Pregnancy losses in Bos indicus-influenced beef and dairy recipients assigned to a fixed-time embryo transfer protocol.

Pregnancy losses from fixed-time embryo transfer (FTET) to calving were evaluated in Bos indicus-influenced beef and dairy recipients. Data from 4366 FTET events were collected from Nelore × Angus recipient heifers, and from 38538 FTET events in Gir × Holstein recipient heifers and cows. In beef recipients, pregnancy losses were greater (P < 0.01) from FTET (day 7 of the experiment) to day 32 compared with day 32-100 and with day 100 to calving (58.7, 39.5, and 36.7%, respectively), and did not differ (P = 0.56) between these latter periods. Recipients that lost the pregnancy from FTET to day 32 gained less (P < 0.01) body condition score after FTET compared with recipients that maintained the pregnancy. Pregnancy losses from day 32 to calving were greater (P < 0.01) in recipients reared in drylots and moved to pastures on day 32 compared with recipients reared on pasture. In dairy recipients, pregnancy losses from FTET (day 7) to day 32 were greater (P < 0.01) than losses from day 32 to calving (50.4 and 29.4%). Pregnancy losses throughout gestation were greater (P < 0.01) when the FTET event was performed during the warm season, and greater (P < 0.01) in recipients with < 3/8 Gir influence. Recipients with ≥ 3/8 Gir influence experienced a lesser (P ≤ 0.05) increase in pregnancy losses during the warm season compared with recipients with < 3/8 Gir influence. Collectively, this experiment provides novel information about pregnancy losses in B. indicus-influenced herds receiving FTET.

Impacts of trace mineral source and ancillary drench on steer performance during a 60-day backgrounding phase.

Nutritional approaches to optimize cattle health and performance during the receiving period are warranted. This experiment evaluated the impacts of supplementing organic complexed Cu, Co, Mn, and Zn on productive and health responses of high-risk beef cattle during a 60-day backgrounding phase. Crossbred steers (120) were purchased at auction and transported to the experimental facility, where BW was recorded (day-1; initial shrunk BW = 227.7 ± 1.3 kg). On day 0, steers were ranked by BW and allocated to one of eight groups and housed in drylot pens equipped with GrowSafe automated feeding systems (Model 8000; two bunks/pen). Groups were randomly assigned to receive a total mixed ration containing: (1) sulfate sources of Cu, Co, Mn, and Zn (INR; n = 40); (2) organic complexed sources of the same minerals (AAC; Zinpro Availa 4 based on a metal:amino acid complex ratio of 1:1 for Zn, Cu, and Mn in addition to cobalt glucoheptonate; Zinpro Corp., Eden Prairie, MN; n = 40); or (3) AAC and an organic complexed trace mineral drench (APF; 30 mL/hd; Zinpro ProFusion, Zinpro Corp.) on day 0 and with morbidity treatment (n = 40). Diets provided the same daily amount of all nutrients and minerals based on 7 g/steer daily of Zinpro Availa 4. Steers were assessed for bovine respiratory disease (BRD) signs daily. Liver biopsies were performed on days 0, 28 and 60. Blood samples were collected on days 0, 2, 6, 10, 13, 21, 28 and 45. No treatment differences were detected (P ≥ 0.23) for feed intake, final BW, average daily gain, or BRD incidence. Mean liver Co concentrations were greater (P = 0.02) in AAC and APF compared to INR steers. Mean liver Cu was greater (P = 0.02) in APF compared to AAC steers. Liver Zn tended to be greater (P = 0.10) on day 28 but less (P = 0.05) on day 60 for INR compared to AAC and APF steers. Plasma cortisol was lowest (P = 0.05) for AAC steers on day 6, whereas AAC steers tended to have greater (P = 0.09) plasma cortisol on day 13 compared with APF. Plasma haptoglobin tended to be greater (P ≤ 0.10) for INR steers on days 28 and 45 compared to AAC and APF. While supplementing cattle with AAC or INR results in similar animal performance and clinical disease, AAC and APF reduce stress and acute phase protein responses.

Characterizing pregnancy losses in Bos indicus beef females receiving a fixed-timed artificial insemination protocol.

