One-Carbon Metabolites Supplementation and Nutrient Restriction Alter the Fetal Liver Metabolomic Profile during Early Gestation in Beef Heifers.

Maternal nutrition is pivotal for proper fetal development, with one-carbon metabolites (OCM) playing a key role in fetal epigenetic programming through DNA and histone methylation. The study aimed to investigate the effects of nutrient restriction and OCM supplementation on fetal liver metabolomics in pregnant beef-heifers, focusing on metabolites and pathways associated with amino-acid, vitamin and cofactor, carbohydrate, and energy metabolism at day 63 of gestation. Thirty-one crossbred Angus heifers were artificially inseminated and allocated to four nutritional treatments in a 2 × 2 factorial arrangement of treatments, with the two factors being dietary intake/rate of gain (control-diet [CON]; 0.60 kg/day ADG, vs. restricted-diet [RES]; -0.23 kg/day ADG) and OCM supplementation (supplemented [+OCM] vs. not supplemented [-OCM]). The resulting treatment groups-CON-OCM, CON+OCM, RES-OCM, and RES+OCM were maintained for 63 days post-breeding. Following this period, fetal liver tissues were collected and subjected to metabolomic analysis using UPLC-tandem mass-spectrometry. We identified 288 metabolites, with the majority (n = 54) being significantly influenced by the main effect of gain (P ≤ 0.05). Moreover, RES showed decreased abundances of most metabolites in pathways such as lysine metabolism; leucine, isoleucine and valine metabolism; and tryptophan metabolism, compared to CON. Supplementation with OCM vs. no OCM supplementation, resulted in greater abundance of metabolites (P ≤ 0.05) affecting pathways associated with methionine, cysteine, S-adenosylmethionine and taurine metabolism; guanidino and acetamido metabolism; and nicotinate and nicotinamide metabolism. Notably, OCM supplementation with a moderate rate of gain increased the concentrations of ophthalmate, N-acetylglucosamine, and ascorbic-acid 3-sulfate, which are important for proper fetal development (P ≤ 0.05). Nutrient restriction reduced the majority of liver metabolites, while OCM supplementation increased a smaller number of metabolites. Thus, OCM supplementation may be protective of metabolite concentrations in key developmental pathways, which could potentially enhance fetal development under nutrient-restricted conditions.

Replacement Nellore heifers receiving supplementation under different herbage allowance: effects on forage characteristics, performance, physiology, and reproduction.

In Brazil, heifers typically calve at 36-48 months. Due to the high demand for meat and the need to reduce slaughter age, high supplementation has become commonly used in beef cattle farming. However, the literature remains scarce on studies that explore the impact of grazing management during the background phase on the productivity and reproductive efficiency of young Nellore heifers. This study aimed to evaluate the effects of two-herbage allowances (HA) on forage characteristics, performance, physiology and reproductive parameters of replacement Nellore heifers. Ninety weaned heifers [169 ± 19 kg of shrunk body weight (SBW); 210 ± 28 days of age] were blocked by initial BW and randomly assigned to receive different HA: (1) High herbage allowance (HHA: 7.2 kg DM/kg BW) and (2) Low herbage allowance (LHA: 3.3 kg DM/kg BW); and divided into six paddocks, totaling 12 paddocks. The experimental period was divided into the growing phase (D173) and the reproductive season (D83). Continuous stocking with a variable stocking rate was used. The supplement was provided daily with expected intake of around 10 g/kg of BW. The HHA pasture showed greater values of canopy height, greater HA, and lower values of CP and CP: in vitro digestible DM ratio than the LHA pasture over the days of the study (P ≤ 0.05). Herbage mass and the green stem proportion were lower in LHA pasture (P < 0.01), while the green leaf (g/kg DM) and senescent stem proportions (g/kg DM) were higher (P = 0.080) when compared to HHA pasture. Heifers maintained on HHA pasture had a higher average daily gain (P < 0.01), forage intake (P < 0.003), higher SBW (P < 0.01), Longissimus area (P < 0.01), and 12th-rib fat thickness (P < 0.01) than those kept in the LHA pasture. The proportion of heifers that reached the weight at maturity on D173 (P = 0.027) and the proportion of pubertal pregnancy heifers (P = 0.042) were greatest in the HHA treatment. The blood urea nitrogen (P = 0.002) was higher in heifers maintained in the LHA pasture. Heifers maintained in HHA pasture showed higher values of relative abundance of mRNA for UGT1A6 (P = 0.004) and IGFBP3 (P = 0.072). The use of HHA criteria increased forage intake, body gain, and carcass attributes of animals, which led to better reproductive performance of Nellore heifers.

Puberty in beef heifers: effects of prenatal and postnatal nutrition on the development of the neuroendocrine axis.

Reproductive maturation is a complex physiological process controlled by the neuroendocrine system and is characterized by an increase in gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) pulsatile secretion. Nutrition during early development is a key factor regulating puberty onset, which is defined as first ovulation in females. In heifers, nutrient restriction after weaning delays puberty, whereas elevated levels of nutrition and energy reserves advance reproductive maturation. Recent studies in cattle and other animal models have shown that the dam's nutrition during gestation can also program the neuroendocrine system in the developing fetus and has the potential to alter timing of puberty in the offspring. Among the metabolic signals that modulate brain development and control timing of puberty is leptin, a hormone produced primarily by adipocytes that communicates energy status to the brain. Leptin acts within the arcuate nucleus of the hypothalamus to regulate GnRH secretion via an upstream network of neurons that includes neurons that express neuropeptide Y (NPY), an orexigenic peptide with inhibitory effects on GnRH secretion, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide with excitatory effects on GnRH neurons. Another important population of neurons are KNDy neurons, neurons in the arcuate nucleus that co-express the neuropeptides kisspeptin, neurokinin B, and dynorphin and have strong stimulatory effects on GnRH secretion. Our studies in beef heifers indicate that increased nutrition between 4 to 8 months of age advances puberty by diminishing NPY inhibitory tone and by increasing excitatory inputs of αMSH and kisspeptin, which collectively lead to increased GnRH/LH pulsatility. Our ongoing studies indicate that different planes of nutrition during gestation can alter maternal leptin concentrations and promote changes in the fetal brain. Nonetheless, at least in Bos indicus-influenced heifers, deficits programmed prenatally can be overcome by adequate postnatal nutrition without negatively impacting age at puberty or subsequent fertility.

