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Theriogenology 75 (2011) 1506-1515. doi:10.1016/j.theriogenology.2010.12.012Received by publisher: 2010-08-02Harvest Date: 2016-01-04 12:21:09DOI: 10.1016/j.theriogenology.2010.12.012Page Range: 1506-151

Our objectives were to determine pregnancy rate, fetal loss, and number of calves born in beef cattle after a fixed-time transfer of an embryo 7 d after a fixed-time artificial insemination (TAI) of cows (Exp. 1) and after transfer of 2 demi-embryos into a single heifer recipient (Exp. 2). In Exp. 1 after synchronization of ovulation, during 2 yr, 297 suckled beef cows were assigned randomly to 1 of 3 treatments: 1) on d 2 cows received a single TAI (TAI-2; n = 99), 2) a fixed-time direct transfer, frozen and thawed embryo placed in the uterine horn ipsilateral to the ovary containing a corpus luteum (CL) on d 9 embryo transfer (ET-9; n = 99), or 3) cows received TAI on d 2 and a frozen and thawed direct transfer embryo placed in the uterine horn ipsilateral to the ovary containing a CL on d 9 (TWIN) treatments (n = 99). Fetal number and viability were determined with ultrasonography at 33 to 35 d and 90 to 100 d after insemination. In Exp. 2, 74 crossbred recipient heifers were assigned randomly to receive either 1) a single whole fresh embryo (WHOLE; n = 37) or 2) 2 identical fresh demi-embryos (SPLIT; n = 37) in the uterine horn ipsilateral to the CL 7 d after an observed estrus. Ultrasonography was used on d 33, 69, and 108 to determine presence and number of embryos or fetuses. Palpation per rectum was used to determine pregnancy status on d 180 of gestation and number of live calves was recorded at birth. In Exp. 1 pregnancy rates on d 30 to 35 were greater (P < 0.05) for TWIN- (48.5%) and TAI-2- (47.5%) than for ET-9- (33.3%) treated cows. Of the 48 pregnant cows in the TWIN treatment, 21 were twin pregnancies whereas there was 1 twin pregnancy in the TAI-2 treatment. As a result, TWIN cows had more fetuses (P < 0.05) as a proportion of all treated cows (69.7%) than TAI-2- (48.5%) or ET-9-(33.3%) treated cows, and cows in the TWIN treatment gave birth to more (P < 0.01) calves (n = 55) compared with cows in the ET treatment (n = 23) whereas cows in the TAI-2 treatment (n = 40) were intermediate. In Exp. 2 heifers receiving SPLIT (81.1%) had greater (P < 0.05) pregnancy rates on d 33 than heifers receiving WHOLE (40.5%). Of the SPLIT heifers that were confirmed pregnant at d 33 after transfer, 57% were gestating twin fetuses. Embryonic or fetal loss from d 33 to birth was greater (P < 0.01) in heifers in the SPLIT treatment (40.0%) compared with the WHOLE treatment (0.0%), but number of calves per female treated was greater (P < 0.05) in heifers in the SPLIT treatment (75.0%) compared with heifers in the WHOLE treatment (40.5%). We conclude that transferring an embryo into a cow 7 d after TAI did not increase the pregnancy rate in Exp.1. However, transferring 2 demi-embryos into a single heifer recipient increased pregnancy rate at 33 d of gestation whereas both methods of inducing twinning resulted in a greater number of calves per female treated. In addition, embryonic or fetal loss associated with unilateral twin pregnancies in heifers occurred at rates greater than those associated with single-fetus pre...

Administration of human chorionic gonadotropin at embryo transfer induced ovulation of a first-wave dominant follicle and increased progesterone and transfer pregnancy rates AbstractEmbryo transfer (ET) has become more widespread in recent years as a way to improve cattle genetics. According to the annual statistical survey of the American Embryo Transfer Association, more than 200,000 fresh and frozen bovine embryos were transferred in 2008. But despite advancements in reproductive technologies that have occurred since ET was commercialized in the 1970s, industrywide pregnancy rates are only 62.4 and 56.9% for fresh and frozen-thawed ET, respectively. Using ET helps avoid problems from failed fertilization; however, fertilization failure has been characterized as a relatively unimportant factor of pregnancy loss. Approximately 10% of pregnancy failures resulted from fertilization failure and another 10% from failed embryo development. Approximately 20 to 25% of the pregnancy loss in an ET program could be characterized as early embryonic loss.

Twelve Angus x Hereford heifers (avg wt = 183.6 kg) were allotted by initial liver copper (Cu) concentrations into one of two treatments. Control (n = 6) heifers were fed a basal diet supplemented to provide a dietary Cu level of 10 ppm. Molybdenum (Mo)-induced Cu-deficient heifers (n = 6) were fed an identical basal diet supplemented with sodium molybdate (Cu:Mo ratio = 1:2.5), with dietary sulfur at .3% of the total diet. Dietary treatments were delivered for 120 d, at which time Mo-supplemented heifers were considered Cu-deficient (286 and 49 ppm liver Cu for control and Mo-induced Cu-deficient, respectively). Peripheral blood neutrophils were enumerated both before and after the administration of an inflammatory stressor, a subcutaneous injection (1.5 mL) of Freund's complete adjuvant. In vitro and in vivo measures of neutrophil chemotaxis were evaluated and the expression of two adhesion molecules, CD18 and L-selectin, were analyzed by flow cytometric procedures. Molybdenum-induced Cu deficiency increased (P < .01) the number of peripheral blood neutrophils; however, in vitro neutrophil chemotaxis was not affected. In vivo neutrophil chemotaxis tended (P < .08) to be increased in Mo-induced Cu-deficient heifers (1.55 vs 2.26 x 10(6) cells/ sponge for control and Mo-supplemented, respectively). No differences in CD18 or L-selectin expression were detected between treatments. However, CD18 expression was decreased (P < .05) in both treatments following adjuvant injection. These data suggest that Mo-induced Cu deficiency results in an increase in peripheral blood neutrophil number, without altering chemotactic ability and adhesion molecule expression.

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To evaluate the potential of using electronic implants (transponders) for maintaining identity from birth to slaughter, calves born and implanted in Montana were followed through the feedlot phase to their ultimate slaughter at commercial packing plants. At spring branding, 138 calves were implanted with electronic identification transponders positioned underneath the scutiform cartilage at the base of the ear. Four steers died prior to weaning. After weaning, 109 steers were transported to a commercial feedlot i n Kansas (group 1) and the remaining 25 steers (group 2) were maintained at the Montana ranch for 1 year and then placed in a commercial feedlot in Colorado. Following the two feeding periods, steers were slaughtered at commercial packing plants in Colorado or Kansas under Food Safety Inspection Service authority. From implanting to weaning (156 days), retention was 100%, and 98.5% of the implants remained operable. Of the 106 steers that survived in the first group, implant retention was 98.1%, and all implants were recovered at slaughter. Of the 25 steers in the second group, identity was maintained on 20 steers up to slaughter, 661 days postbranding. This study illustrated that electronic implants will maintain identity on a very high percentage of cattle from birth to slaughter and that the implants can be recovered at the time of slaughter. EFFICACY OF ELECTRONIC IDENTIFICATION IN BEEF CATTLE A. R. Spell, S. D. Utter, and L. R. Corah SummaryTo evaluate the poten tial of using electronic implants (transponders) for maintaining identity from birth to slaughter, calves born and implanted in Montana were followed through the feedlot phase to their ultimate slaughter at commercial packing plants. At spring branding, 138 calves were implanted with electronic identification transponders positioned underneath the scutiform c artilage at the base of the ear. Four steers died prior to weaning. After weaning, 109 steers were transported to a commercial feedlot i n Kansas (group 1) and the remaining 25 steers (group 2) were maintained at the Montana ranch for 1 year and then placed in a commercial feedlot in Colorado. Following the two feeding periods, steers were slaughtered at commercial packing plants in Colorado or Kansas under Food Safety Inspection Service authority. From implanting to weaning (156 days), retenti on was 100%, and 98.5% of the implants remained operable. Of the 106 steers that survived in the first group, implant retnetion was 98.1%, and all implants were recovered at slau ghter. Of the 25 steers in the second group, identity was maintained on 20 steers up to slaughter, 661 days postbranding. This study illustrated that electronic implants will maintain identity on a very high percentage of cattle from birth to slaughter and that the implants can be recovered at the time of slaughter.

The objective of this project was to study the effects on pregnancy rates of inseminating estrussynchronize d heifers either at observed estrus or at a fixed time. In April, 1994, 574 yearling crossbred heifers, located on six Kansas ranches, were inseminated to achieve this objective. Her d size ranged from 38 to 293 head. The heifers were synchronized with the MGA-prostaglandin (PGF) system. Heifers were either inseminated 12 hr after the onset of estrus or, if not showing estrus, 72 hr after PGF. Pregnancy rates of 491 heifers bred on estrus averaged 56.6% (39.2 to 80.4%). Pregnancy rates for the 83 fixed-time-inseminated heifers average d 39.8% (15.6 to 56.5%). Heifers that responded to the MGA-PGF synchronization system with a standing heat had higher pregnancy rates than those that were inseminate d at a fixed time. However, fixed-time inseminations used in conjunction with inseminations made at estrus increased the total number of heifers bred to proven AI sires.