This experiment evaluated pregnancy losses from day 30 of gestation to calving in Bos indicus females, and evaluated if serum haptoglobin concentrations during early gestation impacts subsequent pregnancy losses. A total of 4926 Nelore females were used, being 1802 nulliparous heifers inseminated as yearlings (precocious heifers), 1356 nulliparous heifers inseminated at 24 months of age (conventional heifers), 887 suckling primiparous cows, and 881 suckling multiparous cows. Cows were assigned to an ovulation synchronization + fixed-time artificial insemination (FTAI) protocol from day -11 to 0 of the experiment. Pregnancy status was verified using transrectal ultrasonography on days 30 and 60 after FTAI, via transrectal palpation on day 150 after FTAI, and according to calf birth. Blood samples were collected from all animals diagnosed pregnant on day 30 after FTAI, and analyzed for serum concentrations of haptoglobin and pregnancy associated glycoproteins (PAG). Pregnancy loss was greater (P < 0.01) from day 60-150 of gestation (10.2 %) compared with day 30-60 of gestation (6.0 %) and with day 150 of gestation to calving (7.4 %), and differed (P = 0.04) between these latter two periods. Pregnancy loss from day 30-60 of gestation did not differ (P = 0.26) among parities, whereas total pregnancy losses (day 30 to calving) were greater (P < 0.01) in precocious (28.4 %) and conventional (27.1 %) heifers compared with primiparous (16.4 %) and multiparous (13.0 %) cows. Serum PAG concentrations on day 30 after FTAI were less (P ≤ 0.03) in cows that lost the pregnancy (5.63 ng/mL) from day 30-60 of gestation, as well as those that lost the pregnancy from day 30 to calving (8.59 ng/mL) compared with cohorts that maintained the pregnancy (9.39 and 9.32 ng/mL, respectively). No differences in serum PAG concentrations on day 30 after FTAI were noted (P ≥ 0.23) according to pregnancy losses from day 60 to calving. Serum haptoglobin concentration on day 30 after FTAI also did not differ (P ≥ 0.48) between cows that maintained or lost the pregnancy. This experiment provides novel information about pregnancy losses after day 30 of gestation in B. indicus cattle, with most losses occurring as fetal mortality and not affected by systemic inflammation during early gestation. Pregnancy losses were nearly doubled in precocious and conventional heifers compared with parous cows, demonstrating the relevance of this reproductive failure to B. indicus replacement heifers.

Supplementing pre- and probiotic ingredients to feedlot steers: effects on health, growth performance, and physiological responses.

Feedlot diets are often enriched with additives to mitigate health disorders and promote cattle performance, including the feed-grade antimicrobials monensin and tylosin. However, alternative feeding strategies are warranted given the increasing regulations regarding the use of antimicrobials in feedlot diets. This study evaluated the performance, physiological, and health responses of feedlot cattle offered a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced or was fed in conjunction with monensin and tylosin. Angus-influenced steers (n = 192) from four different cowherds were weaned on day -1 and transported (800 km) to the feedlot. Steers were allocated to 1 of 24 pens (eight steers/pen) upon arrival on day 0. Pens were assigned to receive (n = 8/treatment) a total-mixed ration (TMR) containing: (1) monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18 g/steer daily of Celmanax and 28 g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) a combination of RT and CC (RTCC). Steers were slaughtered according to BW in four groups balanced by treatment and pens and received treatments for 252 ± 4 days. No treatment effects were detected (P ≥ 0.17) for steer BW gain and morbidity responses. Mean TMR intake was greater and gain:feed ratio was less (P ≤ 0.01) in CC compared with RT and RTCC steers. Mean plasma leptin concentration was greater (P ≤ 0.05) in CC compared with RT and RTCC steers. Steers receiving CC had greater (P ≤ 0.04) concentrations of plasma cortisol, haptoglobin, glucose, and beta-hydroxybutyrate, and less (P ≤ 0.05) concentration of non-esterified fatty acids compared with RT and RTCC steers on day 14 of the experiment. Carcass marbling was greater (P = 0.01) in CC compared with RT steers and tended to be greater (P = 0.07) in RTCC compared with RT steers. Proportion of carcasses that graded Choice or better and Longissimus muscle area were greater (P ≤ 0.05) in CC and RTCC compared with RT steers. Incidence of liver abscesses was less (P = 0.01) in RTCC compared with CC steers and tended to be less (P = 0.09) in RT compared with CC steers. Results from this experiment indicate that the synbiotic supplement may replace monensin and tylosin without reducing steer BW gain, with potential improvements to carcass quality traits.

Supplementing Ca salts of soybean oil via low-moisture molasses-based blocks to improve reproductive performance and overall productivity of beef cows.

