Maternal and non-maternal factors associated with late embryonic and early fetal losses in dairy cows

Factors influencing pregnancy loss between days 30 and 70 in a single cattle herd: A comprehensive analysis of sire, cow, and other contributing factors

This retrospective study utilized a mixed-effects logistic model analysis to investigate variables associated with the probability of pregnancy loss (PL) between days 30 and 70 in a dataset comprising 9507 pregnancies from a single cattle herd over 10 years. The model incorporated fixed-effect variables including cow breed (Holstein, Crossbred, and Brown Swiss), parity (1st, 2nd, 3rd, and 4th or more), insemination seasons, insemination number (≤3 vs >3), estrus nature (spontaneous vs synchronized), postpartum problems, sire breed (Holstein, Fleckvieh, Brown Swiss, and Montbéliarde), zygote genotypic (pure vs crossbred), days in milk (DIM) at insemination, actual 305-day milk yield, and sire conception rate. Additionally, random effects included sire (n = 129), cow (n = 3463), and production years (n = 10). The results revealed that cows inseminated with Brown Swiss sires or sires with lower initial conception rates had higher PL rates. Biparous cows, cows with lower 305-day milk yield, cows inseminated later in DIM, cows receiving the 4th or subsequent insemination, and cows inseminated during winter or autumn had lower PL rates. The estrus type and zygote genotype did not significantly impact PL. The random effects of cow, sire, and production years were estimated at 0.230, 0.054, and 0.112, respectively. In conclusion, the study findings suggested that improving management practices for high-yielding cows, cows in early lactation stages, and cows exposed to thermal stress conditions, along with utilizing Brown Swiss cows and sires with high initial conception rates per insemination, could potentially decrease overall PL rates on the farm. Nonetheless, the results did not support the use of Crossbred cows, sires from different breeds, or specific sires to mitigate PL rates on the farm.

From the laboratory to the field: how to mitigate pregnancy losses in embryo transfer programs?

Pregnancy losses negatively affect the cattle industry, impacting economic indices and consequently the entire production chain. Early embryonic failure has been an important challenge in the embryo industry because proper identification of embryo death at the beginning of gestation is difficult. This review aimed to provide a better understanding on reproductive failure and the relationship between early embryonic loss and different reproductive biotechniques. This review also considers insights and possible strategies for reducing early embryonic loss. The strategies addressed are as follows: i) great impact of rigorous embryo evaluation on reducing embryo losses; ii) selection of recipients at the time of transfer, taking into account health and nutritional status, and classification of the corpus luteum using ultrasound, either in area or vascularization; and iii) paternal effect as one of the factors that contribute to pregnancy losses, with a focus on embryo transfer.

Impact of postpartum time period associated body condition score on reproductive performance in dairy cows

This study was designed to identify the time period at which the body condition score (BCS) most critically affects the reproductive performance after calving in dairy cows. Data were collected from 4865 lactation records (1821 from primiparous and 3044 from multiparous cows) on 28 dairy farms, including the BCS (at calving, and month 1 and the first artificial insemination [AI] after calving), the presence of peri- or postpartum disorders, reproductive data, and the weather. The data on the extent of BCS loss from calving to the first AI was divided into two periods, namely, between calving and month 1 after calving (period 1), and between month 1 and the first AI after calving (period 2). Cows with BCS of 3.0, 3.25 and ≥ 3.5 at the first AI after calving were more likely (P < 0.05-0.01) to be pregnant at 30 (odds ratio [OR]: 1.36, 1.64, and 1.90) and 45 (OR: 1.39, 1.75, and 1.99) days post-AI and more likely (P < 0.05-0.01) to be pregnant within 180 days after calving (hazard ratio [HR]: 1.18, 1.43, and 1.58) than cows with BCS of ≤2.75. In addition, cows who suffered a BCS loss of ≥0.5 units during period 1 tended to be less likely (HR: 0.79, P < 0.1) to be pregnant within 180 days after calving than cows without a BCS loss. Cows with BCS of 3.0, 3.25, and ≥3.5 at calving were less likely (P < 0.1-0.05) to lose their pregnancy (OR: 0.37, 0.33, and 0.16) than cows with BCS of ≤2.75. These results indicate that the linearly higher BCS (3.0, 3.25, and ≥3.5) at the first AI is positively associated with the probability of pregnancy per AI after the first AI and the likelihood of pregnancy within 180 days after calving, whereas a higher BCS loss of ≥0.5 units during period 1 was adversely associated with the likelihood of pregnancy within 180 days after calving.

