Effect of reproductive tract scoring on reproductive efficiency in beef heifers bred by timed insemination and natural service versus only natural service

Determining the clinical utility of a single pre-breeding examination for predicting subsequent reproductive performance in seasonal pasture-based dairy heifers

Heifers that conceive early in the breeding season are key to the maintenance of a compact calving pattern in seasonal dairy herds. The purpose of this prospective observational study was to determine whether a single pre-breeding examination is useful in predicting future reproductive and calving performance in dairy heifers. This evaluation was based on a matrix of easily measurable variables which could be applied to seasonal, pasture-based dairy heifers. The matrix variables were; body weight (≥55% mature body weight at mating start date), body condition score (≥3.5), and the presence of a corpus luteum. Seasonal, pasture-based dairy heifers (n = 572) on six commercial dairy farms were examined at an average of 28 days prior to the breeding season. At this examination, they were classified as READY (meeting all three of the above criteria), INTERMEDIATE (meeting one or two of the above criteria) or PROBLEM (meeting none of the above criteria) based on the matrix and then exposed to a routine artificial insemination (AI) breeding period followed by bull breeding depending on individual farm management. Subsequent pregnancy status was determined by transrectal ultrasonography initially at 30-60 days in calf (DIC), and confirmed at over 60 DIC. After the breeding season, 519 (96%) of heifers were determined to be pregnant, of which 345 (64%) became pregnant within the first three weeks of the breeding season. Farmers collected calving data; including calving difficulty score, from the heifers the following spring. A logistic regression model was used to analyse the association between the matrix categories and the following outcomes: reproductive (21 day submission rate, 1st AI conception rate, 3 wk and 6 wk in calf rate) and calving (assistance and dystocia). Heifers classified as PROBLEM had significantly lower odds of conceiving to the first AI serve and of becoming pregnant within the first three and six weeks of the breeding season (P ≤ 0.05). In conclusion, the proposed matrix could be practically useful for classifying heifers prior to the breeding season.

Effects of two protocols of ovulation synchronization on corpus luteum size and blood flow, progesterone concentration, and pregnancy rate in beef heifers

The objective of this study was to evaluate the effect of 7-day estradiol-progesterone-based [Treat_(C)] and 5-day Co-Synch plus progesterone [Treat_(Co-Sy)] protocols on ovulation time, pre-ovulatory follicle diameter, corpus luteum (CL) size and blood flow, progesterone (P4) concentration and pregnancy rate (PR) in beef heifers. In Experiment 1, a crossover design was applied (n = 9). For Treat_(C), a progesterone intravaginal (PI) device was inserted, plus 2 mg of estradiol benzoate (day 0). On day 7, 500 µg of cloprostenol plus 0.5 mg of estradiol cypionate were administered, and PI was removed. For Treat_(Co-Sy), on day 0, a PI was inserted plus 100 µg gonadotropin-releasing hormone (GnRH). On day 5, PI was removed, plus 500 µg of cloprostenol and 100 µg of GnRH were administered at 69-70 h later. From day one to ovulation day, dominant follicle was evaluated by ultrasonography. On days 4 and 8 post-ovulation, CL was evaluated by color Doppler, and P4 concentration was determined by chemiluminescence. In Experiment 2, a split-plot experimental design was used. Protocols followed were the same as in Experiment 1 [Treat_(C); n = 310 and Treat_(Co-Sy); n = 314]. Heifers were fixed-time artificially inseminated. Pregnancy was determined on day 41. In Experiment 1, the interval between PI removal and ovulation time was different between protocols (P < 0.01). In addition, P4 concentration was related to the CL size (P < 0.001), CL blood flow (P < 0.01) and protocols (P < 0.03). In Experiment 2, PR did not differ between protocols.

Estrous activity and pregnancy outcomes in Holstein heifers subjected to a progesterone based 5-d CO-Synch protocol with or without administration of initial GnRH

The objectives of this study were to investigate whether estrous activity and its impact on pregnancy outcomes would differ in heifers subjected to a 5 d CO-Synch plus progesterone releasing intravaginal device (PRID) protocol with or without an initial GnRH treatment. Holstein Heifers (n = 308) were fitted with a collar-mounted automated activity monitoring system approximately 1 week prior to the initiation of the synchronization protocol (Day -7). Heifers were assigned randomly to a 5 d CO-Synch plus PRID protocol either with (GnRH; n = 154) or without (NGnRH; n = 154) an initial administration of 100 μg of GnRH at the time of PRID insertion (Day 0). Heifers received a single administration of 500 μg of cloprostenol (PGF) at the time of PRID removal (Day 5) and again 24 h later (Day 6). Approximately 72 h after PRID removal (Day 8), heifers were timed-inseminated (TAI) and concurrently 100 μg of GnRH was administered to those not exhibiting estrus. All inseminations were done by one of two technicians using either sex-sorted (n = 252) or conventional (n = 56) frozen-thawed semen. Transrectal ultrasonography was done on Day 0 to determine ovarian cyclicity and normalcy of the reproductive tract and 30 and 45 d post-TAI to determine and confirm pregnancy, respectively. The percentage of heifers determined to be in estrus following PRID removal was greater in the GnRH than in the NGnRH group (94 vs. 82%, respectively; P < 0.01). The mean interval from PRID removal to the onset of estrus was shorter for GnRH- than NGnRH-treated heifers (50.8 vs. 59.2 h, respectively; P < 0.01). Pregnancy per AI (P/AI) at 30 d post-TAI tended to be greater for GnRH than NGnRH heifers (68 vs. 59%, respectively; P = 0.1). However, P/AI at 45 d post-TAI (65 vs. 57%, respectively) and pregnancy loss between 30 and 45 d post-TAI (6 vs. 4.5%, respectively) did not differ. The association between the interval from PRID removal to the onset of estrus and P/AI at 30 d post-TAI was linearly negative for GnRH heifers; for every 1 h increase in the interval from PRID removal to the onset of estrus, the predicted probability of P/AI at 30 d post-TAI tended (P = 0.08) to be reduced by 2.7%. The association between the interval from PRID removal to the onset of estrus and P/AI at 30 d post-TAI was not significant for NGnRH heifers. In addition, the interval from TAI to subsequent estrus, in non-pregnant heifers, was approximately 3 d longer for the GnRH than the NGnRH group (20.7 vs. 17.5 d, respectively). In summary, the initial GnRH treatment in a 5 d CO-Synch plus PRID protocol increased estrus expression and reduced the interval from PRID removal to the onset of estrus in Holstein heifers and tended to increase P/AI at 30 d, but did not affect P/AI at 45 d post-TAI.

mRNA Signatures in Peripheral White Blood Cells Predict Reproductive Potential in Beef Heifers at Weaning

Reproductive failure is a major contributor to inefficiency within the cow-calf industry. Particularly problematic is the inability to diagnose heifer reproductive issues prior to pregnancy diagnosis following their first breeding season. Therefore, we hypothesized that gene expression from the peripheral white blood cells at weaning could predict the future reproductive potential of beef heifers. To investigate this, the gene expression was measured using RNA-Seq in Angus-Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 8) or subfertile (SFH, n = 7) after pregnancy diagnosis. We identified 92 differentially expressed genes between the groups. Network co-expression analysis identified 14 and 52 hub targets. ENSBTAG00000052659, OLR1, TFF2, and NAIP were exclusive hubs to the FH group, while 42 hubs were exclusive to the SFH group. The differential connectivity between the networks of each group revealed a gain in connectivity due to the rewiring of major regulators in the SFH group. The exclusive hub targets from FH were over-represented for the CXCR chemokine receptor pathway and inflammasome complex, while for the SFH, they were over-represented for immune response and cytokine production pathways. These multiple interactions revealed novel targets and pathways predicting reproductive potential at an early stage of heifer development.

Effects of early weaning on productive and reproductive performance of Nelore heifers

We aimed to evaluate the effects of early weaning on the productive and reproductive characteristics of Nelore heifer progeny. Ninety-five calves from primiparous (PRI) and multiparous (MUL) dams were assigned to one of two weaning strategies; 1) early weaning at 150 d (149 ± 1.97) of age (EW; n = 16 from PRI and 31 from MUL); or 2) conventional weaning at 240 d (247 ± 2.41) of age (CW; 16 from PRI and 32 from MUL). All heifers received ~5 g/kg of body weight (BW) of creep-feed as fed from 90 d of age until weaning. After weaning, each group of heifers was transferred to a Brachiaria spp. paddock and received 5 g/kg of BW of a protein-energy supplement until 12 mo of age. Then, heifers were confined and fed a diet with a ratio of 79:31 (corn silage: concentrate) for 4 mo, during which they were submitted to a hormonal protocol to induce puberty and timed artificial insemination (TAI). Reproductive tract score (RTS, 1 to 5 scale: 1 being infantile and 5 being cyclic) and endometrial thickness were determined at 12 mo of age, rump fat thickness (RFT), and BW every 28 ± 4 d through the breeding season, and plasma concentrations of IGF-I were evaluated at 12, 14, and 16 mo. At 15.6 mo of age heifers were submitted to a P4/E2 protocol for TAI at day 0 (D0), and a second TAI was performed at D22 in nonpregnant heifers. Ultrasound was used to determine the presence of corpus luteum on D10 and dominant follicle (DF) diameter and blood perfusion on D2 and D0. Data were analyzed using SAS by ANOVA or logistic regression. Though heifers from EW were lighter (P < 0.05) than CW at postweaning time points and CW presented a greater (P = 0.002) RFT than EW heifers from 11 to 15 mo, weaning strategy did not affect (P > 0.1) body condition score at TAI. Concentrations of IGF-I did not differ (P > 0.1) between heifers weaned at 150 and 240 d. The proportion of pubertal heifers, endometrium tone and thickness, and RTS at 16 mo did not differ (P > 0.1) between EW and CW groups. The diameter of DF on D2 and D0 and follicular blood perfusion on D0 were greater (P < 0.05) for heifers in the CW group than EW group, but P/AI at first and second TAI did not differ (P > 0.1) between groups. In conclusion, early weaning in Nelore heifers moderately reduces postweaning growth but does not affect puberty and reproductive performance before the breeding season when submitted to confinement.

