Improving Feed Efficiency in Sheep Through Rumen Manipulation and Producer Adoption

Improving Feed Efficiency in Sheep Through Rumen Manipulation and Producer Adoption

Summary

All animal procedures were approved by the University of Wyoming (UW) Animal Care and Use Committee. As part of an ongoing, funded study that began on January 7, 2014, mature ewes (n = 80) fed a forage-based pelleted diet were assessed for individual feed intake over a 60 day period using the GrowSafe System at UW and feed efficiency was calculated from this data. For this study, residual feed intake, or RFI, was used as the measure of feed efficiency that is estimated as the deviation of true feed intake from expected feed intake; low RFI animals are considered more feed efficient and high RFI animals less efficient. Rumen fluid samples (~100 mL per ewe) were collected via oral lavage on February 11, 2014 from all ewes and stored at -80° C until they were processed for DNA sequencing.

Hampshire ewes (n=50) from the University of Wyoming were evaluated for pregnancy and number of expected lambs using ultrasound on December 13, 2014. Eight sets of twin lambs (n = 16) served as the recipients and were set to receive rumen fluid inoculations from either a high RFI or a low RFI donor ewe from the study described above. Upon birth of each set of twin lambs, which were born on or between March 25 and April 14, 2014, rumen fluid (~20 mL per donor) were collected from one low RFI donor ewe and one high RFI donor ewe via oral lavage, and one twin lamb was inoculated (via oral gavage) with the low RFI filtrate and the other with the high RFI filtrate within eight hours of birth. A second inoculation (with fresh rumen fluid filtrate collected from the same donor ewes) was performed two weeks later once the rumen had started to effectively function; this served as “booster” to help ensure establishment of appropriate microbial populations. All lambs were raised by their dams in a similar environment (out on pasture). However, upon weaning, only two complete sets of twin lambs remained due to weather (unexpected adverse weather conditions) and pasture-related death loss in the late spring. All remaining lambs were relocated into one pen and are currently receiving the same forage-based pelleted diet as their donors (alongside lambs of the same age in a feed efficiency trial). Individual feed intake is currently being measured using the GrowSafe System for a 70 day trial period that started September 7, 2014. Residual feed intake will be estimated and rumen fluid samples collected and stored as previously described. A No-Cost Extension Request has been submitted in order to repeat twin lamb inoculations and feed efficiency testing, which will occur in May-September 2015.

Using a full eight sets of twin lambs this coming spring, DNA will be extracted from the rumen fluid collected from both donor and twin lambs (n = 4 donors; n = 16 lambs) and sent to the University of Missouri (MU) DNA Core Facility for sequencing at the end of the feed efficiency trial. Sequence data will be analyzed for differences in inoculation type between twins and compared with adult donor sequence data.

Objectives/Performance Targets

The objectives of this research are to:

1) determine if inoculation of lambs at birth with rumen microbiota from adult sheep identified as highly efficient and lowly efficient alters the rumen microbial profile,
2) determine if lambs inoculated with highly efficient and lowly efficient adult microbiota demonstrate increased and decreased feed efficiency, respectively,
3) enhance producer adoption and application of feed efficiency measures in sheep through development of educational materials and generation of a feed efficiency selection index, and
4) determine the long-term economic implications of improving feed efficiency via rumen microbiota inoculation at birth.

Accomplishments/Milestones

In March and April 2014, eight sets of twin lambs were inoculated successfully within eight hours of birth, and a second inoculation was performed two weeks after they were born. However, due to weather and death losses, we had only two complete sets of twin lambs at weaning. These lambs are currently undergoing feed efficiency testing with a separate set of lambs of the same age to determine preliminary viability of this project. A No-Cost Extension Request has been submitted for a second attempt to inoculate a full 12 sets of twin lambs in the spring of 2015, allowing for an extra four sets of twins to be used as replacements if needed. These lambs will be kept with their mothers in covered facilities in order to negate negative weather and pasture-related death loss. A feed efficiency test will then be completed in August-September 2015, and subsequent DNA sequencing from rumen fluid samples will be performed on eight sets of twin lambs.  Producer educational materials are being planned based on the trial outcomes. Educational materials include mailings of informational pamphlets to area producers (e.g., University of Wyoming Ram Test producers) regarding the importance of feed efficiency and ways to include this trait in selection decisions. An update to the current selection index used at the University of Wyoming Ram Test has also been discussed; producers have an interest in having feed efficiency as a part of that index. Finally, preliminary data has been/is being collected for the planned economic analysis.

Impacts and Contributions/Outcomes

At this time, impacts and outcomes are not available due to insufficient number of twin lamb sets to complete the feed efficiency trial and DNA sequencing of rumen fluid.

Collaborators: