Postpartum Beef Cows Research Articles

Assisting Knowledge Dissemination of Postpartum Beef Cows Management using Smartphone-Based Technology

This study led to four key findings: 1) farmers’ demographics and farm characteristics, 2) mobile phone usage, 3) a postpartum cow management knowledge test, and 4) the development of a Postcow mobile app as a learning tool. A total of 40 smallholder beef cattle farmers were selected for the study from October to November 2019. The results revealed that the farmers were 72.50 % males, and over half of the farmers were more than 50 years of age, 57.50 %, with primary school level being their highest education level at 65 %. It was also found that 47.50 % of the respondents had never searched for new knowledge from any sources about postpartum cow management. The responses indicated that all of the respondents used mobile phones with Android operation systems with access to the internet-enabled. The main reason for their use of mobile phones was to make and receive calls (57.14 %), and the most visited platform was Line (52.50 %). With regards to the downloading of any livestock apps, about 90 % of the respondents had never downloaded any before. The results of the farmers’ knowledge test demonstrated that the overall average score was 31.25 % of questions being answered correctly. In terms of mobile app development, the main features included a farmer knowledge test, cow production cycle, after calving management practices, feeding practices, general health care practices, and cow individual records and notifications. Our findings highlighted the need for more emphasis on making farmers aware of new technology for increased farm productivity performances. HIGHLIGHTS Mobile app making farmers aware of new technology for increased farm productivity performances The Postcow app was designed to enable farmers to gain knowledge about postpartum cow management practices All of the farmers have access to the internet and ready to obtain the new technology GRAPHICAL ABSTRACT

Setting the Cycle for Reproductive Success with a Pre-synchronization Program in Postpartum Beef Cows

Abstract Previous experiments from our laboratory determined that postpartum beef cows with a functional corpus luteum (CL) at the start of an estrous synchronization protocol have greater pregnancy success to FTAI than those that did not have a CL. Therefore, it was hypothesized that incorporation a presynchronization program prior to FTAI in postpartum cows will improve pregnancy rates. The goal of this project was to compare the effectiveness of a presynchronization program prior to the 7-d CO-Synch+CIDR fixed timed artificial insemination (FTAI) protocol in postpartum cows. Postpartum cows (n = 310) at two locations were randomly assigned to receive either the presynchronization program, consisting of 2 PGF2α injections 14 d apart and 11 d prior to the start of the 7-d CO-Synch+CIDR protocol, or the 7-d CO-Synch + CIDR protocol. Following estrus synchronization, all cows were inseminated by trained technicians using semen from bulls of known fertility. Pregnancy status to FTAI was assessed using ultrasonographic diagnosis at 30 d post insemination. Data were analyzed using a MIXED procedure of SAS and examined for effects of inseminator, body condition score (BCS), and location and age. Statistical significance was determined at P < 0.05 and a tendency at 0.05< P < 0.10. Age, BCS, and location did not affect (P > 0.05) pregnancy rates. Cows exposed to the pre-synchronization program tended to have greater AI pregnancy rates compared to cows that did not receive the pre-synchronization program (57.7±5.3 vs. 46.9±5.3%, respectively; P = 0.0687). AI pregnancy rates were greater in cows with >1 ng/mL P4 compared to cows with < 1 ng/mL P4 at the start of FTAI (77.7±7 vs. 55.7±6.2%, respectively; P = 0.0204). Furthermore, AI pregnancy rates were decreased by inseminator C (26.1±7.4) compared to the other inseminators this breeding season (A-54.4±7.9; B- 62.3±5.3; D-57.8±7.2; and E -51.1±5.2; P = 0.0026). Based on these data, incorporating a pre-synchronization program to ensure the presence of a CL at the start of a FTAI protocol may improve pregnancy success in postpartum beef cows.

Uterine health and fertility of timed AI postpartum Nelore beef cows raised in the Amazon biome

