Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program

A multilocation study examined pregnancy risk (PR) after delaying AI in suckled beef cows from 60 to 75 h when estrus had not been detected by 60 h in response to a 7-d CO-Synch + progesterone insert (CIDR) timed AI (TAI) program (d -7: CIDR insert concurrent with an injection of GnRH; d 0: PGF injection and removal of CIDR insert; and GnRH injection at TAI [60 or 75 h after CIDR removal]). A total of 1,611 suckled beef cows at 15 locations in 9 states (CO, IL, KS, MN, MS, MT, ND, SD, and VA) were enrolled. Before applying the fixed-time AI program, BCS was assessed, and blood samples were collected. Estrus was defined to have occurred when an estrus detection patch was >50% colored (activated). Pregnancy was determined 35 d after AI via transrectal ultrasound. Cows ( = 746) detected in estrus by 60 h (46.3%) after CIDR removal were inseminated and treated with GnRH at AI (Control). Remaining nonestrous cows were allocated within location to 3 treatments on the basis of parity and days postpartum: 1) GnRH injection and AI at 60 h (early-early = EE; = 292), 2) GnRH injection at 60 h and AI at 75 h (early-delayed = ED; = 282), or 3) GnRH injection and AI at 75 h (delayed-delayed = DD; = 291). Control cows had a greater ( < 0.01) PR (64.2%) than other treatments (EE = 41.7%, ED = 52.8%, DD = 50.0%). Use of estrus detection patches to delay AI in cows not in estrus by 60 h after CIDR insert removal (ED and DD treatments) increased ( < 0.05) PR to TAI when compared with cows in the EE treatment. More ( < 0.001) cows that showed estrus by 60 h conceived to AI at 60 h than those not showing estrus (64.2% vs. 48.1%). Approximately half (49.2%) of the cows not in estrus by 60 h had activated patches by 75 h, resulting in a greater ( < 0.05) PR than their nonestrous herd mates in the EE (46.1% vs. 34.5%), ED (64.2% vs. 39.2%), and DD (64.8% vs. 31.5%) treatments, respectively. Overall, cows showing estrus by 75 h (72.7%) had greater ( < 0.001) PR to AI (61.3% vs. 37.9%) than cows not showing estrus. Use of estrus detection patches to allow for a delayed AI in cows not in estrus by 60 h after removal of the CIDR insert improved PR to TAI by optimizing the timing of the AI in those cows.

Influence of post-insemination nutrition on embryonic development in beef heifers

Previous studies have demonstrated that a decrease in nutrition immediately following AI reduces pregnancy success in beef heifers. The objective of this experiment was to determine if nutrient restriction following AI impacted early embryonic development among non-super ovulated heifers. Beef heifers in eight replications (Rep; Rep 1; n = 14, Rep 2; n = 15, Rep 3; n = 15, Rep 4; n = 14, Rep 5; n = 15, Rep 6; n = 15, Rep 7; n = 25, Rep 8; n = 25) across two locations (UMN, SDSU) were developed in a dry-lot and fed 125% NRC requirements from weaning to timed-AI (d 0). Heifers were timed-AI to a single sire in all replications. Immediately following AI, heifers were assigned, based on age, weight, and estrous response to one of two post-AI nutritional treatments. Half the heifers in each replication continued on the pre-insemination diet, serving as the control treatment (CON) and the remaining heifers were restricted to a sub-maintenance diet (RES). At UMN, heifers in the RES treatment were fed the same diet, but intake was limited to 80% NE_m, while at SDSU, DMI remained the same, but diet composition was altered with the addition of straw to reduce NE_m to 50% of requirements. On d 6, single embryos were collected nonsurgically and recovered embryos (CON; n = 46, RES; n = 42) were evaluated to determine quality (grade 1-9) and stage (1-4). Embryos were then stained and evaluated to determine the number of dead cells and total blastomeres. In Reps 1 through 6, concentrations of IGF-1 were assessed on d 0 and 6 and progesterone concentrations on d 4 and 6. Data were analyzed using the Mixed procedures of SAS. There were no treatment by Rep or treatment by location interactions for any embryo parameter evaluated, thus all data were pooled. Embryo stage and quality were improved (P < 0.01) in the CON (4.4 ± 0.16, 2.2 ± 0.19, respectively) compared to RES treatment (3.7 ± 0.16, 2.9 ± 0.19, respectively). Embryos in the CON treatment had greater total blastomeres (66.9 ± 5.05; P < 0.01) and tended to have a greater percentage of live cells (P < 0.10; 80.9 ± 4.19%) compared to RES (47.9 ± 5.41; 69.7 ± 4.39%, respectively). Progesterone and IGF-1 concentrations did not differ between treatments. In summary, nutrient restriction for 6 days immediately following AI resulted in poorer quality embryos that were delayed in stage of development, suggesting that immediate changes in nutritional status after insemination can alter early embryonic development.

Changes in ovarian function associated with circulating concentrations of estradiol before a GnRH-induced ovulation in beef cows

These studies were conducted to evaluate causes for differences in circulating concentrations of estradiol before a GnRH-induced ovulation. Beef cows were synchronized by an injection of GnRH on day -7 and an injection of prostaglandin F2α (PGF2α) on day 0. In experiment 1, blood samples were collected every 3 h from PGF2α on day 0 to hour 33 after PGF2α and at slaughter (hour 36 to 42; n = 10). Cows were assigned to treatment group based on circulating concentrations of estradiol (E2): HighE2 vs LowE2. At slaughter, follicular fluid (FF) and granulosa cells were collected from the dominant follicle. In experiment 2, blood samples (n = 30) were collected every 8 h from PGF2α until the dominant follicle was aspirated via ultrasound-guided follicular aspiration to collect FF and granulosa cells (hour 38 to 46). In experiment 1, HighE2 had increased abundance of 3β-hydroxysteroid dehydrogenase, cytochrome P450 aromatase, and LHR (P ≤ 0.02), and greater concentrations of estradiol and androstenedione (P ≤ 0.02) in the FF. In experiment 2, HighE2 had increased abundance of CYP11A1, 3β-hydroxysteroid dehydrogenase, cytochrome P450 aromatase, and LHR (P ≤ 0.03) vs either LowE2 or GnRHLowE2. There was a tendency (P = 0.07) for LH pulse frequency to be increased in both the GnRHLowE2 and HighE2 compared with LowE2. HighE2 cows experienced increas in circulating concentrations of estradiol compared with LowE2. In conclusion, animals with greater concentrations of circulating estradiol before fixed-time AI experienced an upregulation of the steroidogenic pathway during the preovulatory period.

147 EFFECT OF OVULATORY FOLLICLE DIAMETER ON THE OOCYTE TRANSCRIPTOME IN BEEF COWS

Inadequate oocyte competence is a potential explanation for reduced pregnancy rates and(or) embryonic/fetal mortality when small dominant follicles are induced to ovulate prematurely with gonadotropin releasing hormone (GnRH). Our hypothesis was that the physiological status of an ovulatory follicle has a direct effect on competence of the oocyte and resulting embryo. The objective was to determine if the transcriptome of oocytes differ depending on whether they are collected from small or large dominant follicles following a GnRH-induced gonadotropin surge. Suckled beef cows (n = 350) were pre-synchronized with a 5-day CIDR protocol. Following pre-synchronization, GnRH1 was administered on Day –9, prostaglandin F on Day –2, GnRH2 (to initiate the ovulatory process) on Day 0, and dominant follicles were transvaginally aspirated on Day 1 before follicular rupture. On Day 0, cows were divided into small (<11.7 mm; no oestrus expression), or large (>12.5 mm; no oestrus expression) groups based on dominant follicle diameter. Oocytes were individually collected after aspiration, and RNA was later extracted from pools of 4 oocytes (n = 6 oocyte pools from both small and large follicles) and sequenced on an Illumina HiSEqn 2000 (single reads, 100 bases; Illumina Inc., San Diego, CA, USA). The sequences were tiled against a ~23 500 member bovine transcript reference obtained from the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/). Tiling to target transcripts required a minimum match of 50 bases with at least 96% identity. Tiling counts were displayed as reads per kilobase of transcript per million mapped reads (RPKM) values, which were obtained by correcting for the length of each target (in kb) and the number of total tiled reads (in millions). Differences between groups were defined by two-tailed t-test and gene lists were selected based on P-values <0.02. Numerous differences in transcript abundance were characterised between oocytes from small and large dominant follicles. Follistatin-like 5 expression was increased (P < 0.02) in oocytes collected from large dominant follicles compared with oocytes collected from small dominant follicles. Several genes were associated with the ubiquitin pathway (e.g. ubiquitin conjugating enzyme, ubiquitin like protein-7) and were up-regulated (P < 0.02) in oocytes from large versus small dominant follicles. In addition, 4 members of the zinc finger protein family were up-regulated (P < 0.02) and 4 members were down-regulated (P < 0.02) in oocytes from large compared with small dominant follicles. In summary, some of the genes that were highly differentially regulated in bovine oocytes between small and large dominant follicles included members of the zinc finger and ubiquitin pathways, which may reflect differences in transcriptional regulation and protein turnover, respectively, between oocytes collected from large and small follicles. Study was supported by AFRI Grant no. 2013–67015–21076 from the USDA National Institute of Food and Agriculture (Washington, DC).

Feeding distiller’s grains as an energy source to gestating and lactating beef heifers: Impact on female progeny growth, puberty attainment, and reproductive processes

This study compared postweaning growth, puberty attainment, and reproductive processes of female progeny (n = 33) born to Angus-Simmental beef heifers treated with either a control diet or a diet in which dried distiller’s grains with solubles (DDGS) were fed as an energy source during late gestation and early lactation. From 192 d of gestation through 118 ± 4 d in lactation, dams were fed either a corn silage–based control diet (CON) orcorn residue with DDGS, where DDGS were supplemented as an energy source (DG). Diets were formulated to provide similar daily NEg between diets, but CP requirements were drastically exceeded in the DG treatment. Heifer progeny (n = 33) were weaned, commingled at 191 ± 4 d of age, and similarly managed for the remainder of the project. Heifer BW and blood samples for progesterone assessment to determine onset of puberty were collected weekly beginning at weaning. At 255 ± 4 d of age, a single follicular wave was mapped via ultrasonography in 10 prepubertal heifers per treatment. Prepubertal antral follicle count and ovarian size were determined at 253 ± 4 d of age. Hip height was recorded at 213,297, and 437 ± 4 d of age. Estrous synchronization and AI was initiated at 447 ± 4 d of age. Binary data were analyzed with the GLIMMIX procedures of SAS and all other data were analyzed with the MIXED procedures of SAS. Progeny from DG-treated dams tended to be heavier (P = 0.08) than progeny from CON-treated dams from weaning until breeding. In addition, DG progeny had a greater (P < 0.01) frame score than CON throughout the developmental period. Ovarian size, antral follicle count, and follicular growth parameters did not differ between treatments. Age at puberty did not differ between CON (303 ± 10 d) and DG (320 ± 10 d) progeny; however, BW at puberty was greater (P = 0.01) for DG (326 ± 7 kg) than CON (298 ± 8 kg) progeny. Pregnancy rates to AI were greater (P = 0.05) in DG progeny (70.6%) than CON (33.3%), but overall breeding season pregnancy rate did not differ (P = 0.97). Moreover, rate of dystocia in female progeny at first parturition and grand-offspring birth BW did not differ due to treatment (P ≥ 0.74). In summary, feeding DDGS as an energy source during late gestation and early lactation to first-parity heifers resulted in female progeny with greater skeletal growth that were heavier at onset of puberty and had increased AI pregnancy rates.

The requirement of GnRH at the beginning of the five-day CO-Synch + controlled internal drug release protocol in beef heifers

The objective of this study was to determine if the omission of GnRH at controlled internal drug release device (CIDR) insertion would impact pregnancy rates to timed AI (TAI) in beef heifers enrolled in a 5-d CO-Synch + CIDR protocol that used 1 PGF2α dose given at CIDR removal. Yearling beef heifers in Ohio in 2 consecutive breeding seasons (2011, n = 151, and 2012, n = 143; Angus × Simmental), Utah (2012, n = 265; Angus × Hereford), Idaho (2012, n = 127; Charolais), and Wyoming (2012, n = 137; Angus) were enrolled in the 5-d CO-Synch + CIDR protocol. At CIDR insertion (d -5), heifers were randomly assigned either to receive 100 μg GnRH (GnRH+; n = 408) or not to receive GnRH (GnRH-; n = 415). At CIDR removal (d 0 of the experiment), 25 mg PGF2α was administered to all heifers. All heifers were inseminated by TAI and given 100 μg GnRH 72 h after PGF2α (d 3). In heifers at the Ohio locations (n = 294), presence of a corpus luteum (CL) at CIDR insertion (d -5) was determined via assessment of progesterone concentrations (2011) and ovarian ultrasonography (2012). Subsequently, in both years, ovarian ultrasound was conducted on d 0 to determine the presence of a new CL. In this same subgroup of heifers, blood samples for progesterone analysis were collected on d 3 to assess luteal regression. Pregnancy diagnosis was performed between 32 and 38 d after TAI. At CIDR withdrawal, presence of a new CL was greater (P < 0.05) in the GnRH+ (55.8%, 82/147) than GnRH- (26.5%, 39/147) treatment. Incidence of failed luteal regression did not differ between the GnRH+ (3.4%) and GnRH- (0.7%) treatments. Pregnancy rate to TAI did not differ between the GnRH+ (50.5%) and GnRH- (54.9%) treatments. In conclusion, although the incidence of a new CL at CIDR removal was increased in the GnRH+ treatment, omission of the initial GnRH treatment in the 5-d CO-Synch + CIDR protocol did not influence TAI pregnancy rate in yearling beef heifers. In addition, a single dose of PGF2α at CIDR removal was effective at inducing luteolysis in yearling beef heifers enrolled in the 5-d CO-Synch + CIDR protocol, regardless of whether or not the initial GnRH treatment was given.

Comparison of three CIDR-based fixed-time AI protocols in beef heifers

Several effective fixed-time AI (FTAI) protocols have been developed to facilitate AI in beef heifers that circumvent the need for estrus detection. Among these are the 5-d CO-Synch + controlled intravaginal progesterone insert (CIDR) protocol (5dCO), PGF2α (PG) 6-d CIDR protocol (PG-6dCIDR), and 14-d CIDR-PG protocol (14dCIDR-PG). Although each of these protocols varies in duration and approach to synchronizing estrus and ovulation, each has been reported as an effective method to facilitate FTAI in beef heifers. Therefore, the objective of this study was to compare FTAI pregnancy rates in beef heifers synchronized with these 3 CIDR-based protocols. Virgin beef heifers (n = 801) at 4 locations were synchronized with 1 of 3 protocols: 1) 5dCO, an injection of GnRH (100 μg) and insertion of a CIDR on d -5, PG (25 mg) and CIDR removal on d 0 with a second injection of PG (>4 h after CIDR removal) on d 0 and FTAI at 72 h after CIDR removal, 2) PG-6dCIDR, PG (25 mg) on d -9, GnRH (100 μg) and insertion of a CIDR on d -6, PG and CIDR removal on d 0, and FTAI at 66 h after CIDR removal, or 3) 14dCIDR-PG, a 14-d CIDR insert from d -30 to -16, PG (25 mg) on d 0, and FTAI at 66 h after PG. All heifers received an injection of GnRH (100 μg) concurrent with FTAI. Timing of treatment initiation was offset to allow all heifers to receive FTAI concomitantly and at random. Pregnancy success was determined between 35 and 40 d after FTAI by transrectal ultrasonography. Blood samples were collected before the beginning of each protocol and at the initiation of each protocol to determine estrous cycling status (77%). Data were analyzed using the GLIMMIX procedures of SAS. As expected, because of the duration of protocols, fewer heifers in the 14dCIDR-PG treatment were pubertal at initiation of synchronization than in the 5dCO (P < 0.05) and PG-6dCIDR (P = 0.10) treatments. Fixed-time AI pregnancy success did not differ between treatments (P = 0.14; 62.6%, 56.9%, and 53.3% for 5dCO, PG-6dCIDR, and 14dCIDR-PG, respectively). However, heifers that had reached puberty by initiation of synchronization had greater (P < 0.01) pregnancy success compared to heifers that were prepubertal (60.7% and 47.3%, respectively). In summary, all 3 protocols had similar FTAI pregnancy success, and puberty status had the greatest impact on pregnancy success.

Triennial Reproduction Symposium: deficiencies in the uterine environment and failure to support embryonic development

Pregnancy failure in livestock can result from failure to fertilize the oocyte or embryonic loss during gestation. The focus of this review is on cattle and factors affecting and mechanisms related to uterine insufficiency for pregnancy. A variety of factors contribute to embryonic loss and it may be exacerbated in certain animals, such as high-producing lactating dairy cows, and in some cattle in which estrous synchronization and timed AI was performed, due to reduced concentrations of reproductive steroids. Recent research in beef cattle induced to ovulate immature follicles and in lactating dairy cows indicates that deficient uterine function is a major factor responsible for infertility in these animals. Failure to provide adequate concentrations of estradiol before ovulation results in prolonged effects on expression and localization of uterine genes and proteins that participate in regulating uterine functions during early gestation. Furthermore, progesterone concentrations during early gestation affect embryonic growth, interferon-tau production, and uterine function. Therefore, an inadequate uterine environment induced by insufficient steroid concentrations before and after ovulation could cause early embryonic death either by failing to provide an adequate uterine environment for recognition of embryo signaling, adhesion, and implantation or by failing to support appropriate embryonic growth, which could lead to decreased conceptus size and failed maternal recognition of pregnancy.

