S.E. Poock

Delayed insemination of nonestrous cows improves pregnancy rates when using sex-sorted semen in timed artificial insemination of suckled beef cows.

This experiment was designed to test the hypothesis that delayed insemination of nonestrous cows would increase pregnancy rates when using sex-sorted semen in conjunction with fixed-time artificial insemination (FTAI). Estrus was synchronized for 656 suckled beef cows with the 7-d CO-Synch + controlled internal drug release (CIDR) protocol (100 μg GnRH + CIDR [1.38 g progesterone] on d 0, 25 mg PGF2α at CIDR removal on d 7, and 100 μg GnRH on d 10, 66 h after CIDR removal). Estrus detection aids (Estrotect) were applied at PGF2α and CIDR removal on d 7, and estrous expression was recorded at GnRH on d 10. Cows were assigned to 1 of 3 treatments: 1) FTAI (concurrent with GnRH, 66 h after CIDR removal) with conventional semen regardless of estrous expression, 2) FTAI with sex-sorted semen regardless of estrous expression, or 3) FTAI with sex-sorted semen for cows having expressed estrus and delayed AI 20 h after final GnRH for cows failing to express estrus. A treatment × estrous expression interaction was found (P < 0.0001). Higher pregnancy rates (P < 0.0001) were achieved with conventional semen (Treatment 1; 77%) than with sex-sorted semen (Treatments 2 and 3; 51 and 42%, respectively) among cows that expressed estrus. However, among cows that failed to express estrus, delayed insemination with sex-sorted semen yielded higher (P < 0.0001) pregnancy rates than with sex-sorted semen at the standard time (Treatments 2 and 3; 3 versus 36%, respectively). Furthermore, among cows that failed to express estrus, FTAI pregnancy rates when using sex-sorted semen at the delayed time (36%) were comparable (P = 0.9) to those achieved using conventional semen at the standard time (Treatment 1; 37%). These results indicate that delaying AI of nonestrous cows by 20 h from the standard FTAI improves pregnancy rates when sex-sorted semen is used with FTAI.

Hot topic: 16S rRNA gene sequencing reveals the microbiome of the virgin and pregnant bovine uterus

We tested the hypothesis that the uterus of virgin heifers and pregnant cows possessed a resident microbiome by 16S rRNA gene sequencing of the virgin and pregnant bovine uterus. The endometrium of 10 virgin heifers in estrus and the amniotic fluid, placentome, intercotyledonary placenta, cervical lumen, and external cervix surface (control) of 5 pregnant cows were sampled using aseptic techniques. The DNA was extracted, the V4 hypervariable region of the 16S rRNA gene was amplified, and amplicons were sequenced using Illumina MiSeq technology (Illumina Inc., San Diego, CA). Operational taxonomic units (OTU) were generated from the sequences using Qiime v1.8 software, and taxonomy was assigned using the Greengenes database. The effect of tissue on the microbial composition within the pregnant uterus was tested using univariate (mixed model) and multivariate (permutational multivariate ANOVA) procedures. Amplicons of 16S rRNA gene were generated in all samples, supporting the contention that the uterus of virgin heifers and pregnant cows contained a microbiome. On average, 53, 199, 380, 382, 525, and 13,589 reads annotated as 16, 35, 43, 63, 48, and 176 OTU in the placentome, virgin endometrium, amniotic fluid, cervical lumen, intercotyledonary placenta, and external surface of the cervix, respectively, were generated. The 3 most abundant phyla in the uterus of the virgin heifers and pregnant cows were Firmicutes, Bacteroidetes, and Proteobacteria, and they accounted for approximately 40, 35, and 10% of the sequences, respectively. Phyla abundance was similar between the tissues of the pregnant uterus. Principal component analysis, one-way PERMANOVA analysis of the Bray-Curtis similarity index, and mixed model analysis of the Shannon diversity index and Chao1 index demonstrated that the microbiome of the control tissue (external surface of the cervix) was significantly different from that of the amniotic fluid, intercotyledonary placenta, and placentome tissues. Interestingly, many bacterial species associated with postpartum uterine disease (i.e., Trueperella spp., Acinetobacter spp., Fusobacteria spp., Proteus spp., Prevotella spp., and Peptostreptococcus spp.) were also present in the uterus of virgin heifers and of pregnant cows. The presence of 16S rRNA gene sequence reads in the samples from the current study suggests that the uterine microbiome is established by the time a female reaches reproductive maturity, and that pregnancies are established and maintained in the presence of a uterine microbiome.

