Gestation Length Research Articles

Factors influencing calving difficulty and gestation length in dairy cows inseminated with beef sires

Producing calves with higher economic value by utilizing semen from beef breeds in dairy herds (Beef-on-Dairy, BoD) has become more common in recent times. Such crossbreed calves promise better carcass conformation and higher consumer acceptance due to the better flavor, but the widespread adaptation of BoD requires careful consideration of the sire breed to maximize the benefits. In this regard, two major traits of interest are calving difficulty and gestation length due to associated costs. In this study, 3,966 BoD calves from crossing Holstein dams with beef sires of the breeds Angus (n = 811), Belgian Blue (n = 2841), Limousin (n = 169) and Wagyu (n = 145) from 122 farms were evaluated to determine differences in calving difficulty and gestation length using binary logit and linear regression models. Lowest calving difficulty was observed for Wagyu crossbreds while Limousin crossbreds had the highest calving difficulty incidences. Selected sires from Angus and Belgian Blue breeds were also compared using chi-square analysis for differences in calving difficulty. The risk of calving difficulty was 1.94 times higher for male calves. Heifers had a significantly higher risk for calving difficulty when compared with the multiparous cows in the study. Calves with higher birth weight and longer gestation length were more prone to calving problems. For gestation length, Angus crossbreds had the shortest gestation (280.2 d), while the longest gestation (287.6) was observed in Limousin crossbreds. To maximize the benefits of the BoD breeding strategy, selecting appropriate sire breeds and within-breed sire selection for economically important traits, such as birth weight, appropriate gestation length, and reduced calving difficulty, may provide a viable solution.

Maternal mitochondrial DNA copy number and methylation as possible predictors of pregnancy outcomes in a Michigan pregnancy cohort

ABSTRACT Background: Little is understood about the role of mitochondria in pregnancy-related adaptations. Therefore, we evaluated associations of maternal early-to-mid pregnancy mitochondrial DNA copy number (mtDNAcn) and mtDNA methylation with birth size and gestational length. Methods: Michigan women (n=396) provided venous bloodspots at median 11 weeks gestation to quantify mtDNAcn marker NADH-ubiquinone oxidoreductase chain 1 (ND1) using real-time quantitative PCR and mtDNA methylation at several regions within four mitochondria-specific genes using pyrosequencing: MTTF (mitochondrially encoded tRNA phenylalanine), DLOOP (D-loop promoter region, heavy strand), CYTB (cytochrome b), and LDLR (D-loop promoter region, light strand). We abstracted gestational length and birthweight from birth certificates and calculated birthweight z-scores using published references. We used multivariable linear regression to evaluate associations of mtDNAcn and mtDNA methylation with birthweight and birthweight z-scores. Cox Proportional Hazards Models (PHMs) and quantile regression characterized associations of mitochondrial measures with gestational length. We also considered differences by fetal sex. Results: Using linear regression and Cox PHMs, mtDNAcn was not associated with birth outcomes, whereas associations of mtDNA methylation with birth outcomes were inconsistent. However, using quantile regression, mtDNAcn was associated with shorter gestation in female newborns at the upper quantiles of gestational length, but with longer gestational length in males at the lower quantiles of gestational length. Maternal LDLR, DLOOP, and MTTF methylation was associated with longer gestational length in females at the upper quantiles and in males at lower gestational length quantiles. Conclusions: Maternal mtDNAcn and mtDNA methylation were associated with gestational length in babies born comparatively early or late, which could reflect adaptations in mitochondrial processes that regulate the length of gestation.

The lifespan of corpora lutea in nonpregnant females is positively correlated with gestation length

Abstract In mammals, a temporary endocrine gland called the corpus luteum forms on the ovary shortly after ovulation and is required for the initiation and maintenance of early pregnancy. However, the corpus luteum persists even when fertilization or pregnancy does not occur, and species-specific variation in the length of this persistence remains enigmatic. Here we perform a comparative evolutionary study across 72 species and show that corpus luteum lifespan in nonpregnant females is positively correlated with gestation length. We argue that the most likely explanation for this correlation is physiological inertia. The corpus luteum begins secreting progesterone prior to implantation, and when pregnancy does not occur it takes time for females to degrade it and prepare the next reproductive cycle. Our study suggests that this physiological inertia is stronger in species with long gestation times.

Prevalence and factors associated with extrauterine growth restriction in premature infants

Background Extrauterine growth restriction (EUGR) is common in preterm infants and has been shown to affect their neurodevelopment. Significant variability exists in the criteria used to define EUGR and a standard definition has not yet been established. Several factors associated with EUGR have been identified, yet EUGR remains a problem in preterm infants. There is still much to be explored regarding risk factors associated with EUGR. Objective To determine the prevalence and factors associated with EUGR in preterm infants. Methods This cross-sectional study included randomly selected premature infants (<37 weeks gestational age) who were admitted to levels II and III Neonatal Ward at Prof. Dr. I.G.N.G. Ngoerah Hospital from May 2022 to August 2023. Results Of 185 subjects, the prevalence of EUGR in preterm infants was 47% and there were significant associations between EUGR and birth weight <1500 g (PR 8.814; 95%CI: 3.943 to 19.7; P=0.000), small for gestational age/SGA (PR 28.95; 95%CI: 3.79 to 220.1; P=0.000), neonatal sepsis (PR 4.29; 95%CI: 2.21 to 8.31; P=0.000), hyaline membrane disease/HMD (PR 2.12; 95%CI: 1.16 to 3.88; P=0.021), use of respiratory support (PR 2.57; 95%CI: 1.35 to 4.92; P=0.005), initiation of enteral nutrition at >48 hours (PR 2.23; 95%CI: 1.21 to 4.09; P=0.014) and length of stay/LOS >14 days (PR 8.11; 95%CI: 4.13 to 15.9; P=0.000). Multivariate analysis revealed birth weight <1500 g (aPR 5.14; 95%CI: 1.55 to 17.06; P=0.007), SGA (aPR 24.26; 95%CI: 2.64 to 222.6; P=0.005), presence of sepsis (aPR 2.35; 95%CI: 1.00 to 5.5; P=0.049), and length of hospital stay >14 days (aPR 4.93; 95%CI: 2.15 to 11.31; P=0.000) maintained positive significant associations with EUGR. Conclusion The prevalence of EUGR in preterm infants is 47%. Birth weight <1500 g, small for gestational age, sepsis, and length of stay >14 days are associated with EUGR in preterm infants.

Regulators of placental antibody transfer through a modeling lens.

Infants are vulnerable to infections owing to a limited ability to mount a humoral immune response and their tolerogenic immune phenotype, which has impeded the success of newborn vaccination. Transplacental transfer of IgG from mother to fetus provides crucial protection in the first weeks of life, and maternal immunization has recently been implemented as a public health strategy to protect newborns against serious infections. Despite their early success, current maternal vaccines do not provide comparable protection across pregnancies with varying gestational lengths and placental and maternal immune features, and they do not account for the dynamic interplay between the maternal immune response and placental transfer. Moreover, progress toward the rational design of maternal vaccines has been hindered by inadequacies of existing experimental models and safety challenges of investigating longitudinal dynamics of IgG transfer in pregnant humans. Alternatively, in silico mechanistic models are a logical framework to disentangle the processes regulating placental antibody transfer. This Review synthesizes current literature through a mechanistic modeling lens to identify placental and maternal regulators of antibody transfer, their clinical covariates, and knowledge gaps to guide future research. We also describe opportunities to use integrated modeling and experimental approaches toward the rational design of vaccines against existing and emerging neonatal pathogen threats.

The effect of pre-partum shearing of Corriedale ewes on placental and lamb development and neonatal behaviour.

To evaluate the effects of early and late pre-partum shearing of Corriedale ewes carrying single fetuses on placental and lamb development and neonatal lamb behaviour. At 70 days of gestation, 37 multiparous Corriedale ewes with known gestation dates were randomly allocated into three groups: S70 (n = 12) and S110 (n = 12), shorn at Day 70 and 110 of gestation, and US (n = 13), that were not shorn pre-partum. Gestation length, lambing duration, placental expulsion time, placental weight, number and weight of cotyledons, and placental efficiency (lamb weight/placental weight) were determined. At birth, body temperature, weight, morphometric measurements, ponderal index (lamb weight/lamb crown-rump length) and behaviour were recorded, with weight remeasured 72 hours later. Four male lambs per group were slaughtered immediately after parturition, and organ weight and perirenal brown fat weight and energy content recorded. Pre-partum shearing, regardless of timing, increased total dried placental weight per ewe. Pre-partum shearing at Day 70 of gestation increased the number and mean weight of the > 2 to ≤ 3-cm cotyledons, while pre-partum shearing at Day 110 of gestation increased only the weight of these cotyledons. At birth and at 72 hours, lambs from ewes shorn either at 70 days of gestation (birth: 5.5 (95% CI = 4.6-6.4) kg, p = 0.001; 72 hours: 6.4 (95% CI = 6.1-6.8) kg, p = 0.002) or at 110 days of gestation (birth: 5.4 (95% CI = 4.4-6.4) kg, p = 0.001; 72 hours: 6.5 (95% CI = 5.9-7.1) kg, p = 0.001) were heavier than lambs from unshorn ewes (birth: 4.0 (95% CI = 3.3-4.8) kg; 72 hours: 4.8 (95% CI = 3.5-6.1) kg). Lambs born to S70 and S110 ewes suckled sooner (31.5 (95% CI = 14.5-48.5) minutes, p = 0.001; and 39.3 (95% CI = 23.7-55.0) minutes, p = 0.001 respectively), than lambs born to the US group (70.3 (95% CI = 38.6-102.1) minutes). There was no evidence for an effect of pre-partum shearing on gestation length, parturition length, time of placental expulsion, placental efficiency, weight and energy of perirenal brown fat, and lamb temperature at birth. Shearing ewes pre-partum may lead to placental changes affecting lamb development and behaviour and associated with higher survival. The findings suggest pre-partum shearing may improve lamb survival, farm profitability and sustainability.

Comparative Phenotypic Traits and Performances of Native Sheep in Naikhongchhari Hilly Area of Bangladesh

Background: Many studies have been conducted to investigate the performance of native sheep in plains and coastal regions, but no studies have been conducted in hilly regions of Bangladesh. Considering this fact, Coastal, Barind and Jamuna River Basin sheep were evaluated for their phenotypic traits, productive and reproductive abilities to gain insights into their performance in the hilly region. Methods: The Coastal, Barind and Jamuna River Basin sheep were collected from Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka for the first time to Regional Station, Naikhongchhari, BLRI and separated based on their phenotypic characteristics. A breeding program was established to ensure purity, using independent culling levels and selection indexes. Ewes were allowed to lamb throughout the year, mated with rams in a 15-20 to 1 ratio. The sheep were kept in a semi-intensive system. Result: The highest lamb birth weight was observed in coastal Region sheep, both male (1.43 kg) and female (1.22 kg), followed by Barind males (1.36 kg) and females (1.15 kg), respectively. The highest average daily gain was found in coastal region sheep (41.87 g/d), which was significantly higher compared to others. The lowest age at first heat, gestation length, age at first lambing, post-partum heat period, days open, lambing interval was observed in Barind sheep. Finally, the study offers valuable insights into the potentialities of native sheep in hilly regions, guiding future research and extension efforts for sheep farming in these areas.

Daily snuff use during pregnancy, gestational length and birth weight; register-based study

BackgroundSnuff is a smokeless source of nicotine that is common in Scandinavia and increasingly used by women of fertile age. Persistent use of snuff during pregnancy has been associated with adverse pregnancy outcomes. Emerging data from the Medical Birth Registry of Norway distinguishes between occasional use and daily use. We provide preliminary estimates of associations between frequency of snuff and gestational length and birth weight.MethodsData on snuff use during pregnancies delivered in 2020 and 2021 were available for the west and central regions of Norway. Associations of snuff use with gestational length and birth weight at term (39–41 weeks) were estimated using quantile regression at the 25th, the 50th and the 75th percentiles, with adjustments for mother’s age, pre-pregnancy weight, and parity. We compared associations with the pregnancy outcomes according to maternal snuff and cigarette use.Results12.4% of 18 042 non-smoking women reported daily use of snuff before pregnancy, and 4.6% reported continuing use during pregnancy, with 1.2% still reporting daily use in the last trimester. Women with daily use through the last trimester delivered babies with a median gestational length reduced by 3.4 days (95% CI: -5.0 to -1.7 days) compared with women who never used snuff. The reduction was even stronger at the 25th percentile of gestational age. The median term birth weight was reduced by 44 g (95% CI: -134 to 46 g). These associations were much weaker for women who quit snuff at some point during pregnancy or used snuff only occasionally. Mothers who smoked daily through the last trimester had a median gestational length reduced by 2.1 days (95% CI: -2.7 to -1.4) and a median term birth weight reduced by 294 g (95% CI: -325 to -262) compared with never-smokers.ConclusionsDaily snuff use through the last trimester reduced the median gestational length by more than three days. Snuff reduced birth weight, but not as much as smoking, suggesting that the predominant effect of smoking on fetal growth is not through nicotine but through the additional toxic chemicals in cigarettes or by reduced oxygen supply to the fetus.

Birth Traits Associated with Pre-Adulthood Disease Manifestations in Calves.

The objective of this study was to explore the relationship between calf birth traits and their susceptibility to diseases before reaching adulthood. A total of 5253 birth traits of Chinese Holstein calves were examined, including gestation length (GL), calf weight at birth (CW), and calving ease score (CES), which ranges from 1 (easy) to 5 (very difficult). Furthermore, monthly medical records were scrutinized for pneumonia and diarrhea in these calves. The study assessed five aspects of disease manifestation in calves: age at first onset, frequency of illness, longest duration of treatment, and total duration of treatment. The link between age at onset and disease manifestation prior to adulthood was analyzed using general linear models and regression models. The GL of calves significantly correlated with the risk of pneumonia, with the risk decreasing as the GL increases. A higher CES was associated with a later onset of diarrhea in calves. Furthermore, the CES was significantly negatively correlated with the duration of diarrhea treatment in calves. These results suggest that implementing different preventive measures for calves with different birth traits and modifying treatment protocols for affected calves could enhance the productivity of dairy cows and reduce losses on farms.

The evolution of gestation length in eutherian mammals.

Eutherian mammals exhibit considerable variation in their gestation lengths, which has traditionally been linked to variation in other traits, including body mass and lifespan. To understand how gestation length variation, including its association with body mass and lifespan variation, changed over mammalian evolution, we conducted phylogeny-informed analyses of 845 representative extant species. We found that gestation length substantially differed in both whether and how strongly it was associated with body mass and lifespan across mammals. For example, gestation length was not associated with lifespan or body mass in Chiroptera and Cetacea but was strongly associated only with body mass in Carnivora. We also identified 52 evolutionary shifts in gestation length variation across the mammal phylogeny and 14 shifts when we jointly considered variation of all three traits; six shifts were shared. Notably, two of these shifts, both positive, occurred at the roots of Cetacea and Pinnipedia, respectively, coinciding with the transition of these clades to the marine environment, whereas a negative shift occurred at the root of Chiroptera, coinciding with the evolution of flight in this clade. These results suggest that the relationship between gestation length and the two other traits has varied substantially across mammalian phylogeny.

Increased offspring size and reduced gestation length in an ectothermic vertebrate under a worst-case climate change scenario

As global temperatures continue to rise, understanding the impacts of warming environments has become increasingly important. Temperature is especially relevant for ectothermic organisms which depend upon consistent and predictable annual temperature cycles for reproduction and development. However, additional research is required in this area to elucidate the potential impacts of climate change on future generations. To understand how projected increases in environmental temperatures may impact reproductive outcomes within natural populations of ectothermic vertebrates, we manipulated minimum ambient temperatures during gestation in Red-sided garter snakes (Thamnophis sirtalis parietalis). Wild snakes were collected in the Interlake region of Manitoba, Canada during their spring mating season and allowed to mate in controlled conditions. For the duration of gestation, mated females were placed into one of two ambient thermal conditions: temperatures emulating those found in the species’ natural habitat or temperatures with a consistent 5 °C increase to match end-of-century climate change projections. We recorded observations for each litter and all neonates resulting from controlled mating trials. We observed no difference in litter sizes or birth rates between thermal conditions. However, we observed a significant reduction in gestation length and significant increase to neonate body mass and body condition associated with increased ambient temperatures. These results suggest that increased minimum temperatures during gestation may confer reproductive benefits for the northern populations of this species even under the most extreme current modeled warming predictions. We discuss the broader implications of this effect, including possible negative ecological outcomes.

Effects of Dichlorvos on Pregnancy Outcomes in Wistar Albino Rats

Dichlorvos is an organophosphate widely used as an insecticide. This study determines the effect of dichlorvos on pregnancy in Wistar rats. Forty-two bred female rats were divided into 7 groups (A, B, C, D, E, F and G) comprising of 6 rats each. Rats in 3 groups received 4.45mg/kg in the 1st, 2nd and 3rd trimester of pregnancy, respectively. The other 3 groups received 8.9mg/kg in 1st, 2nd and 3rd trimester, respectively. The dam to pups’ ratio decreased as the dose of dichlorvos increased except in the third trimester. The percentage birth weight of the treated groups was not different from the control except at third trimester when there was a significant (p 0.05) decrease in the 8.9mg/kg groups. There were no significant (p 0.05) differences in the crown-rump and gestation length within the groups and trimesters except in the third trimester where there was a significant difference (p 0.05) between 8.9mg/kg group and others. The study shows that dichlorvos is capable of altering pregnancy outcomes in female Wistar rats.

Maternal exercise during pregnancy is associated with reduced risk of asthma in the child: A prospective birth cohort study.

The means of primary prevention of asthma are limited. Maternal physical activity during pregnancy promotes fetal lung development and the newborn's lung function; thus, it could lower asthma risk and aid in asthma prevention. The objective of this study is to determine whether maternal physical activity during pregnancy is associated with asthma development in the child. The study population included 963 mother-infant pairs from the prospective Kuopio Birth Cohort study. Data on maternal physical activity during pregnancy, confounding factors, and children's asthma at 5 to 7 years of age were obtained from the Kuopio University Hospital birth registry and questionnaires. Maternal physical activity during pregnancy, when practiced three or more times per week, was associated with a reduced risk of asthma in the child, with an adjusted odds ratio of 0.54 (95% confidence interval 0.33-0.89; p= 0.02). The association was stable across a comprehensive set of adjustments, including length of gestation, mode of delivery, and maternal health indicators (e.g., asthma, smoking, pre-pregnancy body mass index and weight gain during pregnancy, infections, medication, healthy diet, stress), as well as various family environment variables. Maternal physical activity during pregnancy may be associated with marked protection of asthma in childhood and should be studied further as an applicable measure for asthma prevention. The study has been financially supported by grants from the Academy of Finland (no. 349427), the Emil Aaltonen Foundation, the Finnish Cultural Foundation, the Yrjö Jahnsson Foundation, the Juho Vainio Foundation (no. 202200461), the Kuopio Area Respiratory Foundation, and the Ida Montini Foundation.

Gestational urinary concentrations of glyphosate and aminomethylphosphonic acid in relation to preterm birth: the MIREC study.

Few high-quality studies have evaluated associations between urinary glyphosate or its environmental degradate (aminomethylphosphonic acid (AMPA)] and preterm birth (PTB). To quantify associations between urinary glyphosate and AMPA and preterm birth in the pan-Canadian Maternal-Infant Research on Environmental Chemicals (MIREC) study and determine if associations differ by fetal sex. We measured first trimester urinary glyphosate and AMPA concentrations in MIREC participants who were recruited between 2008-2011 from 10 Canadian cities. Of the 1880 participants whose first trimester urine samples were analyzed for glyphosate or AMPA, 1765 delivered a singleton, live birth. Our primary outcome was preterm birth (PTB) defined as births occurring between 20 and <37 weeks. Secondary outcomes were spontaneous preterm births (sPTB) and gestational age. We modelled the hazard of PTB and sPTB using discrete time survival analysis with multivariable logistic regression to calculate odds ratios (OR). We used multivariable linear regression models to quantify associations between analytes and gestational age. To assess effect modification by fetal sex, we stratified all models and calculated interaction terms. In the logistic regressions models we additionally calculated the relative excess risk due to interaction. Six percent (n = 106) of the study population delivered preterm, and 4.7% (n = 83) had a spontaneous preterm birth. Median specific-gravity standardized concentrations of glyphosate and AMPA were 0.25 and 0.21 µg/L. Associations between both glyphosate or AMPA and PTB, sPTB, and gestational age centered around the null value. The adjusted ORs of PTB for each doubling of glyphosate and AMPA concentrations were 0.98 (95% CI: 0.94, 1.03) and 0.99 (95% CI: 0.92, 1.06) respectively. We observed no evidence of differences by fetal sex. In this Canadian pregnancy cohort, neither glyphosate nor AMPA urinary concentrations was associated with PTB or reduced gestational length.

Accuracy Evaluation of Fetal Foot Length and Correlation with Biparietal Diameter for Ultrasonographic Fetal Age Estimation in Uncomplicated Pregnant Women of Chattogram, Bangladesh

Background: Prediction and visual representation of developmental milestones of a growing fetus is most accurately done by ultrasonography. The present study was aimed to evaluate the correlation and accuracy of fetal foot length with fetal biparietal diameter to estimate fetal gestational age in Bangladeshi uncomplicated pregnant women of Chattogram district. Materials and methods: This cross-sectional observational study was conducted on 200 uncomplicated pregnant women of 15th to 28th weeks of gestation during the period from October 2021 to September 2022 in the Department of Anatomy, Chittagong Medical College, Chattogram. Fetal biometric parameters such as fetal foot length and biparietal diameter were measured by ultrasonography. For statistical analysis, Pearson’s correlation test and correlation-regression analysis was done and p-value was considered significant if it was &lt;0.05 at 95% level of confidence. Results: Pearson’s correlation test showed that gestational age had strong positive and highly significant (p=0.000) correlation with both fetal foot length and biparietal diameter. The relation between gestational age and fetal foot length(r=0.986) is less strong than the relation between gestational age and biparietal diameter(r=0.988). Conclusion: This study revealed relationship between fetal foot length and gestational age regarding accuracy. Ultrasonographic measurement of fetal foot length can be practiced alongside traditional biometric parameters for pregnancy dating in modern medical science. IAHS Medical Journal Vol 6(2), December 2023; 35-39

PSX-1 Genomic insights into reproduction traits of Nellore cattle: A meta-analysis of genomic regions

Abstract Enhancing reproductive efficiency could lead to economic benefits for Nellore producers. However, several factors limit our understanding of the main genetic factors controlling reproduction traits in Nellore cattle, including genetic differences between populations and statistical limitations. A meta-analysis can assist in pinpointing the most likely functional candidate genes, quantitative trait loci, and biological processes simultaneously associated with several traits in a group. Hence, the goal of this study was to perform a meta-analysis of genomic regions previously associated with reproduction traits in Nellore cattle, to improve our comprehension of the main genetic mechanisms regulating these traits within the breed. This study incorporated a total of 549 genomic regions sourced from 21 scientific publications, published between 2014 to 2024. The reproduction traits included in this study are scrotal circumference at various ages (365, 450, and 550 d), early pregnancy (&amp;lt; 31 mo of age), early puberty (defined as pregnancy at 18 mo), age at first calving, antral follicle count, calving interval, calving ease, testicular hypoplasia, stayability, heifer rebreeding, gestation length, anti-mullerian hormone concentrations, preweaning calf mortality, and post-natal mortality. All genomic regions identified in the literature were updated to the ARS-UCD1.2 genome assembly, and the Gallo R package was used to identify positional candidate genes associated with each genomic region. A total of 8,441 positional candidate genes were annotated and used in an overrepresentation analysis performed in meshr. The significant genes (adjusted P-values &amp;lt; 0.05) identified in the overrepresentation analysis underwent prioritization analyses using the GUILDify and ToppGene software. Subsequently, enrichment analysis of the prioritized overrepresented candidate genes was performed using the ClusterProfiler R package. The 8,441 annotated genes generated 1,757 overrepresented genes, of which 17 candidate genes were prioritized (FDR P -value ≤ 10-3). The overrepresented candidate genes that were prioritized are: SERTAD2, RFWD3, C1QTNF9B, SLFN14, CATSPERE, GFRA4, ZNF408, NOP58, ADGRG3, KIZ, REM2, FSCN3, DCAF11, ACSM4, ANKRD34B, CMKLR2-AS, and TRV-AAC1-1. The functional enrichment analysis highlighted the following genes: FSCN3 (exhibits highly specific expression in testis), CATSPERE (has a vital role in cellular processes related to reproduction and is necessary for normal fertility), ANKRD34B (associated with cytoplasm found in oocytes or early embryos), and RFWD3 (regulates the transition between phases of the mitotic cell cycle). All other prioritized genes also have roles in regulating metabolic pathways or biological processes related to reproduction, such as sperm capacitation, sperm motility, cilium or flagellum-dependent cell motility, mitotic cell cycle phase transition, and RNA endonuclease activity. The enrichment of the functional candidate genes identified highlights that these genes have an important role in the expression of reproduction traits in Nellore cattle. Candidate genes identified in this study can be used as target genes in gene expression studies, which are necessary to validate our findings.

53 Relationship of Angus yearling bull pulmonary arterial pressure estimates with birth weight, gestation length and growth traits

Abstract Pulmonary arterial pressure (PAP), determines the susceptibility to High Altitude Disease (HAD) of an animal, which causes pulmonary hypertension due to hypoxia. Cattle that reside in elevations greater than 1,500 m are more susceptible to HAD. PAP measures the resistance of blood flow through the lungs and can be used as an indicator of the susceptibility of an animal to HAD. It is estimated that 1.5 million head of cattle are raised in high altitude environments (above 1,500 m) and HAD accounts for 3 to 5% of calf death loss yearly. The objectives of this study were to model the relationship of PAP estimates with birth weight, gestation length and growth traits of developing bulls. PAP estimates were collected from Angus yearling bulls ranging in age from 12 to 18-mo of age from a Montana-based Angus operation (&amp;gt; 1,600 m elevation, 5,400 yearlings/18-mo-old bulls from 2016 – 2023). We hypothesized that the relationship between PAP and performance traits could be described with linear or asymptotic models. We used Akaike’s Information Criterion adjusted for small sample sizes (AICc) to evaluate support for competing models reflecting hypotheses about the effects of bull age at time of testing and performance traits. Models containing an asymptotic relationship between PAP and all measured variables were the best supported from the candidate model sets. Bull age at time of PAP testing was not supported in model selection for any of the performance traits measured. PAP was greater for bulls with greater birth weight (P &amp;lt; 0.01; β = 2.86 ± 0.81; R2marginal = 0.25 %; R2conditional = 0.77 %). PAP was greater for bulls that had greater gestation lengths (P &amp;lt; 0.01; β = 33.74 ± 11.25; R2marginal = 1.40 %; R2conditional = 27.37 %). There were no observed relationships between bull PAP and weaning weight (P = 0.26). PAP was less for bulls that had greater yearling weights (P = 0.04; β = -2.16 ± 1.05; R2marginal = 0.09 %; R2conditional = 0.65 %). In addition, PAP was less for bulls that had greater weaning to yearling gains (P = 0.02; β = -1.21 ± 0.54; R2marginal = 0.12 %; R2conditional = 0.79 %). In summary, PAP was related to birth weight, gestation length, yearling weight, and growth between weaning and yearling; however, these relationships explain very little of the variation of PAP estimates.

109 Dam and calf influences on colostrum yield and quality in beef cattle

Abstract To determine factors affecting colostrum yield and quality, data from 148 cow-calf pairs over 6 experiments were combined. In each experiment, single rear quarter colostrum yield was obtained post-calving but pre-suckling. Colostrum IgG was determined by ELISA, and colostrum lactose, triglycerides (as a measure of total fat), and protein were determined by colorimetric analyses. Total IgG and nutrients were calculated as the concentration multiplied by single-quarter yield. Calf birth weight and expelled placental dry weight were also collected post-calving. Mixed linear models (experiment as a random effect) were used to determine the effects of dam age (primiparous: 2 yr, young: 3 to 4 yr, mature: ≥ 5 yr), dam peripartum body condition score (BCS; thin: &amp;lt; 5, moderate: 5 to 5.99, fleshy: ≥ 6), and calf sex on colostrum yield (single-quarter colostrum weight) and quality. Pearson correlation coefficients were also determined for colostrum yield with dam pre-calving body weight (BW), calf birth weight, calf birth weight relative to dam BW, whole placental dry weight, and gestation length. Mature dams had the greatest (P ≤ 0.03) and primiparous dams had the least (P ≤ 0.001) colostrum yield and total lactose. Colostrum from primiparous dams had greater (P = 0.03) IgG concentration than mature and greater (P ≤ 0.001) protein concentration than young and mature. Mature dams had greater (P ≤ 0.02) total IgG, total protein, and total triglycerides compared with both primiparous and young. Colostrum yield was less (P ≤ 0.04) for thin than moderate and fleshy dams. Total IgG was unaffected (P = 0.11) by dam BCS; however, thin dams had greater (P ≤ 0.04) IgG concentration than moderate and fleshy. Lactose concentration and total lactose were less (P ≤ 0.02) in colostrum from thin compared with moderate dams. Protein concentration was greater (P = 0.001) in thin than moderate dams, but thin dams had less (P ≤ 0.02) total protein compared with moderate and fleshy. Dam BCS did not affect (P ≥ 0.59) colostrum triglyceride concentration or total triglycerides. Colostrum yield and quality were not affected (P ≥ 0.22) by calf sex. Pre-calving dam BW was positively correlated with colostrum yield (r = 0.46, P &amp;lt; 0.001). Colostrum yield was also positively correlated with calf birth weight (r = 0.31, P &amp;lt; 0.001) and whole placental dry weight (r = 0.26, P = 0.007), but tended to be negatively correlated with calf birth weight relative to dam BW (r = -0.14, P = 0.09). Gestation length had no relationship (P = 0.31) with colostrum yield. Overall, colostrum yield and quality are negatively affected in young and thin beef dams. In addition, both dam and calf weight have positive relationships with colostrum yield, likely mediated by endocrine action associated with placental size.

50 Awardee Talk: The role of non-traditional inheritance patterns among Bos indicus-Bos taurus crosses for global beef value chain considerations