This experiment evaluated reproductive and productive responses of beef cows receiving self-fed low-moisture blocks (LMB) enriched or not with Ca salts of soybean oil (CSSO) throughout the breeding season. Non-pregnant, suckled multiparous Angus-influenced cows were assigned to a fixed-time artificial insemination (AI) protocol (day -10 to 0) followed by natural service (day 15-70). Cows were managed in 12 groups (46 ± 4 cows/group) maintained in individual pastures, and groups received LMB enriched with 25 % (as-fed basis) of CSSO or ground corn (CON) from day - 10 to 100. Both treatments were designed to yield a daily LMB intake of 0.454 kg/cow (as-fed basis). Cows receiving CSSO had greater (P < 0.01) mean concentrations of ω-6 fatty acids in plasma samples collected on days 0 and 55. Cows receiving CSSO had greater (P = 0.05) pregnancy rate to fixed-time AI (67.2 vs. 59.3 %), whereas final pregnancy rate did not differ (P = 0.92) between treatments. Pregnancy loss was less (P = 0.03) in CSSO cows (4.50 vs. 9.04 %), which also calved earlier during the calving season (treatment × week; P = 0.04). Weaning rate tended to be greater (P = 0.09) in CSSO (84.8 vs. 79.4 %), although calf weaning age and weight did not differ (P ≥ 0.72) between treatments. Kilos of calf weaned/cow exposed was greater (P = 0.04) in CSSO cows (234 vs. 215 kg). Therefore, supplementing CSSO to beef cows via LMB during the breeding season improved their reproductive and overall productivity during a cow-calf cycle.

Shifts in uterine bacterial communities associated with endogenous progesterone and 17ß-estradiol concentrations in beef cattle.

The relation between circulating concentrations of progesterone and 17ß-estradiol prior to insemination play a key role in optimizing fertility in cattle. This study aimed to determine the impact of endogenous progesterone (P4) and estradiol (E2) concentrations on uterine bacterial community abundance and diversity in beef cattle. Angus-influenced heifers were subjected to an industry standard estrous synchronization protocol. Uterine flushes were collected on d -2 (endogenous P4) and d 0 (endogenous E2) and used for targeting the V4 hypervariable region of 16S rRNA bacterial gene. Plasma was collected on d -2 and 0 for quantification of P4 and E2 concentrations by radioimmunoassay, respectively. Heifers were allotted to one of the following groups: High P4 + High E2 (H-H; n = 11), High P4 + Low E2 (H-L; n = 9), Low P4 + High E2 (L-H; n = 9), Low P4 + Low E2 (L-L; n = 11). Results indicated that Shannon's diversity index tended to be greater for H-L heifers compared to L-H heifers on d 0 (P = 0.10). For H-L heifers from d -2 to d 0, the relative abundance of Actinobacteria decreased and Tenericutes increased (P < 0.01). Within phylum Actinobacteria, the relative abundance of Corynebacterium decreased from d -2 to d 0 in treatment groups H-H, H-L, and L-L (P < 0.05); however, did not differ by d for L-H heifers. Within phylum Tenericutes, the relative abundance of Ureaplasma increased from d -2 to d 0 for H-L heifers (P = 0.01). Additionally for H-L heifers, the relative abundance of Bacteroidetes tended to increase from day -2 to on d 0 (P = 0.07). For H-L heifers, uterine pH increased from day -2 to d 0 (P = 0.05). These results suggest that differing endogenous concentrations of P4 and E2 may be associated with shifts in uterine microbiota and pH, and this could ultimately impact fertility outcomes in beef cattle.

Influence of body condition score and its change after parturition on pregnancy rates to fixed-timed artificial insemination in Bos indicus beef cows.