Comparison of long- versus short-term CIDR-based protocols to synchronize estrus prior to fixed-time AI in postpartum beef cows.

This experiment was conducted to compare pregnancy rates in postpartum beef cows resulting from fixed-time AI (FTAI) after treatment with controlled internal drug release (CIDR)-based protocols to synchronize estrus. Cows assigned to the Show-Me-Synch (n=167) protocol received a CIDR from d 0 to 14, and prostaglandin F(2α) (PGF(2α)) on d 30. Cows assigned to 7-d CO-Synch+CIDR (n=177) received a CIDR and gonadotropin releasing hormone (GnRH) on d 23. On d 30, CIDRs were removed and PGF(2α) was administered. Blood sampling occurred on d -10 and 0 of treatment to determine estrous cyclicity status (progesterone ≥0.5 ng/mL estrous cycling). Treatments were balanced on age, DPP and BCS. Estrous detection was performed using HeatWatch from PGF(2α) to FTAI. Artificial insemination was performed at predetermined fixed times (72 h, Show-Me-Synch; 66h, 7-d CO-Synch+CIDR) and all cows were administered GnRH at FTAI. This experiment was conducted over a two year period; no differences were found between years so the data were pooled for further analysis. Pregnancy rate resulting from FTAI did not differ (P>0.10) between technicians or AI sires. Pregnancy rate resulting from FTAI was similar between treatments (P=0.20); however, cows that exhibited estrus prior to FTAI had a higher pregnancy rate (P<0.01) than for those that did not. Pregnancy rate at the end of the breeding period was similar between treatments (P=0.28). In summary, FTAI pregnancy rates were similar among postpartum beef cows following treatment with either a short- or long-term CIDR-based estrous synchronization protocol.

Comparison of long-term controlled internal drug release-based protocols to synchronize estrus and ovulation in postpartum beef cows1

Two experiments were conducted to examine the necessity of adding a GnRH injection to a 14-d controlled internal drug release (CIDR)-based protocol for synchronization of estrus and ovulation in postpartum beef cows. The experiments were designed to characterize long-term CIDR-based protocols in cyclic and noncyclic postpartum beef cows on the basis of estrous response, follicular dynamics, and serum steroid hormone concentrations. In Exp. 1 and 2, crossbred lactating beef cows (n = 40 and 38, respectively) were randomly assigned to 1 of 2 treatments by age, days postpartum (DPP), BCS, and estrous cyclicity status: 1) cows received a CIDR from d 0 to 14 followed by GnRH 9 d after CIDR removal (d 23) and PGF2α on d 30 (CIDR Select) or 2) CIDR administration from d 0 to 14 followed by PGF2α 16 d later (d 30; Show-Me-Synch). Estrus detection was performed using HeatWatch transmitters applied from CIDR removal to AI. Cows in Exp. 1 were artificially inseminated based on detected estrus whereas cows in Exp. 2 were inseminated at a fixed time. In both experiments, follicle turnover on d 25 of treatment was greater among CIDR Select-treated cows (P < 0.001) compared with Show-Me-Synch-treated cows. In Exp. 1, CIDR Select-treated cows tended to have a reduced (P = 0.06) variance for the interval to estrus after PGF2α than Show-Me-Synch-treated cows. Also, cows assigned to the CIDR Select protocol had greater concentrations of progesterone (P < 0.05) on the day before PGF2α administration as well as greater concentrations of estradiol-17β (P < 0.01) 48 h after PGF2α administration. In Exp. 2, mean dominant follicle diameter on d 23 and at fixed-time AI (FTAI) did not differ between treatments (P > 0.10), but Show-Me-Synch-treated cows had larger follicles at d 28 (P < 0.001) and tended to have larger follicles at PGF2α (d 30; P = 0.06) compared with cows assigned to CIDR Select. In summary, the administration of GnRH on d 23 of a long-term CIDR-based estrus synchronization protocol increased follicle turnover; however, both long-term CIDR-based protocols yielded similar physiological outcomes among estrous-cycling and anestrous postpartum beef cows.

Reproduction in grazing dairy cows treated with 14-day controlled internal drug release for presynchronization before timed artificial insemination compared with artificial insemination after observed estrus.