Abstract Bos indicus-Bos taurus crosses have been effectively used in many production environments globally. Substantially higher amounts of hybrid vigor have been reported in these F1 crosses as compared with those involving only Bos taurus or only Bos indicus breeds. However, for many years, and in many environments, “unusual” aspects of calf growth have been documented among these crosses. Among F1 crosses, Bos indicus-sired calves (Bos indicus x Bos taurus) have birth weight 8 to 12 kg heavier than contemporary Bos taurus-sired calves (Bos taurus x Bos indicus); additionally, pronounced sexual dimorphism occurs where males may weigh 5 to 10 kg more than females from Bos indicus sires (Bos taurus dams) but 1 kg or less from Bos taurus sires (Bos indicus dams) in both natural service and embryo transfer calves. These reciprocal differences have been reported for fetal and placentome size mid gestation. Reciprocal differences in birth weight have also been reported among backcrosses and F2 calves, and also exist for longer gestation length from Bos indicus sires (Bos taurus dams). Increased birth weight and gestation length occur when more Bos indicus is present in the sire vs. the dam, and when Bos indicus influence is inherited through the sire vs. the dam. There is speculation that sex-specific genomic imprinting may be involved for reciprocal birth weight differences that are analogous to mouse interspecific crosses for litter weight. Reports of hybrid vigor retention among inter se matings after the F1 have been variable historically, and this variation may relate to how the foundational F1 parents were produced (Bos indicus- vs. Bos taurus-sired). Breed-of-origin haplotype on BTA5 has been shown to affect heifer pregnancy and rebreeding among F2 Nellore-Angus cows where Nellore-derived haplotypes had much lower performance compared with Angus-derived and hybrid haplotypes. Disproportionate calf sex has been reported among reciprocal F2 Nellore (Bos indicus)-Angus (Bos taurus) with 66.6% male calves from Nellore x Angus F1 sires. When retrospectively evaluating historical literature for reciprocal crosses, it appears that several instances occur with disproportionate calf sex percentage, and this phenomenon warrants further study. The extent that potential reciprocal differences may affect post-weaning growth and carcass traits has not been widely evaluated. Recent investigations have shown reciprocal F1 differences for some cell-mediated immune responses regarding T-lymphocyte proliferation, but no differences for humoral response. There needs to be additional research that completely characterizes the X chromosome of Bos indicus and Bos taurus origins and their roles for multiple production traits. There also needs to be more investigation of non-additive and parent-of-origin effects in genetic evaluations of Bos indicus-Bos taurus composites, particularly with desired first-generation breed percentage. Improved utilization of Bos indicus cattle and crosses will be instrumental in meeting global dietary protein demands.

111 Factors affecting transfer of passive immunity in beef calves

Abstract Data from 9 calving experiments were used to investigate relationships of dam, calf, and colostrum factors with passive transfer in beef calves. Serum was collected at 48.33 ± 1.25 (SD) h of age for 313 calves, and single rear quarter colostrum yields were determined pre-suckling for dams of 117 calves. Serum and colostrum IgG concentrations were determined by ELISA. Relationship of serum IgG with colostrum variables was determined using Pearson correlation coefficients. Serum IgG was positively correlated (P ≤ 0.002) with colostrum IgG (r = 0.47) and protein (r = 0.45) concentrations and colostrum total IgG (r = 0.28) but tended to be negatively correlated (r = -0.17, P = 0.06) with colostrum yield. Based on passive transfer thresholds in the literature, 3 calves (0.96%) had &amp;lt; 8 mg/mL serum IgG, 16 calves (5.1%) &amp;lt; 16 mg/mL, and 43 calves (13.7%) had &amp;lt; 24 mg/mL. For this analysis, calves with serum IgG &amp;lt; 24 mg/mL at 48 h were considered to have failure of passive transfer (FPT). Continuous variables (dam BW and calf size, 48-h serum chemistry panel, and time to stand) were compared for FPT versus non-FPT calves using a mixed model with FPT class (fixed effect) and experiment (random effect). Calves with FPT had less (P ≤ 0.03) circulating triglycerides, glucose, calcium, magnesium, total protein, globulin, and gamma-glutamyl transferase but greater (P ≤ 0.001) circulating non-esterified fatty acids, sodium, chloride, and total bilirubin than non-FPT. Effects of categorical variables on calf 48-h serum IgG were determined using separate mixed models with variable (fixed) and experiment (random). Primiparous dams gave birth to calves that had less (P = 0.05) serum IgG at 48 h than multiparous dams. Calves born to moderate dams (BCS = 5) had less (P = 0.007) serum IgG than those born to fleshy dams (BCS ≥ 6) and tended to have less (P = 0.08) serum IgG than calves born to thin dams (BCS &amp;lt; 5). Calf sex, calving season, calving difficulty score, and vigor score at 10 min did not affect (P ≥ 0.19) serum IgG. Relationships of calf 48-h serum IgG with continuous variables was also determined using Pearson correlation coefficients, and only r ≥ 0.20 or ≤ -0.20 are reported. Serum IgG was positively correlated (P ≤ 0.005) with 48-h serum total protein (r = 0.75), globulin (r = 0.76), gamma-glutamyl transferase (r = 0.32), and potassium (r = 0.20). Serum IgG was negatively correlated (P &amp;lt; 0.001) with gestation length (r = -0.22) and 48-h serum albumin (r = -0.43), sodium (r = -0.24), and total bilirubin (r = -0.27). Overall, beef calves in this dataset generally had successful passive transfer that was associated with several dam, calf, and colostrum factors.