Metabolic and microbial impacts on reproduction in livestock
Swartz, Jeffrey David.
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Variations exist in the reproductive outcomes of livestock animals impacting the financial sustainability of livestock operations. The objectives of this study were to determine if temporal variations in intake, metabolites, hormones, and/or the vaginal microbiota co-varied with reproductive outcomes using two lines of Rambouillet ewes selected for high or low reproductive rates. Ewes were fed from GrowSafe bunks and blood sera were collected before and during gestation. Sera were assayed for glucose, NEFA, cortisol, triiodothyronine, thyroxine, IGF-I, and progesterone concentrations. The vaginal tracts of Rambouillet ewes and crossbred cows were sampled by vaginal lavage. Microbes present in vaginal samples were determined by sequencing of their 16s ribosomal RNA gene and taxonomy was assigned by naïve Bayesian classification using the 16s rRNA gene database of SILVA. Average total intake did not differ (P > 0.05) between lines of ewes throughout the study. However, kg of TDN x total kg of lamb born -1 x ewe -1 was greater (P d 0.05) for LL ewes than for HL ewes. We observed a line and day of gestation effect for progesterone and thyroxine concentrations. Cow and ewe vaginal microbiota did not differ (P > 0.05), although cow microbiota exhibited greater (P d 0.05) diversity compared to ewe microbiota, and both differed (P d 0.05) from other described vaginal ecosystems. Temporal microbial compositions of open, pregnant, and aborted ewes did not vary by individual, by line, or with age. Microbial compositions did cluster by ewe pregnancy status at time of sampling and by the day of trial. Several microbial taxa were found to co-vary with mucus secretions, P4 concentrations, and pH. Rambouillet ewes that became pregnant and those that remained open did not exhibit significant differences in genera composition of their microbial communities. Future research is needed to determine if there are differences in species, strains, or metabolites produced by these communities.