This experiment evaluated pregnancy rates to fixed-time artificial insemination (FTAI) in Bos indicus beef cows according to their body condition score (BCS) at calving and subsequent change until 30 days after FTAI. Non-pregnant, suckling Nelore cows (n = 593 primiparous, 461 secundiparous, and 893 multiparous) were evaluated for BCS at calving and FTAI, and at 30 days after FTAI when cow pregnancy status was verified. Cow BCS at calving was subtracted from BCS recorded at pregnancy diagnosis, and cows classified as those that lost BCS (L), maintained BCS (M), or gained BCS (G) during this period. Cows that calved with BCS ≥ 5.0 had greater (P < 0.01) BCS throughout the experiment, and greater (P < 0.01) pregnancy rates to FTAI compared with cows that calved with BCS < 5.0 (54.8 vs. 34.2%). Pregnancy rates to FTAI were greater (P < 0.01) for G and M cows compared with L cows (50.0%, 47.5%, and 36.0%, respectively), and similar (P = 0.46) between G and M cows. Moreover, pregnancy rates to FTAI in G cows that calved with BCS < 5.0 were less compared with L (tendency; P = 0.08) and M cows (P < 0.01) that calved with BCS ≥ 5.0 (42.2%, 48.3%, and 58.3%, respectively). In summary, pregnancy rates to FTAI were greater in B. indicus cows that calved with a BCS ≥ 5.0 regardless of parity and post-calving BCS change, and greater in M and G cows within those that calved with BCS < 5.0 or ≥ 5.0.

Pregnancy maintenance following sequential induced prostaglandin pulses in beef cows.

The relationship between the maternal endocrine environment and late embryonic mortality (> 28 d of gestation) in cattle is poorly defined. A definitive rise and alterations in secretion patterns of prostaglandin F2α (PGF2α) concentration without luteal regression is a trademark of this period. The objective was to evaluate whether consecutively induced PGF2α pulses would alter steroid hormone production and luteal blood perfusion potentially influencing pregnancy success. Pregnant beef cows (n = 12) were selected to receive either an oxytocin injection (OT, n = 8) or saline injection (CON, n = 4) on d 30 and 31 of gestation to stimulate sequential prostaglandin releases 24 h apart. Blood samples were collected every 30 min for 1 h before and continuing for 4 h post oxytocin administration. Luteal blood perfusion was measured via Doppler ultrasound at the beginning and end of the OT challenge. Concentrations of prostaglandin F2α metabolite (PGFM) were quantified to show effectiveness of the treatment while concentrations of progesterone, estradiol and pregnancy-associated glycoproteins (PAG) were measured to examine the effect of PGF2α release. Control animals exhibited no changes in any quantified hormone and an expected numerical increase in circulating PAG concentrations. Peak concentrations of PGFM in OT cows were observed 2 h post OT administration and concentrations returned to basal levels by the end of the sampling period. Peak concentrations of PGFM were decreased on d 31 compared to d 30. Following OT administration, progesterone and estradiol concentrations did not change in response to PGF2α release but were decreased on d 31 compared to d 30. There were no changes in luteal blood perfusion in response to PGF release on d 30 or d 31. Repeated PGF2α release may alter steroid hormone production; however, it does not negatively affect pregnancy status during the transition between early and late embryonic development.

The effect of subclinical endometritis on reproductive performance in postpartum Bos indicus multiparous beef cows.

The objective was to investigate the prevalence of subclinical endometritis (SE) in postpartum Bos indicus multiparous beef cows using different polymorphonuclear cells (PMN) threshold ratios, and to evaluate the impacts of SE on their reproductive performance. A total of 689 postpartum Nellore cows (45.2 ± 7.8 days postpartum) were submitted to an estrus synchronization protocol + timed-artificial insemination (TAI). Endometrial cytology samples were collected by cytobrush before the beginning of the protocol. Cows were considered positive for SE if: (PMN) ≥ 3% (PMN3), PMN ≥ 5% (PMN5) and PMN ≥ 7% (PMN7). Pregnancy diagnosis was performed at 30 and 100 d after TAI. The prevalence of cows categorized as positive for SE increased (P < 0.05) as the threshold was lowered (PMN7 = 3.9%; PMN5 = 5.5%; PMN3 = 9.1%). Positive SE cows had similar (P > 0.41) BCS, days postpartum, and expression of estrus at TAI compared with negative SE cows. Positive SE cows had decreased (P = 0.04) pregnancy rates compared to negative SE cows in the PMN5 threshold (26.3 ± 8.7% vs 44.5 ± 4.1%); however, no difference (P > 0.45) was observed between positive and negative SE cows in the PMN3 and PMN7 thresholds. Embryonic mortality between days 30 and 100 was not affected by SE (P > 0.16). In conclusion, the prevalence of SE varies based on the PMN threshold used, whereas SE at the beginning of the TAI protocol decreased the pregnancy rates in postpartum Bos indicus beef cows when the PMN5 was used.

Effects of body condition score at initiation of the breeding season on reproductive performance and overall productivity of Bos taurus and B. indicus beef cows.