Effect of Different Slow-Release Urea on the Production Performance, Rumen Fermentation, and Blood Parameter of Angus Heifer.

This study investigated the effect of replacing part of the dietary soybean meal with either polymer-coated urea or gelatinized starch urea on the production performance, blood indexes, and ruminal fermentation of Angus heifers. A total of 210 purebred Angus cattle (BW = 314.26 kg) were divided into three groups: the no urea group (CON), the polymer-coated urea group (PCU), and the gelatinized starch urea group (GSU); 20 g/kg polymer-coated urea or 25 g/kg gelatinized starch urea was used to replace part of soybean meal in the concentrate feed, according to the principle of isometabolic energy and isonitrogenous. The result showed that the PCU group had higher ADG and ADF apparent digestibility, while it had a lower feed-weight ratio. On the 86th day, the serum albumin (ALB) content in the PCU group was significantly higher than that in the CON group. In rumen, compared with the CON group, the contents of acetic acid and total volatile fatty acid were significantly higher in the PCU group, whereas butyric acid and propionic acid were significantly higher in the PCU group and GSU group. Ruminal bacterial diversity analysis found that the abundance of Firmicutes was higher in the PCU group at the phylum level, and an inverse result was observed in Bacteroidetes. The abundance of Paraprevotella was higher in the PCU group, whereas higher abundance of Prevotella was found in the GSU group at the genus level. These results indicate that slow-release urea can replace part of soybean meal in the diet, and the amount of substitution in this trial had no diverse effect on the performance of Angus heifers.

Examining the long-term impacts of ergot alkaloids on fetal heifer development and subsequent growth and reproductive performance.

Consumption of toxic endophyte-infected tall fescue (EI) results in poor reproductive performance in domestic livestock. In this study, the objective was to evaluate the effects of ergovaline exposure during mid-gestation (days 93 through 188 of gestation) on dam performance, the growing female fetus, and the subsequent growth and reproductive performance of the gestationally exposed heifer calves. Pregnant Angus and Simmental-Angus cows were blocked by age (2 to 3, to 7, and >7 y), body weight (BW), and breed; and then randomly assigned to graze either novel endophyte-infected tall fescue (EN; <5% infection rate; n = 27 year 1, n = 16 year 2) or toxic EI (99% infection rate; n = 27 year 1, n = 17 year 2). Weekly BW, body condition scores (BCS), hair coat scores, hair shedding scores (HSS), and blood samples for progesterone (P4) analysis were collected from mid-April through July of 2017 (year 1) and 2018 (year 2). Gestation length, birth weight, placental characteristics, heifer calf growth, onset of puberty, ovarian characteristics, and artificial insemination pregnancy rates were measured. Data were analyzed using the MIXED procedure of SAS. Cows grazing EI pastures had reduced average daily gain, reduced BCS, greater HSS, and decreased P4 concentrations compared to cows on EN pasture (P < 0.01). Birth weights were decreased for heifers whose dams were exposed to EI pastures during their second trimester (P < 0.01). Heifer pregnancy rates were not impacted by EI pasture exposure during gestation for either year of the study. However, a treatment-by-year effect was seen for the pregnancy rate for EI-exposed heifers in year 2; EI-exposed heifers in year 2 had increased pregnancy rates at two of the inseminations. Combined, these data reinforce that consumption of toxic EI during gestation can negatively impact both dam and offspring performance. More studies are needed to evaluate more parameters in an effort to elucidate the possible life-long impacts of ergovaline exposure during gestation.

The U.S. livestock industry incurs over one billion dollars of economic loss every year due to fescue toxicosis, caused by consuming ergot alkaloids produced by an endophytic fungus in some grass species. Identifying means to mitigate the negative effects of fescue toxicosis is needed for U.S. beef producers. Effective treatment for this toxicosis is still needed. The objective of this study was to evaluate the effects of ergovaline exposure during mid-gestation on dam performance, the growing female fetus, and the subsequent growth and reproductive performance of the gestationally exposed heifer calves. We identified specific phenotype traits that undergo developmental programming in utero in response to fescue toxicosis. However, measurements of growth and reproductive performance were not altered by ergot exposure.

Effects of perinatal exposure to daily maximum THI and THI fluctuations on serum total proteins and health of preweaned Holstein heifers raised in a dry climate.

The objective of this study was to assess the effects of the exposure to daily maximum and temperature-humidity index (THI) and to daily THI fluctuations (∆THI = maximum THI-minimum THI) at exposure periods comprising 2 d before birth to birth (-2 d), birth date (0 d), birth to 2 d of age (+2 d), and birth to 7 d of age (+7 d) on serum total proteins (STP), transfer of passive immunity (TPI), and the occurrence of scours and respiratory disease. A total of 841 Holstein heifer calves were retrospectively observed from -2 d until 65 d of age. Colostrum quality was assessed using a colostrometer to ensure a minimum globulin concentration of 52 mg/mL in the colostrum fed to the study calves. Two temperature and relative humidity sensors were installed at the calf yard. Maximum, minimum, and ∆THI values were obtained for each exposure period, and thermal exposure categories were defined as heat stress (HS: maximum THI > 70 units; non-HS: THI ≤ 70 units) and ∆THI (low < 20 units, medium ≥ 20 to ≤30 units, high > 30). The TPI was classified as poor (STP < 5.1 g/dL), fair (5.1 and 5.7 g/dL), good (>5.7 and 6.1 g/dL), and excellent (≥6.1 g/dL). Associations between the thermal exposure categories and the study outcomes were examined using ANOVA, logistic regression, and survival analyses. No differences in STP at -2 d were observed between HS and non-HS calves (6.83 ±â€…0.05 vs. 6.91 ±â€…0.05 g/dL), whereas HS-exposed calves at 0 d tended to have lower STP compared with non-HS calves (6.82 ±â€…0.05 vs. 6.92 ±â€…0.05 g/dL). Calves exposed to small ∆THI at 0 d had greater STP compared with calves exposed to medium ∆THI (7.00 ±â€…0.06 vs. 6.75 ±â€…0.05 g/dL). No association was found between HS, and ∆THI categories and the TPI category. The odds of scours were about 2 times greater in HS calves compared with non-HS calves at all exposure periods. In addition, HS calves were affected by scours between 9 and 15 d earlier than non-HS calves. Furthermore, high ∆THI favored the development of respiratory problems compared with medium and low ∆THI. Assessment of extreme THI values and THI fluctuations provides a research opportunity for assessing thermal stress in dairy heifer calves raised in dry climate.