This study evaluated the effect of uterine health on the fertility of postpartum beef cows. Multiparous lactating Nelore cows (Bos indicus; n = 155) were subjected to a timed artificial insemination (TAI) protocol. Cows were included in a progesterone-estradiol based TAI protocol. On Day 0, before the beginning of the protocol, cows were subjected to evaluation of purulent vaginal discharge (PVD) and collection of uterine tissue using the cytobrush technique. Slides for polymorphonuclear (PMN) cells counting were prepared before the same cytobrush was used for RNA extraction and analysis of IL-1β, IL-6, IL-8, TNFα, GAPDH, and βactin gene transcription. Cows were separated into 4 categories according to the proportion of PMN and PVD: 1) Healthy (HE; n = 87), cows with ≤ 4.75% PMN and PVD of 0; 2) Positive Purulent Vaginal Discharge (PVD+; n = 24), cows with ≤ 4.75% PMN and PVD ≥ 1; 3) Subclinical Endometritis (SCE; n = 29), cows with > 4.75% PMN and PVD of 0, and; 4) Subclinical Endometritis + PVD+ (SCEP; n = 15), cows with > 4.75% PMN and PVD ≥ 1. Cows in the HE group had a greater (P < 0.05) pregnancy per AI (P/IA) than cows in SCE and SCEP groups. However, P/AI in cows from the PVD+ group was not different in comparison to HE and SCE groups (P > 0.05). Cows from the SCE and SCEP groups had a higher (P < 0.001) proportion of PMN cells in the uterus than HE and PVD+ groups. Relative transcription of IL-6 and TNFα did not change among groups (P > 0.05). In contrast, transcription of IL-8 was greater (P = 0.02) in SCEP than HE and SCE groups. The relative transcription IL-1β was greater (P < 0.05) in SCEP than in PVD+, but the cows in the HE and SCE groups were not different from the other groups (P = 0.08). Our results demonstrate that postpartum beef cows, raised in the Amazon biome, with a higher proportion of PMN cells have lower fertility. Moreover, ~ 40% of the postpartum cows included in TAI programs early postpartum had suboptimal uterine conditions (subclinical endometritis, purulent vaginal discharge, or both).

Effect of estradiol preceding and progesterone subsequent to ovulation on proportion of postpartum beef cows pregnant

Two experiments were conducted to examine the effect of plasma concentrations of 17β-estradiol (E2) preceding and progesterone (P4) subsequent to ovulation on proportions of beef cows pregnant following embryo transfer. Timing of ovulation (d 0) among postpartum cows was synchronized and cows that expressed estrus were removed from each study. In Experiment 1, plasma E2 concentration on d 0 was used to classify cows (n = 353) into Low, Medium, and High E2 groups. Pregnancy rate for cows with Low, Medium, or High E2 concentrations were different (P < 0.05). In Experiment 2, there were multiple administrations of PGF2α to evaluate the independent effects of Low or High E2 before ovulation and Low or Normal (no treatment) P4 after ovulation on proportions of cows pregnant. Treatment groups in Experiment 2, therefore, were: Low E2-Low P4 (LL; n = 71), Low E2-Normal P4 (LN; n = 69), High E2-Low P4 (HL; n = 74), and High E2-Normal P4 (HN; n = 73). Concentrations of P4 on d 7 subsequent to ovulation were less (P < 0.05) in cows of the HL compared to HN, and in LL compared to LN groups. Concentrations of E2 on d -2, 0, and change in E2 (d -2 to d 0) had a positive effect (P < 0.008) on pregnancy rates. In summary, relatively greater E2 concentrations preceding ovulation; and relatively greater P4 concentrations subsequent to ovulation combined with lesser E2 concentrations preceding ovulation had a positive effect on proportions of postpartum cows pregnant.

142 Evaluation of estrus detection patches as a tool to classify postpartum beef cows as estrous cycling or anestrous prior to the start of the breeding season

Abstract Estrus detection patches were evaluated as a tool to classify postpartum cows as estrous cycling or anestrous at the start of the breeding season. EstrotectTM Breeding Indicators were applied to 257 postpartum beef cows in three locations 25 days prior to the start of estrus synchronization. Coincident with the start of estrus synchronization, patches were scored using a 1 to 4 scale (1 = 0–25%; 2 = 25–50%; 3 = 50–75%; 4 = 75–100%) with scores of 3 or 4 considered activated. Blood samples were collected from each cow 10 days prior to, and at the start of the estrus synchronization. Serum progesterone concentrations were determined via radioimmunoassay; cows were considered estrous cycling if one or both samples exceeded a concentration of 0.5 ng/ml. Based on progesterone, 54.9% of cows were estrous cycling at the start of estrus synchronization. When missing patches were considered inconclusive results, use of patches to infer estrous cyclicity resulted in 85.0% sensitivity and 79.2% specificity with a positive predictive value of 87.2%. However, 75.1% of all cows presented with missing patches at the start of synchronization. If missing patches were considered activated, sensitivity was 95.7%, but specificity (16.4%) and PPV (58.2%) were poor, as 47.6% of cows presenting with missing patches were anestrous based on progesterone. Across all cows, pregnancy rate to AI was 58.0% (149/257). Cows with activated patches that were classified as false positives based on serum progesterone concentrations achieved a 71.4% (5/7) pregnancy rate to AI, raising questions as to whether sensitivity was underestimated due to inherent Type II errors in classification of cyclicity via progesterone. In summary, estrus detection aids are a sensitive tool to identify estrous cycling postpartum cows prior to the start of the breeding season; however, poor specificity and patch retention are limitations for this application.

