Angus-cross Heifers Research Articles

227 Moderate body weight loss reduces total antioxidant capacity in pregnant beef heifers and one-carbon metabolite supplementation does not mitigate this response

Abstract In beef heifers, body weight (BW) gain and physiological stress are important considerations for reproductive outcomes and whole herd production efficiencies. The objective of this study was to determine if dietary one-carbon metabolite (OCM) supplementation in moderate BW loss pregnant heifers alters circulating total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activity. In a replicated 2 × 2 factorial, Angus-cross heifers (n = 81) were stratified by BW to gain 0.45 kg/d (CON) or lose 0.23 kg/d (RES) and receive corn carrier with OCM supplements (+OCM) or without (−OCM). The OCM supplements consisted of vitamin B12 (20 mg) and folate (320 mg) injections weekly and dietary rumen-protected methionine (7.4 g/d) and choline (44.4 g/d) from breeding (d 0) to d 63 of gestation. The four treatment groups were: CON−OCM (n = 20), CON+OCM (n = 21), RES−OCM (n = 21), and RES+OCM (n = 19). Heifers underwent estrus synchronization and were bred via artificial insemination using female sexed semen to a single sire. Pregnancy was diagnosed and fetal sex was verified on d 35 of gestation. Blood was collected and assayed for total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activity on d −2 (baseline), 35, and 63 of gestation for all three replicates. Data were analyzed using the MIXED procedure of SAS with repeated measures to determine the effect of gain, supplement, day, and their two-way and three-way interactions. The gain × supplement interaction remained in all models, but other interactions were removed if P > 0.10. Replicate and heifer BW were included in the model as covariates and covariance structure was determined by lowest AIC and BIC. Statistical significance was considered at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. There was no BW gain × supplement interaction, or main effect of OCM supplements in total antioxidants. There was a gain × day effect (P ≤ 0.01), in which total antioxidants were increased on d 35 and further increased on d 63 in CON compared with RES treatments. There was no gain × supplement interaction, or main effect of gain or OCM supplements in superoxide dismutase and glutathione peroxidase. However, both superoxide dismutase and glutathione peroxidase were decreased (P ≤ 0.01) on d 63 compared with d 0 and 35. These data suggest that moderate BW loss reduces total antioxidant capacity in pregnant beef heifers, which could affect redox homeostasis. However, OCM supplements did not affect total antioxidant capacity, superoxide dismutase, or glutathione peroxidase. These findings are somewhat surprising considering oxidative stress has been well characterized in nutrient-restricted pregnancies, and given the interconnection between energy metabolism and one-carbon metabolism. Future research is warranted to fully elucidate the therapeutic effects of one-carbon metabolites.

242 Comparison of GnRH administration day in the 7&7 Synch versus 8&6 Synch Protocol for fixed-timed artificial insemination in beef heifers

Abstract The research aimed to investigate the impact of reducing the time interval for progesterone exposure on the ovulatory follicle just before performing fixed-timed artificial insemination (FTAI). This was achieved by adjusting the timing of administering a gonadotropin-releasing hormone agonist (GnRH; specifically, 100 µg gonadorelin, known as Cystorelin). The study assessed the effectiveness of two estrous synchronization protocols, the “7 & 7 Synch” and a modified protocol, by examining estrus expression (EE) and the resulting pregnancy rates (PR) following FTAI. The research utilized frozen conventional Angus semen from Select Sires, Inc. (Plain City, OH), and involved 66 Angus-cross heifers from the beef cattle research unit near Fayetteville at the University of Arkansas. To ensure consistency, the heifers were divided into two treatment groups based on their cyclicity status (CYC) and age. CYC status was determined by assessing a reproductive tract score (RTS) 1 wk before the synchronization process. RTS scores ranged from 1 to 5, with RTS 1-3 indicating pre- or peripubertal status and scores of 4 and 5 indicating cycling. Heifers with an RTS of 1 and 2 were excluded from the study before synchronization commenced. Both treatment groups involved the insertion of a controlled internal drug-releasing device (CIDR; specifically, Eazi-breed, containing 1.38 g of progesterone) into the vagina on d -14. Simultaneously, a prostaglandin F2α analogue (PGF; 500 µg cloprostenol sodium, known as Synchsure) was administered. In the first treatment group (7&7), GnRH was administered on d -7, while in the second group (8&6), GnRH was given on d -6. In both cases, PGF was administered on d 0 when the CIDR was removed, precisely 72 ± 1 h before FTAI, along with another dose of GnRH. Estrus expression (EE) was assessed during FTAI by examining Estrotect patches (Rockway Inc., Spring Valley, WI). EE was considered present when a patch had 50% or more of its color rubbed off, and it was deemed absent when less than 50% of the color had worn off. Pregnancy rates (PR) were determined through ultrasound examination on d 55. EE and PR were analyzed by treatment using the GLIMMIX procedure on SAS 9.4 (SAS Institute Inc., Cary, NC). Statistical differences were declared at α ≤ 0.05 and tendencies declared between 0.05 < P ≤ 0.1. Heifers on the 8&6-d protocol had greater rectal temperatures at breeding compared with 7&7-d heifers (P < 0.0001). AI pregnancy rates were greater in heifers on the 8&6-d protocol compared with the heifers on 7&7-d protocol (P = 0.625) with average pregnancy rates of 39.4% and 30.3%, respectively. Overall, pregnancy rate was greater as well for the 8&6-d heifers compared with the 7&7-d heifers (P = 0.044), with mean overall pregnancy rates of 78.8% and 54.5%, respectively.