Genetic parameters of production and reproduction traits of Egyptian buffaloes under subtropical conditions

This research was aimed to investigate the production and reproduction traits and their genetic parameters of Egyptian buffaloes under subtropical environment. Heritability, phenotypic, and genetic parameters were estimated for productive and reproduction traits of first parity This study revealed the averages TMY, 305-dMY, LL, BW, DP, SP, CI, and AFC were 2260, 2150 kg, 271 days, 38.63 kg, 210.50 days, 195.20 days, 586.86 days, and 36.61 months, respectively. The heritability estimates for productive traits of the first lactation were 0.61, 0.52, 0.47, 0.20, and 0.23 for TMY, 305-dMY, LL, DP, and BW, respectively. Heritability estimates for reproductive traits SP, CI, and AFC were 0.07, 0.09, and 0.35, respectively. Genetic correlations of most of the investigated first parity traits were positive, with an exception of DP. The genetic correlation was negative between SP and BW, and between AFC and LL. Phenotypic correlations of the first parity among all investigated traits were positive except between DP and TMY, 305-dMY, LL, BW, and AFC. High and moderate heritability estimates indicated that the opportunity of genetic upgrading of these parameters could be achieved owing to sire selection. Selection for high milk yield will be associated with genetic improvement in lactation period and birth weight.

Effect of a Single Intrauterine Dose of Human Recombinant Galectin-1 Buffered on Pregnancy Rate in Inseminated Cows

The objective was to evaluate the efficacy of a single dose of exogenous galectin-1 in improving the pregnancy rate in inseminated cows, comparing the pregnancy rate of the two groups (treatment and control Groups) into 107 contemporary groups (YG) established. An ultrasound exam determined the pregnancy rate performed 25 to 35 days after the fixed-time artificial insemination (FTAI) of breeding beef cows (n = 3469). The pregnancy rate of cows that received a single dose of eGAL-1 (200 ± 10 µg), with an intrauterine administration (n = 1901), was compared with the pregnancy rate of cows inseminated using a conventional AI protocol (n = 1568), both comparing into the same YG. YGs were created considering the grouping of cows belonging to the same farm, with the same nutritional score and management, inseminated by the same inseminator and semen batch, and using the same estrus synchronization protocol). The statistical method used calculated the probability of obtaining pregnancy within each group. The administration of a single dose of eGAL-1 can increase the probability of obtaining pregnancy in beef cows by up to 8.68% (p < 0.0001), suggesting that a single dose of eGAL-1 during the FTAI procedure was reasonable in the beef cattle AI routine and can improve the pregnancy rate considerably.

Likelihood of pregnancy in cows identified with different amounts of anechoic intrauterine fluid at the time of insemination

Effects of amount of anechoic intrauterine fluid (IUF) and size of largest follicle at insemination on proportion of cows pregnant as a result of AI (P/AI percentage), as well as factors associated with amount of IUF and size of the follicle were investigated. Follicle size was determined, and amount of IUF in the largest uterine segment was categorized as containing no fluid, ≤10, >10-20, and >20 mm using the ultrasonic monitor grid in 735 cows at time of insemination. Multivariable regression models were constructed to evaluate effects of different variables on P/AI percentage, and variables associated with the IUF score and follicle size. On day 30 post-insemination, the P/AI percentage was greater in cows that had >10 to 20 mm IUF than cows with no IUF (OR = 1.9, P = 0.01), but on day 70 post-insemination, the P/AI percentage was similar in cows with different amounts of IUF. Follicle size was not associated with P/AI percentage on days 30 and 70 post-insemination. Cows in spontaneous estrus, multiparous cows, cows with a cystic structure and a typically functional follicle, and Holstein cows had a greater likelihood for a larger IUF value. Primiparous cows, cows on which there was imposing of a hormonal-ovulation-synchronization regimen, and crossbred cows were more likely to have smaller follicles. In conclusion, amount of IUF at the time of insemination and size of the follicle were not associated with P/AI percentage, and several variables were associated with amount of IUF or follicle size.