181 Uterine and vaginal bacteria and cytokine profiles prior to artificial insemination between resulting pregnant and open postpartum beef cows

Abstract Numerous factors impact reproductive success in beef cattle; however, the presence and activity of bacteria in the reproductive tract and its effects on fertility is relatively unknown. The objective of this study was to evaluate the relationship between reproductive tract bacterial communities and cytokine profiles prior to timed-AI (TAI) and compare between resulting pregnancy status at d30. Sixty-eight beef cows, 80 ± 2.6 d postpartum at TAI, were synchronized and subjected to TAI on d0. Pregnancy was diagnosed via transrectal ultrasonography on d30. Uterine and vaginal flushes were collected on d -21 and -2 for bacterial DNA extraction to sequence the V1-V3 hypervariable regions of the 16S rRNA gene and to measure pro-inflammatory [interlukin-6 (IL-6)] and anti-inflammatory [IL-10 and transforming growth factor-beta (TGFβ)] cytokine concentrations using validated commercial ELISAs. Concentration data were analyzed using repeated measures in PROC MIXED of SAS and correlations were performed in SAS using Pearson correlation. There were no differences in cytokine concentrations by day or status x day. There were no differences in uterine IL-6 or IL-10 concentrations (P &amp;gt; 0.05). Uterine TGFβ concentrations were overall elevated in pregnant cows compared to open cows (72.6 vs. 13.7 ± 12.1 pg/mL, respectively; P &amp;lt; 0.05). On d -2, a positive correlation exists between TGFβ and the relative abundance of Actinobacteria in the uterus of pregnant cows (r=0.93, P = 0.02). There were no differences in vaginal IL-6 or TGFβ concentrations (P &amp;gt; 0.05). On d -2, vaginal IL-10 concentrations were elevated in open cows compared to pregnant cows (741.6 vs. 602.1 ± 47.0 pg/mL, respectively; P &amp;lt; 0.05) and a positive correlation exists between IL-10 and the relative abundance of Lentisphaerae in the vagina of pregnant cows (r=0.89, P = 0.04). These data suggest a possible relationship between bacterial communities and cytokines concentrations within the reproductive tract of beef cattle which may affect fertility.

Comparison of the 7 & 7 Synch protocol and the 7-day CO-Synch + CIDR protocol among recipient beef cows in an embryo transfer program

An experiment was designed to evaluate the effectiveness of the recently developed 7 & 7 Synch protocol to synchronize estrus among recipients prior to embryo transfer (ET). Postpartum beef cows (n = 1358) across thirteen locations were assigned to either the 7-d CO-Synch + CIDR protocol or the 7 & 7 Synch protocol prior to ET. Cows were preassigned to balanced treatments within location based on age and days postpartum, with body condition score recorded at ET. Cows assigned to the 7-d CO-Synch + CIDR protocol were administered gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin acetate) on Day 7, an intravaginal controlled internal drug release (CIDR; 1.38 g progesterone) from Day 7 to Day 14, and prostaglandin F2α (PGF2α; 25 mg dinoprost tromethamine) coincident with CIDR removal on Day 14. Cows assigned to the 7 & 7 Synch protocol were administered PGF2α (25 mg dinoprost tromethamine) coincident with CIDR insertion on Day 0, GnRH (100 μg gonadorelin acetate) on Day 7, and PGF2α (25 mg dinoprost tromethamine) coincident with CIDR removal on Day 14. Cows were observed for visible signs of estrus, with GnRH (100 μg gonadorelin acetate) administered to cows failing to express estrus during the detection period. Embryo transfer was performed approximately seven days after estrus or GnRH administration. Presence of corpora lutea (CL) was determined via transrectal palpation by a single veterinarian blinded to treatment, and embryos were transferred only to cows with palpable CL. Embryo transfer was performed using either fresh or frozen embryos, with embryo stage and grade recorded for each recipient. The proportion of cows expressing estrus was increased (P < 0.0001) among cows assigned to the 7 & 7 Synch protocol (86% [529/615] vs 76% [488/640]). The proportion of cows expressing estrus and presenting with palpable CL at ET was greater (P < 0.0001) among cows following treatment with the 7 & 7 Synch protocol compared to the 7-d CO-Synch + CIDR protocol (76% [466/615] vs 65% [418/640]). Consequently, the proportion pregnant to ET was greater (P < 0.03) following the 7 & 7 Synch protocol (40% [263/653]) compared to the 7-d CO-Synch + CIDR protocol (34% [228/664]). In summary, the 7 & 7 Synch protocol involving administration of PGF2α and treatment with a CIDR for 7 days prior to GnRH improved the likelihood of estrus expression in recipients, increased the proportion of cows eligible to receive an embryo, which resulted in a greater pregnancy rate to ET.