The effects of the exposure to daily maximum temperature-humidity index (THI) and daily THI fluctuations (∆THI, maximum­minimum THI) around birth (−2 d, birth date [0 d], +2 d, and +7 d) on serum total protein (STP) and health of preweaned Holstein heifers were evaluated. Heifer calves exposed to small ∆THI (<20 units) at 0 d had greater STP compared with medium ∆THI (≥20 to ≤30 units). At all exposure periods, heat stress (THI > 70 units) increased the occurrence of scours at earlier age, whereas small and large ∆THI favored the presentation of scours and respiratory disease, respectively.

Puberty classifications in beef heifers are moderately to highly heritable and associated with candidate genes related to cyclicity and timing of puberty.

Introduction: Pubertal attainment is critical to reproductive longevity in heifers. Previously, four heifer pubertal classifications were identified according to attainment of blood plasma progesterone concentrations > 1 ng/ml: 1) Early; 2) Typical; 3) Start-Stop; and 4) Non-Cycling. Early and Typical heifers initiated and maintained cyclicity, Start-Stop started and then stopped cyclicity and Non-Cycling never initiated cyclicity. Start-Stop heifers segregated into Start-Stop-Discontinuous (SSD) or Start-Stop-Start (SSS), with SSD having similar phenotypes to Non-Cycling and SSS to Typical heifers. We hypothesized that these pubertal classifications are heritable, and loci associated with pubertal classifications could be identified by genome wide association studies (GWAS). Methods: Heifers (n = 532; 2017 - 2022) genotyped on the Illumina Bovine SNP50 v2 or GGP Bovine 100K SNP panels were used for variant component estimation and GWAS. Heritability was estimated using a univariate Bayesian animal model. Results: When considering pubertal classifications: Early, Typical, SSS, SSD, and Non-Cycling, pubertal class was moderately heritable (0.38 ± 0.08). However, when heifers who initiated and maintained cyclicity were compared to those that did not cycle (Early+Typical vs. SSD+Non-Cycling) heritability was greater (0.59 ± 0.19). A GWAS did not identify single nucleotide polymorphisms (SNPs) significantly associated with pubertal classifications, indicating puberty is a polygenic trait. A candidate gene approach was used, which fitted SNPs within or nearby a set of 71 candidate genes previously associated with puberty, PCOS, cyclicity, regulation of hormone secretion, signal transduction, and methylation. Eight genes/regions were associated with pubertal classifications, and twenty-two genes/regions were associated with whether puberty was attained during the trial. Additionally, whole genome sequencing (WGS) data on 33 heifers were aligned to the reference genome (ARS-UCD1.2) to identify variants in FSHR, a gene critical to pubertal attainment. Fisher's exact test determined if FSHR SNPs segregated by pubertal classification. Two FSHR SNPs that were not on the bovine SNP panel were selected for additional genotyping and analysis, and one was associated with pubertal classifications and whether they cycled during the trial. Discussion: In summary, these pubertal classifications are moderately to highly heritable and polygenic. Consequently, genomic tools to inform selection/management of replacement heifers would be useful if informed by SNPs associated with cyclicity and early pubertal attainment.

Immunogenicity, safety and dual DIVA-like character of a recombinant candidate vaccine against neosporosis in cattle.

Neosporosis is the major infectious cause of abortion and reproductive losses in cattle worldwide; however, there are no available vaccines or drugs to control this disease. Recently, a dual (positive and negative) DIVA-like (Differentiation of Infected from Vaccinated Animals) vaccine was evaluated in a pregnant mouse model of neosporosis, showing promising immunogenic and protective results. The current report aimed to study the safety, the dose-dependent immunogenicity and the dual DIVA-like character of a recombinant subunit vaccine composed of the major surface antigen from Neospora caninum (rNcSAG1) and the carrier/adjuvant Heat shock protein 81.2 from Arabidopsis thaliana (rAtHsp81.2) in cattle. Healthy heifers were separated and assigned to experimental groups A-F and subcutaneously immunized with 2 doses of vaccine formulations 30 days apart as follows: A (n = 4): 50 µg rNcSAG1 + 150 µg rAtHsp81.2; B (n = 4): 200 µg rNcSAG1 + 600 µg rAtHsp81.2; C (n = 4): 500 µg rNcSAG1 + 1,500 µg rAtHsp81.2; D (n = 3): 150 µg rAtHsp81.2; E (n = 3):1,500 µg rAtHsp81.2, and F (n = 3) 2 ml of sterile PBS. The immunization of heifers with the different vaccine or adjuvant doses (groups A-E) was demonstrated to be safe and did not modify the mean value of the evaluated serum biomarkers of metabolic function (GOT/ASP, GPT/ALT, UREA, Glucose and total proteins). The kinetics and magnitude of the immune responses were dose-dependent. The higher dose of the vaccine formulation (group C) stimulated a broad and potent humoral and cellular immune response, characterized by an IgG1/IgG2 isotype profile and IFN-γ secretion. In addition, this was the first time that dual DIVA-like character of a vaccine against neosporosis was demonstrated, allowing us to differentiate vaccinated from infected heifers by two different DIVA compliant test approaches. These results encourage us to evaluate its protective efficacy in infected pregnant cattle in the future.

