Influence of preovulatory estradiol treatment on the maintenance of pregnancy in beef cattle receiving in vivo produced embryos.

This experiment was designed to determine the role of preovulatory estradiol in pregnancy retention after embryo transfer (ET). Cows were synchronized with the 7-d CO-Synch + CIDR® protocol. On d0 (d-2 =CIDR® removal), cows were grouped by estrual status (estrual [Positive Control] and nonestrual), and nonestrual cows were administered Gonadotropin Releasing Hormone (GnRH) and randomly assigned to either no treatment (Negative Control) or Estradiol (0.1 mg estradiol 17-ß IM). All cows received an embryo on d7. Pregnancy status was retrospectively classified on d56, 30, 24, and 19 by either ultrasonography, plasma pregnancy-associated glycoproteins analysis (PAGs), expression of interferon-stimulated genes, plasma progesterone (P4) concentrations, or a combination of the factors. There was no difference in estradiol concentrations on day 0 h 0 (P > 0.16). At day 0 h 2, Estradiol cows (15.7 ± 0.25 pg/mL) had elevated (P < 0.001) estradiol compared with Positive Controls (3.4 ± 0.26 pg/mL) or Negative Controls (4.3 ± 0.25 pg/mL). On d19, pregnancy rates did not differ (P = 0.14) among treatments. On d24, Positive Controls (47%) had greater (P < 0.01) pregnancy rates than Negative Controls (32%); Estradiol cows were intermediate (40%). There was no difference (P = 0.38) in pregnancy rates between Positive Control (41%) and Estradiol (36%) cows on d30, but Negative Control (27%) cows had (P = 0.01) or tended (P = 0.08) to have decreased pregnancy rates, respectively. Thus, preovulatory estradiol may elicit an effect on early uterine attachment or alter histotroph components, consequently improving pregnancy maintenance through d30.

Timing and duration of nutrient restriction and its impacts on placental development and umbilical blood flow in adolescent sheep.

We hypothesized that nutrient restriction from day 50-90 of gestation decreases umbilical blood flow and that umbilical blood flow would recover to control values upon realimentation during late gestation (d 90 to 130) or remain reduced in ewes that continued to be nutrient restricted. On d 50 of gestation, young nulliparous whiteface ewes (6-8 mo; n = 41) carrying singletons were randomly assigned to two dietary treatments: 100% of NRC recommendations (CON) or 60% of CON (RES). On d 90 of gestation, ewes either remained on CON or RES until d 130, or CON ewes were RES from d 90 to 130, or RES ewes were realimented to CON from d 90 to 130. This resulted in 4 treatment groups on day 130: CON-CON, CON-RES, RES-RES, RES-CON. Umbilical blood flow and fetal and placental measurements were obtained via ultrasonography every 10 days from day 50-110. Non-survival surgeries were performed on days 50, 90, and 130 (n = 6-7 ewes/group) where uterine artery and umbilical blood flows were measured during surgery via ultrasonography. Conceptus weights were recorded and placentomes collected to determine binucleate cell numbers. The study was conducted as a completely randomized design arrangement with repeated measures. Data were analyzed using the MIXED procedure of SAS. There was a nutritional treatment by day interaction (P < 0.01) with CON ewes having greater umbilical blood flow compared with RES by d 90. Fetal biparietal distance, abdominal width, and kidney area increased (P < 0.05) in CON-RES with all these measurements increasing during late gestation. We partially accept our hypothesis as nutrient restriction during mid gestation decreased umbilical blood flow. However, blood flow did not return to control levels upon realimentation. By d 130, fetal and placental weights were similar between RES-RES and CON-CON. Binucleate cell numbers in the fetal trophoblast were not influenced by nutritional treatments. Our findings suggest that refeeding previously nutrient restricted pregnant adolescent ewes to control levels does not reestablish umbilical blood flow. Adequate placental development during mid gestation could protect the fetus from a decreased umbilical blood flow later in gestation when nutrients were limited by 40%.

RNA sequencing and iTRAQ proteomic data from an experiment examining the influence of conceptus presence and preovulatory estradiol on endometrial gene transcripts and proteins around maternal recognition of pregnancy in beef cattle.

RNA sequencing reads and isobaric tags for a relative and absolute quantification (iTRAQ)-Based Proteomic Data were used to determine the impact of conceptus presence and preovulatory estradiol concentration on function of the d16 uterus in beef cattle. Conceptuses and endometrial biopsies were collected from the uterine horn ipsilateral to the corpus luteum. Total cellular RNA was extracted from endometrium for RNA sequencing across two lanes of a NovaSeq S2, 2 × 50-bp run. Two independent uterine luminal fluid pools (ULF) were made for each group: highE2/conceptus, highE2/noconceptus, lowE2/conceptus, and lowE2/noconceptus. Peptides were labeled with iTRAQ reagents and analyzed using 2-dimensional liquid chromatography mass spectrometry. Transcript abundances were determined using DESeq2 (FDR <0.05, FC>2). Scaffold Q+ was used to quantitate peptide and protein identifications in ULF. Datasets include uterine transcript and protein abundances among highE2/conceptus vs highE2/noconceptus and lowE2/conceptus vs lowE2/noconceptus groups. This information can be useful for further investigating the role of specific transcripts and proteins in the maintenance of early pregnancy in beef cattle. This dataset is related to the article 'Influence of conceptus presence and preovulatory estradiol exposure on uterine gene transcripts and proteins around maternal recognition of pregnancy in beef cattle' by E.J. Northrop-Albrecht, J.J.J. Rich, R.A. Cushman, R. Yao, X. Ge, G.A. Perry. Molecular and Cellular Endocrinology.