Effects of inorganic selenium injection on the performance of beef cows and their subsequent calves

Sixty-seven pregnant Angus cows and their subsequent calves were used in a randomized design to evaluate the effect of inorganic Se injection from 80 d of gestation until weaning on cow reproductive parameters, BW and BCS evolution, milk yield and quality, calf growth and calf hematology parameters. The treatments were as follows: 1) Se+: cows were administered Se as sodium selenite at doses of 0.05 mg/Kg of BW at 80, 140, 200, 260 d of gestation and 30, 90, 150 and 240 d of lactation. Calves from Se + cows were Se as sodium selenite subcutaneously injected with a dose of 0.05 mg/Kg of BW at 70, 104, 144 d of age; 2) Control: cows and calves were administered sterile NaCl solution (9 g/l) at the same volume and intervals as Se + treatment. At the start of the experiment, forage Se concentration was 58.6 ppb ± 7.6 ppb, and cow whole blood Se concentration was similar (P > 0.10) between treatments (Se+, 29.3 ± 0.3 ppb; Control, 28.1 ± 0.5 ppb). After Se injection, cow whole blood Se concentration was increased (P < 0.01) in Se + cows in relation to control cows until the end of the experiment. Calf whole blood Se concentration was increased (P < 0.01) at birth and 30 d of age in calves from Se + cows compared to calves from Control cows. However, calf whole blood Se concentration was not different (P > 0.10) between treatments at d 70 after birth. After the first Se injection (70 d of age), calf whole blood Se concentration was increased (P < 0.01) at 104 and 144 d of age in calves from Se + cows compared to calves from Control cows. Cow BW and BCS did not differ (P > 0.10) between treatments throughout the experiment. Ovarian follicle diameter measured by ultrasound 47 d postpartum was greater (P = 0.03) in Se + cows compared to Control cows. Pregnancy rate to fixed time artificial insemination (FTAI), overall pregnancy rate (P > 0.10) and pregnancy loss (P = 0.19) did not differ between groups. Selenium injection did not affect (P > 0.10) milk yield and composition. Calf morphometric parameters, BW at birth and growth rate during lactation were not affected (P > 0.10) by treatments. No significant effect (P > 0.10) was observed between treatments on hematological results of blood samples from calves at weaning. Results of this study shown that inorganic Se injection was an efficient tool to improve Se-status in cow-calf operation under extensive management. Selenium injection increased follicle diameter in postpartum beef cow, however, did not affect the rest of the variables studied.

Treatment with prostaglandin F2α and an intravaginal progesterone insert promotes follicular maturity in advance of gonadotropin-releasing hormone among postpartum beef cows

An experiment was designed to evaluate treatments to promote ovarian follicular maturity in advance of administration of exogenous gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) for control of the bovine estrous cycle. We hypothesized prostaglandin F2α (PGF2α; 500 μg cloprostenol) followed by an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) would induce greater follicle size and serum estradiol at the time of GnRH administration. Postpartum cows (n = 194) in two locations were assigned to one of five treatments based on age, days postpartum, and body condition score. Cows in Treatment 1 were treated with the standard 7-d CO-Synch + CIDR protocol: administration of GnRH and CIDR insertion on Day −10, and administration of PGF2α and CIDR removal on Day −3. Treatments 2–5 were designed in a 2 × 2 factorial arrangement, with Treatment 1 included as an additional reference. On Day −17, cows in Treatments 2–5 received a CIDR insert, either with (Treatments 2 and 3) or without (Treatments 4 and 5) administration of PGF2α at CIDR insertion. On Day −10, all cows were administered GnRH, and CIDR inserts were either removed (Treatments 2 and 4) or remained in place until Day −3 (Treatments 3 and 5). Treatment with PGF2α and CIDR in advance of GnRH (Treatments 2 and 3) resulted in increased diameter of the largest ovarian follicle (P < 0.001) and increased serum concentrations of estradiol (P < 0.0005) on Day −10. In addition, variation among cows in CL status (no CL vs. a single CL vs. multiple CL) on Day −3 tended to be decreased (P = 0.08), with cows more likely to have a single CL rather than no CL or multiple CL. Lastly, the proportion of cows expressing estrus prior to fixed-time artificial insemination tended (P = 0.08) to be improved. Results support the hypothesis that administration of PGF2α and treatment with a CIDR for 7 days prior to GnRH promotes follicular maturity in advance of GnRH administration and may provide an approach by which to enhance response of postpartum beef cows to GnRH-based estrus synchronization programs.

166 Comparison of the 7 and 7 Synch protocol and the 7-day CO-Synch + controlled internal drug release protocol among recipient beef cows in an embryo transfer programme

An experiment was designed to evaluate the effectiveness of the recently developed 7 and 7 Synch protocol to synchronise oestrus and ovulation among recipients before embryo transfer (ET). Postpartum beef cows (n=1358) across 13 locations were assigned to either the 7-day CO-Synch + controlled internal drug release (CIDR) protocol or the 7 and 7 Synch protocol before oestrus detection and subsequent ET. Cows were pre-assigned to balanced treatments within location based on age and days postpartum, and body condition score was recorded at ET. Cows assigned to the 7-day CO-Synch + CIDR protocol were administered gonadotrophin-releasing hormone (GnRH; 100µg of gonadorelin acetate) on Day 0, an intravaginal CIDR insert (1.38g of progesterone) from Day 0 to 7, and prostaglandin F2α (PG; 25mg of dinoprost tromethamine) coincident with CIDR removal on Day 7. Cows assigned to the 7 and 7 Synch protocol were administered PG (25mg of dinoprost tromethamine) coincident with CIDR insertion on Day −7, GnRH (100µg of gonadorelin acetate) on Day 0, and PG (25mg of dinoprost tromethamine) coincident with CIDR removal on Day 7. The 7 and 7 Synch protocol was hypothesised to enhance response to GnRH administration on Day 0 among mixed groups of oestrous cycling and anestrous cows, ultimately resulting in improved oestrous response and synchrony of oestrus before ET. Cows were observed for visible signs of oestrus following oestrus synchronisation, with GnRH (100µg of gonadorelin acetate) administered to cows failing to express oestrus during the detection period. Length of the detection period varied among locations but was consistent across treatments within location. Embryo transfer was performed approximately 7 days after oestrus or GnRH administration. Presence of corpora lutea (CL) was determined via transrectal palpation by a single veterinarian blinded to treatment, and embryos were transferred only to cows with palpable CL. Embryo transfer was performed using fresh or frozen embryos staged and graded according to IETS recommended guidelines, with embryo information recorded for each recipient. Data were analysed using the PROC GLIMMIX procedure of SAS (SAS Institute Inc.). Proportion of cows expressing oestrus was improved (P&amp;lt;0.0001) among cows assigned to the 7 and 7 Synch protocol (86% (529/615) vs. 76% (488/640)). The proportion of recipient females with palpable CL tended to be greater (P=0.07) among cows assigned to the 7 and 7 Synch protocol (82% (478/586) vs. 80% (451/565)). Among cows that expressed oestrus, a greater proportion (P&amp;lt;0.01) had palpable CL following the 7 and 7 Synch protocol (88% (466/529) vs. 86% (418/488)). Consequently, irrespective of embryo type received, the proportion of recipients pregnant to ET was greater (P&amp;lt;0.01) following the 7 and 7 Synch protocol (39%; 263/668) compared with the 7-day CO-Synch + CIDR protocol (33%; 228/690). In summary, the 7 and 7 Synch protocol improved the likelihood of oestrus expression in recipient cows, increased the proportion eligible to receive an embryo, and resulted in greater pregnancy rate to ET.

Changing views on the role of the uterus in post-partum reproductive function in beef cows1.

The paradigm for post-partum management of well-being and reproductive function in beef cows is changing. For many decades, research focused on the hypothalamic-pituitary-ovarian axis in attempts to manage beef cows to resume estrous cycles more quickly, because uterine involution was not considered a factor that was limiting to reproductive function in post-partum beef cows (Kiracofe, 1980). Questions remained, however, about the prevalence of subclinical endometritis in beef cows, and about the impact of sub-clinical reproductive tract health on subsequent reproductive performance and well-being (McNeel et al., 2017a). In a pair of papers published in this issue of the Journal of Animal Science, Ault and colleagues (Ault et al., 2019a,b) investigated the uterine and vaginal microbiome in post-partum beef cows using next generation sequencing and demonstrated that a less diverse uterine microbiome in the post-partum interval close to breeding was associated with a decreased risk of conception to timed artificial insemination. A similar result was reported for the vaginal microbiome of post-partum dairy cows (Bicalho et al., 2017). Beef cows, therefore, may not have as many cases of clinical metritis, but some of the same components of post-partum reproductive health may be influencing post-partum re-breeding efficiency in beef cows as in dairy cows. The results of studies examining the influence of endometrial cytology on reproductive performance in post-partum beef cows have been mixed (Santos et al., 2009; Ricci et al., 2017); however, the papers by Ault and colleagues indicate that the application of next generation sequencing technologies may allow more accurate determination of the relationships between post-partum reproductive tract health and re-breeding efficiency.

Using pregnancy associated glycoproteins (PAG) for pregnancy detection at day 24 of gestation in beef cattle

The objective of this experiment was to determine if circulating concentrations of pregnancy associated glycoproteins (PAG) on day 24 of gestation can be utilized to diagnose pregnancy and embryo viability in beef cattle. Postpartum beef cows (n = 677) and heifers (n = 127) were exposed to a 7-day CO-Synch + CIDR estrus synchronization protocol followed by fixed-time AI (FTAI) on day 0. Blood samples were collected at day 24 after TAI to assess circulating concentrations of PAG utilizing an in-house ELISA. Pregnancy diagnosis was performed 30 and 100 days after FTAI via transrectal ultrasonography. Mean circulating PAG concentration at day 24 differed (P < 0.001) between animals diagnosed pregnant and non-pregnant at day 30 (1.69 ± 0.10 ng/mL vs 0.30 ng/mL ± 0.07 ng/mL; mean ± SEM; respectively). Pregnant heifers had increased PAG concentration at day 24 compared with pregnant cows (P < 0.01; 3.29 ± 0.36 ng/mL vs 1.39 ± 0.10 ng/mL, respectively). Based on receiver operating characteristic (ROC) curve analysis, serum concentration of PAG at day 24 ≥ 0.33 ng/mL in cows and ≥0.54 ng/mL in heifers was 95% accurate at determining pregnancy status at day 30. Heifers that experienced late embryonic mortality between day 30 and 100 of gestation had decreased circulating concentrations of PAG on day 24 (2.02 ng/mL ± 0.73) compared with heifers that maintained an embryo until day 100 (3.69 ng/mL ± 0.39; P = 0.02). However, there was no difference in day 24 PAG concentration (P = 0.39) between cows that maintained or lost a pregnancy (1.31 ng/mL ± 0.25 vs 0.92 ng/ml ± 0.50). In summary, circulating PAG concentration on day 24 of gestation may be a useful marker for early pregnancy detection in beef cattle, and might be a potential marker for predicting embryonic loss.

52 Timing of progesterone exposure effects pregnancy rates following fixed timed artificial insemination in postpartum beef cows

Abstract Advancements in reproductive technologies have improved pregnancy rates in postpartum cows; however, undesirable consequences leading to reduced fertility still occur. Thus, the objectives were to determine if presence of a corpus luteum (CL) at the start of estrous synchronization (AIM1) or if the length of proestrus (interval from progesterone removal to a GnRH-induced LH surge; AIM2) alters fixed timed artificial insemination (FTAI) pregnancy rates. Cycling postpartum cows (n = 285) at two locations were synchronized using the CO-Synch+CIDR® FTAI protocol. Ultrasonographic measurements of luteal area were recorded at CIDR insertion. To determine the impact of proestrus length, cows were randomly assigned to either undergo CIDR removal at the time of PGF2a injection (long proestrus, n = 145), or CIDR removal 24 hours post PGF2a injection (short proestrus, n = 140). Blood samples were collected at CIDR insertion and at insemination for progesterone (P4) analysis. Pregnancy status to FTAI was assessed using ultrasonographic diagnosis at 30 d post insemination. Data were analyzed using a MIXED procedure of SAS and examined for effects of length of proestrus, P4 concentration, luteal area, sire, location, and age. Statistical significance was determined at P 0.05) pregnancy rates. Pregnancy rates were greater in cows with &gt;1 ng/mL P4 compared to cows with 0.05). Cows &gt; 4 y old had higher AI pregnancy rates compared to 2–3 y cows (70.2±7.4 vs. 51±5.8%, respectively; P &gt; 0.05). Based on these data, incorporating a presynchronization program to ensure the presence of a functional CL at the start of a FTAI protocol may improve pregnancy success in postpartum beef cows.

107 Timing of progesterone exposure effects pregnancy rates following fixed time artificial insemination in postpartum beef cows

Abstract Advancements in reproductive technologies have improved pregnancy rates in postpartum cows; however, undesirable consequences leading to reduced fertility still occur. Thus, the objectives were to determine if presence of a corpus luteum (CL) at the start of estrous synchronization (AIM1) or if the length of proestrus (interval from progesterone removal to a GnRH-induced LH surge; AIM2) alters fixed timed artificial insemination (FTAI) pregnancy rates. Cycling postpartum cows (n = 285) at two locations were synchronized using the CO-Synch+CIDR® FTAI protocol. Ultrasonographic measurements of luteal area were recorded at CIDR insertion. To determine the impact of proestrus length, cows were randomly assigned to either undergo CIDR removal at the time of PGF2a injection (long proestrus, n = 145), or CIDR removal 24 hours post PGF2a injection (short proestrus, n = 140). Blood samples were collected at CIDR insertion and at insemination for progesterone (P4) analysis. Pregnancy status to FTAI was assessed using ultrasonographic diagnosis at 30 d post insemination. Data were analyzed using a MIXED procedure of SAS and examined for effects of length of proestrus, P4 concentration, luteal area, sire, location, and age. Statistical significance was determined at P0.05) pregnancy rates. Pregnancy rates were greater in cows with &gt;1 ng/mL P4 compared to cows with 0.05). Cows &gt; 4 y old had higher AI pregnancy rates compared to 2–3 y cows (70.2±7.4 vs. 51±5.8%, respectively; P &gt; 0.05). Based on these data, incorporating a presynchronization program to ensure the presence of a functional CL at the start of a FTAI protocol may improve pregnancy success in postpartum beef cows.

