Factors affecting calving interval of Hereford and Santa Gertrudis cows at the Jornada Experimental Range

TitleFactors affecting calving interval of Hereford and Santa Gertrudis cows at the Jornada Experimental Range
Publication TypeThesis
Year of Publication1973
AuthorsBerhe A
Number of Pages64
Date Published1973
UniversityNew Mexico State University
CityLas Cruces, New Mexico
Thesis TypeM.S. Thesispp
Call Number00469
Keywordscattle, breeding, cattle, calving interval, dissertation, dissertations, theses, thesis
AbstractData collected on Hereford and Santa Gertrudis cows from 1959 through 1972, at the Jornada Experimental Range, were used for calving interval analyses. Different analyses with specific restrictions on ages and years were used to determine the effects of different factors. Analyses were made on all calving intervals and on consecutive calving intervals. The effect of age at first calving, analyzed separately, was found non-significant. The effects of age at calving, year and sex were analyzed within each breed. Age at calving had a significant effect on both breeds a while year effect was significant in the case of Herefords and not in the case of Santa Gertrudis. Sex did not have a significant effect on either breed. Breed, age and year effects were determined by combining the two breeds. Ages three through seven-year-olds and years 63 through 66 were considered for this analysis. There was a significant breed difference. Herefords averaged 417.08 days while Santa Gertrudis had an average of 461.08 days when all intervals were considered. The figures for the consecutive intervals were 391.45 days for Herefords and 405.53 days for Santa Gertrudis. Age and year had significant effects while sex and the two and three factor interactions were non-significant. Crossbreeding data collected during 1967-1972 were used to determined the effects of breed of sire, year, sex and their interactions. Breed of sire has a significant effects when the consecutive intervals were used but was non-significant in the case of all intervals. Yet, cows bred to bulls of their own breed has shorter intervals than cows bred to bulls of a different breed. Hereford cows bred to Brangus and Santa Gertrudis bulls had 30.4 days and 11.02 days longer intervals respectively than Hereford cows bred to Hereford bulls. Similarly, Santa Gertrudis cows bred to Hereford bulls had 31.93 days longer intervals than Santa Gertrudis cows bred to Santa Gertrudis bulls. Year, again, had a significant effect while there was no significant effect due to sex and the two and three factor interactions.