title: Estimating the impact of management decisions on the occurrence of puberty in beef heifers.
abstract: Age and weight at puberty in beef heifers were hypothesized to be jointly dependent random variables with the joint distribution conditional upon values of exogenous variables such as breed, date of birth and postweaning rate of gain. A statistical model was specified that tested the joint dependency hypothesis and measured the impact of variation in the explanatory variables on puberty. Model parameters were estimated by two-stage least-squares procedures from data on 556 beef heifers: 190 raised at the Northern Agricultural Research Center (NARC), Havre, Montana and 366 raised at the Livestock and Range Research Station (LARRS), Miles City, Montana. Results did not support the hypothesis that age and weight at puberty were jointly dependent; weight at puberty did depend upon age at puberty, but age at puberty did not depend upon weight at puberty when postweaning level of nutrition was known. Thus, the appropriate probability distribution was a conditional univariate probability distribution on age. Results were consistent with past research in that breed and breed-cross differences existed, and heifers heavier at weaning and fed higher levels of postweaning nutrition reached puberty at an earlier age and heavier weight.
mesh_terms: D000367:Age Factors; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D004971:Estrus; D005260:Female; D008954:Models, Biological; D011247:Pregnancy; D012741:Sexual Maturation; D014886:Weaning