Progesterone-releasing (controlled internal drug release, CIDR) devices inserted for 14 d are used to presynchronize the estrous cycle for timed artificial insemination (TAI) in beef heifers (14-d CIDR-PGF(2α) program). The objective was to test a similar program in dairy cows by measuring first-service conception rates (FSCR), pregnancy rates after 2 AI, and time to pregnancy compared with a control (AI after observed estrus). Postpartum cows (Holstein, Jersey, or crossbred; n=1,363) from 4 grazing dairy farms were assigned to 1 of 2 programs: 14dCIDR_TAI [CIDR in for 14 d, CIDR out, PGF(2α) injection at 19 d after CIDR removal, GnRH injection 56 h later, and then TAI 16 h later; n=737] or control [AI after observed estrus; reproductive program with PGF(2α) (cycling cows) and CIDR (noncycling cows) to synchronize estrus with the start of the breeding season; n=626]. Body condition was scored (1 to 5; thin to fat) at the start of the trial. The interval from the start of the breeding period (final PGF(2α) injection of either program) to first AI was shorter for 14dCIDR_TAI compared with the control (3.0±0.2 vs. 5.3±0.2 d; mean ± SEM) but 14dCIDR_TAI cows had lesser FSCR than controls (48 vs. 61%). Farm affected FSCR (50, 51, 67, and 58% for farms 1 to 4). The BCS affected FSCR (50, 55, and 62% for BCS=2, 2.5, and 3, respectively). Cows that either calved the year before (carryover) or that calved early in the calving season had greater FSCR than cows that calved later in the calving season (55, 61, and 42%, respectively). The percentage of cows pregnant to AI (first and second inseminations within 31-d breeding season) was similar for 14dCIDR_TAI and control (64 vs. 70%) cows, but farm (64, 62, 80, and 69%) and time of calving (70, 76, and 56%: carryover, early, and late, respectively) affected the percentage. Survival analyses showed an initial advantage for 14dCIDR_TAI (more cows inseminated and more pregnancies achieved early in the breeding season) that was not maintained over time. Conclusions were that the 14dCIDR_TAI program achieved acceptable FSCR (48%) and overall AI pregnancy rates (64%), but did not surpass a control program that used AI after observed estrus (61 and 70%, respectively).

Technical note: Validation of a chemical pregnancy test in dairy cows that uses whole blood, shortened incubation times, and visual readout

Chemical pregnancy testing is an alternative to traditional methods of pregnancy diagnosis (either manual palpation or ultrasound) in postpartum dairy cows and heifers. The objective was to validate a chemical pregnancy test that confers the advantages of using whole blood, rapid incubation times, and visual readout. Blood and milk samples were collected from Holstein dairy cows [n=320; 162±62 (mean ± SD) d in milk] on a confinement farm in northeast Missouri at 28 d after artificial insemination (AI). The samples were assayed for pregnancy-associated glycoproteins (PAG) by using a rapid visual test as well as traditional plasma- and milk-based tests. Transrectal ultrasonography diagnosis for pregnancy at 35 to 38 d after AI was the reference (gold) standard for all PAG tests. One hundred fifty-nine cows were diagnosed as pregnant by the reference standard (pregnancies per AI=49.7%). The tests were ELISA and either optical density (OD; measured with a microtiter plate reader; plasma, milk, and rapid visual tests) or visual readout (rapid visual test) were used to diagnose pregnancy. When OD was used, the percentage of pregnant cows classified correctly (sensitivity) for the plasma, milk, and rapid visual tests were 97±1, 96±2, and 95±1% (±SE), respectively. The sensitivity of the rapid visual test when assessed visually was 98±1%. The specificity (proportion of nonpregnant cows classified correctly) for the plasma, milk, and rapid visual was 94±2%, 94±2%, and 93±2% when an OD was used. When read visually, the specificity of the rapid visual test was lesser (85±3%) because some cows with faint visual signals yielded false positive diagnosis. The overall accuracy (proportion of pregnant and nonpregnant cows diagnosed correctly) was similar for all tests (plasma, milk, rapid visual OD, and rapid visual; 96±1, 95±1, 94±1, and 92±2%, respectively). In a second experiment, lactating Holstein cows (n=291) from 4 commercial confinement dairy farms in western Kentucky were tested 25 to 95 d after AI using the rapid visual test. The OD of the rapid visual test followed the known profile for PAG in circulation during the first trimester of pregnancy. The conclusion is that the rapid visual test has equal sensitivity and accuracy as existing PAG tests. A slightly lower specificity was found when the rapid visual test was read visually.