Physical Traits and Reproductive Measurements Associated with Early Conception in Beef Replacement Heifers

Developing and raising replacement heifers requires a large capital investment for producers. Therefore, it is imperative to discover traits and management practices to eliminate subfertile heifers prior to breeding and pregnancy determination. In this study, four years of data was analyzed from a centralized beef heifer development yard in the Midwest of the United States. The objective of this study was to analyze various heifer physical characteristics and management practices in order to quantify their impact on pregnancy and date of conception. Logistic regression models were built to investigate risk factors associated with conception to artificial insemination (AI), pregnancy by natural service after AI exposure, and pregnancy in the first 21-days of the breeding season. Age at entry, average daily gain from entry to breeding, pelvic width, and year were associated with AI pregnancy (p < 0.05). On the second model, average daily gain from entry to yearling weight, weight at breeding, weight at pregnancy diagnosis, and age at AI were significantly associated with pregnancy. There were no associations with reproductive tract score with any of the response variables analyzed. These results indicate there are physical measurements that can be used to improve the ability to select and develop heifers for improved reproductive performance.

Short Communication: Influence of estrus activity and reproductive tract size and position scores on fertility in Bos indicus and Bos taurus suckled beef cows

The primary objective of this study was to determine if estrus activity and reproductive tract size and position score (SPS) are associated with pregnancy outcomes in Bos indicus (Nelore) and Bos taurus (Angus) beef cows. In study 1, multiparous Nelore cows (n = 1,280) were artificially inseminated at a fixed time (FTAI, day 0) using an estradiol and progesterone (P4)-based estrus synchronization protocol. In study 2, multiparous Angus cows (n = 764) were artificially inseminated at a fixed time (FTAI, day 0) using a gonadotropin-releasing hormone and P4-based estrus synchronization protocol. Estrus activity was assessed using Estrotect heat detector patches and scored on day 0 using the following scoring system: 0 (patch was lost, most likely due to repeated mounting), 1 (<25% activation), 2 (≥25%, <50% activation), 3 (≥50%, <75% activation), or 4 (>75% activation) where patch scores of 1 and 2 signified no or limited estrus activity, whereas scores of 0, 3, and 4 had increased estrus activity. Reproductive tract SPS were assigned on day 0 as SPS1: small and compact resting within the pelvic cavity; SPS2: intermediate, resting partially outside the pelvic cavity; and SPS3: larger and resting outside the pelvic cavity. Pregnancy diagnosis was performed by ultrasound on day 30 and 100 after FTAI. Cows were determined as undergoing pregnancy loss if a viable embryo with heartbeat was detected at day 30 but was no longer present at day 100. Pregnancy rate at day 30 was influenced by estrus activity and SPS in both Nelore (P = 0.004) and Angus (P = 0.009) cows. Specifically, cows with smaller reproductive tracts (SPS1) had greater (P < 0.001) pregnancy rate when estrus was expressed before FTAI. There was no effect of estrus activity nor reproductive tract size on pregnancy loss between day 30 and 100 for both breeds. In summary, estrus activity before FTAI may influence reproductive outcomes differently depending on size and position of the reproductive tract at time of breeding.

Sexual behavior and seminal characteristics of Brahman bulls in the Colombian tropical flooded savanna: effects of reproductive management systems and climatic periods

The objective of this study was to evaluate the seminal traits and sexual behaviors of mature Brahman bulls in a multi-sire system during mating or resting seasons and different climatic periods of the year at the Colombian flooded savannas. Thirty-two Brahman bulls, suitable for reproduction, were used, which were subjected to breeding soundness evaluation, as well as the libido and service capacity tests. Such evaluations were compared among different seasons of the year in relation to the rainfall. Libido and service capacity tests were carried out in paddock for 12 continuous hours. Scrotal circumference and all seminal traits were not influenced by the mating or rest seasons, neither by the different climatic periods. However, libido and service capacity were significantly affected by the climatic periods, decreasing their expression during the intense rainfall season, and increasing during the transition period from summer to the onset of rains, which could be considered the appropriate time to establish mating seasons in this region. Furthermore, a high positive correlation was observed between libido and service capacity confirmed by a logistic model that animals with low libido have low probability of having high service capacity. In conclusion, although Brahman bulls are physiologically adapted to tropical regions, their expression of sexual behavior is markedly influenced by the weather. Hence, the use of libido test may serve as a good predictor of the service capacity, and a useful tool to improve the selection of sires.