Growth and feed efficiency of Nordic Red Dairy Cattle, Holstein, and their F1 crossbreeds when limiting feed energy concentration in prepubertal heifers.

Milk production and overall dairy farm economics depend on rearing dairy heifers. This study investigated the presence of a genotype by environment interaction in Holstein (HOL), Nordic Red Dairy Cattle (RDC), and their F1 crossbreeds (HOLxRDC) when provided different feed rations. The aim of our study was to assess how different energy concentrations in feed rations affect growth, body condition scores, feed intake, and feed efficiency in the 3 groups during the prepubertal period. The 3 breed groups were randomly allocated to receive either a standard or a low energy feed ration. HOL heifers exhibited reduced growth and a lower body condition score when they were fed the low energy feed ration. In contrast, the RDC heifers demonstrated similar growth rates with the different feed rations and maintained similar body condition scores irrespective of feed energy concentration. HOLxRDC crossbred heifers performed as an intermediate between the HOL and RDC groups. There were significant differences in dry matter intake and energy intake in the HOL and HOLxRDC groups depending on feed ration treatment. The RDC heifers had similar feed intake irrespective of treatment. There were no significant differences in the feed conversion ratio between breeds and feed treatments. These results indicate the presence of a genotype by environment interaction in prepubertal HOL and RDC heifers in response to differences in feed ration treatment. Due to the influence of prepubertal growth on future milk production, reproduction, and health status, it is important to be aware of breed-specific requirements during the prepubertal period, particularly in mixed-breed and crossbred groups, to optimize growth rates and production potential.

Influence of differing levels of concentrate on circulating cytokine concentrations in beef heifers.

Components of the immune system (e.g., cytokines and chemokines) can influence reproductive efficiency. Characterizing the influence nutrition has on shifts in circulating cytokine concentrations will allow for a better understanding of reproductive efficiency in beef cattle. This study aimed to determine the effect of diet composition on circulating cytokine concentrations of beef heifers. Using a 3 × 3 Latin square design, pubertal Bos taurus-influenced rumen-cannulated heifers (n = 15) were fed a diet based on different concentrate percentages. The treatment period consisted of 28-d feeding periods with a washout interval of 21 d. Treatment groups were fed 100% grass hay (high forage; HF), 60% grass hay with 40% corn-based concentrate (intermediate; INT), and 25% grass hay with 75% corn-based concentrate (high grain; HG). Heifers were offered 2% of their body weight in feed daily. Blood was collected on days 0 and 28 of the treatment period for cytokine analysis. Plasma cytokine concentrations were quantified using RayBiotech Quantibody Bovine Cytokine Array Q1 kit according to manufacturer instructions. Concentrations of interferon gamma-induced protein 10 (IP10) linearly decreased with an increased concentrate diet (P = 0.037). Concentrations of IP10 differed for heifers consuming HF diet vs. HG diet (3,069.52 vs. 1,001.84 ±â€…669.01 pg/mL, respectively) and heifers consuming INT diet vs. HG diet (2,886.77 vs. 1,001.84 ±â€…669.01 pg/mL, respectively); however, there were no significant differences in IP10 concentrations between HF and INT heifers. There was a tendency for interleukin-1 family member 5 (IL1F5) concentrations to be lower for heifers consuming the HG diet compared to INT diet (P = 0.08). Results suggest that heifers consuming a high-concentrate diet have lower concentrations of IP10 and IL1F5. Additional research is necessary to better understand the dietary influence on the immune system in developing heifers.

Metagenomic and metabolomic analyses reveal differences in rumen microbiota between grass- and grain-fed Sanhe heifers.

Introduction: The aim of this study was to investigate the effects of diets on the composition and function of rumen microbiome and metabolites in Sanhe heifers. Methods: Metagenomic and metabolomic analyses were performed using rumen fluid samples collected from Sanhe heifers (n = 20) with similar body weights and ages from grass-fed and grain-fed systems. Results: The grain-fed group exhibited more intensive rumen fermentation than the grass-fed group. However, the grass-fed group exhibited carbohydrate metabolism and methane production higher than that of the grain-fed group; these increases were observed as a higher abundance of various bacterial phyla (Firmicutes, Bacteroidetes, Actinobacteria, Lentisphaerae, and Verrucomicrobia), families (Lachnospiraceae, Eubacteriaceae, and Eggerthellaceae), and the archaeal family Methanobacteriaceae. A comparison of genes encoding carbohydrate-active enzymes, using Kyoto Encyclopedia of Genes and Genome profiles, revealed noteworthy differences in the functions of rumen microbiota; these differences were largely dependent on the feeding system. Conclusion: These results could help manipulate and regulate feed efficiency in Sanhe cattle.

Effects of a moderate exercise regimen on development and puberty attainment of beef heifers reared in drylots at a high stocking density.

This experiment evaluated growth, physiological responses, and puberty attainment in beef heifers reared in drylots with a high stocking density, and provided or not with a moderate exercise regimen. A total of 180 heifers (75% Angus × 25% Brahman) were used in this experiment replicated over 2 yr. Each year, 90 heifers were ranked by age (264 ±â€…1 d) and body weight (BW on day -3; 200 ±â€…2 kg) on day 0, and assigned to a) one of six drylot pens (10 × 14 m pens; 10 heifers per pen) with a stocking density of 14 m2/heifer (DENS), or b) one of three pastures (2-ha pastures; 10 heifers per pasture) with a stocking density of 2,000 m2/heifer (CON). Beginning on day 15, three DENS pens were given access to an exercise area (DENS-EX) 3 times/wk (1 h). Negligible forage was available for CON, whereas heifers from all treatments received the same limit-fed diet (~13 kg/heifer daily). Shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 225 to calculate BW gain. Temperament was evaluated on days 0, 128, and 224. Heifers were fitted with a pedometer behind their shoulder on day 0 to record physical activity. Pedometer results and blood samples were collected weekly for progesterone analysis. Hair samples from the tail switch were collected every 28 d. Data were analyzed with pen or pasture as an experimental unit, via ANOVA using the MIXED or GLIMMIX procedures of SAS (SAS Inst. Inc., Cary, NC). Heifers from CON had more (P < 0.01) steps per week compared with DENS and DENS-EX (23,973, 6,706, and 12,354 steps/wk, respectively; SEM = 1,247), and DENS-EX heifers had more (P < 0.01) steps per week compared with DENS. No treatment effects (P ≥ 0.91) were detected for heifer BW gain (~0.820 kg/d). Hair cortisol concentrations were greater (P ≤ 0.05) in DENS and DENS-EX compared with CON beginning on day 56. Exit velocity and temperament score were greater (P ≤ 0.05) in DENS compared with DENS-EX and CON on day 224. Puberty attainment was delayed (treatment × day; P < 0.01) in DENS compared with DENS-EX and CON. A greater (P ≤ 0.05) proportion of CON were pubertal by day 105 compared with DENS and DENS-EX (30.0%, 11.6%, and 15.0%, respectively; SEM = 6.5), while a greater (P < 0.05) proportion of CON and DENS-EX were pubertal by day 154 compared to DENS (61.7%, 66.7%, and 43.3%, respectively; SEM = 6.5). Rearing replacement heifers in drylots with high stocking density has detrimental effects on their puberty attainment, and the moderate exercise regimen partially alleviated this negative outcome.

Replacement beef heifers are often reared in drylots with high stocking density to facilitate feeding and management, or to intensify beef production as availability of grazing areas becomes limited. Studies from our group, however, demonstrated that drylot heifers experience delayed puberty attainment compared with heifers reared on pastures. This negative outcome was associated with chronic stress caused by confinement and restricted physical activity; the latter being a key animal welfare factor with direct effects on reproductive development. Based on this rationale, this experiment evaluated growth, stress-related physiological responses, and puberty attainment heifers reared in drylots and exposed or not to a moderate exercise regimen. Moreover, drylot heifers were compared to contemporary cohorts being reared on pasture. As expected, heifers reared in drylots experienced heightened stress-related physiological responses and delayed puberty attainment compared to pasture heifers. Exposing drylot heifers to the moderate exercise regimen did not alleviate the physiological consequences of chronic stress, but lessened the delay in puberty attainment compared with non-exercised drylot cohorts. Therefore, stocking density and exercise opportunities should be considered to improve heifer welfare and reproductive development in intensive drylot systems, as lack of exercise directly contributes to delayed reproductive development of drylot heifers.

Disrupted one-carbon metabolism in heifers negatively affects their health and physiology.

The objective of this study was to determine the dose-dependent response of one-carbon metabolite (OCM: methionine, choline, folate, and vitamin B12) supplementation on heifer dry matter intake on fixed gain, organ mass, hematology, cytokine concentration, pancreatic and jejunal enzyme activity, and muscle hydrogen peroxide production. Angus heifers (n = 30; body weight [BW] = 392.6 ±â€…12.6 kg) were individually fed and assigned to one of five treatments: 0XNEG: total mixed ration (TMR) and saline injections at days 0 and 7 of the estrous cycle, 0XPOS: TMR, rumen-protected methionine (MET) fed at 0.08% of the diet dry matter, rumen-protected choline (CHOL) fed at 60 g/d, and saline injections at days 0 and 7, 0.5X: TMR, MET, CHOL, 5-mg B12, and 80-mg folate injections at days 0 and 7, 1X: TMR, MET CHOL, 10-mg vitamin B12, and 160-mg folate at days 0 and 7, and 2X: TMR, MET, CHOL, 20-mg vitamin B12, and 320-mg folate at days 0 and 7. All heifers were estrus synchronized but not bred, and blood samples were collected on days 0, 7, and at slaughter (day 14) during which tissues were collected. By design, heifer ADG did not differ (P = 0.96). Spleen weight and uterine weight were affected cubically (P = 0.03) decreasing from 0XPOS to 0.5X. Ovarian weight decreased linearly (P < 0.01) with increasing folate and B12 injection. Hemoglobin and hematocrit percentage were decreased (P < 0.01) in the 0.5X treatment compared with all other treatments. Plasma glucose, histotroph protein, and pancreatic α-amylase were decreased (P ≤ 0.04) in the 0.5X treatment. Heifers on the 2X treatment had greater pancreatic α-amylase compared with 0XNEG and 0.5X treatment. Interleukin-6 in plasma tended (P = 0.08) to be greater in the 0XPOS heifers compared with all other treatments. Lastly, 0XPOS-treated heifers had reduced (P ≤ 0.07) hydrogen peroxide production in muscle compared with 0XNEG heifers. These data imply that while certain doses of OCM do not improve whole animal physiology, OCM supplementation doses that disrupt one-carbon metabolism, such as that of the 0.5X treatment, can induce a negative systemic response that results in negative effects in both the dam and the conceptus during early gestation. Therefore, it is necessary to simultaneously establish an optimal OCM dose that increases circulating concentrations for use by the dam and the conceptus, while avoiding potential negative side effects of a disruptive OCM, to evaluate the long-term impacts of OCM supplementation of offspring programming.

The feeding of one-carbon metabolites (including methionine and B vitamins) has been shown to improve fetal growth and milk production in species such as mice, sheep, and dairy cattle. Extending this to beef cattle around the time of breeding is a growing area of research. Our group previously determined that one-carbon metabolite supplementation to beef heifers altered the abundance of circulating methionine-folate cycle intermediates in a dose-dependent manner. Therefore, we aimed to determine a whole-body response to one-carbon metabolite supplementation in heifers by measuring the effects on specific physiological systems as well as a total systemic response. We determined that treatments that negatively altered the methionine-folate cycle yielded a fundamental negative whole-body response to supplementation.

Effect of Milk-Feeding Frequency and Calcium Gluconate Supplementation on Growth, Health, and Reproductive and Metabolic Features of Holstein Heifers at a Rearing Farm.

We compared the effects of milk-feeding in 288 Holstein calves (72 per group) which were fed twice (2F) or thrice (3F) daily, with or without the addition of hydrogenated fat-embedded calcium gluconate (G) supplemented in the starter food and in the daily diet up to the age of 9 months, on the calves' metabolism, growth, health, and reproductive efficiency up to first pregnancy. The calves received 6 L of milk replacer (130 g/L) and had ad libitum access to water and textured calf starter with or without gluconate. Gluconate supplementation promoted a "catch-up" in growth in supplemented calves compared to their counterparts that did not receive gluconate. Gluconate appeared to reduce animal metabolic stress during key events, such as weaning and transfer into open-door pens, reducing fructosamine (352.61 vs. 303.06 in 3FG and 3F, respectively; p = 0.028) and urea (3F revealed the highest values compared with the other three groups: 19.06 for 3F vs. 13.9 (2F), 13.7 (2FG), and 14.3 (3FG), respectively, p = 0.002) from weaning onwards. The feeding of dairy calves with milk replacer three rather than two times per day tended to be associated with better health from weaning to 4 months old; parameters such as ultrasound lung score and calf health score improved over time (p < 0.001). Thrice-daily feeding with milk replacer tended to reduce the number of artificial inseminations per pregnancy in heifers by 0.2 points (p = 0.092). We confirmed significant correlations between early health and growth parameters and reproductive efficiency and a positive correlation between body weight and average daily weight gain and the thickness of the back fat layer in young heifers (r = 0.245; p < 0.0001; r = 0.214; p < 0.0001 respectively). Our study was conducted on a commercial farm with reasonably effective animal management, so baseline welfare was likely satisfactory.

Effects of late gestational nutrient restriction on uterine artery blood flow, placental size, and cotyledonary mRNA expression in primiparous beef females.

Fall-calving primiparous beef females [body weight (BW): 451 ±â€…28 (SD) kg; body condition score (BCS): 5.4 ±â€…0.7] were individually-fed either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to parturition. Doppler ultrasonography of both uterine arteries was conducted pre-treatment and every 21 d from days 181 to 265 of gestation. Expelled placentas were collected, and ipsilateral cotyledonary tissue was sampled to assess relative messenger ribonucleic acid (mRNA) expression. Placentas were separated into ipsilateral and contralateral sides, dissected (cotyledonary vs. intercotyledonary), and dried. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Uterine blood flow included day and nutritional plane × day as repeated measures. We previously reported that post-calving, NR dams weighed 64 kg less and were 2.0 BCS lower than CON, but calf birth weight was not affected. Maternal heart rate was less (P < 0.001) for NR dams than CON after nutritional planes began. Nutritional plane did not affect (P ≥ 0.20) uterine artery hemodynamics, but all variables were affected (P ≤ 0.04) by day. Contralateral cotyledonary and placental weight were less (P ≤ 0.04) and contralateral intercotyledonary weight and number of cotyledons tended to be less (P ≤ 0.10) for NR dams than CON, but ipsilateral and whole placental weights were not affected (P ≥ 0.13). Ipsilateral placental weight as a percentage of total placental weight was greater (P = 0.03) for NR dams than CON. Whole placental cotyledonary: intercotyledonary weight was less (P = 0.01) for NR dams than CON. Placental efficiency was not affected (P = 0.89) by nutritional plane. Cotyledonary relative mRNA expression of GLUT3 and SNAT2 was greater (P ≤ 0.05) and relative expression of GLUT1, GLUT4, and NOS3 tended to be greater (P ≤ 0.07) for NR dams than CON. Nutritional plane did not affect (P ≥ 0.13) relative mRNA expression of GLUT5, 4F2hc, CAT1, LAT1, LAT2, VEGFA, FLT1, KDR, GUCY1B3, and PAG2. Despite less contralateral placental growth, beef heifers experiencing late gestational nutrient restriction maintained uterine artery blood flow and total placental mass and had 4 nutrient transporters and 1 angiogenic factor upregulated in cotyledons, all of which likely contributed to conserving fetal growth.

Nutrient requirements increase substantially during late gestation in the beef female to support fetal, uteroplacental, and mammary growth, and in the still-growing heifer, nutrients are also needed for maternal tissue growth. During pregnancy, the placenta serves as the interface for the metabolism and transport of nutrients, gases, and wastes between maternal and fetal circulations. Inadequate gestational nutrition can result in placental insufficiency and intrauterine growth restriction of the offspring, resulting in postnatal consequences. How late gestational undernutrition in beef heifers impacts the factors involved in placental nutrient transport capacity is poorly understood. We observed that late gestational nutrient restriction in heifers decreased maternal heart rate, but total uterine artery blood flow was not affected. Additionally, total placental mass was maintained, while cotyledonary expression of 4 nutrient transporters and an angiogenic factor were upregulated in placentas of nutrient restricted dams, which collectively allowed for similar calf birth weights as adequately-fed dams.

Do the blood anti-Müllerian hormone concentrations in young females correlate with the ovarian follicular population later in life in water buffalo?

In this longitudinal study, the anti-Müllerian hormone (AMH) levels in blood were determined in 32 Murrah buffalo females at 8, 10, 12, 16 and 19 months of age when females were synchronized and the antral follicular population (AFP) was estimated. Correlations of AFP to the AMH level at 19 months of age and retrospectively to younger ages were investigated. Then females were split into high and low AFP, and their AMH levels were compared for all ages and tested as predictors of AFP categories. The highest AMH level (p < .05) was detected at 8 months, reducing but not differing (p > .05) at 10, 12 and 16 months then reducing again (p < .05) at 19 months of age. The mean AFP was 17.6 ± 6.3 follicles, and it was positively correlated with AMH in all ages tested. High AFP females had approximately two times more antral follicles than low AFP (p < .05) and their AMH levels were higher (p < .01) than in low AFP ones in all ages. Only at 8 months, AMH levels can be used to precociously detect high AFP heifers (a cut-off point of 464.7 pg/mL; p < .05), while low AFP heifers could be detected by AMH measurements at 8, 10, 12 and 16 months of age (p < .05). We conclude that AMH of buffalo calves correlates with AFP of heifers later in life and depending on the age, its levels could be used to identify future females with low or high AFP.

