Location: Animal Genomics and Improvement Laboratory
Project Number: 8042-31310-078-000-D
Project Type: In-House Appropriated
Start Date: Jul 26, 2017
End Date: Jul 25, 2022
Objective:
Objective 1: Develop resources, tools, and selectable markers to improve nutrient use efficiency in dairy cattle. Tools and resources will be developed including: 1) genetically and phenotypically characterized lines of cattle divergently selected for feed efficiency to support genomic selection for greater efficiency and lower CH4 emissions, and identify possible negative consequences of selection on production performance; 2) whole tissue models of cattle intestine (mini-guts, or enteroids) to support tissue-specific investigations ex vivo; and 3) an ‘isolated’ small intestine model to study effects of specific nutrients on intestinal development, function, and gene expression of mature dairy cows in vivo.
Sub-objective 1.A: Develop and phenotypically characterize lines of Holstein dairy cattle divergently selected for RFI during growth (RFIgrowth) to investigate the biological and genetic bases of nutrient use efficiency, and to support genomic selection studies.
Sub-objective 1.B: Characterize and exploit relationships between RFI (RFIgrowth and RFIlac) and enteric CH4 emissions of dairy cattle.
Sub-objective 1.C: Develop ruminant organoids to study gut health and nutrient use efficiency of dairy cattle ex vivo.
Sub-objective 1.D: Develop and validate a short-term isolated duodenal model for the assessment of intestinal epithelial tissue transcriptomic response to alterations in nutrient delivery in vivo.
Objective 2: Evaluate and develop novel dietary strategies to reduce feed and nutritional costs to dairy cattle production. Studies of newborn dairy calves will be conducted to characterize molecular changes controlling gene expression during rumen development and differentiation, and evaluate novel feed additives as alternatives to antibiotics to improve calf health and production performance.
Sub-objective 2.A: Evaluate the effects of non-nutritive feed additives (e.g., phytochemicals) on gut health and nutrient use efficiency of dairy cattle.
Sub-objective 2.B: Characterize molecular phenotypes of the calf rumen transcriptome through strand-specific RNA sequencing (ssRNA-seq) during development.
Sub-objective 2.C: Functionally annotate the calf rumen epigenome and identify transcriptional cis-regulatory modules during development, including histone modification, chromatin accessibility and architecture using Chromatin Immunoprecipitation-sequencing (ChIP-Seq) technologies.
Objective 3: Evaluate in vivo gastrointestinal tissue responses (ruminal and duodenal) of lactating and dry dairy cows to perturbations in luminal factors (changes in nutrient flow) and physiological stressors (transition cow and early lactation). Molecular mechanisms regulating cell proliferation and development of rumen and intestinal epithelia during critical changes in nutrient delivery and the dairy cow production cycle (transition into lactation, ration changes, stage of lactation) will be identified and characterized through transcriptomic studies of serial biopsies from live animal models.
Subobjective 3A, 3B- See project plan
Approach:
To improve feed efficiency and reduce methane emissions of dairy cattle through genetic selection and management, dairy cows divergent in feed efficiency will be developed, and a database of their genetic and production information, including enteric methane emissions, will be compiled for extensive analysis. Whole tissue models of intestine (mini-guts) will be developed from calves to study gut function and nutrient use, and methods to temporarily isolate regions of small intestine of live, adult cows will be established to study nutrient effects on gut function and gene expression. In addition, novel plant-derived compounds will be evaluated as alternatives to antibiotics to improve gut function, disease resistance, and feed efficiency of dairy calves. Epigenetic factors controlling calf rumen development during weaning will be investigated using state-of-the-art molecular technologies. Finally, changes in gastrointestinal cells of dairy cows related to gut growth and function during critical stages of production will be characterized by examining gene expression in gut tissues of cows under different dietary and production conditions over time.