Repeatability of anogenital distance measurements from birth to maturity and at different physiological states in female Holstein cattle

The inverse association between anogenital distance (AGD; the distance from the center of the anus to the base of the clitoris) and fertility, its moderate heritability, and high variability reported in dairy cattle make AGD a promising candidate for further exploration as a reproductive phenotype. In addition to heritability, repeatability (i.e., consistency in measurements taken at different time points) is important for a reproductive phenotype to be considered useful in genetic selection. Therefore, our primary objective was to determine the repeatability of AGD from birth to breeding age (≈16 mo) in Holstein heifer calves, and during different stages of the estrous cycle, gestation, and lactation in Holstein cows. We also determined the associations among AGD, height (at the hip), and body weight (BW) at birth. In calves (n = 48), we recorded BW (kg) and height (cm) at birth and measured AGD (mm) at approximately 0, 2, 6, 9, 12, and 16 mo of age. In cows, AGD was measured at different stages of the estrous cycle (proestrus, estrus, metestrus and diestrus; n = 20), gestation (30, 90, 180, and 270 d; n = 78), and lactation (30-300 d in milk in 30-d increments; n = 30). Calf height and BW at birth had a weak positive association with AGD at birth. The AGD increased linearly from birth to breeding age, but there was no association between the AGD at birth and at breeding age in heifers. Although any 2 consecutive AGD measurements were correlated, 6 mo was the earliest age at which AGD was moderately correlated (r = 0.41) with that of breeding-age heifers. The AGD was neither influenced by the different stages of estrous cycle nor lactation and remained highly repeatable (r ≥ 0.95). Although AGD measurements at 30, 90, and 180 d of gestation (126.9, 126.7, and 127.7 mm, respectively) were strongly correlated (r ≥ 0.97) with each other, AGD at 270 d of gestation (142.8 mm) differed from AGD at all earlier stages of gestation. In summary, AGD measured at birth did not reflect AGD at breeding age in heifers, but AGD measurements in cows had high repeatability at all stages of the estrous cycle, gestation, and lactation, except at 270 d of gestation. Therefore, AGD could be measured reliably at any of the aforesaid physiological states in cows due to its high repeatability, except during late gestation. The earliest gestational stage when pregnancy-associated increase in AGD occurred, however, could not be definitively established in the present study.

Puberty attainment and reproductive performance of yearling Bos indicus-influenced heifers after two sequential treatments with progesterone

Number of pubertal heifers at time of breeding season initiation is a primary determinant to pregnancy success during the breeding season. It was hypothesized that pre-breeding progesterone (P₄) supplementation (induction) would increase the number of heifers pubertal at the time of imposing estrous synchronization treatment regimens and P/AI. Yearling, Bos indicus-influenced (n = 577) or Bos indicus (n = 174) heifers were or were not treated with P₄ (CIDR and Non-CIDR, respectively) for 10 d starting on D-23 (D0 = TAI). Presence of a CL on D-33 or D-23 was considered to indicate heifers were pubertal. On D-13, there was a PGF analogue administered. On D-9, there was treatment with GnRH analogue, 6d-CIDR and PGF. There were inseminations based on estrus (D-2 to D0) or TAI on D0 for non-estrous animals. There were 5.2 % and 62.9 % purebred and crossbred heifers pubertal, respectively. Proportion of prepubertal crossbred than purebred heifers with CL on D-3 was greater as a result of imposing the pubertal induction regimen (P < 0.05 and P> 0.10, respectively). Regardless of puberty status, proportion of heifers in estrus prior to AI in the CIDR group was similar to the heifers of the Non-CIDR group for crossbreds and purebreds. Similarly, P/AI of CIDR group was similar to the Non-CIDR group for crossbreds and purebreds. In summary, imposing the pubertal induction regimen hastened attainment of puberty in yearling crossbred, but not purebred heifers. Puberty induction did not affect estrous response, neither fertility after imposing an estrous synchronization treatment regimen.

Genome-Wide Association Analyses of Fertility Traits in Beef Heifers

The ability of livestock to reproduce efficiently is critical to the sustainability of animal agriculture. Antral follicle count (AFC) and reproductive tract scores (RTS) can be used to estimate fertility in beef heifers, but the genetic mechanisms influencing variation in these measures are not well understood. Two genome-wide association studies (GWAS) were conducted to identify the significant loci associated with these traits. In total, 293 crossbred beef heifers were genotyped on the Bovine GGP 50K chip and genotypes were imputed to 836,121 markers. A GWAS was performed with the AFC phenotype for 217 heifers with a multi-locus mixed model, conducted using the year, age at time of sampling and principal component analysis groupings as the covariates. The RTS GWAS was performed with 289 heifers using an additive correlation/trend test comparing prepubertal to pubertal heifers. The loci on chromosomes 2, 3 and 23 were significant in the AFC GWAS and the loci on chromosomes 2, 8, 10 and 11 were significant in the RTS GWAS. The significant region on chromosome 2 was similar between both analyses. These regions contained genes associated with cell proliferation, transcription, apoptosis and development. This study proposes candidate genes for beef cattle fertility, although future research is needed to elucidate the precise mechanisms.

Rewiring of gene expression in circulating white blood cells is associated with pregnancy outcome in heifers (Bos taurus)

Infertility is a challenging phenomenon in cattle that reduces the sustainability of beef production worldwide. Here, we tested the hypothesis that gene expression profiles of protein-coding genes expressed in peripheral white blood cells (PWBCs), and circulating micro RNAs in plasma, are associated with female fertility, measured by pregnancy outcome. We drew blood samples from 17 heifers on the day of artificial insemination and analyzed transcript abundance for 10,496 genes in PWBCs and 290 circulating micro RNAs. The females were later classified as pregnant to artificial insemination, pregnant to natural breeding or not pregnant. We identified 1860 genes producing significant differential coexpression (eFDR < 0.002) based on pregnancy outcome. Additionally, 237 micro RNAs and 2274 genes in PWBCs presented differential coexpression based on pregnancy outcome. Furthermore, using a machine learning prediction algorithm we detected a subset of genes whose abundance could be used for blind categorization of pregnancy outcome. Our results provide strong evidence that transcript abundance in circulating white blood cells is associated with fertility in heifers.

Beef heifer fertility: importance of management practices and technological advancements

The development of replacement heifers is at the core of cow-calf beef production systems. In 2020, the USDA, National Agricultural Statistics Service reported 5.771 million beef heifers, 500 pounds and over, are under development for cow replacement. A compilation of data from several studies indicate that between 85% and 95% of these heifers will become pregnant in their first breeding season. Several thousands of heifers being raised for replacement may not deliver a calf on their first breeding season and result in economic losses to cow-calf producers. Many management procedures have been developed to maximize the reproductive potential of beef heifers. Such approaches include, but are not limited to the following: nutritional management for controlled weight gain, identification of reproductive maturity by physiological and morphological indicators, and the implementation of an estrous synchronization program. The implementation of management strategies has important positive impact(s) on the reproductive efficiency of heifers. There are limitations, however, because some heifers deemed ready to enter their first breeding season do not become pregnant. In parallel, genetic selection for fertility-related traits in beef heifers have not promoted major genetic gains on this particular area, most likely due to low heritability of female fertility traits in cattle. Technologies such as antral follicle counting, DNA genotyping and RNA profiling are being investigated as a means to aid in the identification of heifers of low fertility potential. To date, many polymorphisms have been associated with heifer fertility, but no DNA markers have been identified across herds. Antral follicle count is an indication of the ovarian reserve and is an indicator of the reproductive health of a heifer. We have been working on the identification of transcriptome profiles in heifers associated with pregnancy outcome. Our current investigations integrating protein-coding transcript abundance and artificial intelligence have identified the potential for bloodborne transcript abundance to be used as indicators of fertility potential in beef heifers. In summary, there is an ongoing pressure for reducing costs and increasing efficiency in cow-calf production systems, and new technologies can help reduce the long-standing limitations in beef heifer fertility.

Decreasing the dose of equine chorionic gonadotropin does not affect ovarian or pregnancy responses of purebred taurine and crossbred beef heifers

In this study there was evaluation of effects of different doses of equine chorionic gonadotropin (eCG: 200, 300, or 400 IU) administrated at progesterone (P4) plus estradiol-based timed AI (TAI). A total of 1080 heifers were included in the study. There was insertion of the intravaginal P4-device plus administration of 2 mg of estradiol benzoate IM. On D7, 12.5 mg of dinoprost tromethamine IM was administered and on D9, the P4 insert was removed and 0.5 mg of estradiol cypionate IM was administered. Heifers were categorized according to Reproductive Tract Status (RTS; 1-5) and were assigned to one of three treatments: 200 IU (n = 387), 300 IU (n = 357), or 400 IU (n = 336) of eCG. Estrous occurrence was evaluated at TAI 48 h later (D11). A subset of heifers (n = 213) had the largest follicle (LF) evaluated on D9 and on D11, and the formation of a new CL evaluated on D18.There was no effect of eCG treatment on LF on D11 (P = 0.79), occurrence of estrus (P = 0.92), and pregnancy at 30 days after AI (P/AI; 52.2%, 49.8%, and 51.5% for 200 IU, 300 IU, and 400 IU, respectively; P = 0.46). Regardless of the treatment, there was a greater P/AI when heifers had a functional CL, at initiation of the estrous synchronization treatment regimen. It, therefore, is efficacious to reduce the dose of eCG to 300 or 200 IU in purebred taurine and crossbred beef heifers without negative effects on ovarian, estrous or pregnancy responses.

Presynchronization with CIDR, with or without GnRH, prior to CO-Synch in beef heifers

Objectives were to compare ovarian responses and pregnancy per AI (P/AI) in Angus-cross beef heifers (n = 521; 4 locations) synchronized with CIDR-CO-Synch (CCOS) versus CIDR-GnRH-CO-Synch (CGCOS) protocols. Heifers were assigned a reproductive tract score (RTS: 1, immature, acyclic; 5, mature, cyclic), body condition score (BCS: 1, emaciated; 9, obese) and temperament score (0, calm, 1, excitable). Heifers in the CCOS (n = 261) group received a CIDR on Day -20 (removed on Day -13), 100 μg GnRH on Day -10, 25 mg PGF2α on Day -3 and were timed inseminated 60 h later, with concomitant GnRH (Day 0). Heifers in the CGCOS (n = 260) group received a CIDR on Day -26 (removed on Day -19), 100 μg of GnRH on days -16 and -10, 25 mg of PGF2α on Day -3 and were timed inseminated 60 h later, with concomitant GnRH (Day 0). Ovarian ultrasonography was done in a subset of heifers (n = 60; 30 in each group) to determine number and size of ovarian follicles and presence of corpus luteum (CL). There was increased (P < 0.05) percentage of heifers with CL in CGCOS group compared to heifers in CCOS group on Day -10 (82.3 vs 68.2%) and on Day -3 (88.3 vs 75.1%). Average size of the largest ovarian follicle on Day 0 was greater for heifers in CGCOS group compared to CCOS group (P < 0.05). However, P/AI did not differ between CCOS and CGCOS groups, 55.0% (143/260) and 59.8% (156/261), respectively (P > 0.1). In conclusion, CIDR presynchronization with or without GnRH (CCOS and CGCOS protocols) in beef heifers resulted in similar P/AI. Adding GnRH to presynchronization with CIDR resulted in more heifers with a CL at PGF2α and increased preovulatory follicle diameter at AI. Future studies are needed with bigger sample size and CIDR + CO-Synch treatment as control to determine economic benefit.