150 Effects of diet type on performance and methane yield in replacement beef heifers

Abstract The objective of this experiment was to determine the relationships among enteric gas production, body weight (BW) gain, and feed intake for growing heifers consuming two energy divergent diets. Fifty-five fall born yearling Angus and Angus cross heifers were used in a 157-d experiment. Heifers were fed two consecutive diets at the Oklahoma State University Range Cow Research Center. Heifers were sorted into one of two drylot pens based on BW. Each drylot pen was equipped with individual intake monitoring system (C-Lock Inc., Rapid City, SD) with a stocking rate of 3.3 heifers per feeder. The first intake segment (HAY) was initiated with a 21 d of adaptation followed by 70 d of data collection. Heifers were offered ad libitum access to long stem unprocessed bermudagrass hay and a salt/mineral/vitamin supplement. After the HAY period, heifers were adapted to a 50% forage, 50% concentrate diet (TMR) during a 14-d adaptation period, followed by 52-d of data collection. Means and standard deviations for phenotypic traits of DMI, ADG, RFI, and CH4 were 6.7 ± 0.7 kg, 0.44 ± 0.13kg, and 194.6 ± 17.56 g/d respectively for HAY and 14.3 ± 1.34 kg, 1.72 ± 0.20 kg, and 280 ± 24.69 g/d respectively for TMR. Pearson correlations between diets for DMI, ADG, and CH4 were 0.32, -0.16, and 0.29, respectively. Coefficient of variation for DMI was 10.8% for HAY and 9.4% for TMR. Coefficient of variation for ADG was 29.9% for HAY and 11.6% for TMR. Methane intensity was calculated as CH4, g/day divided by DMI, kg/d resulting in 29.6 ± 3.5 and 19.9 ± 2.2 g CH4/kg DMI for HAY and TMR, respectively. In summary, HAY DMI was moderately and positively correlated with TMR DMI while ADG was not correlated among the two diet types. The HAY diet generated less total daily CH4, although more CH4 per unit of feed intake.

131 Selenium-form effects on hepatic function and selenoprotein mRNAs in the early pregnant heifer

Abstract Selenium (Se) is an integral component of selenoproteins, with effective scavenging of harmful reactive oxygen species (ROS) by selenoproteins necessary to protect cells from oxidative stress. Due to the presence of Se-deficient soils in large portions of the US, including the southeast cow-calf producing states, grazed forages are insufficient in this trace mineral and dietary supplementation is recommended. We have investigated the effects of providing Se in an inorganic form (ISe, the industry standard) versus a 1:1 mixture (MIX) of ISe to organic Se (OSe), and have observed significant effects on luteal function, endometrial function and conceptus development. Herein, our objective was to determine the effect of form of Se on 1) clinical markers of total antioxidant capacity and liver function, and 2) the expression of mRNAs encoding selenoproteins in the liver. Following consecutive 45-d periods of Se-depletion then repletion, Angus-cross heifers were assigned to 90 d of treatment with a vitamin-mineral mix containing 35-ppm Se as ISe or MIX. Heifers were then inseminated at estrus (d 0) with serum collected at d 0, 7 and 17 to quantify albumin, beta-hydroxybutyrate (BHBA) and aspartate aminotransferase (AST). Liver samples were collected at euthanasia on d 17 (n = 6 pregnant heifers per treatment) for the quantification of the relative abundance of 25 selenoprotein mRNAs using qPCR. There was no effect of treatment on circulating albumin (P > 0.05). Hepatocyte-secreted albumin is the most prominent antioxidant in the circulation, with this result suggesting that albumin-driven redox capacity is not sensitive to the form of Se supplied to achieve a Se-adequate status. Systemic concentrations of BHBA and AST were increased (P < 0.05) in MIX- versus ISe-treated heifers at d 7 and 17 of pregnancy. Circulating BHBA is considered a primary indicator of liver function and the hepatic response to increased metabolic demands, whereas increased AST is conventionally considered a marker for liver damage. These results suggest increased demands on the liver in MIX versus ISe-treated heifers, however not at the level indicative of dysfunction or disease. Additionally, the serum concentration of urea nitrogen was quantified and determined to be reduced (P < 0.05) at estrus in MIX- versus ISe-treated heifers, indicative of form-induced changes in hepatic nitrogen metabolism. Targeted qPCR analysis to determine the effect of treatment on the abundance of encoding selenoproteins by mRNA, including the iodothyronine deiodinases, glutathione peroxidases and thioredoxin reductases, was largely unaffected by treatment, with only the abundance of mRNA encoding Selenoprotein V tending to differ (P = 0.07) with treatment. Overall, this study revealed form of Se-effects on markers of hepatic health and function, as well as blood urea nitrogen, but did not reveal form of Se-effects on the expression of hepatic selenoproteins mRNAs.

129 Selenium-form affects de novo cholesterol synthesis and catabolism of cholesterol and progesterone in the liver of beef heifers

Abstract A deficiency of selenium (Se) in soils and hence forages poses a challenge to producers in the southeast United States, necessitating supplementation of this trace mineral to the diet of pasture fed cattle. Se occurs in either inorganic (ISe) or organic (OSe) forms; ISe is conventionally available in commercial supplements, while OSe is available in grazed forages. We have investigated supplementation with either ISe or a 1:1 mixture of ISe:OSe (MIX) and demonstrated that MIX increases the relative abundance of mRNA encoding the low-density lipoprotein receptor (LDLR) and enzymes involved in de novo cholesterol synthesis in the corpus luteum, concurrent with a MIX-induced increase in systemic progesterone (P4) during the early luteal phase. We also observed a MIX-induced decrease in circulating cholesterol and low-density/very low-density lipoproteins during early gestation, and a MIX-induced increase in conceptus length at maternal recognition of pregnancy (MRP). The objective herein was to investigate the effect of form of Se (ISe versus MIX) on de novo cholesterol synthesis and cholesterol/steroid catabolism in the liver at MRP. We hypothesized form of Se would affect the abundance of transcripts that regulate synthesis, catabolism, and local concentrations of cholesterol and P4. Angus-cross heifers were supplemented with ISe or MIX for at least 90 d before insemination at observed estrus. On d 17 of pregnancy, heifers (n = 6/TRT) were killed and their reproductive tracts and conceptuses recovered. Hepatic samples were collected for qPCR analysis of mRNA transcripts encoding proteins involved in de novo cholesterol synthesis, regulation of cholesterol availability and steroid catabolism. Additionally, on d 7 and d 17 of pregnancy, we quantified systemic concentrations of high-density lipoproteins (HDL), indicative of cholesterol recycling to the liver. We quantified the relative abundance of 22 mRNAs and observed that heifers supplemented with MIX-form Se had an increase in the relative abundance of mRNA encoding the very low-density lipoprotein receptor (VLDLR, P = 0.01). Unexpectedly, we failed to detect an effect of TRT on the abundance of mRNA encoding the high-density lipoprotein receptor (SCARB1, P > 0.05) which was consistent with our inability to detect an effect on the serum concentration of total or free HDL (P > 0.05) during early pregnancy and at MRP. Of the 11 mRNA transcripts encoding enzymes involved in catabolism of cholesterol and progesterone, including steroid alpha reductases (SRD5A1 and SRD5A3) and cytochrome P450 enzymes (CYP4A2, CYP4A11, CYP11A1, and CYP17A1), we were unable to detect a difference in the relative abundance of any transcript. Overall, it appears that the form of Se is altering circulating concentrations of cholesterol and further affecting whole animal physiology and fertility; however, the mechanism involved remains to be fully elucidated and warrants further investigation.

11 Transcriptomic changes in response to form of selenium on the interferon-tau signaling mechanism in the caruncular tissue of beef heifers at maternal recognition of pregnancy

Abstract It is necessary to supplement selenium (Se) to the diet of beef cattle in regions where the soils and forages are deficient in this trace mineral. Supplementation with Se conventionally occurs using an inorganic form (ISe) although the organic forms (OSe) are available when cattle consume forage. Previously we have investigated the effects of supplemental Se as ISe, or a 1:1 mixture of ISe to OSe (MIX) on grazing beef cows and heifers and have observed significant effects on the corpus luteum (CL) and endometrium. The MIX form of Se increased systemic progesterone (P4) during the early luteal phase of the estrous cycle at a time that can significantly improve early embryonic development. We subsequently investigated the effects of MIX form Se versus ISe on the mRNA transcripts encoding IFNτ- and P4-induced proteins in the caruncular (CAR) tissue of the uterine endometrium at maternal recognition of pregnancy (MRP). MIX-supplemented heifers had a decrease in the relative abundance of mRNAs encoding DGAT2, FGF2, IFIT3, ISG15, MX1, OAS2, and RSAD2 in CAR which was coupled with significantly longer conceptuses at MRP. Presently, we examined transcriptomic changes in the CAR tissue of the endometrium at MRP. Angus-cross heifers (n = 20) were exposed to a 45-d period of Se depletion (no supplemental Se) followed by a 45-day repletion period with ISe alone. Heifers were then randomly assigned to 90 days of treatment with a vitamin-mineral mix containing 35-ppm Se as ISe (n = 10), or 1:1 mixture of ISe and OSe (n = 10, MIX). Following insemination, heifers were killed at MRP (d 17) and their reproductive tracts collected. Only heifers with a fully intact recovered conceptus were utilized for further analyses (n = 6 per treatment). Transcriptomic analysis using RNA-sequencing was conducted using total mRNA from CAR biopsies. Differential gene expression was determined using Integrated Differential Expression and Pathway Analysis (iDEP.96), and DEG were subjected to canonical, functional, and network analyses using QIAGEN’s Ingenuity Pathway Analysis (IPA). RNA sequencing results were validated using qPCR. At P < 0.05, there was a total of 2,029 DEGs with 1,038 transcripts upregulated, and 991 transcripts downregulated in MIX versus ISe heifers. Saliently, the interferon JAK/STAT pathway signaling through the STAT1/2 heterodimer was significantly down regulated in CAR samples from MIX heifers, as were the following interferon-responsive genes: IFIT1, IFIT2, IFIT3, IRF1, IRF9, ISG15, ISG20, OAS2, RSAD2, and STAT2. Additionally, there were significant changes in mRNA contribution to the immunotolerant environment (IDO1, ISG20, SCARA1, and TGFB1) to allow the fetal allograft to closely interact with the maternal interface. In combination, these findings suggest more advanced preparation of the CAR and developing conceptus for placentation and to evade immune rejection by the maternal endometrium during implantation.