This experiment was conducted to evaluate reproductive and productive responses of Bos indicus and B. taurus beef cows according to body condition score (BCS) at initiation of the annual breeding season. Non-pregnant, suckling multiparous cows were assigned to a fixed-time artificial insemination treatment regimen followed by natural service. Cows were classified as having a BCS < 5.0 (B. taurus, n = 158; B. indicus, n = 248) or BCS ≥ 5.0 (B. taurus, n = 173; B. indicus, n = 122). Calving rate was greater (P < 0.03) in cows with a BCS ≥ 5.0 (93.7 % and 85.1 % in B. taurus, 83.6 % and 73.3 % in B. indicus), which also calved earlier (P < 0.01) compared with cows with a BCS < 5.0. Cows with a BCS ≥ 5.0 weaned more (P ≤ 0.05) calves compared with those with a BCS < 5.0, which were older (P ≤ 0.04) and weighed more (P ≤ 0.09) at weaning (258 and 252 kg in B. taurus, 213 and 203 kg in B. indicus). Kilograms of calf weaned/cow in the breeding herd were greater (P ≤ 0.03) in cows with a BCS ≥ 5.0 compared with those with a BCS < 5.0 (221 and 200 kg in B. taurus, 159 and 129 d in B. indicus). Collectively, cows with a BCS ≥ 5.0 at initiation of the breeding season had greater reproductive and overall productivity during a cow-calf cycle, and these outcomes were observed in B. taurus and B. indicus cowherds.

Performance, health, and physiological responses of newly received feedlot cattle supplemented with pre- and probiotic ingredients.

Nutritional strategies that optimize immunity of feedlot cattle are warranted due to increasing regulations with the use of feed-grade antimicrobials. This study evaluated physiological, health, and performance responses of cattle receiving a synbiotic supplement (yeast-derived prebiotic + Bacillus subtilis probiotic), which replaced feed-grade antimicrobials or were fed in conjunction with monensin during the initial 45 days in the feedlot. Angus-influenced steers (n = 256) were acquired from an auction facility on day -2, and transported (800 km) to the feedlot. Shrunk BW was recorded upon arrival (day -1). Steers were allocated to 1 of 18 pens (day 0), and pens were assigned to receive (n = 6/treatment) a free-choice diet containing: (1) monensin and tylosin (RT; 360 mg/steer daily from Rumensin and 90 mg/steer daily from Tylan; Elanco Animal Health, Greenfield, IN, USA), (2) yeast-derived ingredient and B. subtilis probiotic (CC; 18 g/steer daily of Celmanax and 28 g/steer daily of Certillus; Church and Dwight Co., Inc., Princeton, NJ, USA), or (3) monensin in addition to yeast-derived and B. subtilis ingredients (RCC) as in RT and CC. Steers were assessed for bovine respiratory disease (BRD) and DMI daily. Steer BW was recorded on days 45 and 46, and averaged for final BW. Blood samples were collected on days 0, 7, 17, 31, and 45. Feed intake was greater (P ≤ 0.05) in CC vs. RCC and RT during the initial 3 weeks upon feedlot arrival. No treatment differences were noted (P ≥ 0.41) for average daily gain, BW, and feed efficiency. Incidence of BRD did not differ (P = 0.77) between treatments (average 80.1%). A greater proportion (P ≤ 0.03) of RT steers diagnosed with BRD required a second antimicrobial treatment compared with CC and RCC (57.3, 37.3, and 38.6%, respectively). Removal of steers from the trial due to severe morbidity + mortality was greater (P = 0.02) in RT vs. CC (22.4 and 7.0%), and did not differ (P ≥ 0.16) among RCC (12.9%) vs. RT and CC. Plasma glucose concentrations were greater (P ≤ 0.02) in CC vs. RCC and RT on day 7. Plasma concentrations of nonesterified fatty acids were greater (P ≤ 0.02) in RT and RCC vs. CC on day 7, and in RT vs. CC on day 17. Steers receiving the synbiotic supplement had improved response to BRD treatment, suggesting heightened immunocompetence from partially enhanced metabolism and the nutraceutical effects of B. subtilis and yeast compounds.

Effects of nutrient restriction on the metabolic profile of Bos indicus-influenced and B. taurus suckled beef cows.

Recent research from our group demonstrated that Bos indicus-influenced suckled beef cows had greater resilience to withstand nutrient restriction and establish pregnancy compared with B. taurus cows exposed to the same conditions. To further understand these findings, differences in metabolic profile between these same B. indicus-influenced and B. taurus females were explored. Suckled beef cows (n = 134) were enrolled in a completely randomized design with a 2 × 2 factorial arrangement of treatments. On day -21, Angus (AN; Bos taurus) and Brangus (BN; B. indicus-influenced) cows were randomly assigned to 1) a diet that met daily energy maintenance requirements (MAINT), or 2) a diet that restricted intake to 70% of the daily energy maintenance requirements (RESTR). Cows were exposed to an estrus synchronization protocol and received an embryo 7 d after ovulation was pharmacologically induced on day 0. Blood samples were collected on days -21 and 19 to determine circulating concentrations of non-esterified fatty acids (NEFA), ß-hydroxybutyrate (BHB), insulin, glucose, and IGF-1. Pregnancy status after embryo transfer was determined on day 28. As a consequence of the proposed diets, cows in the RESTR diet had less body condition score (BCS) on day 19 (P = 0.008) across breed types. Moreover, BCS change from day -21 to 19 was included as independent covariate into subsequent analyses, allowing for the comparison of breed types under an equivalent level of body reserve mobilization. A breed × diet interaction was observed for plasma insulin (P = 0.03) and IGF-1 (P = 0.04) on day 19, where AN-RESTR cows had less plasma concentrations on day 19 compared with AN-MAINT cows. Diets did not impact (P > 0.10) plasma insulin and IGF-1 concentrations in BN cows. No diet or breed effects were observed in circulating concentrations of NEFA, BHB, and glucose (P > 0.10). Across breed types and nutritional treatment, there was positive linear effect (P ≤ 0.04) of plasma concentrations of insulin and IGF-1 on the probability of pregnancy to fixed-time embryo transfer. In summary, the negative impacts of nutrient restriction on the somatotropic axis, independently of body tissue mobilization, were heightened in Bos taurus females compared with B. indicus-influenced cohorts, which corroborate with the differences observed in fertility between these subspecies.

Induced prostaglandin release alters steroid concentrations but not pregnancy survival in cows.

Embryonic mortality (EM) is a major factor limiting reproductive efficiency in cattle, and despite negative connotations related to reproductive performance, prostaglandin F2α (PGF2α) is capable of being released by the uterus by Day 30 of gestation. Therefore, the objective was to evaluate differences in PGF2α release after an oxytocin challenge between cows with high circulating concentrations of pregnancy-associated glycoproteins (PAGs) vs low PAG because of the association of increased PAG concentrations with pregnancy success. At Day 30 of gestation, pregnant cows were divided into oxytocin treatment (OT; n = 13) and control (CON; n = 12) groups. Treatment cows were further subdivided by circulating PAG concentration (high PAG, n = 7; and low PAG, n = 6). Blood samples were collected every 30 min beginning 1 h before oxytocin administration and continuing for 4 h. Prostaglandin F2α metabolite (PGFM), progesterone, estradiol-17ß (E2), and PAG concentrations were quantified. The peak concentration of PGFM occurred 2 h after oxytocin injection in treatment animals and returned to baseline levels by 4 h. No correlations were observed between PAG and PGFM, progesterone, or E2 concentrations (P > 0.05). There was no difference in initial or final PGFM concentrations between groups (P > 0.05). Progesterone and E2 concentrations decreased in cows after treatment of oxytocin (P < 0.05); however, only progesterone returned to basal concentrations by the end of the sampling period. In summary, cows with high vs low PAG concentrations at Day 30 of gestation have a similar PGFM response to oxytocin challenge.

Symposium review: Linking activity-sensor data and physiology to improve dairy cow fertility.