Cyclicity, estrus expression and pregnancy rates in beef heifers with different reproductive tract scores following progesterone supplementation

Two experiments were conducted to determine effects of progesterone (P4) on cyclicity, estrus expression rate (EER) and artificial insemination pregnancy rate (AIPR) in beef heifers with various reproductive tract scores (RTS; 1 to 5; 1, immature, acyclic; 5, mature, cyclic). In Experiment 1, Angus-cross heifers (n = 100, 20 per RTS category; mean (±SEM) age, 15 ± 0.8 mo) were randomly assigned to receive a CIDR (Days -17 to -10) or no CIDR (untreated control), with weekly blood samples and ultrasonography (Days 0-85). Among heifers with RTS 2 to 4, median interval to cyclicity were shorter (P < 0.05) for heifers in CIDR versus control. In Experiment 2, Angus-cross heifers (n = 11,098) were assigned RTS, body condition score (BCS; 1 to 9; 1, emaciated; 9, obese) and temperament score (calm versus excitable). Heifers with RTS 2-5 (n = 10,569) were allocated to CO-Synch (n = 5099) or CO-Synch + CIDR (n = 5470). Estrus was detected until AI (72 h after PGF2α), with pregnancy diagnosis ∼70 d later. Controlling for RTS (P < 0.0001), BCS (P < 0.0001), temperament (P < 0.0001), age (P < 0.0001), treatment by RTS (P < 0.01), treatment by BCS (P < 0.01), and treatment by age, EER differed between CO-Synch and CO-Synch + CIDR (71.0 vs 75.9%, respectively, P < 0.0001). Accounting for RTS (P < 0.0001), BCS (P < 0.0001), temperament (P < 0.0001), age (P < 0.0001), heifers detected in estrus (P < 0.0001), RTS by treatment (P < 0.01), BCS by treatment (P < 0.01), and age by treatment, AIPR differed between CO-Synch versus CO-Synch + CIDR (55.3 vs 61.0%, P < 0.0001). In conclusion, exogenous P4 hastened cyclicity in pre- and peri-pubertal beef heifers. Further, it increased EER and AIPR. However, RTS, BCS and age influenced EER and AIPR. Among RTS 4 and 5, EER was greater for CO-Synch + CIDR vs CO-Synch. Among RTS 3 to 5, AIPR was greater for CO-Synch + CIDR versus CO-Synch. Progesterone status or supplementation at onset of synchronization protocols was critical to pregnancy outcomes, emphasizing heifer development for early puberty or progesterone supplementation.

Pregnancy associated glycoproteins (PAGs) and pregnancy loss in high vs sub fertility heifers

Reproductive inefficiency and infertility are major financial burdens to domestic livestock. Variables associated with these reproductive losses during early gestation include contributions from the oocyte, uterus, sperm, embryo and placenta. Bovine pregnancy associated glycoproteins (PAG) are produced by the binucleate cells of the ruminant placenta and can be used to diagnose pregnancy. Increased circulating concentrations of PAG early in gestation have been correlated with pregnancy success and decreased concentrations are predictive of impending embryonic mortality in both beef and dairy cattle. The objectives of the current study were to determine whether: 1) heifer fertility status is associated with circulating concentrations of PAG and pregnancy loss; and 2) PAG concentrations within the same animal are repeatable across multiple pregnancies. We hypothesized maternal PAG concentrations would be increased in high fertility compared to subfertile heifers but not repeatable across subsequent pregnancies in the same heifer. Serial embryo transfer (ET; n = 4 rounds) was used to classify predominately Angus heifers (n = 92) as highly fertile (HF = 30; 100% pregnancy success) or subfertile (SF = 62; average = 33%; range = 25-75% pregnancy success) based on day 28 ultrasound diagnosis. Blood samples were collected at both day 28 and 44 for quantification of circulating PAG concentrations by an in house PAG ELISA with antibodies raised against early secreted PAGs. Pregnancy was terminated at day 44 of gestation and heifers were allowed 30 days recovery before synchronization for the next ET. Only heifers that were diagnosed pregnant by ultrasound were used in this study (HF: n = 30, SF: n = 62). Serum concentrations of PAGs were not different between HF (5.90 ± 0.27 ng/mL) and SF (5.56 ± 0.31 ng/mL; P = 0.16) heifers at day 28 of gestation nor was there a difference at day 44 of gestation (P = 0.32). Subfertile heifers had increased pregnancy loss between days 28 and 44 of gestation. Based on odds ratio analysis, SF heifers had a 2.41 times chance to undergo pregnancy loss between day 28-44 compared to HF heifers (P < 0.05). There was no correlation (P > 0.05) in maternal circulating concentrations of PAG between pregnancies on day 28 or 44 of gestation in samples obtained from HF heifers. In summary, circulating concentrations of PAG are not different between HF and SF heifers; however, HF classified heifers have decreased pregnancy loss between days 28 and 44 of gestation.