83 Effects of cottonseed meal supplementation on growth performance of heifers grazing mature summer forage

Abstract As perennial warm-season grasses mature in late summer, dry matter intake (DMI) of growing heifers may be limited due to low protein (7.2 ± 2.5 %) and increased NDF content (67.5 ± 2.7%), which may compromise growth potential. Cottonseed meal (CSM) supplementation may improve forage digestibility by increasing rumen degradable protein offered, but research regarding the specific effects of CSM supplementation on gain performance and composition of gain in heifers is limited. It was hypothesized that supplementation of CSM to heifers grazing mature forage would have greater growth performance compared with heifers not receiving CSM. Objectives for this experiment were to compare the effects of two CSM supplementation strategies on the growth performance of heifers grazing mature summer forage. In two consecutive summers, commercial Angus cross heifers (n = 63) weighing 266.08 ± 32.74 kg were blocked by BW (light, medium, and heavy) and allocated to 9 paddocks (1.64 ha) of WW-B. Dahl Bluestem (Bothriochloa bladhii) for 67 to 70 d. This was a RCBD with a factorial arrangement of 3 treatments by 3 BW blocks, with paddock and year as random effects. Heifers received one of three supplementation strategies: no cottonseed meal (CON), 454 g/animal of CSM daily (CSM1), or 908 g/animal of CSM every other day (CSM2). Initial and final shrunk BW were measured; ADG and percent of BW gained were calculated. Ultrasound of initial and final longissimus muscle area (LMA), backfat (BF), and intramuscular fat (IMF) were measured; percent gained was calculated, respectively. There were no treatment by block interactions for any measured variable. Heifers receiving CSM1 and CSM2 had greater final BW than heifers receiving CON (317 and 320.8 vs 302.6 kg, respectively; (P = 0.01). Likewise, percent of BW gained was greater (P = 0.02) for CSM1 and CSM2 supplemented heifers compared with CON heifers (19.4 and 20.2 vs 14.6%, respectively). The ADG of CSM1 and CSM2 supplemented heifers was greater (P = 0.01) than CON (0.74 and 0.78 vs 0.54 kg/d, respectively). Treatment did not affect the percent of BF (P = 0.24) or IMF gained (P = 0.39). Heifers receiving CSM1 and CSM2 tended to gain proportionally more LMA than heifers receiving CON (13.58 and 13.77 % vs 7.24%, respectively; P = 0.07). As anticipated, BW block affected final BW (P < 0.001) and percent BW gained (P = 0.02), as well as percent LMA gained (P = 0.02). In conclusion, CSM supplementation significantly affected growth performance of heifers grazing late summer WW-B. Dahl Bluestem forage versus no supplementation. In addition, there was no difference in growth performance between heifers receiving 454 g/d of CSM supplementation or 908 g/animal every other day, indicating flexibility for feeding strategy.

137 Replacement Heifer Gain, Feed Intake and Efficiency While Consuming an Unprocessed Hay Diet Followed by a Mixed Concentrate/Forage Diet

Abstract The objective of this study was to evaluate weight gain, feed intake, and feed efficiency in beef heifers while consuming two diets divergent in energy density. Fifty-four yearling Angus and Angus cross heifers (initial body weight = 307.5 ± 30.35 kg) were subject to sequential intake trials using SmartFeed individual intake measuring technology (C-Lock Inc., Rapid City, SD) in drylot pens at the Oklahoma State University Range Cow Research Center. The first intake period (HAY) was initiated on July 15 (d -21) with a 21-d adaptation period and a 70-d intake period. Bermudagrass hay (10.3% CP, 2.0 Mcal ME, and 56% TDN) and a salt/mineral/vitamin supplement was offered on an ad libitum basis throughout the experiment. The second intake period was initiated on d-92 and included 14 d of adaption with 42 d of data collection. A mixed diet (12.4% CP, 45% NDF, and 65% TDN) consisting of 50% chopped bermudagrass hay, concentrate feeds, and a liquid supplement containing minerals and vitamins (TMR) was offered on an ad libitum basis. In both periods, weights were recorded every 14 days, and ADG was calculated by regressing body weight over time. Dry matter intake (DMI) and residual feed intake (RFI) were calculated at the end of each feeding period. Statistical regression equations were used to predict RFI for both HAY and TMR, including average metabolic body weight and average daily gain for each of their respective trials. For RFI, cattle were classified as inefficient, average, or efficient based on 0.5 SD away from the mean RFI score. Descriptive statistics for HAY evaluated traits of DMI, ADG, and RFI (means ± SD) were 5.49 ± 0.84 kg, 0.15 ± 0.16 kg, and 0.0 ± 1.01 kg, respectively. Means ± SD for DMI, ADG, and RFI for TMR were 9.54 ±1.26 kg, 1.45 ± 0.38 kg, and 0.0 ± 0.15 kg. Spearman rank correlations for DMI, ADG, and RFI were 0.35 (P = 0.0089), 0.16 (P = 0.2367), and 0.52 (P < 0.0001), respectively. This initial study suggests that intake of hay and a mixed diet may be modestly correlated, while there is no relationship of weight gain when consuming forage and weight gain consuming a mixed, processed diet.

73 Comparison of GnRH Administration day in the 7 & 7 Synch Versus 8 & 6 Synch Protocol for Fixed-Timed Artificial Insemination in Beef Heifers

Abstract The study was conducted to identify effects of a decreased interval of progesterone on the ovulatory follicle before fixed-timed artificial insemination (FTAI) by altering the day of a gonadotropin-releasing hormone agonist (GnRH;00µg gonadorelin; Cystorelin) administration. Evaluation of the 7 & 7 Synch and altered estrous synchronization protocols was done using estrus expression (EE) and FTAI pregnancy rates (PR). Using frozen conventional Angus semen (Select Sires, Inc. Plain City, OH), Angus-cross heifers (n = 68) from the University of Arkansas beef cattle research unit near Fayetteville were stratified into two treatment groups by cyclicity status (CYC) and age. Cyclicity status was determined by using a reproductive tract score (RTS) taken one week prior to beginning synchronization. Scores ranged from 1-5, where RTS 1-3 were considered pre- or peripubertal while scores 4 and 5 were considered cycling. Heifers with a RTS of and 2 were culled prior to synchronization. Each treatment used a controlled internal drug releasing device (CIDR; Eazi-breed; 1.38g progesterone) inserted intravaginally on –14 d simultaneous to the administration of a prostaglandin F2α analogue (PGF; 500 µg cloprostenol sodium; Synchsure). In the first treatment (7 & 7), GnRH was administered on –7 d. In the second treatment (8 & 6), GnRH was administered on –6 d. Both treatments were then administered PGF simultaneous to CIDR removal on 0d, 72 ±h prior to FTAI and the administration of GnRH. Estrus expression was recorded at the time of FTAI using an Estrotect patch (Rockway Inc., Spring Valley, WI). Estrus expression was determined as a patch with 50% or more of the color rubbed off. On the contrary, a patch with less than 50% of the color rubbed off, was not. Pregnancy rates was determined via ultrasound on 58 d. Estrus expression and PR were analyzed by treatment using the GLIMMIX procedure on SAS 9.4 (SAS Institute Inc., Cary, NC) with CYC as a fixed effect for EE; CYC and EE as fixed effects for PR. Statistical differences were determined with α ≤ 0.05 and tendencies were observed between 0.06-0.1. There was an effect of CYC on EE (P = 0.001) and a tendency to affect PR (P = 0.088). There was no treatment effect on EE (P = 0.892) or PR (P = 0.708). In conclusion, the altered time of GnRH administration in the 7 & 7 synch at 72 ± hours did not affect EE or PR; however, research will continue to investigate adjusting length of time from PGF injection to FTAI to evaluate the effects.

