Brahman × British crossbred heifers (n = 40 and 38 heifers in yr 1 and 2, respectively) were used to evaluate the effects of calf weaning age and subsequent management system on growth and reproductive performance. On d 0, heifers were ranked by BW (89 ± 16 kg) and age (72 ± 13 d) and randomly assigned to a conventional management group that was normally weaned on d 180 (NW; n = 10 heifers annu...

Three trials involving 128 heifers were conducted to determine whether norgestomet implants administered during the mid- and late luteal phases after breeding could be used to synchronize a second estrus in nonpregnant, inseminated heifers without adversely affecting pregnancy in pregnant heifers. All heifers were initially synchronized with Syncro-Mate B and artificially inseminated 47 h after...

Rapid growth large frame (RL, n = 61) or average growth medium frame (AM, n = 71) biotype heifers fed to achieve either moderate (MOD, .6 kg/d) or high ADG (HI, 1.0 kg/d) were used to determine whether puberty occurs at similar body composition or metabolic status. A heifer was considered pubertal after being detected in estrus and then forming a functional corpus luteum. Live animal estimates ...

A study was conducted to examine the effects of low dietary Mn on growth performance of pregnant heifers and fetal development of their offspring. Twenty pregnant Angus (n = 9) and Simmental (n = 11) heifers averaging 17 mo of age and 447.6 kg of initial body weight were used in the 267-d study. Heifers were selected from a previous study examining the effects of supplemental Mn on growth and r...

A 3-yr study was conducted to determine the effect of heifer development system on ADG, reproductive performance, and subsequent feed efficiency as a pregnant heifer. Crossbred Angus heifers (n= 299) were assigned by initial BW to be developed grazing corn residue (CR) or in a drylot (DL). Corn residue heifers grazed native pasture 33 d prior to grazing CR 73 d. Corn residue heifers were then p...

Angus x Hereford heifers were used to determine endocrine and ovarian function preceding nutritionally induced anovulation. Six heifers were fed to maintain body condition score (M), and 12 heifers were fed a restricted diet (R) until they became anovulatory. Starting on d 13 of an estrous cycle, heifers were given PGF2alpha every 16 d thereafter to synchronize and maintain 16 d estrous cycles....

The contraceptive effect of active immunization against GnRH was evaluated in beef heifers. Crossbred heifers were randomized by breed and weight (initial weight = 227.3 +/- 1.2 kg) and assigned to one of three treatment groups. Animals in Group IB (n = 48) were actively immunized against GnRH; heifers in Groups NB (n = 48) and NN (n = 49) did not receive the anti-GnRH vaccine. Sixteen weeks af...

Energy and protein retained in 50, 38, and 54 nonimplanted Holstein and Angus heifers, steers, and bulls, respectively, 17 pens (237 cattle) of beef breed implanted heifers, and 65 pens (535 cattle) of beef breed implanted steers were compared to values predicted by the 1984 National Research Council (NRC), Cornell Net Carbohydrate and Protein System (CNCPS), and the model of Oltjen et al. (OLT...

The objective of this experiment was to determine the relative importance of olfaction and visual observation of heifer mounting behavior to the detection of estrus by bulls. An observation pen was designed to allow the evaluation of the preference of five sexually experienced bulls under three sets of stimuli. The observation pen was 4 m x 17 m with a smaller enclosure (2 m x 4 m) at each end ...

Two experiments were conducted to determine whether extending the interval between removal of melengestrol acetate (MGA) from feed and injection of prostaglandin F2α (PGF) from 17 to 19 d would affect synchronization of estrus, conception, and pregnancy rates of beef heifers. In both experiments, heifers were fed MGA for 14 d, and PGF was given at either 17 or 19 d after cessation of MGA feedin...