Acute effects of estradiol-17ß on plasma volume and uterine cell proliferation in sheep.

Ovarian steroids play an important role in increasing plasma volume in pregnant females and preparing the uterus for implantation. We hypothesized that a short duration of increased estradiol-17ß (E2) would increase plasma volume and uterine cell proliferation in ovariectomized ewes. Adult non-pregnant Romanov ewes (n = 15) were ovariectomized. After ovariectomy, ewes were individually housed and were offered water at ad libitum intake and were fed a pelleted diet at maintenance once daily according to body weight. After at least 30 days post-ovariectomy ewes were fasted and received an implant placed in the axillary region that contained 100 mg of E2 (E2; n = 8) or a sham implant with no E2 (CON, n = 7). After 24 h, ewes were weighed prior to plasma volume measurement procedures. Plasma volume was determined using the Evans blue dye method. Blood samples were taken at 0 (pre dye injection), 5, 10, 15, 20, 25, 30, 40, 50 and 60 min after dye injection. After the final blood collection, ewes were euthanized with an overdose of sodium pentabarbital and uterine weights were recorded. Uterine cross-sections were fixed in formalin for immunohistochemical localization of Ki67 (a marker of proliferating cells) followed by image generation of luminal epithelium and endometrial stroma (5 areas each/tissue section) and analysis to determine the proportion of proliferating cells. Plasma volume tended to be greater in E2 vs CON (2.75 ± 0.11 vs. 2.54 ± 0.12 L, P = 0.07) and uterine weights were greater in E2 vs CON (27.25 ± 2.35 vs. 17.35 ± 2.51 g, P < 0.01). Water intake after implant placement was similar in E2 and CON (3.85 vs. 4.87 ± 0.67 L; P = 0.28). Cell proliferation in the luminal epithelium was greater in E2 vs CON (6.55 vs. 1.2 ± 1.75%, P = 0.02) and stromal cells tended to be greater in E2 vs CON (0.59 vs 0.37 ± 0.06%, P = 0.07). Our results demonstrate that E2-treatment tends to increase plasma volume acutely and increases uterine cell proliferation in ewes.

iTRAQ-Based proteomic dataset for bovine pre-ovulatory plasma and follicular fluid containing high and low Estradiol.

This is isobaric tags for a relative and absolute quantification (iTRAQ)-Based Proteomic Data on bovine plasma (PL) and follicular fluid (FF) containing high and low pre-ovulatory circulating concentration of estradiol (E2). The PL and FF were collected from nine beef cows that were identified to initiate a new follicular wave on day -4 during synchronization. Follicular dynamics and ovulatory response were monitored using transrectal ultrasonography. Blood samples were collected at slaughter and FF was aspirated from dominant follicles (DF; >10 mm). Estradiol concentrations in PL and FF were measured by radioimmunoassays. Plasma and FF were labeled as containing high E2 (PL HE2 and FF HE2) or low E2 (PL LE2 and FF LE2). Abundant proteins (albumin, IgG, IgA, and alpha-1-antitrypsin) were depleted from the four PL and FF samples. Peptides were labeled with iTRAQ reagents and analyzed using 2-dimentional liquid chromatography ESI-based mass spectrometry. Proteins were identified and quantified using SEQUESTTM search engine embedded in Proteome Discoverer. The proteins matched with at least one unique peptide at minimum 95% confidence were considered positive identifications. Protein expression levels were determined by assigned fold change of >2.0 or <0.5 between any pair from the four sample types. The paired comparisons made were PL HE2 and PL LE2, FF HE2 and FF LE2, PL HE2 and FF HE2, and PL LE2 and FF LE2. Protein Analysis Through Evolutionary Relationships (PANTHER) and Database for Annotation, Visualization and Integrated Discovery (DAVID) were used to classify protein functions. This dataset includes the overview of workflow for identification and quantification of proteins and details on 231 proteins identified which includes 103 up- and down-regulate proteins. This dataset can be useful for further probing of the identified regulated proteins to better understand folliculogenesis and ovulation, particularly in bovine. This dataset is related to the article 'iTRAQ-Based Proteomic Analysis of Bovine Pre-ovulatory Plasma and Follicular Fluid' by P. A. Afedi, E. L. Larimore, R. A. Cushman, D. Raynie, G. A. Perry. Domestic Animal Endocrinology. https://doi.org/10.1016/j.domaniend.2021.106606.

iTRAQ-based proteomic analysis of bovine pre-ovulatory plasma and follicular fluid.