Treatment of cows that fail to respond to pre-synchronization treatments with a CIDR-Ovsynch regimen improves the overall pregnancy percentage after a double Ovsynch treatment regimen

In this study, there was evaluation of pregnancy per AI (P/AI) as a result of the first postpartum AI following four ovulation-synchronization treatments. Treatment regimens were Ovsynch-56 (OVS, n = 875; GnRH1-7d-PGF_2α-56h-GnRH2-16h-FTAI), CIDR-OVS (n = 1001; OVS plus CIDR inserts between GnRH1 and PGF_2α), Double-Ovsynch (DOVS, n = 663; imposing Pre-OVS followed by breeding-OVS 7 days later), and Modified-DOVS (M-DOVS, n = 1397; imposing Pre-OVS followed either by breeding-OVS or CIDR-OVS based upon the ovarian structure at GnRH1). Cows with a corpus luteum were assigned to a breeding-OVS treatment regimen and those that did not have a corpus luteum were assigned to the CIDR-OVS treatment regimen. Compared with OVS, the P/AI of the cows in the M-DOVS (OR = 1.5, P = 0.001) and CIDR-OVS (OR = 1.4, P = 0.017) was greater at day 30. At day 70, only in the M-DOVS group was there a greater P/AI compared with the OVS group (OR = 1.7, P < 0.001). Pregnancy loss between days 30 and 70 was greater in cows of the CIDR-OVS (OR = 1.9, P = 0.014) compared with those of the OVS group. In cows of the M-DOVS, the dominant ovarian structures (follicle, corpus luteum or cyst) at different time-points of the pre-synchronization period and occurrence of estrus at the end of this period were not associated with P/AI at day 30 post-AI. In conclusion, imposing CIDR-OVS in cows that did not respond to pre-synchronization treatments, resulted in an enhanced pregnancy percentage with the use of the DOVS.

Pregnancy loss in beef cattle: A meta-analysis

Pregnancy loss in beef cattle causes both management and economic challenges to a producer. A meta-analysis was conducted to quantify reproductive failures that occur during fertilization, early embryonic development, and late embryonic/early fetal development periods of gestation in beef cattle. The meta-analysis included more than 56,000 diagnostic records in 159 studies from 48 papers with 12 studies included in fertilization and pre- blastocyst loss analysis (FERT; days 1-7 of gestation), 107 in early embryo (EEM; days 7-32), and 40 in late embryo/early fetal period (LEF; days 32-100) analysis. Although fertilization rates are reportedly high in beef cattle, significant developmental failure occurs within the first 7 days of gestation. Approximately 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. By the conclusion of the first month of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant. Overall, LEF between days 32-60 and 100 was 5.8 %. Bos indicus animals had greater (P =  0.001) EEM compared to Bos taurus, but there was no difference (P =  0.39) for the LEF period between subspecies. Primiparous cows had greater EEM (P =  0.002) compared to nulliparous heifers and multiparous cows; and nulliparous heifers had a greater LEF compared to primiparous and multiparous cows (P =  0.048). Collectively, these cumulative findings provide a baseline assessment of pregnancy loss specific to beef cattle.

Sanitary program to reduce embryonic mortality associated with infectious diseases in cattle

Among reproductive disorders in dairy and beef cattle worldwide, embryonic mortalities stand out as one of the most frequent. Because of the multifactorial etiology, the clinical and laboratory diagnoses of embryonic mortality causes in cattle are quite complex. Often, infectious causes may account for up to 50% of bovine embryonic mortality rates after 30 days of conception. This review will address the main causes of early and late embryonic mortality, with emphasis on infectious causes and, particularly, those more frequent in the Brazilian cattle herds. In addition, we will discuss ways of controlling and prophylaxis including those related to reproductive and sanitary management, with emphasis on immunoprophylaxis of the three most frequent reproductive infectious diseases in Brazilian dairy and beef cattle herds.