Concentrations of vitamin B12 and folate in maternal serum and fetal fluids, metabolite interrelationships, and hepatic transcript abundance of key folate and methionine cycle genes: the impacts of maternal nutrition during the first 50 d of gestation.

Adequate maternal nutrition is key for proper fetal development and epigenetic programming. One-carbon metabolites (OCM), including vitamin B12, folate, choline, and methionine, play a role in epigenetic mechanisms associated with developmental programming. This study investigated the presence of B12 and folate in maternal serum, allantoic fluid (ALF), and amniotic fluid (AMF), as well as how those concentrations in all three fluids correlate to the concentrations of methionine-folate cycle intermediates in heifers receiving either a control (CON) or restricted (RES) diet for the first 50 d of gestation and fetal hepatic gene expression for methionine-folate cycle enzymes. Angus cross heifers (n = 43) were estrus synchronized, bred via artificial insemination with semen from a single sire, and randomly assigned to one of two nutrition treatments (CON = 20, RES = 23). Heifers were ovariohysterectomized on either day 16 (n = 14), 34 (n = 15), or 50 of gestation (n = 14), where samples of maternal serum (n = 42), ALF (n = 29), and AMF (n = 11) were collected and analyzed for concentrations of folate and B12. Concentrations of B12 and folate in ALF were greater (P < 0.05) in RES compared to CON. For ALF, folate concentrations were also greater (P < 0.01) on day 34 compared to day 50. There was a significant (P = 0.04) nutrition × fluid interaction for B12 concentrations where concentrations were greatest in restricted ALF, intermediate in control ALF, and lowest in CON and RES serum and AMF. Folate concentrations were greatest (P < 0.01) in ALF, intermediate in serum, and lowest in AMF. Additionally, positive correlations (P < 0.05) were found between ALF and AMF folate concentrations and AMF concentrations of methionine, serine, and glycine. Negative correlations (P < 0.05) between AMF folate and serum homocysteine were also observed. Both positive and negative correlations (P < 0.05) depending on the fluid evaluated were found between B12 and methionine, serine, and glycine concentrations. There was a downregulation (P = 0.05) of dihydrofolate reductase and upregulation (P = 0.03) of arginine methyltransferase 7 gene expression in RES fetal liver samples compared with CON fetal liver on day 50. Combined, these data show restricted maternal nutrition results in increased B12 and folate concentrations present in fetal fluids, and increased expression of genes for enzymes within one-carbon metabolism.

180 Supplementation of One-Carbon Metabolites to Beef Heifers During Early Gestation Increases Fetal Organ Weight at Day 63 of Gestation

Abstract We hypothesized a low maternal plane of nutrition will impair fetal growth in early gestation and that supplementation of one-carbon metabolites (OCM) will rescue the growth restriction. The experimental design was a 2 × 2 factorial with 2 levels of gain, each with or without supplementation of OCM. Angus-cross heifers were bred with female-sexed semen from a single sire. At breeding (d 0), beef heifers were individually fed using a Calan gate system and assigned to treatment (n = 8 per treatment): Control intake (targeted: 0.45 kg/d, actual: 0.60 kg/d ADG) without OCM (CON-OCM), CON with OCM (CON+OCM), Restricted intake (targeted/actual: -0.23 kg/d ADG) without OCM (RES-OCM), or RES with OCM (RES+OCM). The OCM supplement consisted of ruminal-protected choline (60 g/d) and methionine (10 g/d) in a fine-ground corn carrier fed daily, and weekly injections of folate (320 mg) and vitamin B12 (10 mg). The -OCM heifers received the corn carrier and saline injections. Heifers were slaughtered and fetal tissues collected on d 63. Data were analyzed using the MIXED procedures of SAS. Fetal body weight tended (P = 0.07) to be lighter and stomach complex weight was lighter (P = 0.03) in RES than CON. When organ weights were normalized to total brain weight to assess allometric growth, OCM × gain interactions were observed in heart (P = 0.04), left longissimus dorsi (P = 0.04), and right hemisphere (P = 0.01) with CON+OCM greater than CON–OCM. The normalized left hemisphere trend to be greater in RES+OCM than RES-OCM (P = 0.08). These data suggest that OCM supplementation during early gestation increases allometric growth of fetal cardiac and skeletal muscle tissue. Day 63 is within the period of peak primary myogenesis in cattle, therefore differences in muscle growth during this time could have lasting implications in post-natal calf growth and performance.

