The objective was to test the efficacy of an intravaginal progesterone insert and injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in cattle. Cattle were assigned to one of three treatments before a 31-d breeding period that employed artificial insemination. Control cattle were not treated, and treated cattle were administered PGF2alpha or an intravaginal progesterone-releasing insert (CIDR) for 7 d and treated with PGF2alpha on d 6. The treatments were applied in one of three experiments that involved postpartum beef cows (Exp. 1; n = 851; 56+/-0.6 d postpartum), beef heifers (Exp. 2; n = 724; 442.5+/-2.8 d of age), and dairy heifers (Exp. 3; n = 260; 443.2+/-4.5 d of age). Luteal activity before treatment was determined for individual cattle based on blood progesterone concentrations. In Exp. 1, there was a greater incidence of estrus during the first 3 d of the breeding period in CIDR+PGF2alpha-treated cows compared with PGF2alpha-treated or control cows (15, 33, and 59% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001). The improved estrous response led to an increase in pregnancy rate during the 3-d period (7, 22, and 36% for control, PGF2alpha, and CIDR+PGF2alpha, respectively; P < 0.001) and tended to improve pregnancy rate for the 31-d breeding period for cows treated with CIDR+PGF2alpha, (50, 55, and 58% for control, PGF2alpha, and CIDR+PGF2alpha, respectively, P = 0.10). Improvements in rates of estrus and pregnancy after CIDR+PGF2alpha, were also observed in beef heifers. Presence of luteal activity before the treatment period affected synchronization and pregnancy rates because anestrous cows (Exp. 1) or prepubertal heifers (Exp. 2) had lesser synchronization rates and pregnancy rates during the first 3 d of the breeding period as well as during the entire 31-d breeding period. The PGF2alpha, and CIDR+PGF2alpha but not the control treatments were evaluated in dairy heifers (Exp. 3). The CIDR+PGF2alpha-treated heifers had a greater incidence of estrus (84%) during the first 3 d of the breeding period compared with the PGF2alpha-treated heifers (57%), but pregnancy rates during the first 3 d or during the 31-d breeding period were not improved for CIDR+PGF2alpha compared with PGF2alpha-treated heifers. In summary, the concurrent treatment of CIDR and PGF2alpha improved synchronization rates relative to PGF2alpha alone or control. Improved estrus synchrony led to greater pregnancy rates for beef cows and beef heifers but failed to improve pregnancy rates for dairy heifers.

The objective of this study was to evaluate the effects of acclimation to handling on growth, plasma concentrations of progesterone (P4) and cortisol, temperament, and reproductive performance of Brahman-crossbred heifers. Over 2 consecutive years, 37 Braford and 43 Brahman x Angus heifers were initially evaluated, within 30 d after weaning, for BW and puberty status via transrectal ultrasonography and plasma P4 concentrations (d 0 and 10), and for temperament by measurements of chute score, pen score, and exit velocity (d 10 only). On d 11, heifers were stratified by breed, puberty status, temperament score, BW, and age and randomly assigned to receive or not (control) the acclimation treatment. Acclimated heifers were exposed to a handling process 3 times weekly (Mondays, Wednesdays, and Fridays) for 4 wk (d 11 to 39 of the experiment). The acclimation treatment was applied individually to heifers by processing them through a handling facility, whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma P4 concentrations and transrectal ultrasonography, and BW were assessed again on d 40 and 50, d 80 and 90, and d 120 and 130. Blood samples collected before (d 10) and at the end of the acclimation period (d 40) were also analyzed for plasma concentrations of cortisol. Heifer temperament was assessed again on d 40 of the study. No interactions containing the effects of treatment, breed, and year were detected. Acclimated heifers had reduced (P< 0.01) ADG compared with control heifers (0.50 vs. 0.58 kg/d, respectively). Attainment of puberty and pregnancy, however, was hastened (P = 0.02 and 0.04, respectively) in acclimated heifers compared with control. Acclimated heifers had reduced chute score (P < 0.01) and concentrations of cortisol (P < 0.01) and P4 (P = 0.03; prepubertal heifers only) compared with control heifers after the acclimation period (1.37 vs. 1.84 for chute score; 37.8 vs. 50.5 ng/mL of cortisol; 0.52 vs. 0.78 ng/mL of P4). Results from this study indicated that, although acclimation to handling decreased ADG, it resulted in decreased chute score, reduced plasma concentrations of cortisol and prepubertal P4, and enhanced reproductive performance of Brahman-crossbred heifers.

No abstract

Early conceptus development (Days 10-12) in the pig is characterized by rapid remodeling and elongation of the trophoblastic membrane. Endometrial synthesis and secretion of retinol-binding protein (RBP; transporter of retinol) into the uterine lumen parallels the rapid morphological transformation of the conceptus. Hence, retinoic acid, a powerful morphogen, may serve a critical function in trophoblastic remodeling and conceptus elongation through the various isoforms of retinoic acid receptor (RAR). We hypothesize that various transcripts for RAR will be expressed, possibly differentially, in the early developing porcine conceptus on Days 10-12 of gestation. Conceptuses were collected from pregnant gilts and individually frozen in liquid nitrogen after classification for morphological size. A total of 36 conceptuses (4 groups of 9) representing spherical (2-9 mm), early tubular (10-12 mm), late tubular (13-60 mm), and filamentous (> 100 mm) morphologies were assembled for qualitative assessment of mRNA for RAR alpha, RARbeta, RARgamma, RBP, and transforming growth factor beta (TGFbeta)-2 and -3 with reverse transcription polymerase chain reaction (RT-PCR). RBP gene expression was affected by stage of conceptus development (p < 0.05) as RBP expression increased in a linear fashion from 2-mm to 8-mm spherical conceptuses, decreased slightly in the tubular stage, and increased dramatically in filamentous conceptuses. RAR alpha, RARbeta, and RARgamma gene expression was evident at all stages of conceptus development. RAR alpha gene expression increased (p < 0.05) in a linear fashion from 2- to 8-mm spherical conceptuses, and expression plateaued in the 9- to 12-mm conceptuses. Expression of RAR alpha declined slightly at the tubular stage but dramatically increased in filamentous conceptuses. RARbeta gene expression was present across all stages of conceptus development although in diminutive amounts. RARgamma gene expression was evident in all stages of conceptus development but was not affected (p > 0.05) by developmental stage. Gene expression for TGFbeta-2 was not detected by RT-PCR at any stage of conceptus development, whereas TGFbeta-3 expression increased (p < 0.05) from the 2- to 8-mm conceptuses and remained high throughout trophoblastic elongation into the filamentous stage. The presence of mRNA for the RAR alpha, RARbeta, and RARgamma in elongating porcine conceptus provides evidence that RAR, particularly RAR alpha, may function as an important acceptor for retinoic acid and possibly regulate gene expression prior to and during rapid trophoblastic elongation in the porcine conceptus.

The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 degrees C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P < .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P > .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P < .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P < .05) BW and a greater (P < .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF > LF > FF; P < .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers.