- Animals: sheep
- Animal Production: inoculants, livestock breeding
- Education and Training: extension, mentoring
- Farm Business Management: budgets/cost and returns, value added
Improvements in livestock feed efficiency can translate to reducing feed usage while maintaining animal performance, and in turn, may improve profitability for producers. Mammals have sterile gastrointestinal (GI) tracts until birth that are continually colonized by microbial populations until weaning, when microbial populations become stabilized. The GI tract microbiota has been demonstrated to differ in composition and abundance with differences in host feed efficiency. Furthermore, altering GI tract microbiota has been shown to improve overall GI health and enhance nutrient uptake efficiency in humans and rodents. The objectives of this study were to: 1) determine if inoculation of lambs at birth with rumen microbiota from adult donor sheep identified as highly efficient and lowly efficient alters recipient rumen microbial profile, 2) determine if lambs inoculated with microbiota from highly efficient adults demonstrate increased feed efficiency post-weaning, and if lambs inoculated with microbiota from lowly efficient adults demonstrate decreased post-weaning efficiency, 3) determine and improve producer adoption and application of feed efficiency measures in sheep, and 4) determine the long-term economic implications of improving feed efficiency via rumen microbiota inoculation at birth. Ultimately, our goal was to improve feed efficiency in sheep through 1) development of producer-friendly tools and strategies that improve feed efficiency, and 2) improved producer knowledge and use of feed efficiency measures and applications. Mature Targhee ewes (n = 60; initial BW = 45.8 ± 2.5 kg) fed a forage-based pelleted diet were assessed for individual feed intake over a 70 d period using the GrowSafe System and residual feed intake (RFI), a measure of feed efficiency, was calculated. Low RFI animals are considered more feed efficient, and high RFI animals less efficient. Rumen fluid samples were collected from the selected ewes (donors; n = 4) at the end of the trial and stored until processing. Five sets of Hampshire twin lambs (recipients; n = 10) received rumen fluid inoculations from either a high RFI or a low RFI donor ewe at birth, and again two weeks later to help encourage establishment of appropriate microbial populations. All lambs were raised by their dams in a similar environment in one pen, weaned, and received the same forage-based pelleted diet as their donors. Individual feed intake was measured using the GrowSafe System for a 70 d trial period, RFI was estimated, and rumen fluid samples were collected at d 35 from the twin lambs. VFA concentrations were measured and DNA was extracted for sequencing from the rumen fluid of the donors and recipients. Paired-end reads were filtered, quality trimmed, and compared with a database of known 16S rDNA genes. Operational taxonomic units (OTU) were defined as sequence clusters with ≥ 97% identity. Of the 5 sets of twin lambs, 3 sets exhibited the same feed efficiency status as their donor compared with their respective twin. Results from the rumen microbiome metagenomics analyses suggest that low RFI recipients and donors exhibit greater rumen microbial diversity compared with high RFI recipients and donors, respectively. However, there were no patterns to suggest that recipients had similar rumen microbial communities to either their donor or to their respective twin. While further research is necessary to determine whether rumen manipulation may be successful, selecting for feed efficiency remains an economical trait to select on. Therefore, education materials will be developed and distributed to enhance producer awareness and understanding of feed efficiency measures and tools, including the economic analysis performed in this study. Finally, producer adoption will be determined via feedback on materials and information assessed using surveys and interviews.
Mammals are born with sterile gastrointestinal (GI) tracts which are continually colonized by microbial populations until weaning, when microbial populations become stabilized (Tannock, 2007). Microbial type and abundance are highly variable among individuals and once established in the GI tract, composition of microbiota is highly resilient to short-term changes. There is evidence that the GI tract microbiome may be genetically associated with the host. In mice, approximately 5% of the variation in taxa among individuals was attributed to family and litter, and composition of GI microbiota was not significantly different among littermates, suggesting that host genetics play a significant role in composition and variation of taxa (Ley et al., 2005; Benson et al., 2010). Similarly, in human twins it was reported that intestinal microbial profiles were 98.5% similar and they also shared 98% similarity with their mother, while unrelated individuals only shared 96% similarity in microbial profiles (Turnbaugh et al., 2009).
While there is evidence that the GI tract microbiome is genetically influenced, there is also data to suggest that changes in the composition of GI tract microbiota have been associated with several diseases in humans and mice, including obesity, coronary heart disease, diabetes and inflammatory bowel disease (Anderson et al., 2009; Benson et al., 2010; Spor et al., 2011). In response to these associations, altering the microbiome has become an area of interest, particularly in human health, in an effort to overcome GI tract diseases. In a study by Van Nood et al. (2013), infusion of healthy donor feces through a nasoduodenal tube into human patients (n = 16) with a Clostridium difficile infection allowed 15 of those patients (94%) to fully recover and stay in remission for 10 weeks. Patients were able to increase diversity of fecal microbiota over a two week period after infusion until they became undistinguishable from the fecal microbiota diversity of the donors (van Nood et al., 2013).
Similarly, the GI tract microbiota have been observed to differ in composition and abundance between obese and thin individuals, as well as differences in metabolic pathways utilized. Obese mice were reported to have a shift in relative abundance of taxa compared with their lean counterparts, and obese mice seemed to be more efficient at harvesting energy from food than lean mice (Ley et al., 2005). Furthermore, mice and rats that have been inoculated with microbiota from obese donors exhibited decreased feed intake and increased adiposity, which suggested an increased ability to utilize nutrients (Backhed et al., 2004; Turnbaugh et al., 2009; Liou et al., 2013). It is of interest as to whether similar influence can occur in the rumen, especially in domesticated livestock, to improve feed efficiency.
Including feed efficiency as a trait of selection has been gaining interest in the sheep industry because it can be an important trait to producers to reduce input costs or improve stocking ratios, both of which can translate into increased profitability. Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between the actual feed intake and that predicted based on the individual’s ADG (Koch et al., 1963); a lower RFI measurement (i.e. more negative) denotes better feed efficiency. Because RFI is moderately heritable and is independent of growth and mature body size, it has become a commonly applied measure of feed efficiency for livestock (Carberry et al., 2012). Limited research has been done to determine whether inoculation with donor rumen microbiota will change microbial profiles and metabolic pathways in ruminants.
The goal of this Western SARE Graduate Student Grant was to determine the potential to improve feed efficiency of sheep through manipulation of the rumen microbiota (i.e. rumen microbial species) at birth. We hypothesized that inoculation of lambs at birth with rumen microbiota from feed efficient adult sheep would alter lamb rumen microbiota and result in improved feed efficiency post-weaning. Human and laboratory animal research have demonstrated that microbiota can be positively altered through similar inoculation processes. The specific objectives of this grant included:
Objective 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.
Objective 2. Determine if lambs inoculated with highly efficient and lowly efficient adult microbiota demonstrate increased and decreased feed efficiency, respectively.
Objective 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.
Objective 4. Determine the long-term economic implications of improving feed efficiency via rumen microbiota inoculation at birth.
Our long-term goal was to improve feed efficiency in sheep, and increase producer knowledge and awareness of the importance of feed efficiency in improving resource utilization and profitability. Improvements in feed efficiency can result in 1) decreased feed usage; 2) increased stocking ratios; and 3) improved producer profitability through less input costs (e.g., decreased feed usage) or greater outputs (e.g., increased stocking ratios).