Effect of manipulating progesterone before timed artificial insemination on reproductive and endocrine parameters in seasonal-calving, pasture-based Holstein-Friesian cows

Incidence and timing of pregnancy loss following timed artificial insemination or timed embryo transfer with a fresh or frozen in vitro-produced embryo

The aim of this study was to characterize the incidence and timing of pregnancy loss from service event (timed artificial insemination or timed embryo transfer) to parturition. Lactating Holstein-Friesian cows were randomly assigned to receive either artificial insemination (AI, n = 243) or embryo transfer (ET, n = 863) with a fresh or frozen in vitro-produced blastocyst derived from oocytes collected from the ovaries of elite dairy donors (n = 14 Holstein Friesian and n = 8 Jersey) and elite beef donors (n = 21 Angus) using transvaginal ovum pick-up. In addition, oocytes were collected from the ovaries of beef heifers of known pedigree following slaughter at a commercial abattoir (n = 119). Blood samples were collected on d 7 from all cows to determine progesterone concentration and from subsets of cows on d 18 (n = 524) and d 25 (n = 378) to determine mRNA abundance of interferon-stimulated gene-15 and pregnancy-specific protein B concentration, respectively, to provide an early pregnancy diagnosis. Transrectal ultrasonography was conducted to determine pregnancy status on d 32, d 62 and d 125 after synchronized ovulation. Parturition date was recorded for all cows that reached a term delivery. The predicted probability of pregnancy (%) varied at each time point (d7, 18, 25, 32, 62, 125, parturition) depending on treatment (AI: 77.0, 60.2, 52.3, 48.8, 47.0, 44.6, 44.0; fresh ET: 100.0, 69.5, 60.3, 56.1, 48.4, 46.8, 45.5; frozen ET: 100.0, 61.7, 52.2, 41.6, 32.9, 31.8, 30.2). Irrespective of treatment, the largest proportion of pregnancy loss occurred in the period from service event (AI on d 0 or ET on d 7) to d 18, with minimal loss occurring between d 62 and parturition (AI: 1.8%, fresh ET: 1.9%, frozen ET: 3.5%). Treatment differences in the predicted probability of pregnancy per service event were detected between fresh ET vs frozen ET on d 32 and both AI and fresh ET vs frozen ET on d 62, 125 and at parturition. There was greater probability of pregnancy loss between d 32 and 62 following ET (Fresh: 11.3%, Frozen: 18.0%) than AI (4.0%). The percentage of cows that calved following transfer of a fresh embryo (45.5%) was similar to AI (44.0%), but less when a frozen embryo was transferred (30.2%). In conclusion, AI and fresh ET led to a greater probability of a cow becoming pregnant and maintaining the pregnancy to term than frozen ET. Cows that were still pregnant on d 62 had a very strong likelihood of maintaining the pregnancy to full-term parturition, irrespective of treatment. Further work is required to improve the likelihood of pregnancy establishment and reduce embryonic and fetal mortality following transfer of a cryopreserved in vitro-produced embryo.

When Implementing the Presynch-11/Ovsynch Reproductive Management Program, the Fertility of Lactating Dairy Cows Improved When They Received Timed Artificial Insemination Compared with the Inclusion of Estrus Detection

Artificial insemination 12 h following observed standing estrus is a standard estimate of the fertility levels of cattle. The main objective of this study was to determine if controlling ovarian development with a fertility program could alter the fertility of lactating dairy cows. Lactating dairy cows (n = 1356) 60-66 days in milk (DIM) were randomly assigned to receive timed AI following Presynch-11/Ovsynch (Presynch-11) or a combination of estrus detection and timed AI using the Presynch-11/Ovsynch program (Estrus + TAI). Cows in standing estrus, following the first two cloprostenol sodium (CLO) injections, in the Estrus + TAI group were artificially inseminated using the AM/PM rule. Cows in this group that were not observed in standing estrus received Ovsynch and TAI beginning 11 d after the second CLO injection. Cows in the Presynch-11 group received two injections of 500 µg CLO 14 d apart but were not observed for estrus. The first GnRH (100 µg) of Ovsynch was administered 11 d following the second CLO injection. All cows in the Presynch-11-Ovsynch group received TAI following Ovsynch. Cows in this treatment were then assigned randomly to receive either CLO or dinoprost 7 d following the first GnRH of Ovsynch. The final GnRH of Ovsynch was administered 56 h later and TAI 16 h after the final GnRH. Pregnancies/AI (P/AI) were greater (p < 0.001) for the Presynch-11 group compared with the Estrus + TAI group (45 vs. 31%). Primiparous cows had greater fertility following observed standing estrus compared with multiparous cows. Days in milk at the first AI were greater (p < 0.01) in the Presynch-11 group vs. the Estrus + TAI group (98 vs. 80) but less variable (p < 0.01). The range of DIM at the first AI was 95 to 101 in the Presynch-11 group and 60 to 101 in the Estrus + TAI group. Within the Presynch-11 group, there were no differences in the rate of luteolysis or P/AI for the prostaglandin type at the final PGF2α of Ovsynch. Multiparous cows treated with Presynch-11 had >60% chance of pregnancy compared with multiparous cows receiving AI following standing estrus. In summary, lactating dairy cows receiving timed AI following the Presynch-11/Ovsynch program had improved fertility compared with a group of cows that received AI following standing estrus or, if not observed in estrus, timed AI. This comparison indicated that controlling ovarian development with GnRH and PGF2α positively impacted the fertility of lactating dairy cows.

Effect of postpartum body condition score change on the pregnancy outcomes of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after a synchronized estrus versus a synchronized ovulation

Our objective was to compare insemination rate and pregnancies per artificial insemination (P/AI) of lactating Jersey cows inseminated at first service with sexed Jersey or conventional beef semen after submission to a Double-Ovsynch protocol for timed artificial insemination (TAI) versus a protocol to synchronize estrus at similar days in milk (DIM). Secondary objectives were to determine the effect of protocol synchrony and postpartum body condition score (BCS) change on P/AI. Lactating Jersey cows (n = 1,272) were allocated by odd versus even ear tag number, which was randomly allocated within the herd, within parity and semen type for submission to a Double-Ovsynch protocol (DO; n = 707) or a protocol to synchronize estrus (ED; n = 565). All ED cows detected in estrus were inseminated (EDAI; n = 424), with undetected cows receiving TAI after an Ovsynch protocol (EDTAI; n = 141). There was a treatment by parity interaction on insemination rate with 100% of DO cows receiving TAI, but a tendency for fewer primiparous ED cows to be detected in estrus and AI than multiparous cows (69.5% ± 0.04% vs. 77.1% ± 0.02%, respectively). For cows inseminated with sexed Jersey or conventional beef semen, DO cows tended to have and had more P/AI than EDAI cows (sexed, 49.2% ± 0.03% vs. 43.6% ± 0.03%; beef, 64.2% ± 0.04% vs. 56.3% ± 0.05%, respectively) and had more P/AI than EDAI+EDTAI cows (sexed, 49.1% ± 0.03% vs. 40.6% ± 0.03%; beef, 65.5% ± 0.04% vs. 56.2% ± 0.04%, respectively). Overall, 29.1% of DO cows expressed estrus with 5.0% and 24.2% of cows detected in estrus ≥24 h before and at TAI, respectively, and there was no difference in P/AI 61 ± 4 d after AI based on expression of estrus at TAI. The synchronization rate was greater for DO than EDAI cows (92.1% ± 0.01% vs. 79.2% ± 0.02%, respectively); however, synchronized DO cows had more P/AI than synchronized EDAI cows (55.0% ± 0.02% vs. 49.2% ± 0.03%, respectively). There was an interaction between BCS change from 7 to 39 ± 2 DIM and treatment on P/AI 61 ± 4 d after AI with no difference between DO and EDAI cows that lost = 0.25 (49.8% ± 0.04% vs. 51.0% ± 0.05%, respectively) or maintained or gained (55.6% ± 0.04% vs. 50.8% ± 0.05%, respectively) BCS, but within cows that lost ≥0.5 BCS, DO cows had more P/AI than EDAI cows (54.1% ± 0.04% vs. 36.1% ± 0.04%, respectively). In conclusion, submission of lactating Jersey cows to a Double-Ovsynch protocol for first insemination increased insemination rate and fertility to first insemination compared with AI after a detected estrus regardless of semen type and expression of estrus, particularly for cows with excessive postpartum BCS loss.

Comparison of reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen based on expression of estrus, pregnancy outcomes, and cost per pregnancy

Our objective was to evaluate reproductive management programs for submission of Holstein heifers for first insemination with conventional or sexed semen. In experiment 1, nulliparous Holstein heifers (n = 462) were submitted to a 5-d progesterone-releasing intravaginal device (PRID)-Synch protocol [d 0, GnRH + PRID; d 5, PGF_2α - PRID; d 6, PGF_2α; d 8, GnRH + TAI] and were randomly assigned for PRID removal on d 5 or 6 of the protocol followed by timed artificial insemination (TAI) with conventional semen. Delaying PRID removal decreased early expression of estrus before scheduled TAI (0.9 vs. 12.2%), and pregnancies per AI (P/AI) did not differ between treatments. In experiment 2, nulliparous Holstein heifers (n = 736) from 3 commercial farms were randomized within farm to 1 of 3 treatments for first AI with sexed semen: (1) CIDR5 [d -6, GnRH + controlled internal drug release (CIDR); d -1, PGF_2α - CIDR; d 0, PGF_2α; d 2, GnRH + TAI]; (2) CIDR6 (d -6, GnRH + CIDR; d -1, PGF_2α; d 0, PGF_2α - CIDR; d 2, GnRH + TAI); and (3) EDAI (PGF_2α on d 0 followed by once-daily estrous detection and AI). Delaying CIDR removal decreased early expression of estrus before scheduled TAI (0.004 vs. 27.8%); however, CIDR5 heifers tended to have more P/AI at 35 (53 vs. 45 vs. 46%) and 64 (52 vs. 45 vs. 45%) days after AI than CIDR6 and EDAI heifers, respectively. Overall, CIDR5 and CIDR6 heifers had fewer days to first AI and pregnancy than EDAI heifers which resulted in less feed costs than EDAI heifers due to fewer days on feed until pregnancy. Despite greater hormonal treatment costs for CIDR5 heifers, costs per pregnancy were $16.66 less for CIDR5 than for EDAI heifers. In conclusion, delaying PRID removal by 24 h within a 5-d PRID-Synch protocol in experiment 1 suppressed early expression of estrus before TAI, and P/AI for heifers inseminated with conventional semen did not differ between treatments. By contrast, although delaying CIDR removal by 24 h within a 5-CIDR-Synch protocol in experiment 2 suppressed early expression of estrus before TAI, delaying CIDR removal by 24 h tended to decrease P/AI for heifers inseminated with sexed semen. Further, submission of heifers to a 5-d CIDR-Synch protocol for first AI tended to increase P/AI and decrease the cost per pregnancy compared with EDAI heifers.

Omega-6 Fatty Acids: A Sustainable Alternative to Improve Beef Production Efficiency

Simple Summary

The global beef industry is currently challenged with improving production efficiency while fostering judicious use of limited natural resources. Sustainable management systems are warranted to ensure that worldwide demands for beef and ecological stewardship are met. Supplementing cattle with omega-6 fatty acids is a nutritional intervention shown to sustainably enhance productivity across different sectors of the beef industry. The purpose of this review is to discuss recent research that describes the advantages of supplementing omega-6 fatty acids on traits that are critical to beef production efficiency, including reproduction, immunocompetence, growth, and quality of carcass and beef products.

Abstract

Global beef production must increase in the next decades to meet the demands of a growing population, while promoting sustainable use of limited natural resources. Supplementing beef cattle with omega-6 fatty acids (FAs) is a nutritional approach shown to enhance production efficiency, with research conducted across different environments and sectors of the beef industry. Omega-6 FA from natural feed ingredients such as soybean oil are highly susceptible to ruminal biohydrogenation. Hence, our and other research groups have used soybean oil in the form of Ca soaps (CSSO) to lessen ruminal biohydrogenation, and maximize delivery of omega-6 FA to the duodenum for absorption. In cow–calf systems, omega-6 FA supplementation to beef cows improved pregnancy success by promoting the establishment of early pregnancy. Cows receiving omega-6 FA during late gestation gave birth to calves that were healthier and more efficient in the feedlot, suggesting the potential role of omega-6 FA on developmental programming. Supplementing omega-6 FA to young cattle also elicited programming effects toward improved adipogenesis and carcass quality, and improved calf immunocompetence upon a stress stimulus. Cattle supplemented with omega-6 FA during growing or finishing periods also experienced improved performance and carcass quality. All these research results were generated using cattle of different genetic composition (Bos taurus and B. indicus influenced), and in different environments (tropical, subtropical, and temperate region). Hence, supplementing omega-6 FA via CSSO is a sustainable approach to enhance the production efficiency of beef industries across different areas of the world.

Effect of PGF2α treatments during early corpus luteum development on circulating progesterone concentrations and ovulation in breeding-age Holstein heifers

The objective of this study was to test the effect of low circulating concentrations of progesterone (P4) on pre-ovulatory follicle development in heifers as part of an overarching objective to develop a model to understand this phenomenon in dairy cattle without the confounding factors of lactation. Holstein heifers between 12 and 13 mo of age were pre-synchronized to ensure all heifers were on d 6 of the estrous cycle at the start of the Ovsynch program. Only heifers with CL regression and ovulation to the following pre-treatment strategy were used in the study: 0.5 mg cloprostenol (PGF_2α), 2 d later, 0.1 mg GnRH, 6 d later, GnRH (G1; 1st GnRH of Ovsynch). Heifers (n = 159) responding to pre-treatment were randomly assigned to 4 groups and completed the Ovsynch program: high P4 control (HPC), low P4 control (LPC; PGF_2α 24 h after G1), PG2 (PGF_2α 24 and 48 h after G1) and PG3 (PGF_2α 24, 48, and 96 h after G1). Only heifers that had ovulation to G1 remained in the study. Blood samples were collected in all heifers on d 7 (n = 157) and in a subset of heifers on d 1, 2, 3, 4 (n = 82) after G1 to measure serum P4. Pre-ovulatory follicle size at G1 (13.0 ± 0.1 mm; P = 0.53) and mean serum P4 24 h after G1 (d 1; 3.62 ± 0.11 ng/mL; P = 0.46) did not differ among treatments. HPC heifers had greater (P < 0.001) mean serum P4 compared to LPC, PG2 and PG3 on d 2, 3, 4, and 7. On d 2, 3 and 4, mean serum P4 of LPC, PG2 and PG3 heifers did not differ (P > 0.10). On d 7, LPC heifers had greater (P < 0.001) serum P4 compared to PG2 and PG3 heifers. Mean ± SEM serum P4 on d 7 after G1 was 8.43 ± 0.39, 2.55 ± 0.36, 1.58 ± 0.20, and 1.21 ± 0.15 ng/mL for HPC, LPC, PG2, and PG3, respectively. Percentage of heifers with P4 < 0.50 ng/mL on d 7 was greater (P < 0.05) for LPC, PG2 and PG3 (27, 32 and 26%, respectively) compared to HPC (0%). A greater (P < 0.05) proportion of heifers ovulated before G2 in the LPC, PG2 and PG3 than in the HPC. For heifers that ovulated after G2, low serum concentrations of P4 in LPC, PG2 and PG3 induced double ovulations in 6/97 heifers after the final GnRH of Ovsynch compared to 0/33 in HPC. In summary, PGF_2α treatments during early CL development reduced circulating P4 concentrations 7 d after G1 compared with both HPC and LPC. However, it did not effectively control CL and follicle function to be utilized as a model to test high vs. low serum P4 on fertility parameters in Holstein heifers.

Economics of Twin Pregnancies in Dairy Cattle

Simple Summary

Twinning in dairy cattle is not desirable due to negative effects on both cows that calve twins and calves born as twins that result in economic losses to dairy farms. Although a twin pregnancy could bring additional income from extra calves and it could shorten gestation length, twinning compromises milk production, increases the incidence of dystocia and perinatal mortality, decreases calf birth weight, increases the incidence of metabolic diseases, decreases fertility, increases the incidence of freemartinism, increases overall culling risks, and shortens the productive lifespan of cows. Based on a summary of economic analyses from several studies, the estimated losses due to twinning range between $59 to $161 per twin pregnancy. When twins are diagnosed early during gestation, management options might include doing nothing, terminating the pregnancy, or attempting manual embryo reduction. Based on a recent economic analysis of these options, attempting manual embryo reduction decreased the economic losses of a twin pregnancy by $23 to $45.

Abstract

Twinning in Holstein dairy cows has increased over time concurrent with increased milk production. Twinning in dairy cattle is not desirable due to the negative effects on both cows that calve twins and calves born as twins that result in economic losses to dairy farms. Although a twin pregnancy could bring additional income from extra calves and shorten gestation length, twinning compromises milk production, increases the incidence of dystocia and perinatal mortality, decreases calf birth weight, increases the incidence of metabolic diseases, decreases fertility, increases the incidence of freemartinism, increases overall culling risks, and shortens the productive lifespan of cows. Based on a summary of economic analyses from several studies, the estimated losses due to twinning range between $59 to $161 per twin pregnancy. Most twinning in dairy cows is dizygotic and directly related to the incidence of double ovulations, and economic losses are greater for unilateral than for bilateral twins. Hormonal manipulation before artificial insemination that allows for timed artificial insemination is a primary strategy for decreasing twinning in dairy cows before it occurs by decreasing the incidence of double ovulation thereby decreasing conception of dizygotic twins and the associated negative economic consequences. When twins are diagnosed early during gestation, management options might include doing nothing, terminating the pregnancy, or attempting manual embryo reduction. Based on a recent economic analysis of these options, attempting manual embryo reduction decreased the economic losses of a twin pregnancy by $23 to $45.

Uterine infusion of bacteria alters the transcriptome of bovine oocytes

Postpartum uterine infection reduces fertility in dairy cattle; however, the mechanisms of uterine infection-mediated infertility are unknown. Paradoxically, infection-induced infertility persists after the resolution of disease. Oocytes are a finite resource, which are present at various stages of development during uterine infection. It is likely that oocyte development is influenced by uterine infection-induced changes to the follicular microenvironment. To better understand the impact of infection on oocyte quality we employed global transcriptomics of oocytes collected from heifers after receiving intrauterine infusion of pathogenic Escherichia coli and Trueperella pyogenes. We hypothesized that the oocyte transcriptome would be altered in response to intrauterine infection. A total of 452 differentially expressed genes were identified in oocytes collected from heifers 4 days after bacteria infusion compared to vehicle infusion, while 539 differentially expressed genes were identified in oocytes collected from heifers 60 days after bacteria infusion. Only 42 genes were differentially expressed in bacteria-infused heifers at both Day 4 and Day 60. Interferon, HMGB1, ILK, IL-6, and TGF-beta signaling pathways were downregulated in oocytes collected at Day 4 from bacteria-infused heifers, while interferon, ILK, and IL-6 signaling were upregulated in oocytes collected at Day 60 from bacteria-infused heifers. These data suggest that bacterial infusion alters the oocyte transcriptome differently at Day 4 and Day 60, suggesting different follicle stages are susceptible to damage. Characterizing the long-term impacts of uterine infection on the oocyte transcriptome aids in our understanding of how infection causes infertility in dairy cattle.

Effects of estrous expression and intensity of behavioral estrous symptoms on variables associated with fertility in beef cows treated for fixed-time artificial insemination

This experiment was conducted to evaluate effects of estrous expression and intensity of behavioral estrous expression, assessed by evaluating physical activity, on variables associated with fertility in beef cows. The following treatment regimen was imposed on lactating, multiparous cows (n = 273): 100-μg injection of GnRH and an intravaginal progesterone (P4) releasing device (CIDR) administered on d -10, 25-mg injection of prostaglandin F_2α at CIDR removal on d -3, and another GnRH injection + fixed-time artificial insemination (TAI) 60-66 h following CIDR removal (d 0). Cows were fitted with a pedometer on d -10, and an estrous detection patch on the tail-head on d -3. Cows were classified as not expressing estrus (NOESTR) or expressing estrus with net physical activity greater (HIESTR) or less than the median (LWESTR). Only data from cows responsive to the estrous synchronization treatment regimen were utilized (NOESTR, n = 119; LWESTR, n = 50; HIESTR, n = 50). Diameter of dominant follicles on d 0 and corpus luteum volume on d 7 were greater in HIESTR compared with LWESTR and NOESTR groups (P < 0.01). Plasma P4 concentrations on d 7 and pregnancy rates to TAI were greater in HIESTR and LWESTR than the NOESTR group (P < 0.01). Hence, if there was estrous expression during the period of the GnRH-based TAI treatment regimen, there were greater pregnancy rates to TAI, whereas when there was greater intensity of behavioral estrous symptoms, there were larger dominant follicles and corpora lutea dimensions but not greater pregnancy rates.

Cattle adapted to tropical and subtropical environments: social, nutritional, and carcass quality considerations

Beef production needs to increase from 60 million to 130 million tons by 2050 to feed a growing world population, and 70% of this production increase is expected from beef industries located in subtropical and tropical regions of the world. Bos indicus-influenced cattle predominate in these regions but are often managed using practices developed for Bos taurus breeds reared in temperate climates. Hence, a fundamental step to meet the increasing global demand for beef is to develop specific management for B. indicus-influenced cattle in tropical or subtropical environments. Bos taurus and B. indicus are different subspecies, and diverge in social and biological functions due to selection pressure caused by complex evolutionary and domestication processes. Bos indicus cattle display different social responses compared with B. taurus counterparts, which must be taken into account by management planning as these traits directly impact cattle performance and welfare. In tropical and subtropical regions, warm-season perennial C4 grasses are the dominant forages, and their availability has a significant influence on the productivity of beef cattle systems. The resilience of C4 grasses under adverse conditions is one of their most important characteristics, even though these forages have reduced nutritive value compared with forages from temperate climates. Accordingly, nutritional planning in tropical and subtropical conditions must include management to optimize the quantity and quality of C4 forages. Nutritional requirements of cattle raised within these conditions also require special attention, including inherent metabolic compromises to cope with environmental constraints and altered energy requirements due to body composition and heat tolerance. Nutritional interventions to enhance beef production need to be specifically tailored and validated in B. indicus-influenced cattle. As an example, supplementation programs during gestation or early life to elicit fetal programming or metabolic imprinting effects, respectively, yield discrepant outcomes between subspecies. Bos indicus-influenced cattle produce carcasses with less marbling than B. taurus cattle, despite recent genetic and management advances. This outcome is mostly related to reduced intramuscular adipocyte volume in B. indicus breeds, suggesting a lesser need for energy stored intramuscularly as a mechanism to improve thermotolerance in tropical and subtropical climates.

