Characterization of puberty and growth near puberty in five cattle breeds and their diallel crosses

Abstract

Pubertal measurements and monthly weight and height measurements of 424 bulls and 475 heifers involved in a diallel mating of Angus, Brahman, Hereford, Holstein and Jersey cattle were analyzed to characterize puberty and early growth. At six months of age, 90 heifers and 210 bulls were assigned to individual feeding pens and provided a 72% TDN ration ad libitum. The remaining heifers were placed on pasture with supplementation. The remaining bulls were placed in drylots and fed the same ration as the penned animals. Body weight and hip height were recorded monthly for fed cattle and quarterly for pastured heifers. Monthly feed consumption was recorded for all individually fed animals. Puberty of heifers was defined as first ovulatory estrus, heifers were rectally palpated at 21 day intervals from six months of age or when marked by an altered bull. Puberty of bulls was defined as first observed sperm cell in an ejaculation. Bulls were electroejaculated monthly from six months of age until puberty was determined. At puberty, the date, weight, height, and for heifers, internal pelvic horizontal and vertical dimensions were recorded. Weights, heights and weight-height ratios for ages at 45-day intervals from 270 to 630 days of age were interpolated from the monthly or quarterly weights to avoid the necessity of further age adjustment..