Several studies have demonstrated that the intensity of estrous expression is associated with ovulation, ovarian and uterine function, and fertility, and is dependent on social hierarchy and the housing system used. Data from recent studies involving spontaneous and induced estrus have shown that a greater relative increase and longer estrus (captured by different automated activity monitors; AAM) are both associated with improved pregnancy per artificial insemination (AI; around 10 to 14% increase) and decreased pregnancy losses. Intensity and duration of estrus were surprisingly weakly associated with preovulatory follicle diameter and concentrations of plasma estradiol at estrus, whereas ovulation failure was associated with low estrus intensity. Studies have also shown that the display of estrous behavior near AI was associated with the modification of expression of genes related to the immune system, adhesion molecules, and prostaglandin synthesis in the endometrium. Transcripts in leukocytes and in the conceptus tissue associated with maternal recognition of pregnancy as well as conceptus elongation were all associated with differences in the intensity of estrous expression. Most recently, studies from the United States and Canada have demonstrated that reproductive programs emphasizing detection of estrus using AAM can be successful and comparable to intensive timed AI protocol-based programs that incorporate GnRH and PGF2α treatments. Further, one study concluded that the administration of GnRH at AI for spontaneous estrus events greatly improved pregnancy per AI, but only for cows with reduced intensity of estrous expression, showing the potential to use AAM data as a tool in targeted reproductive programs. Quantitative information from estrus events could be used to improve estrus detection and develop decision-making strategies at the farm level. Future studies in this field should aim to better understand ovarian, conceptus, and endometrial mechanisms associated with either the expression or the intensity of estrus, and to refine the identification of phenotypes related to estrus (relative increase, absolute increase, baseline levels, duration, and repeatability within cow) to improve data usage, estrus detection, and possibly genetic selection.

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 ±â€¯0.10 ng/mL vs 0.30 ng/mL ±â€¯0.07 ng/mL; mean ±â€¯SEM; respectively). Pregnant heifers had increased PAG concentration at day 24 compared with pregnant cows (P < 0.01; 3.29 ±â€¯0.36 ng/mL vs 1.39 ±â€¯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 ±â€¯0.73) compared with heifers that maintained an embryo until day 100 (3.69 ng/mL ±â€¯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 ±â€¯0.25 vs 0.92 ng/ml ±â€¯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.

Short communication: administering an appeasing substance to Bos indicus-influenced beef cattle at weaning and feedlot entry.

The bovine appeasing substance (BAS) is expected to have calming effects in cattle experiencing stressful situations. Therefore, this study investigated the impacts of BAS administration during two of the most stressful events within beef production systems: weaning and feedlot entry. In experiment 1, 186 Bos indicus-influenced calves (73 heifers, 113 bulls) were weaned at 211 ± 1 days of age (day 0). At weaning, calves were ranked by sex and BW, and assigned to receive BAS (Nutricorp, Araras, SP, Brazil; n = 94) or water (CON; n = 92). Treatments (5 ml) were topically applied to the nuchal skin area of each animal. Calf BW was recorded and samples of blood and tail-switch hair were collected on days 0, 15 and 45. Calves that received BAS had greater (P < 0.01) BW gain from day 0 to 15 compared with CON. Overall BW gain (days 0 to 45) and BW on days 15 and 45 were also greater (P ≤ 0.03) in BAS v. CON. Plasma haptoglobin concentration was less (P < 0.01) in BAS v. CON on day 15, whereas cortisol concentrations in plasma and tail-switch hair did not differ between treatments (P ≥ 0.13). In experiment 2, 140 B. indicus-influenced bulls (∼27 months of age) from 2 different pasture-based systems (70 bulls/origin) were transported to a commercial feedlot (≤ 200-km transport; day -1). On day 0, bulls were ranked by source and BW, and assigned to receive BAS (n = 70) or CON (n = 70) and the same sampling procedures as in experiment 1. Bulls receiving BAS had greater (P = 0.04) BW gain from day 0 to 15, but less (P < 0.01) BW gain from day 15 to 45 compared to CON. No other treatment effects were detected (P > 0.14). Therefore, BAS administration to beef calves alleviated the haptoglobin response associated with weaning, and improved calf growth during the subsequent 45 days. Administration of BAS to beef bulls at feedlot entry improved BW gain during the initial 15 days, but these benefits were not sustained throughout the 45-day experiment.

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.

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

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

Effects of polyunsaturated fatty acids supplementation on reproductive parameters associated with the performance of suckled beef cows.