Effect of two prostaglandin injections on days 5 and 6 in a timed AI protocol after estrus expression on pregnancy outcomes in dairy cows during cold or hot seasons of the year

The objective of this study was to test whether prostaglandin (PG) injection on day 30 postpartum (pp) and detection of estrus can affect the efficacy of injecting PG on days 5 and 6 in the timed artificial insemination (TAI) protocol on pregnancy rate in a large dairy herd in hot or cold seasons. Out of 2235 cows, 1998 received an injection of PG at 30±3 d pp and estrus was observed. Cows that displayed estrus during the estrous observation period after PG injection were classified as estrus (E), while those that did not show estrus were classified as nonestrus (NE). Cows in each group were assigned to two treatments: CO-72 (control treatment) (ECO-72 and NECO-72) (day 44 GnRH, day 51 PGF2α, day 54 GnRH+TAI) or PG–PG (EPG–PG and NEPG–PG) (day 44 GnRH, day 49 PGF2α, day 50 PGF2α, day 52 GnRH+TAI). Pregnancy was diagnosed on days 33 and 47 after artificial insemination (AI). The proportion of cows in estrus on the day of TAI was higher (P≤0.05) for cows that received two PG than for cows that received one PG. Pregnancies per AI (P/AI) on days 33 and 47 for cows inseminated during and after a voluntary waiting period in the NEPG–PG treatment had higher rates than for cows in the EPG–PG, ECO-72 and NECO-72 treatments. Moreover, P/AI were significantly (P≤0.05) affected by parity. Primiparous had higher P/AI (37.0 %) than multiparous cows (31.6 %). Cows inseminated in cold months had higher P/AI and reduced PL (35.6 % and 20.8 %) than cows inseminated in hot months (29.1 % and 30.6 %, respectively). In conclusion, treatments with PG on days 5 and 6 after the first GnRH injection increased P/AI. Estrus detection before the beginning of TAI protocol did not affect fertility. To maximize P/AI cows exhibiting heat at any time during the synchronization protocol should be inseminated.

Estrous expression during a fixed-time artificial insemination protocol enhances development and interferon-tau messenger RNA expression in conceptuses from Bos indicus beef cows

Expression of estrus (EST) near the time of fixed-time artificial insemination (FTAI) increases pregnancy success in beef females. This outcome has been associated with improved pregnancy establishment and maintenance, although research is still warranted to validate this theory. Hence, this experiment compared ovarian, uterine and conceptus factors associated with pregnancy establishment in Bos indicus beef cows according to estrous expression during a FTAI protocol. One hundred lactating multiparous Nelore cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device on day -11, a 12.5 mg injection of prostaglandin F2α on day -4, P4 device removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of equine chorionic gonadotropin on day -2, and FTAI on day 0. An estrous detection patch was attached to the tailhead of each cow on day -2, and estrous expression was defined as removal of >50% of the rub-off coating from the patch at FTAI. Overall, 39 cows expressed EST, 55 did not express EST (NOEST), and six cows lost their patch and were discarded from the experiment. Ovarian ultrasonography was performed at FTAI, and on days 7 and 15 of the experiment. Blood samples were also collected on days 7 and 15. Only cows without a corpus luteum (CL) on day 0, and with a CL on days 7 and 15 remained in the experiment (EST, n=36; NOEST, n=48). On day 15, cows were randomly selected within each group (EST, n=29; NOEST, n=30) for conceptus collection via transcervical flushing, followed by endometrial biopsy in the uterine horn ipsilateral to the CL. Within cows not assigned to conceptus collection, blood samples were collected for whole blood RNA extraction (day 20) and pregnancy status was verified by transrectal ultrasonography (day 30). Diameter of dominant follicle on day 0 and plasma P4 concentrations on day 7 were greater (P⩽0.02) in EST v. NOEST cows. Conceptus length and messenger RNA (mRNA) expression of prostaglandin E synthase and interferon-tau were greater (P⩽0.04) in EST v. NOEST cows. Moreover, EST cows diagnosed as pregnant on day 30 had greater (P<0.01) blood mRNA expression of myxovirus resistance 2 on day 20 compared with NOEST. In summary, estrous expression near the time of FTAI enhanced pregnancy establishment factors in B. indicus cows, including conceptus development and mRNA expression of interferon-tau.

Supplementing an immunomodulatory feed ingredient to improve thermoregulation and performance of finishing beef cattle under heat stress conditions

This experiment compared physiological and productive responses in finishing beef cattle managed under heat stress conditions, and supplemented (SUPP) or not (CON) with an immunomodulatory feed ingredient (Omnigen-AF; Phibro Animal Health, Teaneck, NJ). Crossbred yearling cattle (¾ Bos taurus × ¼ Bos indicus; 64 heifers and 64 steers) were ranked by initial body weight (BW) (440 ± 3 kg) and sex, and allocated to 1 of 16 unshaded drylot pens (8 heifers or steers/pen). Pens within sex were randomly assigned to receive SUPP or CON (n = 8/treatment). Cattle received a total-mixed ration (91% concentrate inclusion and 1.21 Mcal/kg of net energy for gain; dry matter [DM basis]) during the experiment (day 0 to 106). The immunomodulatory feed was offered as a top-dress to SUPP pens (56 g/d per animal; as-fed basis) beginning on day 7. Cattle BW were recorded on day 0, 14, 28, 42, 56, 70, 84, 98, and 106. Feed intake was evaluated from each pen by recording feed offer daily and refusals biweekly. Intravaginal temperature of heifers was recorded hourly from day 1 to 6, 29 to 41, and 85 to 97. Environmental temperature humidity index (THI) was also recorded hourly throughout the experiment, and averaged 79.8 ± 0.6. Concurrently with BW assessment, hair samples from the tail-switch were collected (3 animals/pen) for analysis of hair cortisol concentrations. Blood samples were collected on day 0, 28, 56, 84, and 106 from all animals for plasma extraction. Whole blood was collected on day 0, 56, and 106 (3 animals/pen) for analysis of heat shock protein (HSP) 70 and HSP72 mRNA expression. Cattle were slaughtered on day 107 at a commercial packing facility. Results obtained prior to day 7 served as independent covariate for each respective analysis. Heifers receiving SUPP had less (P ≤ 0.05) vaginal temperature from 1500 to 1900 h across sampling days (treatment × hour, P < 0.01; 39.05 vs. 39.19 °C, respectively; SEM = 0.04), when THI ranged from 85.3 to 90.1. Expression of HSP70 and HSP72 was less (P ≥ 0.03) for SUPP cattle on day 106 (22.6- vs. 51.5-fold effect for HSP70, SEM = 9.7, and 11.0- vs. 32.8-fold effect for HSP72; treatment × day, P ≤ 0.04). No treatment effects were detected (P ≥ 0.22) for performance, carcass traits, plasma concentrations of cortisol and haptoglobin, or hair cortisol concentrations. Results from this study suggest that SUPP ameliorated hyperthermia in finishing cattle exposed to heat stress conditions, but such benefit was not sufficient to improve productive responses.

