Determining the relationship between growth EBVs, feed intake, and feed efficiency in range sheep


Performance Narrative: Activities Performed

Eighty ewe (Targhee and Rambouillet) lambs were recruited from the MAES flock at weaning (Aug 2021) and placed in pens with growsafe feed bunks. Following a 14-day adaptation period, feed intake data was collected for 42 days, until October 25th, 2021. Six lambs were removed from the study due to low intake and not adapting to the growsafe bunks. Rumen fluid samples were collected during the last week of the trial and frozen for future DNA extraction and microbial sequencing. All lambs were genotyped on the ovine 50K GGP SNP chip. Estimated Breeding Values from the October 1st run of NSIP through Lambplan will be used for the initial analysis. The second feeding period was completed in June 2022. Following this feeding period, microbial DNA was extracted from rumen fluid and sequenced in summer 2022. Since then subsequent statistical analysis has identified differences between production phases, estimated breeding values, and between microbial communities.


Both growsafe feeding periods were completed. All lambs have been genotyped on the Ovine 50K GGP SNP chip. Estimated Breeding Values for weight traits are known and being incorporated into the analysis. 16S rRNA sequencing was performed over the summer and subsequent analysis performed through the summer and fall 2022.

Estimate the Total Percentage (%) of work Completed on the Project……….100% # Accomplishment/Activity Relevance to Objective
Both feeding trials were completed. The completion of this work completes half of objective one. It is also integral to objective three as the phenotype is needed to build a genomic breeding value for feed efficiency
All sheep have been genotyped on the 50K chip This is essential to objective three. In order to build a genomic foundation for feed efficiency breeding values, genotypes need to be associated with phenotypes. This is a first step towards genomic evaluation of feed efficiency.
Relationships between growth EBVs, feed intake, and efficiency were assessed This is relevant to objective two by identifying the relationships between these parameters that will improve efficiency of the industry.
Challenges and Developments # Challenge or Development Corrective Action or Project Change
Regional drought significantly increased feed costs and reduced supply for all livestock producers in 2022. We sourced hay/feed for the second feeding part of the trial several months early to prevent possible shortages during the feeding period.
Outcome and Indicator Results to Date # Outcome/Indicator Quantifiable Results
Characterize feed intake and efficiency over two life stages (growth/maintenance) using the GrowsafeTM system. Phase 1 – Growth

Phase 2 – Maintenance

# of Ewes



Age, days

121 ± 5

355 ± 5

Initial BW, kg

27.8 ± 4.39

35.2 ± 8.02

MBW, kg

14.5 ± 1.70

16.7 ± 2.15

ADG, kg day

0.26 ± 0.12

-0.02 ± 0.16

DMI, kg day

2.01 ± 0.38

2.18 ± 1.62

RFI, DMI kg day

0.00 ± 0.24

0.00 ± 1.34

Build a foundation for genetic and genomic evaluation of feed efficiency within the Targhee and Rambouillet breeds. Using approximately 50,000 SNPs per individual to be used for GWAS analysis we identified one significantly associated marker for feed efficiency on chromosome 2, in DMTF2, which is involved with somitogenesis in early embryos, eventually giving rise to skeletal muscle.
Quantify the relationship between lamb growth EBVs, feed intake, and feed efficiency as measured by residual feed intake from GrowsafeTM systems. We found that RFI is not associated with PWWT EBVs or ADG in either production stage. We do fin that PWWT EBVs are associated with body weight and feed intake. Likely the feed intake relationship is driven by animals with higher PWWT EBVs being larger and therefore requiring more feed intake, not related to efficiency.
Results will be shared with the sheep research community Four abstracts/posters/presentations were presented at regional and national meetings in 2022: ASAS National Meeting, ASAS Western Section, Montana Wool Growers Convention, NC214 Multistate Meeting, and the Montana Ram Sale.
Upcoming Activities # Activities Anticipated Completion
Thesis and manuscript(s) preparation May 2023