Improved ruminant health and productivity through neonatal microbiome manipulation

Summary

This project was comprised of two parts;

Part 1 (the Pilot Trial) was designed to determine the effect of diet and genotype on the rumen microbiome of ewes, as a prelude to the manipulation of their offspring. The main purpose of the Pilot Trial was to identify and provide two different rumen microbe populations which could be used in the second part of the project.

Part 2 of the trial (Lamb Trials x 2) was then designed to identify the extent to which early exposure of ruminant neonates to different maternal microbes (through inoculation with foreign microbes versus naturally-acquired microbes) influences their subsequent health and growth efficiency through immune priming and the establishment of an efficient microbiome.

These trials were designed to deliver against the following objectives:

a) Define the characteristics of the rumen microbiome of sheep of different breeds and with different growth characteristics,

b) Determine the extent to which phenotypic differences in growth and health can be attributed to differences in the maternally-derived microbiome in the early post-natal period,

c) Determine the extent to which the immune system is affected by early life manipulations,

d) Determine the potential for early-life microbiome manipulations for sheep (and potentially cattle).

The pilot trial imposed two different dietary treatments on White Suffolk and Poll Merino ewes (24 Poll Merino and 24 White Suffolk ewes). This trial was the first to show that there are differences in microbial profiles induced by both genotype and diet in these breeds of commercially utilised sheep.

The two subsequent lambing trials, looked at the effects of natural maternal inoculation, compared to an imposed inoculation, of known rumen microbial populations of lambs at birth. These trials ran over separate lambing blocks, both involving 49 lambs grown out to a week 18 slaughter date, with both Merino and White Suffolk lambs. Lamb Trial 1 examined the differences between naturally-inoculated lambs (Maternal Control) and those given rumen fluid, either from ewes fed a Roughage type diet or ewes fed a High Spec. (effectively high grain) diet. Lamb Trial 2 employed a similar experimental design, except the lambs were either naturally-inoculated, or given fluid from ewes fed a High Spec. diet only (sickness in the Roughage inoculation group in Lamb Trial 1 forced removal of the Roughage treatment in Lamb Trial 2).

Briefly, the inoculation of lambs with 10ml of mature ewe rumen fluid daily, for one week following birth, resulted in significant differences in rumen bacterial communities at all phylogenetic levels (phyla, class order, family, genus and species) to those of un-inoculated (Maternal treatment) lambs. These differences were evident in rumen samples at weaning (10 weeks of age), and in rumen and intestinal samples at slaughter (18 weeks of age). Both the efficiency and the health of the inoculated animals appears to have been detrimentally affected by artificial inoculation, with the effects differing across inoculation and breeds. While this appears to be a negative result, we have demonstrated that lifelong changes (up until slaughter at week 18) in the rumen and intestinal microbiome can be induced by early intervention in microbial establishment.

Questions raised by the project results for future investigation include;

a) Is this lifelong effect seen with other early life interventions, such as manipulation of the Maternal diet to alter the natural inoculation of the lamb?

b) Can beneficial effects be seen by 'assisting' the colonisation of the lamb through pre and probiotics, rather than via inoculation?

c) Can a beneficial effect be demonstrated after manipulating the neonatal microbiome or is the system of Maternal inoculation and natural colonisation of the lamb rumen close to optimum