Effect of manipulating progesterone before timed artificial insemination on reproductive and endocrine outcomes in high-producing multiparous Holstein cows

Our objective was to evaluate the effect of manipulating progesterone (P4) concentrations before timed artificial insemination (TAI) on reproductive and endocrine outcomes in high-producing Holstein cows. Multiparous lactating Holstein cows (n = 80) were synchronized for first TAI using a Double-Ovsynch protocol and were randomly assigned to receive 25 mg of PGF_2α 1 d after the first GnRH treatment of the Breeding-Ovsynch protocol that included a once-used P4 insert (low-P4 group) or to receive 2 new P4 inserts during the Breeding-Ovsynch protocol (high-P4 group). Blood samples were collected thrice weekly from -10 to 32 d relative to TAI for all cows and from 32 to 67 d after TAI for pregnant cows and were analyzed for P4 and pregnancy-specific protein B (PSPB) concentrations. Expression of IFNτ-stimulated gene 15 (ISG15) was assessed in blood leukocytes 18 and 20 d after TAI. As expected, P4 concentrations were greater for high-P4 cows than for low-P4 cows from 3 to 8 d before TAI. Incidence of double ovulation was 3-fold greater for low-P4 cows than for high-P4 cows (33 vs. 10%), which resulted in more twin pregnancies 32 d after TAI for low-P4 cows than for high-P4 cows (29 vs. 0%). Low-P4 cows had larger preovulatory follicles at the last GnRH treatment of the Double-Ovsynch protocol and greater P4 concentrations than high-P4 cows after TAI. Relative expression of ISG15 mRNA 18 and 20 d after TAI was greater for low-P4 cows than for high-P4 cows and for pregnant cows than for nonpregnant cows. Overall, PSPB concentrations tended to be greater for low-P4 cows than for high-P4 cows, and pregnant cows had greater P4 concentrations than nonpregnant cows. In summary, cows with low P4 before TAI had increased preovulatory follicle diameter, PSPB concentrations, relative expression of ISG15 mRNA 18 and 20 d after TAI, double ovulations, and twinning compared with cows with high P4 before TAI. Increasing P4 before TAI may effectively decrease double ovulation and twinning in high-producing multiparous Holstein cows.

Effects of Separation of Cows and Calves on Reproductive Performance and Animal Welfare in Tropical Beef Cattle

Nursing a calf suppresses postpartum ovarian activity prolonging the period of anestrus. Diverse methods are used to reduce the effect of suckling; the most popular, restricted suckling, reduces the number of encounters mother-calf. Temporal weaning of the calf for periods of 24 h, 48 h, or even 72 h also suppress the effect of suckling and is commonly applied to cow-calf operations in the tropics. Early weaning of the calf, usually three to five months after birth, is a practice gaining popularity over the traditional system of weaning at seven months. Furthermore, the use of nose-flaps in the calf to avoid suckling is a common procedure in South America. Finally, weaning during the first week after calving is an established method to reduce postpartum anestrus. The objective of the present review is to discuss the effects of these methods on the reproductive performance of beef cattle and their animal welfare implications.

Absence of a corpus luteum and relatively lesser concentrations of progesterone during the period of pre-ovulatory follicle emergence results in lesser pregnancy rates in Bos indicus cattle

Concentrations of progesterone before AI have had variable effects on fertility in both Bos indicus and Bos taurus cattle. The aim of this study was to determine if fertility and concentrations of progesterone after AI were affected in Bos indicus females when pre-ovulatory follicles develop in the absence or presence of a corpus luteum (CL). Between 6.5-7.5 days after a synchronised oestrus, all follicles ≥4 mm in diameter were aspirated (Day 0) and cloprostenol was administered on Days 0 and 1 (LP4, n = 36) or on Days 4 and 5 (HP4, n = 40). Animals were inseminated on detection of oestrus until Day 9. Breeding continued using natural mating between Days 9 and 19, AI on detection of oestrus between Day 19 and 29 and natural mating between Days 29-90. Mean concentrations of progesterone were less on Days 2-4 in the LP4 compared to the HP4-treated animals but similar on Days 14 and 20. In the LP4- compared to the HP4-treated animals, the odds of being detected in oestrus and ovulating close to the first AI were similar, but odds of pregnancy to first AI (OR = 0.19, 95% CI 0.07 - 0.52) and after 1, 4 and 13 weeks of breeding were less (P ≤  0.051). Absence of a CL and relatively lesser concentrations of progesterone during emergence of pre-ovulatory follicles resulted in lesser pregnancy rates to AI in Bos indicus cattle but did not affect concentrations of P4 after ovulation.