Bovine follicular fluid (FF) creates a unique microenvironment in follicles necessary for follicle growth, oocyte maturation, and estradiol (E2) production. The objective of this study was to analyze changes in proteins in FF and plasma (PL) from animals with high E2 (HE2) or low E2 (LE2) during the preovulatory period. Beef cows were synchronized, and follicular dynamics and ovulatory response were monitored using transrectal ultrasonography. Nine cows were selected and slaughtered, blood samples were collected at slaughter and FF was aspirated from dominant follicles (DF; >10 mm). Abundant proteins (albumin, IgG, IgA, and alpha-1-antitrypsin) were depleted from both PL and FF. Peptides were labeled with iTRAQ reagents and quantified using 2-dimentional liquid chromatography ESI-based mass spectrometry. Estradiol was associated with protein changes in PL and FF. Protein expression changes between FF HE2 and FF LE2 were greater than between PL HE2 and PL LE2. There were 15 up-regulated proteins and 10 down-regulated proteins in FF HE2 compared to FF LE2, and 7 proteins up-regulated and 9 proteins down-regulated in PL HE2 compared to PL LE2. Several of the differentially expressed proteins function in follicle development and were mainly categorized under cellular process and metabolic process. Pathway analysis identified the up- and down-regulated proteins were predominantly associated with the complement and coagulation cascades. The data demonstrate E2 regulates a wide range of reproductive associated proteins in bovine PL and FF and can provide the basis for further investigation of specific processes involved in such regulation.

Effect of estradiol preceding and progesterone subsequent to ovulation on proportion of postpartum beef cows pregnant.

Two experiments were conducted to examine the effect of plasma concentrations of 17ß-estradiol (E2) preceding and progesterone (P4) subsequent to ovulation on proportions of beef cows pregnant following embryo transfer. Timing of ovulation (d 0) among postpartum cows was synchronized and cows that expressed estrus were removed from each study. In Experiment 1, plasma E2 concentration on d 0 was used to classify cows (n = 353) into Low, Medium, and High E2 groups. Pregnancy rate for cows with Low, Medium, or High E2 concentrations were different (P < 0.05). In Experiment 2, there were multiple administrations of PGF2α to evaluate the independent effects of Low or High E2 before ovulation and Low or Normal (no treatment) P4 after ovulation on proportions of cows pregnant. Treatment groups in Experiment 2, therefore, were: Low E2-Low P4 (LL; n = 71), Low E2-Normal P4 (LN; n = 69), High E2-Low P4 (HL; n = 74), and High E2-Normal P4 (HN; n = 73). Concentrations of P4 on d 7 subsequent to ovulation were less (P < 0.05) in cows of the HL compared to HN, and in LL compared to LN groups. Concentrations of E2 on d -2, 0, and change in E2 (d -2 to d 0) had a positive effect (P < 0.008) on pregnancy rates. In summary, relatively greater E2 concentrations preceding ovulation; and relatively greater P4 concentrations subsequent to ovulation combined with lesser E2 concentrations preceding ovulation had a positive effect on proportions of postpartum cows pregnant.

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.

Impacts of chronic and increasing lipopolysaccharide exposure on production and reproductive parameters in lactating Holstein dairy cows.

Lipopolysaccharide (LPS) administration causes immunoactivation, which negatively affects production and fertility, but experimental exposure via an acute bolus is unlikely to resemble natural infections. Thus, the objectives were to characterize effects of chronic endotoxemia on production parameters and follicular development in estrous-synchronized lactating cows. Eleven Holstein cows (169 ± 20 d in milk; 681 ± 16 kg of body weight) were acclimated to their environmental surroundings for 3 d and then enrolled in 2 experimental periods (P). During P1 (3 d) cows consumed feed ad libitum and baseline samples were obtained. During P2 (7 d), cows were assigned to continuous infusion of either (1) saline-infused and pair-fed (CON-PF; 40 mL/h of saline i.v.; n = 5) or (2) LPS infused and ad libitum fed (LPS-AL; Escherichia coli O55:B5; 0.017, 0.020, 0.026, 0.036, 0.055, 0.088, and 0.148 µg/kg of body weight/h i.v. on d 1 to 7, respectively; n = 6). Controls were pair-fed to the LPS-AL group to eliminate confounding effects of dissimilar nutrient intake. Infusing LPS temporally caused mild hyperthermia on d 1 to 3 (+0.49°C) relative to baseline. Dry matter intake of LPS-AL cows decreased (28%) on d 1 of P2, then progressively returned to baseline. Relative to baseline, milk yield from LPS-AL cows was decreased on d 1 of P2 (12%). No treatment differences were observed in milk yield during P2. Follicular growth, dominant follicle size, serum progesterone (P4), and follicular P4 and 17ß-estradiol concentrations were similar between treatments. Serum 17ß-estradiol tended to increase (115%) and serum amyloid A and LPS-binding protein were increased (118 and 40%, respectively) in LPS-AL relative to CON-PF cows. Compared with CON-PF, neutrophils in LPS-AL cows were initially increased (45%), then gradually decreased. In contrast, monocytes were initially decreased (40%) and progressively increased with time in the LPS-AL cows. Hepatic mRNA abundance of cytochrome P450 family 2 subfamily C (CYP2C) or CYP3A was not affected by LPS, nor was there a treatment effect on toll-like receptor 4 or LBP; however, acyloxyacyl hydrolase and RELA subunit of nuclear factor kappa B tended to be increased in LPS-AL cows. These data suggest lactating dairy cows become tolerant to chronic and exponentially increasing LPS infusion in terms of production and reproductive parameters.

Feeding distillers dried grains in replacement of forage in limit-fed dairy heifer rations: Effects on metabolic profile and onset of puberty.

The objective of this study was to determine the effect of increasing the inclusion rate of distillers dried grains (DDGS) in replacement of forage in limit-fed diets on the metabolic profile and onset of puberty in dairy heifers. A 16-wk randomized complete block design study was conducted using 48 Holstein heifers (199 ± 2 d of age) with 3 treatments. Treatments were (1) 30% DDGS (30DG), (2) 40% DDGS (40DG), and (3) 50% DDGS (50DG), with the remainder of the diet consisting of grass hay and 1.5% mineral mix. Heifers were housed in groups of 6 and individually limit-fed using Calan gates at 2.65, 2.50, and 2.35% of body weight (BW) on a dry matter (DM) basis for 30DG, 40DG, and 50DG, respectively. Jugular blood samples were collected during wk 0, 4, 8, 12, and 16 for metabolite and metabolic hormone analysis. Additional samples were taken during wk 16 for plasma fatty acid analysis. When heifers weighed 200 kg, coccygeal vein blood samples were taken twice per week for progesterone analysis to estimate onset of puberty. Blood samples continued until cycling was confirmed via ultrasound for the presence of a corpus luteum. A quadratic response and a linear tendency in the proportion of total fatty acids as linoleic acid were observed. Linear and quadratic responses for plasma concentrations of linoleic acid and arachidonic acid occurred. Overall results for fatty acid analysis demonstrated that total fatty acid and polyunsaturated fatty acids concentration in the blood were linearly increased, with a quadratic response for polyunsaturated fatty acids with 30DG and 50DG having the greatest concentrations. No interactions of treatment by week were observed for any of the metabolites and metabolic hormones measured. Glucose, insulin, insulin-like growth factor-1, leptin, and triglycerides were similar across treatments. A linear response of plasma urea nitrogen and a quadratic response tendency for cholesterol concentration were observed. Age and BW at puberty were similar across treatments. Limit-feeding heifers with greater inclusion rates of DDGS maintained energy status without the accumulation of excess adipose tissue as indicated by leptin. Treatments had no detrimental effects on age or BW at puberty.

Influence of post-insemination nutrition on embryonic development in beef heifers.

Previous studies have demonstrated that a decrease in nutrition immediately following AI reduces pregnancy success in beef heifers. The objective of this experiment was to determine if nutrient restriction following AI impacted early embryonic development among non-super ovulated heifers. Beef heifers in eight replications (Rep; Rep 1; n = 14, Rep 2; n = 15, Rep 3; n = 15, Rep 4; n = 14, Rep 5; n = 15, Rep 6; n = 15, Rep 7; n = 25, Rep 8; n = 25) across two locations (UMN, SDSU) were developed in a dry-lot and fed 125% NRC requirements from weaning to timed-AI (d 0). Heifers were timed-AI to a single sire in all replications. Immediately following AI, heifers were assigned, based on age, weight, and estrous response to one of two post-AI nutritional treatments. Half the heifers in each replication continued on the pre-insemination diet, serving as the control treatment (CON) and the remaining heifers were restricted to a sub-maintenance diet (RES). At UMN, heifers in the RES treatment were fed the same diet, but intake was limited to 80% NEm, while at SDSU, DMI remained the same, but diet composition was altered with the addition of straw to reduce NEm to 50% of requirements. On d 6, single embryos were collected nonsurgically and recovered embryos (CON; n = 46, RES; n = 42) were evaluated to determine quality (grade 1-9) and stage (1-4). Embryos were then stained and evaluated to determine the number of dead cells and total blastomeres. In Reps 1 through 6, concentrations of IGF-1 were assessed on d 0 and 6 and progesterone concentrations on d 4 and 6. Data were analyzed using the Mixed procedures of SAS. There were no treatment by Rep or treatment by location interactions for any embryo parameter evaluated, thus all data were pooled. Embryo stage and quality were improved (P < 0.01) in the CON (4.4 ± 0.16, 2.2 ± 0.19, respectively) compared to RES treatment (3.7 ± 0.16, 2.9 ± 0.19, respectively). Embryos in the CON treatment had greater total blastomeres (66.9 ± 5.05; P < 0.01) and tended to have a greater percentage of live cells (P < 0.10; 80.9 ± 4.19%) compared to RES (47.9 ± 5.41; 69.7 ± 4.39%, respectively). Progesterone and IGF-1 concentrations did not differ between treatments. In summary, nutrient restriction for 6 days immediately following AI resulted in poorer quality embryos that were delayed in stage of development, suggesting that immediate changes in nutritional status after insemination can alter early embryonic development.