Evaluation of age, weaning weight, body condition score, and reproductive tract score in pre-selected beef heifers relative to reproductive potential

Background

Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer's reproductive life span. As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season.

Results

None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable ('pregnant to artificial insemination', 'pregnant to natural service', 'not pregnant'). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination (49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season (89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season, compared to 87.5% if the heifers were older than 368 days.

Conclusion

Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.

A two-injection prostaglandin F2α presynchronization treatment decreases pregnancy rates of cycling replacement beef heifers

Improving artificial insemination (AI) pregnancy rates in replacement heifers improves the genetic advancement within a herd. Heifers that have completed at least three estrous cycles prior to breeding have greater pregnancy rates compared to acyclic females. Therefore, it was hypothesized that a presynchronization treatment program consisting of two injections of prostaglandin F_2α (PGF_2α) prior to the start of the CO-Synch + 5 d CIDR protocol would initiate earlier attainment of puberty and more estrous cycles prior to AI, thus increasing AI pregnancy rates. All heifers were managed the same at two locations over the course of 2 yr. Heifers were randomly assigned to receive either the two-injection PGF_2α presynchronization treatment (PreSynch; n = 105) or no presynchronization (Control; n = 106) prior to the start of estrous synchronization. On the first day of the trial, reproductive tract scores (RTSs), pelvic areas, body condition scores, and weights were collected on all heifers. All heifers were synchronized with the CO-Synch + 5 d CIDR protocol and fixed-time artificially inseminated with semen from a bull of known fertility. Blood samples were collected three consecutive times at 7 d intervals starting 45 d prior to estrous synchronization to determine the onset of puberty via analyzing progesterone concentrations. Pregnancy status to AI was assessed using ultrasonography diagnosis at approximately 30 and 60 d post insemination. Data were analyzed using PROC MIXED of SAS and reported as least square mean. The PreSynch treatment decreased AI pregnancy rates (52.2% vs. 38.1 ± 6.3% for Control vs. PreSynch, respectively; P = 0.06) and did not result in earlier attainment of puberty in beef heifers (P > 0.05). The PreSynch treatment did not impact pregnancy rates in heifers with an RTS of 3 or 4 (P > 0.05). However, PreSynch heifers with an RTS of 5 had decreased pregnancy rates (68.3% vs. 46.9 ± 10.1% for Control vs. PreSynch, respectively; P < 0.05). Finally, PreSynch heifers with increased body condition of 6 had decreased pregnancy rates when compared to Control heifers (37.5% vs. 62.5 ± 11.6%, respectively; P < 0.05). On the basis of these data, implementation of heifer breeding soundness examination at least 3 wk prior to the start of the breeding season may be beneficial for selecting replacement females; however, presynchronization with prostaglandins immediately prior to estrous synchronization will negatively affect AI pregnancy rates in cycling pubertal heifers.

Plasma metabolomic profiles differ at the time of artificial insemination based on pregnancy outcome, in Bos taurus beef heifers

Infertility remains the most prevalent reason for cattle being removed from production environments. We utilized metabolomic profiling to identify metabolites in the blood plasma that may be useful in identifying infertile heifers at the time of artificial insemination (AI). Prior to AI, phenotypic parameters including body condition, weight, and reproductive organ measurements were collected. These were determined not effective at differentiating between fertile and infertile heifers. Analysis of the resulting metabolomic profiles revealed 15 metabolites at significantly different levels (T-test P ≤ 0.05), with seven metabolites having a greater than 2-fold difference (T-test P ≤ 0.05, fold change ≥2, ROC-AUC ≥ 0.80) between infertile and fertile heifers. We further characterized the utility of using the levels of these metabolites in the blood plasma to discriminate between fertile and infertile heifers. Finally, we investigated the potential role inflammation may play by comparing the expression of inflammatory cytokines in the white blood cells of infertile heifers to that of fertile heifers. We found significantly higher expression in infertile heifers of the proinflammatory markers tumor necrosis factor alpha (TNFα), interleukin 6 (IL6), and the C-X-C motif chemokine 5 (CXCL5). Our work offers potentially valuable information regarding the diagnosis of fertility problems in heifers undergoing AI.

