with frequency of calvings that were reported for those dates. Because distribution of birth dates throughout the year largely is random, percentages of births on individual dates were expected to be equal (3.3% for d 1 through 28, 3.2% for d 29, 3.0% for d 30, and 1.9% for d 31). However, the percentages of birth dates recorded on d 1, 2, 10, 15, and 20 were higher than the expected percentages and sometimes were twice the mean percentages for remaining days. Frequency of birth dates that were recorded on d 1 was highest (3.9%) of all days of the month. Some of this increase apparently was the result of estimated birth dates that were not coded as such. The highest frequencies for birth dates on d 1 (5.9 to 7.4%) were found for registered cows during months that initiated dairy show class groups (March, June, September, and December). Comparison of birth date with calving date of the dam confirmed those results. Calving dates appeared to be more accurate than recorded birth dates for both registered and grade cows.