Supplementation of metabolizable protein during late gestation and fetal number impact ewe organ mass, maternal serum hormone and metabolite concentrations, and conceptus measurements.

To examine the effects of maternal metabolizable protein (MP) supplementation during late gestation on serum hormone and metabolites and organ masses, multiparous ewes (n = 45) carrying singletons or twins were allotted randomly (within pregnancy group) to 1 of 3 treatments: 60% (MP60), 80% (MP80), or 100% (MP100) of MP requirements. Blood samples were drawn before the initiation of diets (day 100) and before slaughter (day 130) for chemistry panel analysis and weekly for hormone analysis including progesterone (P4) and estradiol-17ß (E2). At day 130, ewe organ masses were recorded. Despite being fed isocaloric diets, MP60 ewes gained less weight throughout pregnancy compared with MP80 and MP100 ewes which were similar. Although diet did not impact E2 or P4 concentrations, ewes carrying twins had greater (P < 0.05) concentrations of both as gestation advanced. Albumin, aspartate aminotransferase, and total protein were reduced (P < 0.05) in MP60 compared with MP100 ewes near term. There was a diet by fetal number interaction (P = 0.03) for lactate dehydrogenase. Twin-carrying MP80 ewes had greater lactate dehydrogenase compared with all other groups on day 130 of gestation. Ewes that were fed MP80 had greater body weight on day 130 of gestation compared with MP60 ewes. Kidney and heart weights were lighter in MP60 ewes compared with MP80 ewes. There was a maternal diet by fetal number interaction (P = 0.05) on fetal weight per unit empty ewe body weight. In ewes carrying singletons, MP60 ewes supported less fetal weight compared with MP100. In contrast, MP60 ewes supported more fetal mass compared with MP100 ewes when carrying twins. The level of protein, and not just total energy, in the diet appears to impact some aspects of the maternal system. Moreover, it appears some measurements of mobilizing maternal body resources are enhanced in ewes carrying twins.

Effects of excess metabolizable protein on ovarian function and circulating amino acids of beef cows: 1. Excessive supply from corn gluten meal or soybean meal.

In the dairy industry, excess dietary CP is consistently correlated with decreased conception rates. However, the source from which excess CP is derived and how it affects reproductive function in beef cattle is largely undefined. The objective of this experiment was to determine the effects of feeding excess metabolizable protein (MP) from feedstuffs differing in rumen degradability on ovulatory follicular dynamics, subsequent corpus luteum (CL) development, steroid hormone production and circulating amino acids (AA) in beef cows. Non-pregnant, non-lactating mature beef cows (n=18) were assigned to 1 of 2 isonitrogenous diets (150% of MP requirements) designed to maintain similar BW and body condition score (BCS) between treatments. Diets consisted of ad libitum corn stalks supplemented with corn gluten meal (moderate rumen undegradable protein (RUP); CGM) or soybean meal (low RUP; SBM). After a 20-day supplement adaptation period, cows were synchronized for ovulation. After 10 days of synchronization, gonadotropin releasing hormone (GnRH) was administered to reset ovarian follicular growth. Starting at GnRH administration and daily thereafter until spontaneous ovulation, transrectal ultrasonography was used to diagram ovarian follicular growth, and blood samples were collected for hormone, metabolite and AA analyses. After 7 days of visual detection of estrus, CL size was determined via ultrasound. Data were analyzed using the MIXED procedures of SAS. As designed, cow BW and BCS were not different (P⩾0.33). Ovulatory follicular wavelength, antral follicle count, ovulatory follicle size at dominance and duration of dominance were not different (P>0.13) between treatments. Cows supplemented with CGM had greater post-dominance ovulatory follicle growth, larger dominant follicles at spontaneous luteolysis, shorter proestrus, and larger ovulatory follicles (P⩽0.03) than SBM cows. No differences (P⩾0.44) in peak estradiol, ratio of estradiol to ovulatory follicle volume, or plasma urea nitrogen were observed. While CL volume and the ratio of progesterone to CL volume were not affected by treatment (P⩾0.24), CGM treated cows tended to have decreased (P=0.07) circulating progesterone 7 days post-estrus compared with SBM cows. Although total circulating plasma AA concentration did not differ (P=0.70) between treatments, CGM cows had greater phenylalanine (P=0.03) and tended to have greater leucine concentrations (P=0.07) than SBM cows. In summary, these data illustrate that excess MP when supplemented to cows consuming a low quality forage may differentially impact ovarian function depending on ruminal degradability of the protein source.

Effects of excess metabolizable protein on ovarian function and circulating amino acids of beef cows: 2. Excessive supply in varying concentrations from corn gluten meal.