87 Bacterial communities of the uterus and vagina between resulting pregnant and non-pregnant postpartum beef cows

Abstract The prevalence of reproductive losses costing 1 billion dollars annually to the beef and dairy industries has led researchers to evaluate strategies to improve reproductive efficiency. The microbiome of the reproductive tract has been a recent focus in humans due to its effects on health and fertility; however, little research has evaluated the uterine and vaginal microbiomes of cattle. The present study evaluated the reproductive tract bacterial communities of postpartum beef cows undergoing estrus synchronization and the differences between cows who became pregnant and those who failed to conceive. Forty postpartum Angus cows were subjected to a 7 Day Co-Synch protocol with a pre-synchronization step 21 days prior (day -21) to artificial insemination (AI). Uterine and vaginal flushes were collected on day -21, -9, and -2 of the protocol for pH and bacterial DNA extraction to sequence the V1-V3 hypervariable regions of the 16S rRNA gene. Transrectal ultrasound was performed 30 days after AI for pregnancy diagnosis. Ten pregnant and non-pregnant animals were selected and used for analysis. Decreased numbers of bacterial species present in the uterus of cows were identified, independent of pregnancy status, leading up to AI with an average of 1180 ± 97 species on day -21 to 427 ± 99 on day -2 (P &lt; 0.0001). Principal coordinate analyses depicted significant clustering of bacterial communities by day in the uterus (P = 0.001) and vagina (P = 0.001) as well as pregnancy status in the uterus at day -2 (P = 0.005). Additionally, at day -2, multiple significantly different uterine bacterial genera were present at &gt;1% in non-pregnant cows while present at &lt;1% in pregnant cows. Uterine pH increased in non-pregnant cows but decreased in pregnant cows. In summary, the results suggest uterine bacterial abundances prior to AI may influence the uterine environment and reproductive outcomes.

Bacterial taxonomic composition of the postpartum cow uterus and vagina prior to artificial insemination1.

The current study characterized the taxonomic composition of the uterine and vaginal bacterial communities during estrous synchronization up to timed artificial insemination (TAI). Postpartum beef cows (n = 68) were subjected to pre-synchronization step 21 d prior to TAI (day -21), followed by an industry standard 7 Day Co-Synch on day -9 and TAI on day 0. Uterine and vaginal flushes were collected on days -21, -9, and -2 of the protocol and pH was immediately recorded. Pregnancy was determined by transrectal ultrasound on day 30. Bacterial DNA was extracted and sequenced targeting the V1 to V3 hypervariable regions of the 16S rRNA bacterial gene. Results indicated 34 different phyla including 792 different genera present between the uterus and vagina. Many differences in the relative abundance of bacterial phyla and genera occurred between resulting pregnancy statuses and among protocol days (P < 0.05). At day -2, multiple genera were present in >1% abundance of nonpregnant cows but <1% abundance in pregnant cows (P < 0.05). Uterine pH increased in nonpregnant cows but decreased in pregnant cows (P > 0.05). Overall, our study indicates bacterial phyla and genera abundances shift over time and may potentially affect fertility by altering the reproductive tract environment.

Uterine and vaginal bacterial community diversity prior to artificial insemination between pregnant and nonpregnant postpartum cows1.

The present study evaluated the bovine vaginal and uterine bacterial community diversity and its relationship to fertility. Postpartum beef cows (n = 68) were synchronized beginning on day -21 and ending with timed artificial insemination (TAI) on day 0. Pregnancy was diagnosed 30 d after TAI. Uterine and vaginal flushes were collected on day -21, -9, and -2 for bacterial DNA extraction to sequence the V1 to V3 hypervariable regions of the 16S rRNA gene. Results indicated a decrease in the number of bacterial species over time in the uterus of resulting pregnant and nonpregnant beef cows (P < 0.0001). Principal coordinate analyses (PCoA) depicted clustering of samples, indicating closely related bacterial communities, by day in the uterus and vagina (P < 0.0001). At day -2, uterine samples from nonpregnant and pregnant animals clustered separately (P < 0.0001), with nonpregnant animal samples clustering tightly together. Overall, the current study suggests the shift in the reproductive bacterial communities' diversity and phylogenetic relationship leading up to the time of breeding may contribute to successful pregnancy establishment.

Mechanisms linking nutrition and reproduction in postpartum cows

The reproductive physiology of postpartum cows is different from that of heifers because of the combined effects of the past pregnancy and lactation. Neither lactation nor pregnancy has a major effect on postpartum fertility when calving is free from disease and lactation is moderate. Postpartum beef cows in good body condition have conception rates nearly equivalent to those of virgin heifers once their uteri are involuted and they initiate ovarian cycles. However, cows will experience infertility when nutrient requirements for maintenance and lactation exceed nutrient intake (postpartum beef cows) or when nutrients are specifically partitioned toward lactation (postpartum dairy cows). The subsequent loss of body fat that occurs in either case has effects on a variety of reproductive processes and reproduction becomes less efficient. The mechanisms that lead to abnormal reproduction in nutritionally compromised postpartum cattle have been investigated intensively. Much of the effort has focused on the nature of the signal (endocrine or otherwise) that controls pituitary secretion of LH and FSH, the response of the ovary to LH and FSH, and other ovarian effects that are independent of gonadotrophins. Reproductive studies in ruminants have tended toward studies of follicular development and this focus relates back to solving the problem of anoestrus. Less work has been done on the effects of nutrition on the early embryo, the health of which may be predetermined by factors affecting the oocyte within the preovulatory follicle. Few studies have examined the effect of nutrition on uterine function in postpartum cattle. Solutions to postpartum reproduction will probably arise from a variety of approaches that include traditional physiology as well as more modern genomic and proteomic technologies.