19 Evaluation of Fixed-time Artificial Insemination and Estrus Expression in Angus-cross Heifers with Female Sex-sorted Semen Using 6-day and 7-day CIDR Protocols at Multiple Time Intervals

Abstract The objective was to investigate the influence of progesterone exposure time and breeding time on fixed-time artificial insemination (FTAI) protocols using sex-sorted semen in Angus-cross heifers (n = 85; mean BW = 324 kg.). Heifers were assigned randomly into four treatment groups. Treatments 1 and 2 used a 6-day CO-synch + controlled internal drug release (CIDR) protocol with gonadotropin releasing hormone (GnRH) administration and CIDR insertion on day 0 and prostaglandin F2α (PGF) administration on day 6, upon simultaneous CIDR removal. Treatment 1 heifers underwent FTAI 72 h post CIDR removal, and Treatment 2 heifers underwent FTAI 80 h post CIDR removal. Treatments 3 and 4 used a 7-d CO-synch + CIDR protocol with GnRH administration and CIDR insertion on d 0 and PGF administration on d 7, upon simultaneous CIDR removal. Treatment 3 heifers underwent FTAI 54 h post CIDR removal, and Treatment 4 heifers underwent FTAI 62 h post CIDR removal. Estrus expression was determined using an estrus detection patch (Estrotect™, Rockway Inc., Spring Valley, WI). Estrus expression was classified as a patch with 50% or more of the color rubbed off and the absence of estrus expression as a patch with less than 50% of the color rubbed off. All heifers were inseminated using female sex-sorted semen from a single Angus sire (SexedULTRA 4M™, STgenetics, Navasota, TX). Pregnancy was determined by ultrasound 57 d following FTAI. Pregnancy rates and patch scores were analyzed using the GLIMMIX procedure of SAS 9.4 with treatment as a fixed effect. There was no effect of treatment on the first service AI rates (P = 0.91) or on estrus expression (P = 0.17) in heifers. In conclusion, the combinations of progesterone and breeding time in this study did not affect first service AI conception rates or estrus expression in beef cattle heifers.

PSVIII-24 The effect of growth rate on cytokine presence in uterine environment in beef heifers

Abstract Heifer development is the foundation of performance in breeding herds. Growth rate during development may alter uterine immune responses impacting reproductive efficiency and, thus, productivity of that animal. Angus-cross heifers (n = 48) were blocked by BW [4 blocks; weight class (WC)], placed in pens (4 heifers per pen), and pens (n = 12) were randomly assigned treatments (4 pens per treatment): 1) control; targeted 0.68 kg/day, 2) high; targeted 1.25 kg/day, and 3) low; targeted 0.11 kg/day. A randomized complete block design with pen as the experimental unit utilized mixed model ANOVAs to determine if treatment influenced BW, BCS, and uterine cytokines. Beginning at the start of treatment (d 0) BW and BCS were taken every 2 weeks. Uterine flushes were performed at d 0 and d 57. Cytokine concentrations above the detectable limit were categorized into a quartiles (1=0–25%; 2=25–50%; 3=50–75%; 4=75–100%). Samples that were below the detection limit were assigned a category value of 0. At the end of the study high treatment pens had greater BW compared to control and low pens (P = 0.01). Concentrations of MCP-1, TNFα, IL-17A, IL-8, and VEGF-A decreased from d 0 to d 57 (P &amp;lt; 0.05). Pens on the high treatment tended to have IL-17A concentrations in the upper quartiles compared to control and low (P = 0.06). Pens in WC 1 and 2 tended to be in the lower quartile score for VEGF-A compared with WC 4 (P = 0.07) and WC 3 was intermediate. In conclusion, these data show that growth rate and size during heifer development may impact cytokine profiles in the uterine environment of nulliparous heifers. This may impact the ability to conceive early in the first breeding season, thus potentially altering long-term reproductive efficiency.

Evaluation of whole corn substitution in diets based on steam-flaked corn containing different concentrations of wet distillers grains with solubles for beef cattle

Our objective was to determine effects of substituting steam-flaked corn (SFC) with whole shelled corn (WSC) in finishing diets containing wet distillers grains with solubles (WDGS) on cattle performance, carcass characteristics, digestion, and rumen microbial ecology. The study used 642 Angus-cross heifers (411.7 ± 18.0 kg of initial BW) assigned to 36 pens. Treatments (2 × 3 factorial) were 6 SFC-based finishing diets with 0 or 20% WSC and 0, 15, or 30% WDGS (DM basis). Ruminal fluid was collected to evaluate ruminal characteristics, and feces and manure were collected to determine nutrient digestion and losses. Heifers fed 20% WSC diets had greater ( P < 0.01) DMI, but ADG and G:F were not affected ( P ≥ 0.11) by WSC concentration. The percentage of carcasses grading USDA Choice tended to be lower ( P = 0.07) for cattle fed diets with 20 versus 0% WSC. Increasing dietary WDGS decreased G:F ( P < 0.01) and tended to decrease ADG ( P = 0.10), increased DMI ( P = 0.08), and decreased hot carcass weight ( P = 0.09). Dietary WSC affected ruminal pH ( P < 0.01) and VFA molar concentrations ( P = 0.05). Ruminal acetate:propionate decreased (quadratic, P < 0.03) with increasing WDGS. Bacterial diversity was not affected by WSC ( P = 0.63) but increased with increasing WDGS ( P = 0.01). Substituting SFC with 20% WSC in cattle finishing diets did not affect animal performance but decreased carcass quality. In contrast, increasing dietary WDGS decreased animal performance but did not affect carcass characteristics.