In the dairy industry, excess dietary CP is consistently correlated with decreased conception rates. However, amount of excess CP effects on reproductive function in beef cattle is largely undefined. The objective of this experiment was to determine the effects of excess metabolizable protein (MP) supplementation from a moderately abundant rumen undegradable protein (RUP) source (corn gluten meal: 62% RUP) on ovarian function and circulating amino acid (AA) concentrations in beef cows consuming low quality forage. Non-pregnant, non-lactating beef cows (n=16) were allocated by age, BW and body condition score (BCS) to 1 of 2 isocaloric supplements designed to maintain BW for 60 days. Cows had ad libitum access to corn stalks and were individually offered a corn gluten meal-based supplement daily at 125% (MP125) or 150% (MP150) of National Research Council (NRC) MP requirements. After a 20-day supplement adaptation period, cows were synchronized for ovulation. After 10 days of synchronization, follicular growth was reset with gonadotropin releasing hormone. Daily thereafter, transrectal ultrasonography was performed to diagram ovarian follicular waves, and blood samples were collected for hormone, metabolite and AA analyses. After 7 days of observation of estrus, corpus luteum (CL) size was determined via ultrasound. Data were analyzed using the MIXED procedures of SAS. No differences (P⩾0.21) in BW and BCS existed throughout the study; however, plasma urea N at ovulation was greater (P=0.04) in MP150. Preovulatory ovarian follicle size at dominance, duration of dominance, size at spontaneous luteolysis, length of proestrus and wavelength were not different (P⩾0.11) between treatments. However, ovulatory follicles were larger (P=0.04) and average antral follicle count was greater (P=0.01) in MP150 than MP125. Estradiol concentration and ratio of estradiol to ovulatory follicle volume were not different due to treatment (P⩾0.25). While CL volume 7 days post-estrus was greater (P<0.01) in MP150 than MP125, circulating progesterone 7 days post-estrus and ratio of progesterone to CL volume were not different (P⩾0.21). Total AA were not different (P⩾0.76) at study initiation or completion; however, as a percent of total AA, branched-chain AA at ovulation were greater (P=0.02) in MP150. In conclusion, supplementation of CP at 150% of NRC MP requirements from a moderately undegradable protein source may enhance growth of the ovulatory follicle and subsequent CL compared with MP supplementation at 125% of NRC MP requirements.

Effects of supplementing calcium salts of polyunsaturated fatty acids to late-gestating beef cows on performance and physiological responses of the offspring.

This experiment compared performance and physiological responses of the offspring from cows supplemented with Ca salts of PUFA or SFA + MUFA during late gestation. Ninety-six multiparous, nonlactating, pregnant Angus × Hereford cows were ranked by BW, BCS, and age and divided into 24 groups of 4 cows/group at the end of their second trimester of gestation (d -7). Cows conceived during the same estrus synchronization + AI protocol, with semen from a single sire; hence, gestation length was 195 d for all cows at the beginning of the experiment (d 0). Groups were randomly assigned to receive (DM basis) 405 g/cow daily of soybean meal in addition to 1) 190 g/cow daily of Ca salts of PUFA based on eicosapentaenoic, docosahexaenoic, and linoleic acids or 2) 190 g/cow daily of Ca salts of SFA + MUFA based on palmitic and oleic acids (CON). Groups were maintained in 2 pastures (6 groups of each treatment/pasture) and received daily 10.1 kg/cow (DM basis) of grass-alfalfa hay. Groups were segregated into 1 of 12 drylot pens (6 by 18 m) and individually offered treatments 3 times/wk from d 0 until calving. Cow BW and BCS were recorded, and blood samples were collected on d -7 of the experiment and also within 12 h after calving. Calf BW was also recorded within 12 h of calving. Calves were weaned on d 280 of the experiment, preconditioned for 45 d (d 280 to 325), transferred to a growing lot on d 325, and moved to a finishing lot on d 445, where they remained until slaughter. At calving, PUFA-supplemented cows had a greater ( < 0.01) proportion (as % of total plasma fatty acids) of PUFA, including linoleic, linolenic, arachidonic, docosapentaenoic, and docosahexaenoic acids. At weaning, calves from CON-supplemented cows were older ( = 0.03), although no treatment differences were detected ( = 0.82) for calf weaning BW. During both growing and finishing phases, ADG was greater ( ≤ 0.06) in calves from PUFA-supplemented cows. Upon slaughter, HCW and marbling were also greater ( ≤ 0.05) in calves from PUFA-supplemented cows. Collectively, these results indicate that supplementing eicosapentaenoic, docosahexaenoic, and linoleic acids to late-gestating beef cows stimulated programming effects on postnatal offspring growth and carcass quality. Therefore, supplementing late-gestating beef cows with Ca salts of PUFA appears to optimize offspring productivity in beef production systems.

Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program.

