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An experiment was designed to evaluate modifications to the 7 & 7 synch protocol with the hypothesis that tandem administration of prostaglandin F2a (PG) and gonadotropin-releasing hormone (GnRH) during the presynchronization portion of the protocol would generate a convergent ovarian response among anestrous and estrous cycling females. Nulliparous (n = 153), primiparous (n = 92), and multiparous (n = 413) Angus-cross females across four locations were blocked based on parity and pre-treatment cyclicity status (presence or absence of a corpus luteum) as assessed via transrectal ovarian ultrasonography. Within block, females were randomly assigned to one of three treatments. Females assigned to the 7 & 7 Synch treatment received an intravaginal progesterone-releasing insert (CIDR) and administration of PG on day 0, administration of GnRH on day 7, and administration of PG coincident with CIDR removal on day 14. Females assigned to 7 & 7 Synch + G received the same treatment schedule with the modification that GnRH was administered in tandem with the PG on day 0. Females assigned to 7 & 7 Synch + G + P received GnRH in tandem with PG on both day 0 and day 7 of the treatment schedule. Fixed-time artificial insemination (FTAI) was performed at 54 h after CIDR removal for nulliparous females and at 66 h for primiparous and multiparous females. Transrectal ovarian ultrasonography was performed on day 7 and day 14 to characterize the largest follicle diameter (LFD) as well as the presence/absence and number of corpora lutea (CL). Expression of estrus before FTAI was characterized in three locations using estrus detection patches (Estrotect. Approximately 75 to 90 days after FTAI, pregnancy status was determined via transrectal ultrasonography. Day 7 CL status was affected by treatment (P = 0.002), with a greater proportion of females presenting with CL on Day 7 when treated with the modified treatments (64%) as compared with the 7 & 7 Synch treatment (31%). Day 14 LFD was affected by treatment (P = 0.002), with a larger average LFD among females treated with 7 & 7 Synch + G + P (12.0 mm) as compared with 7 & 7 Synch (11.4 mm) or 7 & 7 + G (10.7 mm). Pregnancy rate to FTAI was affected by pre-treatment cyclicity status (P < 0.0001) and semen type (P = 0.0003) and tended to be affected by treatment (P = 0.09) with 7 & 7 Synch + G + P tending to result in a greater proportion pregnant (58.86%) as compared with 7 & 7 Synch (49.17%) and 7 & 7 Synch + G (48.79%). Tandem administration of GnRH and PG on days 0 and 7 of the 7 & 7 Synch protocol effectively generated a convergent ovarian response among anestrous and estrous cycling beef females and tended to result in increased pregnancy rates to FTAI. [ABSTRACT FROM AUTHOR]

Crossbreeding dairy cows with beef sires has increased in the U.S. dairy industry. This beef x dairy mating results in dairy-beef which has altered the U.S. fed beef supply. The predominant mating has been Holstein x Angus, thus research was conducted to determine the effects of Holstein x SimAngus breeding on growth performance, carcass characteristics, and fresh meat quality. Starting on d 1, Holstein steers (n = 9) and Holstein x SimAngus (HolSim) steers (n = 12) were fed once daily at 0830 h, until an end weight of 635 kg was reached. Holstein steers averaged 421 d and HolSim steers averaged 432 days on feed. Daily feed offered was delivered into a semi-autonomous feed monitoring system designed to measure individual animal intake and feeding behavior (GrowSafe System Ltd). Steer body weight was recorded every 28 d. Data collected were used to calculate dry matter intake (DMI), average daily gain (ADG), and gain to feed ratio (G:F). Steers were humanely slaughtered under USDA inspection, immediately following slaughter hot carcass weight (HCW) was recorded and 48 h following slaughter, carcass length, body width, backfat thickness and area of the longissimus muscle (LM) was recorded. Strip loins were collected from each carcass and aged for 14 d. After aging, Warner-Bratzler shear force (WBSF) and slice shear force (SSF) were determined. Remaining steaks were placed under retail display for 7 d. Objective color was measured after 0, 1, 3, 5, and 7 d in retail display. No differences were observed for ADG and G:F between Holstein and HolSim steers (P > 0.05). A tendency was observed for Holstein steers to have a greater DMI compared with HolSim steers (P = 0.0646). The HolSim steers had greater HCW and dressing percentages compared with Holstein steers (P < 0.0001). The HolSim carcasses had shorter carcass lengths and body widths compared with Holstein carcasses (P = 0.0005). Holstein carcasses had less backfat compared with HolSim carcasses (P = 0.0034). The LM area was larger in HolSim carcasses (P < 0.0001). No differences were observed for WBSF or SSF (P > 0.05). Strip steaks from HolSim steers had less deoxymyoglobin and greater oxymyoglobin values on d 0 of retail (P < 0.05). Strip steaks from HolSim steers had greater a* and saturation index values on d 7 in retail (P < 0.05). Strip steaks from HolSim steers had decreased metmyoglobin values and greater oxymyoglobin values on d 7 in retail (P < 0.05). Thus, indicating strip steaks from HolSim steers had increased red color. Growth performance data in this study confirm previous literature reported when comparing dairy x dairy to beef x dairy steers. Carcass and fresh meat data suggest that Holstein x SimAngus steers had improved yield production compared with Holstein steers without a loss in quality when steers were fed to a weight constant end point. [ABSTRACT FROM AUTHOR]

