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.

Effects of bismuth subsalicylate and calcium-ammonium nitrate on ruminal in vitro fermentation of bahiagrass hay with supplemental molasses.

There is a need to increase efficiency of beef production. Decreasing losses of CH4 and improving byproduct utilization are popular strategies. Two feed additives were tested to find potential solutions. Three randomized complete block design experiments were performed using batch culture systems to evaluate the effects of bismuth subsalicylate (BSS) and calcium-ammonium nitrate (CAN) on in vitro ruminal fermentation of bahiagrass hay and supplemental molasses. The first experiment contained four treatments: (1) basal substrate; (2) basal substrate with 0.75% urea (DM basis); (3) basal substrate with 1.2% CAN and 0.38% urea (DM basis); and (4) basal substrate with 2.4% CAN (DM basis). Treatments 2, 3, and 4 were isonitrogenous. The second experiment had a 4 × 3 factorial arrangement of treatments with 4 concentrations of BSS (0.00, 0.33, 0.66, and 1.00%; DM basis) and 3 concentrations of CAN (0.0, 1.2, and 2.4%; DM basis). The third experiment had the following treatments: (1) basal substrate; (2) basal substrate with 0.05% BSS (DM basis); (3) basal substrate with 0.10% BSS (DM basis); and (4) basal substrate with 0.33% BSS (DM basis). For all experiments, basal substrate consisted of Pensacola bahiagrass hay (Paspalum notatum Flüggé; 80% substrate DM) and molasses (20% substrate DM). All data were analyzed using the MIXED procedure of SAS. In Exp. 1, in vitro organic matter (OM) digestibility (IVOMD) was linearly reduced (P < 0.001) with the inclusion of CAN, and CH4, in mmol/g OM fermented, was decreased linearly (P < 0.001). The volatile fatty acid (VFA) profile was not impacted by the inclusion of nonprotein nitrogen (NPN) or CAN (P > 0.05). In Exp. 2, except for CH4 production (P < 0.05), there were no BSS × CAN interactions. Linear reductions in total gas production (P < 0.001), IVOMD (P < 0.001), and total concentration of VFA (P = 0.007) were observed with the inclusion of BSS up to 1%. The inclusion of BSS decreased H2S production in a quadratic manner (P = 0.024). In Exp. 3, IVOMD was not impacted by the inclusion of BSS (P > 0.05); however, production of H2S was linearly decreased (P = 0.004) with the inclusion of BSS up to 0.33%. In conclusion, in vitro fermentation was negatively impacted by the inclusions of BSS, up to 1%, and CAN, up to 2.4%; however, BSS decreased production of H2S when included up to 0.33% without impeding fermentation, while CAN decreased CH4 production.

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.

Pre-synchronization of ovulation timing and delayed fixed-time artificial insemination increases pregnancy rates when sex-sorted semen is used for insemination of heifers.

This study was conducted to determine effects of pre-synchronization of ovulation timing among heifers and delayed fixed-time artificial insemination (TAI) with sex-sorted semen on proportion of heifers pregnant after TAI (PR/AI). Heifers were assigned to one of eight treatments: 1 and 2), 7-d CO-Synch + CIDR treatment regimen with administration of gonadotropin-releasing hormone and a CIDR insert on Day 0, prostaglandin F2α (PGF) at CIDR removal on Day 7, and TAI occurring 54 h later with conventionally processed (CTRL54-CNV) or sex-sorted semen (CTRL54-SEX); 3 and 4), same as CTRL54 but TAI delayed to 72 h with conventionally processed (CTRL72-CNV) or sex-sorted semen (CTRL72-SEX); 5 and 6), same as CTRL54 but additional administration of PGF on Day -7 and TAI with conventionally processed (PRE54-CNV) or sex-sorted semen (PRE54-SEX); 7 and 8), same as PRE54 treatments but TAI delayed to 72 h with conventionally processed (PRE72-CNV) or sex-sorted semen (PRE72-SEX). Proportion of heifers pregnant after TAI was greater (P ≤  0.02) with conventionally processed semen compared with sex-sorted semen, yet PR/AI did not differ (P =  0.14) between heifers in PRE72-CNV and PRE72-SEX groups. There were greater PR/AI in the PRE72-SEX (P =  0.03) than CTRL54-SEX group (46.1 % and 36.9 %) and there was no difference (P =  0.31) in PR/AI between CTRL54-CNV and PRE72-SEX groups (50.4 % and 46.1 %). In conclusion, pre-synchronization of ovulation timing among heifers combined with delayed TAI resulted in increased PR/AI with sex-sorted semen compared with the 7-d CO-Synch+CIDR treatment regimen.