A multilocation study examined pregnancy risk (PR) after delaying AI in suckled beef cows from 60 to 75 h when estrus had not been detected by 60 h in response to a 7-d CO-Synch + progesterone insert (CIDR) timed AI (TAI) program (d -7: CIDR insert concurrent with an injection of GnRH; d 0: PGF injection and removal of CIDR insert; and GnRH injection at TAI [60 or 75 h after CIDR removal]). A total of 1,611 suckled beef cows at 15 locations in 9 states (CO, IL, KS, MN, MS, MT, ND, SD, and VA) were enrolled. Before applying the fixed-time AI program, BCS was assessed, and blood samples were collected. Estrus was defined to have occurred when an estrus detection patch was >50% colored (activated). Pregnancy was determined 35 d after AI via transrectal ultrasound. Cows ( = 746) detected in estrus by 60 h (46.3%) after CIDR removal were inseminated and treated with GnRH at AI (Control). Remaining nonestrous cows were allocated within location to 3 treatments on the basis of parity and days postpartum: 1) GnRH injection and AI at 60 h (early-early = EE; = 292), 2) GnRH injection at 60 h and AI at 75 h (early-delayed = ED; = 282), or 3) GnRH injection and AI at 75 h (delayed-delayed = DD; = 291). Control cows had a greater ( < 0.01) PR (64.2%) than other treatments (EE = 41.7%, ED = 52.8%, DD = 50.0%). Use of estrus detection patches to delay AI in cows not in estrus by 60 h after CIDR insert removal (ED and DD treatments) increased ( < 0.05) PR to TAI when compared with cows in the EE treatment. More ( < 0.001) cows that showed estrus by 60 h conceived to AI at 60 h than those not showing estrus (64.2% vs. 48.1%). Approximately half (49.2%) of the cows not in estrus by 60 h had activated patches by 75 h, resulting in a greater ( < 0.05) PR than their nonestrous herd mates in the EE (46.1% vs. 34.5%), ED (64.2% vs. 39.2%), and DD (64.8% vs. 31.5%) treatments, respectively. Overall, cows showing estrus by 75 h (72.7%) had greater ( < 0.001) PR to AI (61.3% vs. 37.9%) than cows not showing estrus. Use of estrus detection patches to allow for a delayed AI in cows not in estrus by 60 h after removal of the CIDR insert improved PR to TAI by optimizing the timing of the AI in those cows.

Changes in ovarian function associated with circulating concentrations of estradiol before a GnRH-induced ovulation in beef cows.

These studies were conducted to evaluate causes for differences in circulating concentrations of estradiol before a GnRH-induced ovulation. Beef cows were synchronized by an injection of GnRH on day -7 and an injection of prostaglandin F2α (PGF2α) on day 0. In experiment 1, blood samples were collected every 3 h from PGF2α on day 0 to hour 33 after PGF2α and at slaughter (hour 36 to 42; n = 10). Cows were assigned to treatment group based on circulating concentrations of estradiol (E2): HighE2 vs LowE2. At slaughter, follicular fluid (FF) and granulosa cells were collected from the dominant follicle. In experiment 2, blood samples (n = 30) were collected every 8 h from PGF2α until the dominant follicle was aspirated via ultrasound-guided follicular aspiration to collect FF and granulosa cells (hour 38 to 46). In experiment 1, HighE2 had increased abundance of 3ß-hydroxysteroid dehydrogenase, cytochrome P450 aromatase, and LHR (P ≤ 0.02), and greater concentrations of estradiol and androstenedione (P ≤ 0.02) in the FF. In experiment 2, HighE2 had increased abundance of CYP11A1, 3ß-hydroxysteroid dehydrogenase, cytochrome P450 aromatase, and LHR (P ≤ 0.03) vs either LowE2 or GnRHLowE2. There was a tendency (P = 0.07) for LH pulse frequency to be increased in both the GnRHLowE2 and HighE2 compared with LowE2. HighE2 cows experienced increas in circulating concentrations of estradiol compared with LowE2. In conclusion, animals with greater concentrations of circulating estradiol before fixed-time AI experienced an upregulation of the steroidogenic pathway during the preovulatory period.

Feeding distillers dried grains in replacement of forage in limit-fed dairy heifer rations: Effects on growth performance, rumen fermentation, and total-tract digestibility of nutrients.

The objective of this study was to determine the effects of increasing dietary concentration of distillers dried grains (DDGS) in dairy heifer rations. A 16-wk randomized complete block design study was conducted using 48 Holstein heifers [199±2 d of age; body weight (BW) 206±2kg] to evaluate effects of dietary treatment on dry matter (DM) intake, average daily gain, growth performance, rumen fermentation, and nutrient digestibility. Treatments were (1) 30% DDGS with the diet fed at 2.65% of BW, (2) 40% DDGS with the diet fed at 2.50% of BW, and (3) 50% DDGS with the diet fed at 2.35% of BW. The remainder of the diet consisted of grass hay and 1.5% mineral mix. Heifers were individually limit-fed using Calan gates. Heifers were weighed every 2 wk and the ration amount offered was adjusted accordingly. Frame measurements and body condition score were recorded every 2wk. Rumen fluid was collected via esophageal tubing during wk 12 and 16 for pH, ammonia N, and volatile fatty acid analysis. Total-tract digestibility of nutrients was evaluated during wk 16 using fecal grab sampling. No treatment by week interactions were found for any of the growth parameters measured, and growth parameters did not differ among treatments. Heifer DM intake linearly decreased with increasing concentrations of DDGS. Body weight and average daily gain were similar among treatments, whereas gain:feed linearly increased across treatments, with a tendency for a treatment by time interaction. As the dietary concentrations of DDGS increased, rumen ammonia N linearly increased. Acetate proportion and acetate:propionate linearly decreased as DDGS increased, whereas propionate linearly increased. There were treatment by time interactions for propionate proportion and acetate:propionate. Increasing dietary concentrations of DDGS linearly increased total-tract digestibility of DM, organic matter, and crude protein. Limit-feeding diets with greater concentrations of DDGS improved gain:feed and total-tract digestibility of DM and crude protein, and maintained frame growth without increasing body condition score. Results demonstrated that replacing forage with DDGS at up to a 50% inclusion rate in limit-fed rations can maintain heifer growth performance.