Timed artificial insemination plus heat II: gonadorelin injection in cows with low estrus expression scores increased pregnancy in progesterone/estradiol-based protocol

The use of tail chalk and estrus/heat expression scores (HEATSC) evaluation is instrumental in identifying cows with greater estrus expression and greater artificial insemination pregnancy rates (P/AI) in cows submitted to timed artificial insemination (TAI), and cows with low or no estrus expression present lower P/AI. It was intended in this study to improve the pregnancy rates in TAI for Bos indicus beef cows, and gonadotrophin-releasing hormone (GnRH) injection was hypothesized to increase pregnancy rates in a TAI program for cows submitted to progesterone–estradiol-based protocols with low or no estrus expression, evaluated by HEATSC. Cows (n= 2284) received a progesterone device and 2 mg estradiol benzoate, after 8 days the device was removed and 1 mg estradiol cypionate, 150 μg of d-cloprostenol and 300 IU equine chorionic gonadotropin was administered. All cows were marked with chalk and HEATSC evaluated (scales 1 to 3) at TAI performed on day 10. Animals with HEATSC1 and HEATSC2 (n= 937) received 100 μg de gonadorelin (GNRH group; n= 470), or 1 ml saline (Control group; n= 467), and cows with HEATSC3 (named HEAT group; n= 1347) received no additional treatment. The larger dominant follicle, evaluated on day 8and at TAI (day 10), was greater in HEAT group (P= 0.0145 and P <0.001, respectively). Corpus luteum (CL) area and progesterone concentration was evaluated on day 17, and CL area was larger in HEAT group, intermediary in Control and lower in GnRH group (Control= 2.68 cm2, GnRH= 2.37 cm2, HEAT group= 3.07 cm2, P <0.001). Greater progesterone concentrations were found in HEAT group than in Control and GnRH groups (Control= 4.74 ng/ml, GnRH= 4.29 ng/ml, HEAT group= 6.08 ng/ml, P<0.001). There was a difference in ovulation rate, greater in HEAT group than GnRH and Control groups (Control= 72.5%; GnRH= 81.25%; HEAT group= 90.71%; P= 0.0024). Artificial insemination pregnancy rates was greater in HEAT group (57.09% (769/1347) than in Control and GNRH groups, with positive effect of GnRH injection at the time of TAI in P/AI (Control= 36.18% (169/467), GnRH= 45.95% (216/470); P<0.0001). In conclusion, GnRH application in cows with low HEATSC (1 and 2) is a simple strategy, requiring no changes in TAI management to increase pregnancy rates in postpartum beef cows submitted to progesterone–estradiol-based TAI protocols, without reaching, however, the pregnancy rates of cows that demonstrate high estrus expression at the TAI.

Effect of sperm kinematics and size of follicle at ovulation on pregnancy rate after timed AI of beef cows

The objectives of this study were to evaluate whether the diameter of the preovulatory follicle and the post-thaw sperm kinematics are factors that affect successful establishment of a pregnancy after timed AI (TAI) of postpartum beef cows. Nelore cows (n = 346) were subjected to an estradiol-progesterone based TAI protocol. At TAI, cows were categorized according to the diameter of the preovulatory follicle (POF) in the Early Ovulation (EO group, n = 184), and Late Ovulation (LO group, n = 162) groups. Sperm were classified, according to CASA analysis, as Hyper-activated (H+), and Non-Hyper-activated (H-). The H + and H- semen was used to inseminate cows that were classified to be in the EO and LO groups. Thus, after distribution, the groups were: EOH+ (n = 89), EOH- (n = 95), LOH+ (n = 96), and LOH- (n = 66). Pregnancy per AI (P/AI) was greater (P < 0.05) for EOH+ (66.3%, 59/89), EOH- (65.3%, 62/95), and LOH- (72.7%, 48/66) groups than for LOH + group (52.1%, 50/96). The results of the study indicate that cows with a smaller POF are less likely to become pregnant when insemination is with semen considered as hyper-activated (H+). In contrast, when inseminations are performed with semen categorized to be non-hyper-activated (H-), cows of the EO and LO groups had acceptable and similar pregnancy rates as a result of timed AI.