Early career achievement award: supplementing omega-6 fatty acids to enhance early embryonic development and pregnancy establishment in Bos indicus and B. taurus beef cows

Our research group investigated the impacts of supplementing Ca salts of soybean oil (CSSO), a source of omega-6 fatty acids (FAs), on reproductive performance of beef cows. Initial studies were conducted with Nelore (Bos indicus) cows grazing tropical pastures. Cows were assigned to fixed-time artificial insemination (AI) and supplemented or not with 100 g/d (as-fed basis) of CSSO, and supplementation regimens ranged from days -11 to 28 relative to AI. Overall, CSSO supplementation during the 21 d after AI increased (P < 0.01) pregnancy rates from 38.1% (623/1,635 as pregnant/total nonsupplemented cows) to 49.0% (843/1,720 as pregnant/total CSSO-supplemented cows), and these outcomes were associated with enhanced early embryonic development and pregnancy establishment when omega-6 FA were supplemented. To verify this rationale, our group compared FA incorporation in grazing Nelore cows (n = 90) supplemented or not with CSSO (100 g/d; as-fed basis) beginning at fixed-time AI until slaughter at day 19 of gestation. Supplementing CSSO increased (P ≤ 0.05) incorporation of linoleic acid and its omega-6 derivatives in plasma, endometrium, corpus luteum, and conceptus, whereas the same responses were not observed (P ≥ 0.25) for omega-3 FA. Complementing these findings, grazing Nelore cows (n = 100) were supplemented or not with CSSO (100 g/d; as-fed basis) beginning at fixed-time AI, and assigned to transcervical uterine flush on day 15 of gestation. Supplementing CSSO increased (P ≤ 0.04) conceptus length (2.58 vs. 1.15 cm) and mRNA expression of interferon-tau (4.1-fold increase) and prostaglandin E synthase 2 (2.6-fold increase), which are critical regulators of pregnancy establishment. These outcomes were recently replicated in B. taurus beef cows consuming temperate forages. Pregnancy rates were greater (P = 0.01) in Angus cows receiving CSSO (100 g/d; as-fed basis) for 21 d after fixed-time AI (60.2%; 226/383 as pregnant/total cows) compared with nonsupplemented cows (51.7%; 193/388 as pregnant/total cows). Supplementing CSSO to Angus × Hereford cows (n = 96) beginning after AI also increased (P = 0.05) mRNA expression of interferon-tau in day 15 conceptuses (1.8-fold increase). Collectively, our research demonstrated that post-AI CSSO supplementation favors incorporation of omega-6 FA into maternal and embryonic tissues, which enhances interferon-tau synthesis by the conceptus and increases pregnancy rates to fixed-time AI in B. indicus and B. taurus beef cows.

Supplementing Ca salts of soybean oil after artificial insemination increases pregnancy success in Bos taurus beef cows

Two experiments investigated the effects of supplementing Ca salts of soybean oil (CSSO) during early gestation on reproductive function and pregnancy rates to AI in Bos taurus beef cows. In Exp. 1, 771 suckled, lactating, multiparous Angus cows were divided into 22 groups of approximately 35 cows per group and timed inseminated on day 0. After AI, groups were assigned randomly to receive (as-fed basis) 100 g of ground corn + 100 g of soybean meal per cow/d, in addition to 1) 100 g/cow daily of CSSO (n = 11) or 2) 87 g of prilled saturated fat + 13 g of limestone per cow/d (CON; n = 11). Groups were maintained in individual tall fescue-dominated pastures and offered treatments from day 0 to 21. Pregnancy status was determined between days 45 and 55 via transrectal ultrasonography. Cows receiving CSSO had greater (P = 0.01) pregnancy rates to timed AI compared with CON (60.2 vs. 51.7%; SEM = 4.2). In Exp. 2, 90 suckled, lactating, multiparous Angus × Hereford cows housed in 18 drylot pens (5 cows per pen) were assigned to the same timed AI program and treatments from Exp. 1 (9 pens per treatment) and received 20 kg/d (DM basis) of grass-alfalfa hay. Transrectal ultrasonography was performed to verify ovulation and corpus luteum (CL) volume before AI (day 0), on days 7 and 15. After ultrasonography on day 15, cows diagnosed without a CL on day 0, but with a CL greater than 0.38 cm3 in volume on days 7 and 15 (2 or 3 cows per pen; CSSO, n = 20; CON, n = 24), were assigned to conceptus collection via transcervical flushing and endometrial biopsy in the uterine horn ipsilateral to the CL. Blood samples were collected for FA analysis on days 0, 7, and 15. Blood was collected from cows not assigned to conceptus collection for whole-blood RNA extraction on day 20 and for pregnancy diagnosis on day 30 by measuring concentrations of pregnancy-associated glycoproteins. Cows receiving CSSO had greater (P ≤ 0.04) mean plasma concentrations of linoleic acid and ω-6 FA compared with CON on days 7 and 15. Moreover, CSSO supplementation increased (P = 0.05) mRNA expression of interferon-tau by the conceptus and blood mRNA expression of interferon-stimulated gene 15 and 20,50-oligoadenylate synthetase on day 20 in gestating cows. Hence, post-AI CSSO supplementation to B. taurus beef cows improved pregnancy rates to timed AI, which can be associated with increased mRNA expression of interferon-tau by the conceptus when CSSO is supplemented during early gestation.

Level of circulating concentrations of progesterone during ovulatory follicle development affects timing of pregnancy loss in lactating dairy cows

The objective of this experiment was to determine the effect of high versus low progesterone (P4) during the pre-dominance or dominance phase (or both) of ovulatory follicle development on follicular dynamics and fertility of lactating dairy cows. Progesterone (P4) was manipulated to reach high (H) or low (L) serum concentrations during the pre-dominance phase (d 0 to 4 of the wave) and dominance phase (d 5 to 7 of the wave) of a second follicular wave ovulatory follicle, creating 4 treatments: H/H, H/L, L/H, and L/L. Luteolysis was induced with PGF_2α on d 7 of the wave and ovulation was induced with GnRH 56 h after PGF_2α. Cows (n = 558) received artificial insemination (AI) 16 h following GnRH. Pregnancy was determined at 6 intervals during gestation and at calving to quantify pregnancy loss beginning at d 23 post-AI utilizing pregnancy-specific protein B (PSPB) in novel within-cow comparisons. Cows with single ovulations assigned to the L/L treatment had greater pre-ovulatory follicle diameter compared with cows assigned to the L/H or H/L treatments. Cows with single ovulations had greater pre-ovulatory follicle diameter compared with cows with double ovulations. Low P4 in H/L, L/H, and L/L increased double ovulation rate compared with H/H. Cows with double ovulations had greater pregnancies per AI (P/AI) on d 23 post-AI compared with cows with single ovulations but had greater losses if ovulations were unilateral. Cows with low P4 during the entire period of the ovulatory follicle development also had greater P/AI on d 23 post-AI compared with cows with high P4 during both phases. However, full-term P/AI was not different between treatments. This was a result of the greater incidence of pregnancy losses between d 35 and 56 of gestation for cows with unilateral double ovulations compared with bilateral double ovulations and single ovulatory cows. Cows with single ovulation and low circulating P4 during the dominance period of follicle development had increased pregnancy losses between d 35 and 56 of gestation compared with cows with single ovulations and high P4. The PSPB measurements on d 16 and 23 post-AI were highly accurate in the prediction of pregnancy at d 28. The PSPB differed on d 23 and 28 between cows that had versus cows that did not have pregnancy losses between d 28 and 35 of gestation. In summary, circulating concentrations of P4 during ovulatory follicle development affected numbers of follicles ovulated and timing of subsequent pregnancy losses.

Impacts of estrus expression and intensity during a timed-AI protocol on variables associated with fertility and pregnancy success in Bos indicus-influenced beef cows

This experiment evaluated the impacts of estrus expression and intensity, estimated by physical activity during a timed-AI protocol, on reproductive performance of Bos indicus-influenced beef cows. A total of 290 lactating, primiparous, and multiparous nonpregnant Nelore × Angus cows received a 2 mg injection of estradiol benzoate and an intravaginal progesterone (P4) releasing device (CIDR) on d -11, a 12.5 mg injection of PGF2α on d -4, CIDR removal in addition to 0.6 mg injection of estradiol cypionate and 300 IU injection of eCG on d -2, and timed-AI on d 0. Cows were fitted with a pedometer behind their left shoulder on d -4. An estrus detection patch was attached to the tail-head of each cow on d -2. Pedometer results were recorded on d -2 and 0. Estrus expression was defined as removal of >50% of the rub-off coating from the patch on d 0. Net physical activity during estrus was calculated by subtracting total steps from d -4 to -2 (nonestrus basal activity) from total steps from d -2 to 0 (proestrus + estrus period) of each cow. Cows that did not express estrus were classified as NOESTR. Cows that expressed estrus were ranked by net physical activity; those above the median were classified as HIESTR and the remaining cows as LWESTR. Ovarian ultrasonography was performed on d 0 and 7. Blood was collected on d 0, 7, 20, and 30. Pregnancy status was verified by ultrasonography on d 30. Only data from cows responsive to the estrus synchronization protocol were utilized (NOESTR, n = 59; LWESTR, n = 100; HIESTR, n = 98). Diameter of dominant follicle on d 0, corpus luteum volume on d 7, and plasma P4 concentrations on d 7 were greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR and also greater (P ≤ 0.05) for LWESTR vs. NOESTR. Plasma P4 concentrations on d 0 were greater (P < 0.01) in NOESTR vs. HIESTR and LWESTR and similar (P = 0.93) between HIESTR and LWESTR. Whole blood mRNA expression of myxovirus resistance 2 on d 20 was greater (P ≤ 0.05) in HIESTR vs. LWESTR and NOESTR, and similar (P = 0.72) between LWESTR and NOESTR. Pregnancy rates were less (P ≤ 0.04) in NOESTR vs. HIESTR and LWESTR (52.4%, 68.9%, and 73.5%, SEM = 7.2), and similar (P = 0.57) between HIESTR and LWESTR. Hence, expression of estrus during a timed-AI protocol improved ovarian dynamics and pregnancy success, whereas estrus intensity modulated key biological markers associated with fertility but not pregnancy rates in B. indicus-influenced cows beef cows.

Post-artificial insemination supplementation with calcium salts of soybean oil influences pregnancy establishment factors in beef cows

The objective of this experiment was to compare hormonal, uterine, and conceptus factors associated with pregnancy establishment in beef cows supplemented or not with Ca salts of soybean oil (CSSO) for 21 d beginning after timed AI. One hundred lactating multiparous Nelore cows were allocated to 20 groups of 5 cows/group and timed inseminated on d 0 of the experiment. After AI, groups were randomly assigned to receive (as-fed basis) 100 g of protein-mineral mix + 100 g of ground corn per cow per day, in addition to 1) 100 g/cow daily of CSSO ( = 10) or 2) 100 g/cow daily of kaolin (CON; rumen-inert indigestible substance; = 10). Groups were maintained in 4 pastures (5 groups from the same treatment within each pasture) with ad libitum access to forage. Groups were segregated daily and individually offered treatments from d 0 to 21. Blood samples were collected and transrectal ultrasonography was performed to verify ovulation and corpus luteum (CL) volume immediately before AI (d 0) and on d 7 and 15. After ultrasonography on d 15, 60 cows (30 cows/treatment and 3 cows/group) diagnosed without the presence of a CL on d 0 but with a CL greater than 0.38 cm3 in volume on d 7 and 15 were assigned to conceptus collection via transcervical flushing with PBS followed by endometrial biopsy in the uterine horn ipsilateral to the CL. Additional blood samples were collected for whole-blood RNA extraction (d 20), and pregnancy status was verified by transrectal ultrasonography (d 30) in cows not assigned to conceptus collection. Cows receiving CSSO had greater ( ≤ 0.04) mean plasma linoleic acid concentration, plasma linoleic:linolenic acid ratio, plasma progesterone (P4) concentration, and CL volume during the experiment compared with CON cows. Moreover, CSSO supplementation increased ( ≤ 0.04) length and mRNA expression of and by the conceptus as well as blood mRNA expression of interferon-stimulated genes on d 20 in gestating cows. No treatment differences were detected ( ≥ 0.30) for endometrial mRNA expression of and . In summary, post-AI CSSO supplementation to B. indicus beef cows increased plasma concentration of linoleic acid and enhanced pregnancy establishment factors, which included CL development and plasma P4 concentration, conceptus growth, and mRNA expression of as well as blood mRNA expression of interferon-stimulated genes.