87 Functional rumen microbiological survey of triplet-bearing Polypay ewes from parturition to weaning

Abstract

Abstract Ewes transitioning from late gestation to early lactation face a number of challenges including physiological stress, dietary changes, and metabolic adaptations, particularly when bearing and rearing multiple offspring. Furthermore, rumen microbial composition and function has been correlated with milk production and nutrient density in transitioning dairy cows. However, limited research has evaluated the rumen microbial community of ewes during early lactation. The objective of this study was to conduct a functional microbiological survey of the ewe rumen from parturition to weaning. We hypothesized that ewes would experience fermentative disturbances post-parturition and that the rumen microbiota, and consequently, circulating metabolites, would recover over time. Nine multiparous Polypay ewes bearing triplets were fed a lactation diet consisting of alfalfa hay and concentrate mix to meet protein and energy requirements. One lamb of each triplet set was randomly selected and placed on milk replacer 24 h after birth. The two lambs remaining on the ewe were weaned at 56 d of age. Blood and rumen samples from ewes were collected via jugular venipuncture and oral intubation, respectively, at 2, 7, and 15 d of lactation in addition to at the time of weaning. Rumen bacterial functional guilds were enumerated via serial dilution. Ruminal short-chain fatty acids (SCFA) were quantified via HPLC and serum metabolites by LC-MS. All data were analyzed using PROC Mixed with repeated measures in SAS (v. 9.4, SAS Inst. Inc., Cary, NC). Total starch-utilizing bacteria remained steady during early lactation but increased 100-fold by weaning (P = 0.03). In contrast, the starch-utilizing guild sub-population lactobacilli increased 10-fold by d 15 of lactation (P < 0.01) and remained constant through weaning (P > 0.05). No differences were found in the viable number of rumen cellulolytic bacteria (P = 0.37) throughout the study. Ruminal propionate concentrations increased 35% (P = 0.04) from d 2 to weaning and serum propionate (36.8 ± 4.42 µM; P = 0.08) and glucose (59.8 ± 2.97 mg dL-1; P < 0.01) peaked on d 15 of lactation. While ruminal acetate did not fluctuate in early lactation, it increased 58% by weaning (P < 0.01) leading to an 88% increase in serum acetate (P < 0.01). Ruminal butyrate increased 49% by d 15 (P = 0.01) and this was reflected in a 7-fold increase in serum butyrate (P = 0.02). However, serum β-hydroxybutyrate did not differ from parturition through weaning (P = 0.51). Results of this experiment demonstrate that rumen bacterial functional guilds, as well as rumen and serum metabolites, were lowest two days post-parturition and increased over the course of lactation. This may suggest that ruminal fermentation is suppressed post-parturition, which could have implications for early lactation management strategies of triplet-bearing ewes.