To evaluate the effects of a polyunsaturated fatty acids (PUFA) supplement on reproductive parameters of suckled beef cows, two experiments were conducted. In Experiment (Exp.) 1, 60 primiparous cows were randomly assigned to one of two treatments: CTRL - 1.36 kg/day of corn gluten feed (CGF) and MEGR - 1.36 kg/day of CGF and 0.23 kg/day of calcium salts of soybean oil. Supplementation occurred from 30 days before fixed-time artificial insemination (TAI) until 7 days post-TAI. The expression of interferon-stimulated genes (ISG) was measured on days 18 and 21. Pregnancy rates were diagnosed on days 30 and 100. Treatment altered plasma fatty acid profile (P<0.05), however, did not change cow BW (P=0.52) or body condition score (BCS) (P=0.52). Treatment did not alter (P=0.12) pregnancy rates to TAI or final pregnancy rates (P=0.56). Treatments did not impact messenger RNA (mRNA) expression of the ISG OAS1 or MX2 on days 18 (P=0.67; P=0.96, respectively) or 21 (P=0.72; P=0.17, respectively). Length of gestation was greater (P=0.02) for MEGR, however, treatments did not alter calf birth weight (P=0.20). In Exp. two, 66 multiparous cows were assigned to one of two treatments: MEG - 0.65 kg/day of CGF+0.23 kg/day of calcium salts of palm oil and MEGR - 0.65 kg/day of CGF+0.23 kg/day of Ca salts of soybean oil. Cows were supplemented from 30 days prepartum to 30 days postpartum. On day 35 after TAI, pregnancy status, embryo crown-to-rump length (CRL), and plasma concentrations of pregnancy-specific protein-B (PSPB) were evaluated. Treatment altered plasma fatty acid profile (P<0.05). In addition, cows from the MEG treatment had greater BW (P<0.01) and BCS (P<0.01) than those in the MEGR treatment, as well as heavier calves at weaning (P=0.03). Treatment did not affect resumption of estrous cycle (P=0.29). There were no differences in pregnancy rates to TAI (P=0.87) or final pregnancy rates (P=0.29). No differences between treatments were detected on CRL (P=0.24) and plasma concentrations of PSPB (P=0.46). Birth weight (P=0.12) and calving distribution (P=0.52) were not altered. We concluded that PUFA supplementation altered plasma fatty acid profile, however, did not impact the remaining reproductive parameters evaluated.

Physiologic and innate immunity responses to bacterial lipopolysaccharide administration in beef heifers supplemented with OmniGen-AF.

Nutritional alternatives to strengthen animal immunocompetence are critical for welfare and productivity in livestock systems, such as beef cattle operations. This experiment evaluated physiological and innate immunity effects of supplementing an immunomodulatory feed ingredient (Omnigen-AF; Phibro Animal Health, Teaneck, NJ, USA) to beef heifers administered bacterial lipopolysaccharide (LPS). In total, 8 non-pregnant, non-lactating nulliparous Angus×Hereford heifers (676±4 days of age) were ranked by BW (473±8 kg), and assigned to crossover design containing two periods of 34 days each. Heifers were housed in individual pens and had ad libitum access to meadow foxtail (Alopecurus pratensis L.) hay, water and a granulated commercial vitamin+mineral mix. Within each period, heifers received (as-fed basis) 227 g/day of dried distillers grains including (OMN) or not (CON) 56 g of Omnigen-AF for 34 days. On day 28 of each period (0800 h), heifers received an intravenous bolus dose (0.5 µg/kg of BW, diluted in 5 ml of 0.9% sterile saline) of bacterial LPS (Escherichia coli 0111:B4). Hay DM intake was recorded daily from day 0 to 34. Blood was collected at -1, 0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 24, 48, 72, 96, 120 and 144 h relative to LPS administration. Heifer intravaginal temperature was recorded every 10 min from -0.5 to 10 h relative to LPS administration. No treatment effect was detected (P=0.35) for hay DM intake during the experiment. No treatment effects were detected (P⩾0.64) for intravaginal temperature and plasma concentrations of tumor necrosis-α, cortisol and haptoglobin, which increased (time effect, P<0.01) for OMN and CON heifers and peaked at 4.5, 2, 4 and 48 h, respectively, after LPS administration. No treatment effects were detected (P⩾0.35) for whole blood mRNA expression of chemokine ligand 5, tumor necrosis-α, cyclooxygenase 2 and interleukin 8, which also increased (time effect, P<0.01) for OMN and CON heifers and peaked at 0.5, 1.5, 2 and 2.5 h, respectively, after LPS administration. Whole blood mRNA expression of interleukin 8 receptor and L-selectin were also similar (P⩾0.61) between OMN and CON heifers, and decreased (time effect, P<0.01) for both treatments reaching nadir levels at 1 and 2.5 h, respectively, after LPS administration. Collectively, OMN supplementation did not modulate the physiological and innate immunity responses of beef heifers to bacterial LPS administration.