Transcriptome profiles in peripheral white blood cells at the time of artificial insemination discriminate beef heifers with different fertility potential

Background

Infertility is a longstanding limitation in livestock production with important economic impact for the cattle industry. Female reproductive traits are polygenic and lowly heritable in nature, thus selection for fertility is challenging. Beef cattle operations leverage estrous synchronization in combination with artificial insemination (AI) to breed heifers and benefit from an early and uniform calving season. A couple of weeks following AI, heifers are exposed to bulls for an opportunity to become pregnant by natural breeding (NB), but they may also not become pregnant during this time period. Focusing on beef heifers, in their first breeding season, we hypothesized that: a- at the time of AI, the transcriptome of peripheral white blood cells (PWBC) differs between heifers that become pregnant to AI and heifers that become pregnant late in the breeding season by NB or do not become pregnant during the breeding season; and b- the ratio of transcript abundance between genes in PWBC classifies heifers according to pregnancy by AI, NB, or failure to become pregnant.

Results

We generated RNA-sequencing data from 23 heifers from two locations (A: six AI-pregnant and five NB-pregnant; and B: six AI-pregnant and six non-pregnant). After filtering out lowly expressed genes, we quantified transcript abundance for 12,538 genes. The comparison of gene expression levels between AI-pregnant and NB-pregnant heifers yielded 18 differentially expressed genes (DEGs) (ADAM20, ALDH5A1, ANG, BOLA-DQB, DMBT1, FCER1A, GSTM3, KIR3DL1, LOC107131247, LOC618633, LYZ, MNS1, P2RY12, PPP1R1B, SIGLEC14, TPPP, TTLL1, UGT8, eFDR≤0.02). The comparison of gene expression levels between AI-pregnant and non-pregnant heifers yielded six DEGs (ALAS2, CNKSR3, LOC522763, SAXO2, TAC3, TFF2, eFDR≤0.05). We calculated the ratio of expression levels between all gene pairs and assessed their potential to classify samples according to experimental groups. Considering all samples, relative expression from two gene pairs correctly classified 10 out of 12 AI-pregnant heifers (P = 0.0028) separately from the other 11 heifers (NB-pregnant, or non-pregnant).

Conclusion

The transcriptome profile in PWBC, at the time of AI, is associated with the fertility potential of beef heifers. Transcript levels of specific genes may be further explored as potential classifiers, and thus selection tools, of heifer fertility.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4505-4) contains supplementary material, which is available to authorized users.

Determining potential pregnancy status differences based on a new method of yearling heifer prebreeding examination

The study objective was to evaluate the Ready-Intermediate-Problem (RIP) replacement heifer evaluation matrix's ability to classify heifers into groups with differing reproductive outcomes. Beef heifers (n = 341) from six Kansas herds were classified according to RIP matrix guidelines and then exposed to AI breeding, bull breeding, or a combination of both as per the management plans for each participating herd. Following the breeding season the heifers were evaluated to determine pregnancy status, AI pregnancy status, days bred, and the number of 21 day cycles needed during the breeding season to become pregnant. After the breeding season, 298 (87%) of the heifers were pregnant, 204 (68%) of which became pregnant in the first 21 days of the breeding season. There was a significant interaction (P = 0.01) in RIP classification and pregnancy by 21 day cycle. Ready classified heifers had a significantly greater risk of becoming pregnant after a single AI exposure (P = 0.03) and in the first 21-day cycle (P = 0.02) compared to Problem classified heifers, and significantly less risk of being non-pregnant at the end of the breeding season (P < 0.01) compared to Problem classified heifers. The RIP matrix can be useful for classifying heifers prior to the onset of the breeding season. Further research is needed to evaluate the matrix in other settings and populations of U.S. beef heifers as well as at different intervals between evaluation and the start of breeding season.

A field investigation of a modified intravaginal progesterone releasing device and oestradiol benzoate based ovulation synchronisation protocol designed for fixed-time artificial insemination of Brahman heifers

Pregnancy rates (PR) to fixed-time AI (FTAI) in Brahman heifers were compared after treatment with a traditional oestradiol-based protocol (OPO-8) or a modified protocol (OPO-6) where the duration of intravaginal progesterone releasing device (IPRD) was reduced from 8 to 6 days, and the interval from IPRD removal to oestradiol benzoate (ODB) was increased from 24 to 36 h. Rising 2 yo heifers on Farm A: (n = 238 and n = 215; two consecutive days AI); B (n = 271); and C (n = 393) were allocated to OPO-8 or OPO-6. An IPRD was inserted and 1mg ODB i.m. on Day 0 for OPO-8 heifers and Day 2 for OPO-6 heifers. On Day 8, the IPRD was removed and 500 μg cloprostenol i.m. At 24h, for OPO-8 heifers, and 36 h, for OPO-6 heifers, post IPRD removal all heifers received 1mg ODB i.m. FTAI was conducted at 54 and 72 h post IPRD removal for OPO-8 and OPO-6 heifers. At Farm A, OPO-6 heifers, AI on the second day, the PR was 52.4% to FTAI (P = 0.024) compared to 36.8% for OPO-8 heifers. However, no differences were found between OPO-8 and OPO-6 protocols at Farm A (first day of AI) (39.9 vs. 35.7%), or Farms B (26.2 vs. 35.4%) and C (43.2% vs. 40.3%). Presence of a corpus luteum at IPRD insertion affected PR to FTAI (43.9% vs. 28.8%; P < 0.001). This study has shown that the modified ovulation synchronisation protocol OPO-6 may be a viable alternative to the OPO-8 protocol for FTAI in B. indicus heifers.