Factors affecting puberty in replacement beef heifers.

Puberty is defined as when ovulation is accompanied by visual signs of estrus and subsequent normal luteal function. Age at puberty is an important trait in relation to reproductive success, productive life span, and profitability in beef operations. Although puberty and initiation of normal estrous cycles are complex events that require maturation of the hypothalamic-pituitary-ovarian axis, it has been well documented that nutrition, age, and genetics are regulators of age at puberty. However, their role is mainly as regulators of the endocrine maturation that must occur for sustained ovarian cyclicity to be initiated. Increased growth rate between 4 and 7 months of age is apparently sufficient to induce early puberty, and this increased growth rate decreased the negative feedback of estradiol on LH secretion during the prepubertal period. As puberty approaches, a progressive decrease in the negative feedback of estradiol on GnRH secretion allows increased pulse frequency of LH, thus stimulating follicular growth and increased estradiol production. In addition, expression of estrogen receptors in the anterior hypothalamus and ventromedial nucleus is negatively correlated with LH pulse frequency. Although a significant number of genes and pathways are involved in neuromaturation for the initiation of normal estrous cycles, the inhibitory effects of neuropeptide Y on GnRH/LH release appear to decrease, and the stimulatory effect of melanocyte-stimulating hormone alpha on GnRH appears to increase as puberty approaches. Thus, a thorough understanding of the metabolic and neuroendocrine changes that occur to initiate normal estrous cycles is needed to facilitate management of the important reproductive event.

Effects of administration of prostaglandin F at initiation of the seven-day CO-Synch+controlled internal drug release ovulation synchronization protocol for suckled beef cows and replacement beef heifers.

Two experiments were conducted to determine the effect of administering PGF at the initiation of the 7-d CO-Synch+controlled internal drug release (CIDR) fixed-timed AI (TAI) protocol on pregnancy rates of suckled beef cows and replacement heifers. Within location, cows were stratified by days postpartum (DPP), BCS, and parity (Exp. 1; = 1,551) and heifers were stratified by BCS (Exp. 2; = 999) and randomly assigned to 1 of 2 treatments: 1) CO-Synch+CIDR (100-µg injection of GnRH at CIDR insertion [d -10] with a 25-mg injection of PGF at CIDR removal [d -3] followed by injection of GnRH and TAI on d 0) or 2) PG-CO-Synch+CIDR (a 25-mg injection of PGF on d -10 of the CO-Synch+CIDR protocol). Follicle diameter and corpus luteum (CL) development were assessed on d -10 and -3, and pregnancy status was determined on d 30 to 35. Blood was collected on d -20, -10, -3, and 0 relative to TAI to determine concentrations of progesterone (P4). In Exp. 1, TAI pregnancy rates did not differ ( = 0.667) between treatments and were affected by BCS ( = 0.003) and DPP ( = 0.006). Concentrations of P4 were greater ( < 0.0001) on d -3 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (4.1 ± 0.2 and 3.4 ± 0.2 ng/mL, respectively). Follicle diameter on d -3 differed ( = 0.05) between PG-CO-Synch+CIDR (13.4 ± 0.3 mm) and CO-Synch+CIDR (12.5 ± 0.3 mm) treatments. Cows with P4 > 2.5 ng/mL on d -10 had greater ( = 0.024) pregnancy rate to TAI (56.5%) compared with cows with 2.5 ng/mL < P4 > 1 (43.0%), whereas cows with P4 < 1 ng/mL were intermediate (51.6%). Cows with a CL on d -10 had greater ( = 0.012) pregnancy rates to TAI than cows without a CL (66.3 vs. 39.4%, respectively). In Exp. 2, TAI pregnancy rates did not differ ( = 0.316) between treatments. Concentrations of P4 differed ( < 0.0001) on d -3 with greater concentrations of P4 for CO-Synch+CIDR than for PG-CO-Synch+CIDR (3.75 ± 0.20 ng/mL and 3.60 ± 0.21 ng/mL, respectively). Follicle diameter was similar ( = 0.749) between treatments on d -10 and -3. Regardless of treatment, cyclic status tended ( = 0.062) to improve pregnancy rates to TAI (55 vs. 45%, for cycling and noncycling heifers, respectively). We concluded that addition of PGF to the 7-d CO-Synch+CIDR protocol decreased concentrations of P4 in cows and heifers and increased follicle diameter at CIDR removal in cows but failed to increase TAI pregnancy rates.