Presynchronization with prostaglandin F2α and prolonged exposure to exogenous progesterone impacts estrus expression and fertility in beef heifers.

To determine the effects of two presynchronization strategies in conjunction with delayed fixed-time artificial insemination (TAI) on pregnancy rates to TAI (PR/AI), 1700 Angus beef heifers at three locations in South Dakota were enrolled in a completely randomized design with a 2 by 2 factorial arrangement of treatments. Within location, all heifers were randomly assigned to one of four treatments: 1) PG54 (n = 434), heifers were administered prostaglandin F2α (PGF; 25 mg im) 7 d prior [Day -14] to the initiation of the 7-d CO-Synch + controlled internal drug releasing (CIDR) protocol wherein they received gonadotropin-releasing hormone (GnRH; 100 µg im) and a CIDR insert on Day -7, PGF at CIDR removal on Day 0, and a second injection of GnRH concurrently with TAI 54 ± 2 h later; 2) PG72 (n = 426), heifers were exposed to the same treatment as PG54, however, TAI was performed 72 ± 2 h after CIDR removal; 3) PG-CIDR54 (n = 422), same as PG54 but heifers received a CIDR insert on Day -14 rather than Day -7, in addition to PGF administration; 4) PG-CIDR72 (n = 418), same as PG-CIDR54, however, TAI was performed 72 ± 2 h after CIDR removal. Estrus detection patches were applied to all heifers on Day 0 and were evaluated for activation at TAI. Pregnancy was diagnosed via transrectal ultrasonography between 30 and 47 d after TAI. The percentage of heifers exhibiting estrus between Day 0 and TAI was greater (P < 0.01) in the PG72, PG-CIDR54, and PG-CIDR72 treatments compared to the PG54 treatment (78.11, 86.59, and 91.09 vs. 31.05%, respectively). Furthermore, estrus response was greater (P < 0.01) in PG-CIDR72 heifers when compared to PG72. Pregnancy rates to TAI differed among treatments and were greater (P < 0.05) in the PG72 and PG-CIDR54 treatments when compared to PG-CIDR72 (48.8 and 50.4 vs. 38.4%, respectively), and were greater (P = 0.03) in PG-CIDR54 vs. PG54 (43.1%). Moreover, a tendency (P = 0.10) was determined on PR/AI between PG54 and PG72. In conclusion, presynchronization strategies and prolonged exposure to exogenous progesterone have the potential to alter estrus expression and improve fertility in replacement beef heifers.

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.

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.

Estrus synchronization and fixed-time artificial insemination alter calving distribution in Bos indicus influenced beef heifers.