Early metabolic imprinting events increase marbling scores in fed cattle

Early weaning of calves to a high concentrate diet results in greater fat deposition and suggests early postnatal metabolic imprinting events may be exploited as a management tool to improve cattle value. Our objective was to implement a short, high energy dietary intervention before a typical grazing period to manipulate intramuscular fat deposition in finishing cattle. Fall-born, Angus-sired steer calves (n = 24) were stratified by sire and randomly assigned to normal weaned (NW) or metabolic-imprinted (MIP) treatments. At 105 ± 6d (135kg), MIP calves were transitioned to a diet containing 20% CP and 1.26 Mcal/kg NEg. Metabolic-imprinted calves were fed ad libitum as a group. Normal weaned calves remained on their dam until 253 ± 6 d of age. At this time, treatment groups were combined and grazed for 156 d on a mixed summer pasture. Following the grazing phase, steers were adapted to a corn silage-based feedlot diet and performance was monitored on 28-d intervals. Calves were staged for harvest based on backfat endpoint (target 1.0 to 1.2 cm). Metabolic-imprinted calves were heavier (P < 0.05) than NW calves (341 vs. 265 ± 4.2 kg) at normal weaning age. During the grazing phase, NW steers gained more weight than (P < 0.05) MIP steers (0.69 vs. 0.35 ± 0.03 kg/d). Feedlot performance and USDA yield grade were similar (P > 0.20) between treatments. However, MIP steers produced heavier (P < 0.05) carcasses (564 vs. 524 ± 5.6 kg) with higher (P < 0.001) marbling scores (645 vs. 517 ± 23). Therefore, calves consuming a high concentrate diet for 148 d after early weaning produced higher quality carcasses. This suggests early weaning and feeding a high concentrate before grazing is a viable strategy to increase marbling deposition compared with a traditional production system.

Induction of precocious puberty in heifers III: Hastened reduction of estradiol negative feedback on secretion of luteinizing hormone1

Precocious puberty (<300 d of age) can be induced in beef heifers by early weaning and feeding a high-concentrate diet. The objective of this experiment was to determine whether precocious puberty occurs as a result of a hastened reduction of estradiol negative feedback on secretion of LH. Thirty crossbred Angus and Simmental heifers were weaned at 83 +/- 2 d of age and 114 +/- 3 kg of BW, blocked by BW, and randomly assigned to receive a high-concentrate (60% corn; H) or control (30% corn; C) diet and to receive ovariectomy (OVX), OVX plus an estradiol implant (OVXE), or to remain intact (INT). Residual ovarian tissue after OVX necessitated withdrawal of 6 heifers during the course of the experiment, resulting in the following treatment groups: OVX-C, n = 3; OVX-H, n = 5; OVXE-C, n = 4; OVXE-H, n = 2; INT-C, n = 5; INT-H, n = 5. To determine concentrations of progesterone and estradiol, blood samples were collected weekly beginning at a mean age of 160 d. To characterize LH concentrations, serial blood samples were collected at 12-min intervals for 12 h at mean ages of 119, 149, 188, 217, 246, 281, 323, 365, 407, and 449 d. By a mean age of 202 d, heifers fed the H diet were heavier (P < 0.05) than those fed the C diet. Heifers in the INT-H treatment attained puberty earlier (P < 0.05) than in the INT-C treatment (275 +/- 30 vs. 385 +/- 14 d of age, respectively). Overall mean concentrations of estradiol did not differ between OVXE-H and OVXE-C, between INT-H and INT-C, or between OVXE and INT treatments. The OVX treatments exhibited greater LH pulse frequency than the OVXE and INT treatments by the first serial blood collection (treatment x age, P < 0.05). The frequency of LH pulses was greater (P < 0.05) in the INT-H than the INT-C treatment by a mean age of 246 d and was greater (P < 0.05) in the OVXE-H than the OVXE-C treatment by a mean age of 281 d. In the OVXE-H treatment, LH secretion increased and subsequently "escaped" from estradiol negative feedback (detection of > or = 1 LH pulse/h) earlier (P < 0.05) than in the OVXE-C treatment (307 +/- 30 and 420 +/- 21 d of age, respectively). It is concluded that advancing the reduction of estradiol negative feedback on secretion of LH is the mechanism by which early weaning and feeding a high-concentrate diet results in precocious puberty in heifers.

Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2alpha in combination with melengestrol acetate

Nonlactating Bos indicus x Bos taurus cows were used in three herds to determine the efficacy of different PGF2alpha treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 microg of GnRH. Cows were fed MGA (0.5 x mg x cow(-1) x d(-1)) on d 1 to 7. On d 7, cows received either a single injection of PGF2alpha (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 microg; n = 297), or half the recommended dose of PGF2alpha (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 microg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment x herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment x herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2alpha treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus x Bos taurus cows.