Performing Department
(N/A)
Non Technical Summary
The maternal environment during pregnancy including the mother's nutritional status, can directly influence the growth and development of the fetus and impact metabolism, growth, and health borth short-term and long-term. In beef cattle, poor nutritional management of the pregnant female, such as undernutrition, can significantly affect offspring growth, development, and adult productivity later in life. Rising cattle feed and labor costs drive producers to seek strategies to reduce these expenses, especially during the costly fall and winter months. One strategy is to allow pregnant cattle to graze pastures after the growing season, resulting in a diet of low-quality, low-protein grasses. In this scenario, fetuses exposed to low-protein diets through the diet of their mothers can have restricted growth and altered muscle tissue composition and quantity, as muscle tissue is developed primarily prenatally. Changes to offspring muscle development during pregnancy not only influences fetal growth but can also impact skeletal muscle and animal size postnatally, ultimately influencing meat products available to consumers. Additionally, feeding supplemental protein to cattle grazing low-protein forages can increase forage utilization, allowing longer grazing periods and greater body weight gains. These impacts can ultimately reduce feed and labor costs for the rancher and potentially improve financial return at sale. Thus, maternal nutrition during pregnancy, especially in regard to protein content in the diet, may be impactful for the growth of the pregnant cow, utilization of grazed forages, optimal development of the offspring, and production of quality meat products available to the consumer.The primary project goals are to evaluate the impacts of feeding supplemental protein to pregnant cattle grazing low-protein forages on skeletal muscle development and growth of the offspring, while supporting the PD's establishment of a well-funded research and teaching laboratory with the primary mission of enhancing longevity, productivity, and overall success of cow-calf herds. We will provide protein supplementation to 25 pregnant beef heifers on a single, low-quality pasture, while another 25 pregnant beef heifers will graze the same pasture without supplementation during the second trimester of pregnancy (mid-gestation). We will evaluate the calves born to all 50 heifers, collecting muscle biopsies and recording weights throughout their lives to determine if the mother's diet influenced skeletal muscle development and weight gain of the offspring. Specific variables examined will include muscle fiber size and number, collagen content, fat content, and gene expression in muscle tissue. These variables will help us understand how maternal diet during pregnancy affects skeletal muscle development, impacting meat toughness or tenderness, muscle size, and genetic control of these traits. Results will be communicated to production and scientific audiences at international, national, and local venues through presentations, radio and webinar series, and written publications, including peer-reviewed articles and local research reports. Achieving the primary projectgoals will help develop targeted feeding strategies for pregnant cattle, improve cow health and body weight, increase utilization of low-quality forages, and positively impact skeletal muscle development in the gestating offspring and future meat production. Furthermore, the development of the PD as a young scientist is an invaluableaspect of this project, and directing the management and execution of this project, presenting research across the world, and training to perform hands-on procedures and handle large datasets from experts in the fieldwill allow the PD to gain global networks of collaborators, discuss research findings with international and local audiences, and effectively interpret results and communicate implications for cow-calf production. This project has societal impacts on ranchers, industry leaders, stakeholders, graduate students, researchers, and consumers alike, and successful direction of this project and interpretation of results will provide valuable insights to herd improvement strategies that translate into improving beef industry's contributions to the growing global food supply.
Animal Health Component
75%
Research Effort Categories
Basic
0%
Applied
75%
Developmental
25%
Goals / Objectives
My long-term research goals are to evaluate the multifaceted impacts of maternal nutrition in beef cattle on developmental programming outcomes observed in the offspring postnatally. My mission is to develop successful management approaches for pregnant beef cattle to improve herd longevity, productivity, and overall success. These efforts will focus on enhancing offspring skeletal muscle formation and will contribute to supplying beef to the global population. In this proposal, I focus on the fetal programming impacts of providing protein and energy supplementation to mid-gestation beef heifers on skeletal muscle size, number, and composition, gene expression, and offspring growth performance at key postnatal stages.The short-term goals of this project are to determine the mechanisms connected with the impacts of maternal nutrition on skeletal muscle and the growth performance of female offspring. I hypothesize that providing protein and energy supplementation to beef heifers in mid-gestation will positively impact offspring muscle fiber diameter and number, collagen and adipocyte content, gene expression, and overall postnatal growth performance.This proposal will address my Specific Objectives, which are to evaluate the impacts of providing a protein and energy supplement to beef heifers during mid-gestation on: 1) the differential expression of genes acting in pathways related to skeletal muscle development of calves at birth, weaning, and at one year of age; 2) muscle fiber diameter and number, and adipocyte and collagen content in skeletal muscle of beef calves at key postnatal stages; and 3) offspring postnatal growth performance.
Project Methods
The experimental procedures for this project will take place near Streeter, ND at the Central Grasslands Research Extension Center (CGREC). Briefly, Angus-based heifers (n = 120, ~14 to 15 months of age) will be selected from the CGREC herd and managed on native range pastures in the spring and summer of 2024. Heifers will be acclimated to a precision feed delivery system (SmartFeed; C-Lock, Rapid City, SD, USA) before beginning the trial. Heifers will be subjected to a 7-day CIDR + Co-Synch estrus synchronization protocol and bred via artificial insemination (AI) using sexed semen. Pregnancy diagnosis via transrectal ultrasound will be conducted at d 35 and d 65 after AI to determine pregnancies with the targeted sex(anticipating n = 50 total). At d 90 of pregnancy, heifers will be blocked by body weight and randomly assigned to one of two dietary treatments. Control heifers (CON, n = 25), will be allowed to graze on a single, native range fall pasture from d 90 to d 180 of pregnancy, and supplemented heifers (SUPP, n = 25), will graze alongside CON heifers and be given access to a protein/energy supplement in the SmartFeed system from d 90 to d 180 of pregnancy. Daily supplement allowances will be adjusted to achieve target body weight gain of 0.45 kg/heifer/day. Dietary treatments will conclude at d 180 of pregnancy and all heifers will receive a diet formulated to meet 100% of requirements through calving. The pregnant heifers will be weighed, and body condition scores will be recorded at breeding, during the supplementation period, at calving, pasture turn out, and at weaning to evaluate the impact of protein/energy supplementation during mid-gestation on pre- and post-calving body weight gain and body condition.Calving characteristics including gestation length, calving distribution, calf body weight and other calf morphometric characteristics will be recorded to determine if mid-gestation protein/energy supplementation in the dam impacted pregnancy length or growth measurements in the neonatal calf without the confounding effects of milk in effect. At birth, weaning, and at one year of age, biopsies of the Longissimus muscle will be collected from calves (n = 20 per treatment group at each stage). Samples will be snap-frozen in liquid nitrogen and stored at -80 ºC for gene expression analysis and fixed in fresh 10% (wt/vol) buffered formalin for histological analysis (n = 20 per group at each stage). For gene expression analysis, RNA from frozen tissue will first be extracted from muscle samples (n = 8 per group at each stage) using the RNeasy Plus Universal Mini Kit (Qiagen, Germantown, MA, USA). The Agilent 2100 Bioanalyzer and agarose gel electrophoresis will be used to confirm sample integrity and purity analyses. RNA-seq analysis will be conducted on the Illumina NovaSeq 600 platform using pair-end sequencing (150-bp reads) at a depth of 20 M reads/sample. Library preparation and RNA sequencing will be performed by NovoGene Co. (Sacramento, CA, USA). Strand-specific RNA libraries will be prepared using the NEBNext Ultra II Directional RNA Library Prep Kit for Illumina (New England Biolabs, Ipswich, MA, USA). After quality control, reads will be mapped to the ARS-UCD1.2 Bos taurus reference genome using STAR aligner and the gene annotation file (release 100) from the Ensembl database. Differential expression analysis will be performed using the DESeq2 package within RStudio (Posit Software, PBC), with functional analysis conducted using KEGG and STRING databases. We will compare transcriptome profiles for animals within treatments and time points and the respective interaction. We will also identify over-represented biological processes and pathways of the differentially expressed genes identified using the ShinyGo web tool. We will identify significant results after p-value multiple testing correction (FDR ≤ 0.05). Power analysis from our previous transcriptomic data suggests that a minimum of 8 samples per treatment are adequate for detecting statistical differences at FDR < 0. 1. Muscle samples will also be embedded in paraffin and sliced into 5 μm sections for staining. Histological images will be processed and saved using a Mica Microhub microscope (Leica Microsystems, Inc., Buffalo Grove, IL, USA). Images will be analyzed using ImagePro-Premiere software (Media Cybernetics, Inc., Silver Spring, MD, USA).Body weights and/or body condition scores of the dam and offspring will be summarized for each treatment group by month or key time point in development/pregnancy (e.g., supplementation period, birth/calving, pasture turn out, weaning). Quantification of offspring muscle fiber numbers, size, collagen content, adipocyte content, offspring postnatal growth performance, and maternal body weight will be analyzed using SAS (SAS 9.4, Cary, NC, USA), and results will be interpreted as using the main effects of maternal treatment, day in development, and the respective interaction of treatment and day.Effforts and Evaluation: We hypothesize that providing protein/energy supplementation to beef heifers during mid-gestation will contribute several alterations to progeny skeletal muscle development, transcriptome profiles, and postnatal growth performance. Specifically, we anticipate that protein and energy supplementation of the dam during mid-gestation will increase fiber number and size, reduce collagen content, increase adipogenesis, and increase body weight of the progeny through the post-weaning phase. Additionally, providing supplemental protein to animals consuming low-quality forages may support increased digestibility and utilization of available forages, which may help to extend the fall/winter grazing period. We anticipate that supplementation may also support greater maternal body weights and body condition scores prior to calving, which is an important aspect of energy and nutrient partitioning during early lactation/rebreeding and may also support the postnatal growth of the suckling calf. Evaluations of project success include the development of economically feasible supplementation strategies that help to manage the cow and the gestating calf while strategically grazing low-quality forages to reduce feed and labor costs. Developing and incorporating improved teaching strategies for undergraduate courses in animal sciences, acquiring additional funding, achieving regular publication of results, and attending multiple scientific and producer meetings will also be critical evaluations of project success. The progress of the PD's mentee in developing their own reports, publications, and grant applications and finishing their degree program will support project success. Efforts that will be employed to disseminate these results and the implications on the beef industry researchers, stakeholders, and producers include: giving scientific presentations at international, national, regional, and local venues; discussing results at Extension meetings, workshops, and in-service events with producers, Extension agents, and stakeholders; producing peer-reviewed articles for submission to reputable journals to serve researchers and industry leaders; writing producer-targeted articles for submissions to the North Dakota Livestock Research Report, Central Grasslands Research Extension Center Annual Report, and Extension bulletins; and discussing research implications on real-world scenarios through radio and podcast outlets and youth beef webinars. Efforts to help deliver science-based learning to the appropriate audience will also be conducted through formal and informal classroom learning and curriculum development as part of the teaching strategy improvement area of this project.