Impacts of economic factors influencing net returns of beef feedlot heifers administered two implant programs and fed for differing days-on-feed from pooled randomized controlled trials.

The objective of this research was to evaluate the effects of two implant programs and differing days-on-feed (DOF) on net returns of beef feedlot heifers using sensitivity analyses of key economic factors. Crossbred beef heifers [n = 10,583; initial weight 315 kg (± 20.1 SD)] were enrolled across three trials (one Kansas, two Texas feedlot trials). Heifers were blocked by arrival and randomly allocated to one of six pens, resulting in a total of 144 pens and 24 blocks. Pen was randomly assigned to treatment as a 2 × 3 factorial. Implant programs were: IH + 200-Revalor-IH at initial processing, and a terminal implant after approximately 90 DOF (Revalor-200), or, XH-a single implant at initial processing (Revalor-XH). The DOF treatments were: heifers fed to a standard baseline endpoint (BASE) or heifers fed for an additional + 21 or + 42 d beyond BASE. Pen-level partial budgets were used for economic sensitivity analyses, which varied price points of single pricing components with all other components fixed. Variable components were live-fed cattle prices, base carcass prices (i.e., dressed), Choice-Select spread (CS-spread), and feed and yardage prices (FYP). For each, a Low, Mid-Low, Middle, Mid-High, and High price was chosen. Linear mixed models were fit for statistical analyses (α = 0.05). There were no significant two-way interactions (P-values ≥ 0.14). Regardless of the variable component evaluated, XH heifers had poorer net returns than IH + 200 at all prices (P ≤ 0.04). Selling live, the + 21 and (or) + 42 heifers had lower net returns than BASE at every fed cattle price point (P < 0.01). Selling dressed, the + 21 and (or) + 42 heifers had lower returns than BASE at Low, Mid-Low, and Middle fed cattle base prices (P < 0.01); there were no significant DOF differences at Mid-High, or High prices (P ≥ 0.24). Net returns were lower for + 42 than BASE at all CS-spreads (P ≤ 0.03), while BASE and + 21 did not differ significantly. Longer DOF had lower net returns than BASE when selling live at every FYP (P < 0.01) except at the Low price (P = 0.14). Selling dressed, there was no significant effect of DOF at Low or Mid-Low FYP (P ≥ 0.11); conversely, extended DOF had lower net returns than BASE at Middle, Mid-High, and High FYP (P < 0.01). Overall, there was minimal economic evidence to support extending feedlot heifer DOF beyond the BASE endpoint, and when feeding longer, larger reductions in return were observed when marketing live as opposed to dressed.

Replacing alfalfa hay with a novel alfalfa leaf pellet product (ProLEAF MAX) and/or alfalfa stems (ProFiber Plus) in the diet of developing dairy heifers alters dry matter intake, but does not negatively impact growth or development.

Alfalfa is a commonly grown forage in the Intermountain West region of the United States and is often included in the diet of dairy cattle. Alfalfa provides a variety of different nutrients, but the nutrient content of alfalfa varies depending on factors such as the soil, region, cutting, and climate. However, alfalfa leaves tend to have less variation in their nutrient content than alfalfa stems. Fractionating alfalfa may be one way to improve control of nutrients provided when developing a ration for developing dairy heifers. The purpose of this study was to determine whether including fractionated alfalfa in the diet impacts the growth or conception rates of developing dairy heifers. Heifers were allocated to one of three treatments: a control group fed a typical diet (CON; n = 8), a diet that replaced alfalfa with fractionated alfalfa leaf pellets and alfalfa stems (ProLEAF MAX + ProFiber Plus; PLM + PFP; n = 8), or a diet that replaced alfalfa with alfalfa stems (PFP; n = 8) for 85 d. Heifers were fed individually twice daily and weight, hip height (HH), and wither height (WH) were recorded every 14 d. Additionally, blood was collected every 28 d, and conception rates were recorded at the end of the trial. Heifers receiving the PFP diet consumed less dry matter (P = 0.001) than the CON treatment. Analyses were then conducted to determine nutrient intake and heifers receiving the PFP diet also consumed less neutral detergent fiber (P = 0.02), acid detergent fiber (P = 0.02), crude protein (P = 0.001), and net energy for maintenance (P = 0.001) than heifers consuming the CON diet; however, no differences (P > 0.10) were observed between heifers fed the CON and PLM + PFP diets. Analysis of body weight gain over the feeding period showed no difference (P = 0.52) among heifers consuming the different treatment diets. Additionally, treatment did not affect average daily gain (P = 0.49), gain:feed (P = 0.82), HH gain (P = 0.20), or WH gain (P = 0.44) among heifers receiving different diets. Treatment × time altered (P < 0.001) blood urea nitrogen when analyzed as a repeated measure. Total feed cost was lowest (P < 0.001) for the PFP diet and cost of gain tended (P = 0.09) to be increased for the PLM + PFP diet compared to the CON diet. Overall, these data indicate that including alfalfa stems in a developing heifer diet may decrease dry matter intake, lower input costs, and increase profitability, without negatively impacting growth.

Maternal pre- and postpartum supplementation of a Bacillus-based DFM enhanced cow and calf performance.

This study evaluated the effects of maternal supplementation of a Bacillus-based direct-fed microbial (DFM) on the physiology and growth performance of Bos indicus-influenced cow-calf pairs. On day 0 (~139 d before expected calving date), 72 fall-calving, Brangus crossbred beef heifers (20 to 22 mo of age) pregnant with first offspring were stratified by their initial body weight (BW; 431 ±â€…31 kg) and body condition score (BCS; 6.0 ±â€…0.36; scale 1 to 9), and randomly allocated into 1 of 12 bahiagrass pastures (1 ha and six heifers per pasture). Treatments were randomly assigned to pastures (six pastures per treatment) and consisted of heifers supplemented with 1 kg/d of soybean hulls (dry matter, DM) that was added (BAC) or not (CON) with DFM containing Bacillus subtilis and B. licheniformis (Bovacillus; Chr. Hansen A/S, Hørsholm, Denmark). Treatments were provided from days 0 to 242 (139 ±â€…4 d prepartum to 104 ±â€…4 d postpartum). Calves were weaned on day 242 (96 ±â€…30 d of age) and then allocated into 1 of 16 drylot pens and fed the same concentrate at 3.25% of BW (DM) until day 319. Maternal treatment effects were not detected (P ≥ 0.29) for herbage allowance and forage chemical composition. Heifer BCS on days 39 and 63 tended (P ≤ 0.09) to be greater for BAC vs. CON heifers, whereas heifer BCS on day 91 was greater (P = 0.01) for BAC vs. CON heifers. Heifer BCS did not differ (P ≥ 0.20) between treatments on days 179 and 242. Plasma glucose concentration did not differ from days 0 to 63 (P ≥ 0.14) but were greater (P < 0.01) on day 179 and tended (P = 0.09) to be greater on day 242 for BAC vs. CON heifers. Calf BW at birth, ADG from birth to weaning, and BW at weaning did not differ (P ≥ 0.19) between treatments, but calf BW at drylot exit (day 319) was greater (P = 0.05) for BAC vs. CON calves. Maternal treatment effects were not detected (P ≥ 0.42) for calf serum concentration of IgG at birth and postvaccination plasma concentrations of glucose, cortisol, and haptoglobin. Serum titers against bovine respiratory syncytial virus (BRSV) were greater (P = 0.04) for BAC vs. CON calves on day 287, whereas seroconversion against parainfluenza-3 virus (PI-3) was greater (P < 0.01) for BAC vs. CON calves on day 271. Thus, maternal supplementation of a Bacillus-based DFM increased prepartum BCS gain and postpartum plasma glucose concentration of heifers and led to positive carryover effects on postweaning BW gain and humoral immune response in their offspring.

Direct-fed microbials (DFM), such as Bacillus spp., have been shown to produce a wide variety of enzymes related to nutrient digestion and to support gastrointestinal tract immune function and integrity, leading to increased nutrient digestibility and cattle performance. Nutritional management of beef cows during gestation and early lactation has been associated with enhanced future offspring growth performance and immune response following birth. The present study combined the use of Bacillus-based DFM for pregnant heifers during critical production stages (late gestation and early lactation) to promote the overall performance of heifers and their offspring. Heifers offered Bacillus-based DFM had greater body condition score at calving and postpartum plasma concentration of glucose, whereas their offspring had similar body weight at birth, but greater growth performance when fed relatively high amounts of protein and energy in drylot compared to cohorts born from heifers that did not receive Bacillus-based DFM supplementation.

Magnitude and persistence of higher estrus-associated temperatures in beef heifers and suckled cows.

Higher estrus-associated temperatures (HEAT) are a hallmark feature in sexually active females. The overarching aim of this study was to characterize the variability, magnitude, and persistence of HEAT in heifers and suckled beef cows as well as identify associated factors when occurring during thermoneutral conditions at the onset of the spring breeding season. In both heifers and cows, estrus was induced using a 7-d controlled internal drug release (CIDR)-PGF2α protocol. Vaginal temperature after prostaglandin F2α administration was recorded every 5 min using a Thermochron iButton affixed to a blank CIDR (containing no progesterone). Estrus was defined as when a heifer first stood to be mounted or when a cow had an Estrotect patch score of 3 or 4. Level of HEAT varied among individual animals. When comparing common HEAT variables using a mixed model with date nested within a year, maximum HEAT (39.9 ±â€…0.1 and 40.0 ±â€…0.1 °C) and duration (15.5 ±â€…0.8 and 15.4 ±â€…0.7) were similar in heifers and cows, respectively. However, the magnitude and persistence of HEAT differed. Total area under the HEAT curve was 117.1 ±â€…13.5 and 158.7 ±â€…12.3 for heifers vs cows, respectively (P = 0.0571). Further, 42.9% of heifers and 49% of cows had maximum HEAT ≥ 40 °C which persisted up to 6.5 and 10 h, respectively. When ambient conditions were predominantly thermoneutral, temperature humidity index had minimal impact on HEAT (mixed model, repeated measures over time). Toward identifying associated factors with different aspects of HEAT using best fit hierarchical linear regression models, baseline vaginal temperature and baseline duration were the most highly associated independent variables. Follicle size, estradiol and progesterone levels, and other available animal-related variables (e.g., age, weight, hair coat score) explained only a small amount of variation in HEAT. In summary, level of HEAT varies in estrus females even under thermoneutral conditions. Because HEAT can persist for an extended time, direct effects on fertility important components are unavoidable. Whether HEAT is a good or bad component of the periovulatory microenvironment is the basis of ongoing and future studies.

When striving for a pregnancy, estrus is a critically important event. Higher estrus-associated temperatures (HEAT) are a hallmark feature in sexually active females. The importance of HEAT for pregnancy, however, remains unclear. Toward filling this critical knowledge gap, efforts described in the current study focused on examining variability of HEAT in individual animals, 2) defining the magnitude and persistence of HEAT, 3) identifying HEAT-associated factors, and 4) examining the similarity of HEAT between heifers and suckled beef cows when occurring at the onset of a spring breeding season. Although the magnitude and persistence of HEAT varied, 42.9% of heifers and 49% of cows reached temperatures ≥ 40 °C which in some cases persisted up to 6.5 and 10 h, respectively. When attempting to identify factors that could explain why some females exhibiting estrus remained hot for an extended time, available animal and environmental data contributed little. Even so, because HEAT can persist for an extended time, direct effects on fertility important components are unavoidable. Whether too much HEAT is good or bad for pregnancy is the basis of ongoing and future studies.