Growth of the conceptus from day 33 to 45 of pregnancy is minimally associated with concurrent hormonal or metabolic status in postpartum dairy cows

A hypothetical explanation for pregnancy loss in postpartum dairy cows is that the metabolic environment of the cow inhibits the growth of the conceptus and places the pregnancy at risk for loss. The objective of the current study, therefore, was to model the association between cow-level metabolic indicators and conceptus growth during early pregnancy (day 33-45 after AI) and to determine if an association (if present) is large enough to cause pregnancy loss. Metabolic indicators included milk production, changes in body weight and body condition score, parity, and concentrations of circulating hormones and metabolites (glucose, non-esterified fatty acids, growth hormone, IGF1, progesterone, and pregnancy-associated glycoproteins). One-hundred cows were enrolled. Cows that became pregnant with single conceptus pregnancies (n=53) weighed more (P<0.007) and had fewer uterine polymorphonuclear neutrophils (uterine health indicator; P<0.051) compared with cows that failed to become pregnant. The embryo and amniotic vesicle were measured by using ultrasound on day 33, 35, 38, 40, 42, and 45 of pregnancy. Most of the cow-level indicators that were included in the model of conceptus growth failed to achieve statistical significance. Day of pregnancy had the largest effect on conceptus growth (size and cross-sectional area of the embryo and amniotic vesicle; P<0.001). There were effects of sex of fetus (male fetuses larger than female), insulin (negative association), and body weigh change (positive association) on embryo length and cross-sectional area but these effects were small when compared with the range in conceptus length or area that we observed. The conclusion was that the capacity of the cow to become pregnant was associated with body weight and uterine health but we failed to find a large association with metabolic status on conceptus growth from day 33 to 45 of pregnancy in lactating dairy cows.

Comparison of a 16- versus a 19-day interval between controlled internal drug release removal and prostaglandin F2α following a 14-day controlled internal drug releasetreatment and fixed-time artificial insemination in postpartum beef cows1

This experiment compared 2 long-term controlled internal drug release (CIDR)-based protocols to synchronize estrus before fixed-time artificial insemination (FTAI) in postpartum beef cows. Cows were assigned to treatments by age, BCS, and days postpartum. Cows assigned to the 14- to 19-d CIDR-PGF2α protocol (n = 196) received CIDR inserts (1.38 g progesterone [P4]) from d 0 to 14 and PGF2α (25 mg, i.m.) 19 d after CIDR removal on d 33. Cows assigned to the 14-to-16-d CIDR-PGF2α protocol (n = 195) received CIDR inserts from d 3 to 17 and PGF2α 16 d after CIDR removal on d 33. Cows were artificially inseminated on d 36, 72 h after PGF2α, with GnRH (100 μg, i.m.) at FTAI. Cows were exposed for natural service 14 d after FTAI for 75 d. Blood samples for P4 were collected at d -10 and 0 to determine pretreatment estrous cyclicity status and again at PGF2α. Blood samples for estradiol (E2) were collected at PGF2α and FTAI. HeatWatch estrus detection transmitters were used from CIDR removal until FTAI to determine onset of estrus after CIDR removal and PGF2α. Dominant follicle diameter was determined at PGF2α and FTAI. Pregnancy diagnosis was performed 70 d after FTAI and confirmed at d 140 of gestation. Estrous response after CIDR removal was similar between treatments. Cows in both treatments had similar size dominant follicles on d 33 at PGF2α and d 36 at FTAI. Progesterone at PGF2α was greater (P = 0.03) for 14-to-16-d compared to 14-to-19-d treated cows. Mean concentrations of E2 at PGF2α were similar between treatments but were greater (P = 0.01) at FTAI for 14-to-16-d compared to 14-to-19-d treated cows. Estrous response after PGF2α was greater (P < 0.01) for 14-to-19-d compared to 14-to-16-d treated cows (47.4 vs. 29.7%, respectively). Pregnancy rate resulting from FTAI was affected by the treatment × age group interaction (P = 0.08). Pregnancy rate after FTAI among cows ≥ 4 yr tended to be greater (P = 0.06) for 14-to-19-d compared to the 14-to-16-d treated cows, suggesting that the 14-to-19-d schedule works better for older age cows compared with the 14-to-16-d schedule. Final pregnancy rates were similar between the 2 treatments. In summary, these data indicate that a range in intervals from CIDR removal to PGF2α may be feasible when using long-term CIDR-based protocols in cows and raise questions that warrant further study regarding the benefits of extending this interval based on cow age.

Efficacy of feeding a lacteal-derived colostrum replacer or pooled maternal colostrum with a low IgG concentration for prevention of failure of passive transfer in dairy calves

OBJECTIVE To compare the efficacy of a lacteal-derived colostrum replacer (LDCR) for the prevention of failure of passive transfer of immunity (FPT) in calves with that of pooled maternal colostrum (MC). DESIGN Randomized field trial. ANIMALS 568 heifer calves from 1 California dairy. PROCEDURES Calves were randomly allocated to 1 of 2 treatment groups and fed 2 doses (200 g of IgG) of an LDCR or 3.8 L of pooled MC. From each calf, blood samples were collected before and approximately 24 hours after treatment. Serum IgG and total protein (TP) concentrations were quantified with standard methods, and the apparent efficiency of IgG absorption was calculated. RESULTS At 24 hours after treatment, mean serum TP and IgG concentrations were significantly lower for calves fed pooled MC (TP, 4.77 g/dL; IgG, 7.50 g/L), compared with those for calves fed the LDCR (TP, 5.50 g/dL; IgG, 15.15 g/L). Calves fed the LDCR were 95% less likely to develop FPT (OR, 0.05; 95% confidence interval, 0.03 to 0.08) than were calves fed pooled MC. However, the mean IgG concentration in the pooled MC fed during the study (21.1 g/L) was substantially lower than that (64.3 g/L) determined for representative samples of pooled MC from other southwestern US dairies during a national survey. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that, on this particular dairy, calves fed an LDCR were at less risk of developing FPT than were calves fed pooled MC. The LDCR evaluated was a viable alternative for the prevention of FPT in calves.

Predicting hyperketonemia by logistic and linear regression using test-day milk and performance variables in early-lactation Holstein and Jersey cows

Although cowside testing strategies for diagnosing hyperketonemia (HYK) are available, many are labor intensive and costly, and some lack sufficient accuracy. Predicting milk ketone bodies by Fourier transform infrared spectrometry during routine milk sampling may offer a more practical monitoring strategy. The objectives of this study were to (1) develop linear and logistic regression models using all available test-day milk and performance variables for predicting HYK and (2) compare prediction methods (Fourier transform infrared milk ketone bodies, linear regression models, and logistic regression models) to determine which is the most predictive of HYK. Given the data available, a secondary objective was to evaluate differences in test-day milk and performance variables (continuous measurements) between Holsteins and Jerseys and between cows with or without HYK within breed. Blood samples were collected on the same day as milk sampling from 658 Holstein and 468 Jersey cows between 5 and 20 d in milk (DIM). Diagnosis of HYK was at a serum β-hydroxybutyrate (BHB) concentration ≥1.2 mmol/L. Concentrations of milk BHB and acetone were predicted by Fourier transform infrared spectrometry (Foss Analytical, Hillerød, Denmark). Thresholds of milk BHB and acetone were tested for diagnostic accuracy, and logistic models were built from continuous variables to predict HYK in primiparous and multiparous cows within breed. Linear models were constructed from continuous variables for primiparous and multiparous cows within breed that were 5 to 11 DIM or 12 to 20 DIM. Milk ketone body thresholds diagnosed HYK with 64.0 to 92.9% accuracy in Holsteins and 59.1 to 86.6% accuracy in Jerseys. Logistic models predicted HYK with 82.6 to 97.3% accuracy. Internally cross-validated multiple linear regression models diagnosed HYK of Holstein cows with 97.8% accuracy for primiparous and 83.3% accuracy for multiparous cows. Accuracy of Jersey models was 81.3% in primiparous and 83.4% in multiparous cows. These results suggest that predicting serum BHB from continuous test-day milk and performance variables could serve as a valuable diagnostic tool for monitoring HYK in Holstein and Jersey herds.