An experiment was designed to evaluate later timepoints for fixed-time artificial insemination (FTAI) of beef heifers, with the hypothesis that use of a later timepoint would allow a greater proportion of heifers to express estrus prior to FTAI and result in greater conception rates among estrous heifers inseminated with sex-sorted semen. Estrus was synchronized using the 14-d CIDR®-PG protocol (1.38 g progesterone CIDR intravaginally inserted Day -33 and removed Day -19, PGF2a; 500 µg cloprostenol administered Day -3) for 1640 heifers in 7 locations. Heifers were blocked by reproductive tract score and body weight and randomly assigned to one of three FTAI timepoints: 66 ± 2 h, 70 ± 2 h, or 74 ± 2 h after PGF2a administration. Estrus detection aids (Estrotect) were applied at PGF2a administration, with activation recorded at FTAI. Heifers that expressed estrus prior to FTAI were serviced with sex-sorted semen (SexedULTRA 4M™). Heifers that failed to express estrus were serviced with conventional semen and administered gonadotropinreleasing hormone (GnRH; 100 µg gonadorelin). The proportion of heifers that expressed estrus by FTAI (66 h: 63%; 70 h: 68%; 74 h: 72%) was greater at 74 h versus 66 h (P < 0.01). Conception rates did not differ significantly between treatments among heifers that expressed estrus and were serviced with sex-sorted semen (66 h: 55%; 70 h: 53%; 74 h: 52%). Among heifers that failed to express estrus and were serviced with conventional semen, conception rates were greater (P = 0.02) when FTAI was performed at 66 h versus 70 h (66 h: 39%; 70 h: 26%; 74 h: 32%). Results indicate that performing FTAI later following the 14-d CIDR®-PG protocol increases the proportion of heifers that express estrus and are serviced with sex-sorted semen, but does not improve conception rates of estrous heifers inseminated at later timepoints. [ABSTRACT FROM AUTHOR]

Abstract: A method for timed artificial insemination (AI) that is used for beef cows, beef heifers, and dairy heifers employs progesterone-releasing inserts, such as the controlled internal drug release (CIDR; Zoetis, New York, NY, USA) that are left in place for 14 days. The 14-day CIDR treatment is a method of presynchronization that ensures that cattle are in the late luteal phase of the estrous cycle when PGF2α is administered before timed AI. The objective of this study was to test the effectiveness of the 14dCIDR-PGF2α program in postpartum dairy cows by comparing it with the traditional “Presynch-Ovsynch” (2xPGF2α-Ovsynch) program. The 14dCIDR-PGF2α cows (n = 132) were treated with a CIDR insert on Day 0 for 14 days. At 19 days after CIDR removal (Day 33), the cows were treated with a luteolytic dose of PGF2α, 56 hours later were treated with an ovulatory dose of GnRH (Day 35), and 16 hours later were inseminated. The 2xPGF2α-Ovsynch cows were treated with a luteolytic dose of PGF2α on Day 0 and again on Day 14. At 12 days after the second PGF2α treatment (Day 26), the cows were treated with GnRH. At 7 days after GnRH, the cows were treated with PGF2α (Day 33), then 56 hours later treated with GnRH (Day 35), and then 16 hours later were inseminated. There was no effect of treatment or treatment by parity interaction on pregnancies per AI (P/AI) when pregnancy diagnosis was performed on Day 32 (115/263; 43.7%) or Days 60 to 90 (99/263; 37.6%) after insemination. There was an effect of parity (P < 0.05) on P/AI because primiparous cows had lesser P/AI (35/98; 35.7%) than multiparous cows (80/165; 48.5%) on Day 32. Cows observed in estrus after the presynchronization step (within 5 days after CIDR removal or within 5 days after the second PGF2α treatment) had greater P/AI than those not observed in estrus (55/103; 53.4% vs. 60/160; 37.5%; observed vs. not observed; P < 0.01; d 32 pregnancy diagnosis). When progesterone data were examined in a subset of cows (n = 208), 55.3% of cows had a “prototypical” response to treatment (i.e., the cow had an estrous cycle that was synchronized by the presynchronization treatment and then the cow responded appropriately to the subsequent PGF2α and GnRH treatments before timed AI). Collectively, cows with a prototypical response to either treatment had 52.2% P/AI that was greater (P < 0.001) than the P/AI for cows that had a nonprototypical response (19%) (P/AI determined at 60–90 days of pregnancy). In conclusion, we did not detect a difference in P/AI when postpartum dairy cows were treated with 14dCIDR-PGF2α or 2xPGF2α-Ovsynch before timed AI. The primary limitation to the success of either program was the failure of the cow to respond appropriately to the sequence of treatments. [Copyright &y& Elsevier]