Evaluating sire effects on cow fertility: Timed AI and repeat-breeder dairy cows

In this single herd observational study, there is investigation of the effects of 81 sires (with 11,424 artificial inseminations) on conception rates in 1790 Holstein cows for 5 years. Sires were catagorized based on the published sire conception rate (SCR) into different sire fertility groups (low, average and high fertility sires). The performance of different-sire fertility groups was assessed in timed artificial insemination (TAI) and repeat-breeder (RB) cows. With this aim, two logistic regression models with sire, inseminator, cow, and lactation random effects were applied to data on pregnancies assessed at days 30 and 70 post-insemination. Fixed effects of sire fertility group, sire breed, cow-fertility status, insemination type, postpartum problems, milk yield, temperature humidity index, and year were evaluated. Results from the analysis indicated there was a significant individual sire effect on conception rates, and large heterogeneity in values for this variable among sires. Results indicate that SCR could be assessed to predict low fertility sires reasonably well, and the predicted probabilities for pregnancy per AI (P/AI) at 30 and 70 days post-insemination for high fertility sires were consistent for the most part with values for the SCR. The sire breed did not affect conception rates at days 30 and 70 post-insemination nor its interactions with insemination type (estrous detection AI (EDAI) compared with TAI) and cow-fertility status (RB compared with non-RB). Predicting response probabilities for sires with at least 100 inseminations in each insemination group resulted in greater conception probabilities in cows in which there was EDAI than those in the TAI group.

Late embryonic losses in supplemented grazing lactating dairy cows: Risk factors and reproductive performance

The main objective of this study was to evaluate the risk factors for late embryonic loss (LEL) in supplemented grazing dairy cows. Additional objectives were to assess the incidence of LEL and its association with the reproductive performance of cows. A data set containing productive, reproductive, and health records of 13,551 lactations was used. A retrospective case-control study involving 631 cows with LEL (cases) and 2,524 controls (4 controls per case within each study year) was run. A case of LEL was defined when the embryo had no heartbeat or there was evidence of detached membranes or floating structures including embryo remnants by ultrasonography (US) at 28 to 42 d post-artificial insemination (AI), whereas a non-case was defined as a cow diagnosed with positive pregnancy by US 28 to 42 d post-AI and reconfirmed as pregnant 90 ± 7 d post-AI. Four controls per case were randomly selected from the non-cases with a temporal matching criterion (±3 d around the date of the fecundating AI of the case). Multivariable logistic models were offered with the following predictors: year of LEL (2011 through 2015), season of LEL (summer vs. fall vs. winter vs. spring), parity (1 vs. 2 vs. ≥3), uterine disease (UD), non-uterine disease (NUD), body condition score at parturition, body condition score at 28 to 42 d post-AI (BCS-LEL), days in milk (DIM), and daily milk yield (MY). Statistical significance was set at P < 0.05 and a tendency was set at P ≤ 0.10. We found that 4.7, 22, and 23% of cows had LEL, UD, and NUD, respectively. Cases tended to have higher daily MY than controls (32.5 vs. 31.8 kg); also, cases had much longer calving to pregnancy interval (226 vs. 118 d), lower hazard of pregnancy [hazard ratio = 0.39, 95% confidence interval (CI) = 0.35-0.43], and higher odds for non-pregnancy [odds ratio (OR) = 2.89, 95% CI = 2.37-3.54] than controls. We found that the odds for LEL increased with parity number (OR = 2.48, 95% CI = 1.99-3.08 for parity ≥3) and with BCS-LEL <2.50 (OR = 1.81, 95% CI = 1.33-2.47). Conversely, the odds for LEL decreased with BCS-LEL >3.00 (OR = 0.70, 95% CI = 0.53-0.91). The odds for LEL increased with UD (OR = 1.23, 95% CI = 1.01-1.49), NUD (OR = 1.24, 95% CI = 1.01-1.54), DIM (OR = 1.03, 95% CI = 1.00-1.05), and daily MY (OR = 1.14, 95% CI = 1.04-1.25) in univariable models only. Finally, the odds for LEL were not associated with year, season, DIM, and body condition score at parturition. In conclusion, LEL is associated with extended calving to pregnancy interval, and among its risk factors are parity number and BCS-LEL.

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.