To determine the effects of estrus synchronization (ES) and fixed-time artificial insemination (TAI) on calving distribution in Bos indicus influenced heifers, 751 Bos taurus × Bos indicus beef heifers were enrolled in a completely randomized design at 2 locations from January to May of 2016. Within location, all heifers were randomly assigned to one of two treatments: 1) SYNCH (n = 371); heifers were exposed to the 5-day CO-Synch + CIDR protocol where they were treated with 100 µg of GnRH, 25 mg of PGF2α, and a controlled internal drug releasing insert (CIDR) on d 0; heifers received 50 mg of PGF2α at CIDR removal on d 5, and were treated with 100 µg of GnRH and TAI 66 ± 2 h later on d 8; or 2) CONTROL (n = 380); heifers were exposed to natural service without ES or TAI. On d 9, all heifers were exposed to bulls for the remainder of the breeding season at each location. Blood samples were collected on d -9 and on d 0 to determine pretreatment estrous cyclicity (progesterone ≥ 1.0 ng/mL). Pregnancy was diagnosed via transrectal ultrasonography 54 d after TAI by determining the presence of a viable fetus. Fetal age was estimated based on fetal size and structural features at the time of pregnancy diagnosis. Pregnancy rates on d 54 differed (P < 0.001) between locations, but did not differ (P = 0.777) between CONTROL and SYNCH treatments. Pregnancy rates on d 54 were greater (P < 0.001) in cycling compared with non-cycling heifers (63.9 vs 42.4%). A greater (P < 0.05) proportion of SYNCH heifers became pregnant in the first 19 d of the breeding season compared with CONTROL heifers (52.2 vs 46.4%). Overall breeding season pregnancy rates did not differ (P = 0.982) between treatments. In summary, ES and TAI increased the percentage of heifers that conceived in the first 19 d of the breeding season, and therefore, potentially altered the calving distribution by ensuring that more heifers calve early during the subsequent calving season.

Effects of recombinant bovine somatotropin administration at breeding on cow, conceptus, and subsequent offspring performance of beef cattle.

The effects of administration of recombinant bovine ST (bST) on plasma hormone concentrations of cows, conceptus development, and postnatal calf performance were examined. Lactating beef cows ( = 190) were exposed to a fixed-time AI (TAI) protocol from d -10 to 0 (TAI on d 0). Cows were blocked by breed and stratified by days postpartum and then randomly assigned to receive, subcutaneously 1) 2 injections of saline (1 mL of 0.9% saline), 1 on d 0 at TAI and a second injection on d 14 (CTRL; = 53); 2) an injection of 325 mg of bST on d 0 and a saline injection on d 14 (bST0; = 48); 3) a saline injection on d 0 and an injection of 325 mg of bST on d 14 (bST14; = 49); or 4) 2 injections of 325 mg of bST, 1 on d 0 and a second injection on d 14 (bST0+14; = 40). Pregnancy status, crown-to-rump length (CRL) on Day 35, and crown-to-nose length (CNL) on Day 65 were determined via transrectal ultrasonography. Blood samples were collected on d 0, 7, 14, 21, 35, and 65, relative to TAI, to determine plasma concentrations of progesterone (P4), IGF-1, and pregnancy-specific protein B (PSPB) and also on d 18 and 21 for isolation of peripheral blood leukocytes for RNA extraction and measurement of interferon-stimulated genes transcript abundance. Individual calf BW was determined at birth and every 30 d until weaning. A subset of 24 calves was randomly selected for liver biopsies at birth to determine mRNA expression of target genes. Administration of bST to cows increased ( < 0.0001) concentrations of plasma IGF-1 for 14 d after injection compared with CTRL but did not affect fetal CRL and CNL ( = 0.23). Cows receiving bST only on d 0 had a greater ( = 0.05) transcript abundance in myxovirus resistance 2 on d 21 compared with 2bST cows (2.0- and 0.8-fold for bST0 and 2bST, respectively), whereas cows receiving bST14 and CTRL were intermediate (1.2- and 0.9-fold, respectively). Calf BW did not differ ( ≥ 0.100) among treatments on d 0, 30, 60, 90, 120, and 150 relative to birth. Injection of bST only on d 0 tended ( = 0.062) to increase calf liver mRNA expression of at birth compared with the calves born to cows in other treatments. Therefore, during a TAI protocol, the administration of 1 or 2 injections of 325 mg of bST to lactating beef cows enhanced their plasma concentrations of IGF-1 but failed to improve fetal size and plasma concentrations of maternal PSPB and P4 and had no effect on postnatal calf growth performance.