103 Effect of a single Revalor-XH or Revalor-200/Revalor-200 re-implant program and zinc supplementation on performance, carcass characteristics, and liver mineral of feedlot heifers

Abstract A 169-d study utilizing 208 Angus-cross heifers (291 ± 23 kg; 4 sources) in a 2×2 factorial examined the effects of implant strategy and Zn supplementation on growth and mineral status of heifers. Factors included 2 implant (Merck Animal Health, Madison, NJ) strategies: extended-release Revalor-XH on d 0 (REV-XH; 20 mg estradiol+200 mg trenbolone acetate) or Revalor-200 on d 0 and 91 (REV-200; 20 mg estradiol+200 mg trenbolone acetate) and 2 supplemental Zn (mg/kg dry matter [DM]; ZnSO4) strategies: national (30; NRC) or industry (100; IND) recommendations. Heifers were blocked by weight within source (n = 5 or 6 heifers/pen; 9 pens/treatment), received a corn silage-based diet (d 0-56), then transitioned to a corn-based diet fed via concrete bunks. Data were analyzed in Proc Mixed of SAS; fixed effects of implant (IMP), Zn, interaction, and source with the repeated effect of time for average daily gain (ADG) and liver mineral. Initial weight served as a covariate for performance and carcass data. Revalor-200 had greater ADG from d 0-28 and 91-120, while REV-XH peaked during d 56-91 (IMP × time; P = 0.02), corresponding to likely periods of greatest hormone payout from each implant. Liver Mn concentrations decreased on d 14 regardless of implant while d 105 and 164 concentrations were lesser for REV-200 (IMP × time; P = 0.02). Hot carcass weight, DM intake, carcass-adjusted ADG and feed efficiency were not different between IMP strategies (P ≥ 0.18). Steers fed IND tended to be heavier on d 91 (P = 0.06) and were heavier on d 120 (P = 0.05) than NRC; however, final BW did not differ due to Zn (P = 0.37). The similar performance between implant strategies and superior performance during peak hormone payout by heifers supplemented IND vs. NRC suggests increased Zn may support rapid growth.

The effects of maternal nutrition during the first 50 d of gestation on the location and abundance of hexose and cationic amino acid transporters in beef heifer uteroplacental tissues.

We hypothesized that maternal nutrition during the first 50 d of gestation would influence the abundance of hexose transporters, SLC2A1, SLC2A3, and SLC2A5, and cationic amino acid transporters, SLC7A1 and SLC7A2, in heifer uteroplacental tissues. Angus-cross heifers (n = 43) were estrus synchronized, bred via artificial insemination, and assigned at breeding to 1 of 2 dietary intake groups (CON = 100% of requirements to achieve 0.45 kg/d of BW gain or RES = 60% of CON intake) and ovariohysterectomized on day 16, 34, or 50 of gestation (n = 6 to 9/d) in a completely randomized design with a 2 × 3 factorial arrangement of treatments. Uterine cross-sections were collected from the horn ipsilateral to the corpus luteum, fixed in 10% neutral buffered formalin, sectioned at 5 µm, and stained via immunofluorescence for transporters. For each image, areas of fetal membrane (FM; chorioallantois), luminal epithelium (ENDO), superficial glands (SG), deep glands (DG), and myometrium (MYO) were analyzed separately for relative intensity of fluorescence as an indicator of transporter abundance. Analysis of FM was only conducted for days 34 and 50. No transporters in target areas were influenced by a day × treatment interaction (P ≥ 0.06). In ENDO, all transporters were differentially abundant from days 16 to 50 of gestation (P ≤ 0.04), and SLC7A2 was greater (P = 0.05) for RES vs. CON. In SG, SLC7A1 and SLC7A2 were greater (P ≤ 0.04) at day 34 vs. day 16. In DG, SLC2A3 and SLC7A1 were greater (P ≤ 0.05) for CON vs. RES heifers; furthermore, SLC7A1 was greater (P < 0.01) at day 50 vs. days 16 and 34 of gestation. In MYO, SLC7A1 was greater (P < 0.01) for CON vs. RES and was greater (P = 0.02) at days 34 and 50 vs. day 16. There were no differences in FM (P ≥ 0.06). Analysis of all uterine tissues at day 16 determined that SLC2A1, SLC2A3, and SLC7A2 were all differentially abundant across uterine tissue type (P < 0.01), and SLC7A1 was greater (P = 0.02) for CON vs. RES. Analysis of all uteroplacental tissues at days 34 and 50 demonstrated that all transporters differed (P < 0.01) across uteroplacental tissues, and SLC7A1 was greater (P < 0.01) for CON vs. RES. These data are interpreted to imply that transporters are differentially affected by day of gestation, and that hexose and cationic amino acid transporters are differentially abundant across utero-placental tissue types, and that SLC7A1 is responsive to maternal nutritional treatment.

Maternal nutrient restriction alters endocrine pancreas development in fetal heifers

Maternal nutrient restriction during pregnancy alters fetal programming, which modifies the growth and health of the offspring in postnatal life. In cattle, nutrient restriction during pregnancy can be a result of environmental or economic factors, but little is known about how it alters the physiology of the fetus and affects future reproductive or growth efficiency. This study used female monozygotic twins, produced through in vitro fertilization and embryo splitting, to determine the effect of moderate maternal nutrient restriction on fetal development. Recipient Angus cross heifers pregnant with one twin were fed a diet meeting 100% National Research Council (NRC) total energy requirements (n = 4; control), whereas recipient heifers pregnant with the second twin were fed at 70% of NRC total energy requirements (n = 4; restricted) from gestational day (GD) 158 to GD 265 in Calan gate feeders. Recipient heifers were killed at GD 265. Change in maternal metabolic body weight was greater from zero in restricted heifers than controls (P < 0.05); restricted heifers lost weight during the nutrient restriction period. There was no difference in last rib back fat or rib eye area between groups (P > 0.10). There was no difference in fetal weight, uterine weight, or total placentome weight between groups (P > 0.10). The pancreas weight was reduced in restricted fetuses compared with control fetuses (P < 0.01), but there were no other differences in fetal organ weights (P > 0.10). Plasma insulin concentrations were reduced in restricted fetuses compared with controls (P < 0.01), but there was no effect of maternal diet on plasma glucose or glucagon concentrations in the fetus (P > 0.10). Histological analyses of the fetal pancreas revealed no differences in endocrine cell number or localization. Results indicate that a modest late gestation nutritional restriction impairs development of the fetal pancreas in the cow. Additional research will be needed to determine if these developmental changes lead to altered glucose and insulin homeostasis in the adult.

The effects of maternal nutrient restriction and day of early pregnancy on the location and abundance of neutral amino acid transporters in beef heifer utero-placental tissues.

We hypothesized that maternal nutrition and day of gestation would influence the abundance of the neutral amino acid transporters SLC1A1, SLC1A5, SLC7A5, SLC38A2, and SLC38A7 in heifer utero-placental tissues. Angus-cross heifers (n = 43) were estrus synchronized and bred via AI. At breeding, heifers were assigned to one of two dietary intake groups (CON = 100% of requirements to achieve 0.45 kg/d gain or restricted heifers (RES) = 60% of CON intake) and ovariohysterectomized on day 16, 34, or 50 of gestation (n = 6 to 9/d). Thus, the experimental design was a completely randomized design with a 2 × 3 factorial arrangement of treatments. Uterine cross sections were taken from the horn ipsilateral to the CL, fixed in 10% NBF, sectioned at 5 µm, and stained for transporters. For each image, the areas of fetal membrane (FM; chorioallantois), endometrium (ENDO), superficial glands (SG), deep glands (DG), and myometrium (MYO) were analyzed separately for relative intensity of fluorescence as an indicator of transporter abundance. Analysis of FM was only conducted on days 34 and 50. In ENDO, SLC7A5 was greater (P < 0.01) in CON compared with RES heifers. In SG, SLC1A1 was greater (P = 0.02) in day 16 RES compared with day 16 CON and days 34 and 50 RES. In DG, SLC1A1 was greater (P = 0.02) on day 16 compared with 50 of gestation. In MYO, SLC1A1 was greater (P = 0.02) in day 50 CON compared with day 16 CON and day 50 RES. Additionally, in MYO SLC38A2 was greater (P = 0.02) in day 16 RES compared with day 16 CON and day 34 RES. In FM, SLC7A5 tended (P = 0.08) to be greater in CON vs RES. Analysis of all uterine tissues on day 16 determined that expression of SLC1A1, SLC1A5, SL38A2, and SL38A7 differed across uterine tissue type (P < 0.01); however, only SLC7A5 tended (P = 0.10) to differ and be greater in CON compared with RES heifers. Analysis of all utero-placental tissues on days 34 and 50 determined that SLC1A1, SLC7A5, SLC38A2, and SLC38A7 were greater (P ≤ 0.03) in CON compared with RES heifers. Furthermore, abundance of all transporters investigated on days 34 and 50 differed across utero-placental tissue types (P < 0.01). These data support our hypothesis that maternal nutrition and day of gestation influence the abundance of neutral amino acid transporters in utero-placental tissues from days 16 to 50 of gestation. Additionally, these data combined with previously published works help further elucidate nutrient supply and demands of the maternal and fetal system during early gestation in beef heifers.

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

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

168 Comparison of different Doppler ultrasound settings for pregnancy diagnosis based on corpus luteum perfusion at 21 days after AI in beef cattle

Colour Doppler ultrasonography of the corpus luteum (CL) can be used for early pregnancy diagnosis to improve reproductive efficiency and increase the use of AI in beef cattle. The objective of the present study was to determine the diagnostic performance of different Doppler ultrasonography settings for pregnancy diagnosis based on CL perfusion at 21 days after fixed-time AI in beef heifers and cows. Yearling Angus-cross heifers (n=25) and suckled Angus-cross cows (n=84) aged 2-13 years were submitted to a 5-day CO-Synch + controlled internal drug release (CIDR) and timed AI at 60 or 72h after CIDR removal for heifers and cows, respectively. Animals were evaluated by a single operator using colour Doppler ultrasonography (Esaote MyLab Delta) at Day 21. Three settings for colour flow mapping (720, 960, and 1500Hz) and one setting for power Doppler (960Hz), which differed in pulse repetition frequency, were evaluated. The other settings remained unchanged with a probe frequency of 6.3MHz, wall filter of 3, and gain of 61. The pregnancy status (pregnant or non-pregnant) of cows and heifers was determined at 21 days following insemination using colour Doppler ultrasonography. Cows and heifers were considered to be pregnant if the CL blood flow area covered &amp;gt;10% of the periphery of the CL and contained at least two colour internal tracts penetrating towards the centre of the CL. Cattle were evaluated using transrectal B-mode ultrasonography on Day 35 to determine actual pregnancy status. Differences between diagnostic performance variables were evaluated using logistic regression, and setting, category (heifer or cow), and the interaction were included as fixed effects. Pregnancies per AI at Day 35 after fixed-time AI were 47.7% (52/109). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for pregnancy diagnosis at Day 21 for each setting are included in Table 1. There were no differences in sensitivity and NPV between settings (P&amp;gt;0.9), category (P&amp;gt;0.9), or the interaction (P&amp;gt;0.9). There was no effect of setting (P&amp;gt;0.5) or category×setting interaction (P&amp;gt;0.8) on specificity and PPV. There was, however, an effect of category (P&amp;lt;0.01). Colour Doppler ultrasonography had less specificity (59.1% compared with 90.2%) and PPV (75% compared with 89.3%) in heifers than in cows. In conclusion, colour Doppler ultrasonography settings that were evaluated did not affect the diagnostic performance for pregnancy diagnosis at Day 21 after AI, although, numerically the colour flow mapping at 960Hz appears to maximise diagnostic accuracy. In addition, the false-positive rate was greater in heifers, which warrants further research. Table 1.Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for pregnancy diagnosis for four colour Doppler ultrasound settings (colour flow mapping (CFM) at 720, 960, and 1500Hz and power Doppler (PWD) at 960Hz) at 21 days after fixed-time AI Item CFM720 CFM960 CFM1500 PWD960 Sensitivity,% 100 100 92.3 100 Specificity,% 80.7 87.7 87.7 80.7 PPV,% 82.5 88.1 87.3 82.5 NPV,% 100 100 92.6 100