Developing the rumen superpower
The rumen serves as a fermentation vat that allows for the digestion and extraction of energy from fibrous feedstuffs that simple-stomached animals cannot utilize. This ability to turn ordinarily undigestible feeds into valuable meat and milk products should be considered nothing short of a superpower, and it is what makes ruminants a unique, valuable, and sustainable source of food.
Interestingly, ruminants are born with an undeveloped rumen and are, therefore, unable to make good use of fibrous feedstuffs until their rumens have properly developed. As such, it is critical to prioritize rumen development early in life so that, later in life, they can more thoroughly digest and make use of fibrous feedstuffs.
Before starting, it is important to note that a vast majority of all rumen development research has focused on the young dairy calf. While the physiological processes of rumen development likely vary little between species, feeding strategies do vary and some strategies for feeding young calves may not be applicable to young kids.
The fermentation of feeds within the rumen produces volatile fatty acids (VFA) consisting mostly of acetate, propionate and butyrate. These VFAs are the predominant energy source for ruminants not consuming milk. However, these VFAs cannot be well absorbed until the rumen is well developed.
Rumen development is primarily driven by the intake of concentrates, not hay or milk. Penn State University has an excellent resource that helps visualize the different impacts these three feeds have on rumen development.
Fermentation of concentrates – specifically nonfiber carbohydrates (starch, sugars and pectins) – results in increased production of propionate and butyrate, which are the two VFAs that drive rumen epithelial development. As the rumen epithelium develops, fibrous feedstuffs become more digestible. This is why adequate intakes of a high-quality starter are important for young dairy ruminants prior to putting them on a feedstuff consisting mostly of forage or other nonforage fiber sources.
Another aspect of starter feed that is important for healthy rumen development is what is called “scratch factor.” Scratch factor relates to feed particle size and abrasiveness. Abrasiveness is important because it ensures that old, dead epithelial cells are “scratched away” and the rumen papillae can continue to develop and grow, which will maximize VFA absorption. Put simply, it’s rumen wall exfoliation.
In the dairy calf world, texturized starters with whole corn provide the scratch necessary for healthy papillae development. In situations where fine ground or complete pelleted feeds are offered to calves, cottonseed hulls or chopped hay or straw may be used to provide scratch in the ration. Just keep in mind, fiber will limit intake. For preweaned calves, cottonseed hulls are best kept to less than 10% of the ration and chopped hay or straw should be kept to less than 5% of the ration.
The primary thing to keep in mind here is that microbial populations shift with changing feedstuffs and dictate the proportions of the three primary VFAs produced in the rumen. This is why diet transitions should be made gradually.
Two primary groups of bacteria within the rumen are amylolytic bacteria (which digest nonfiber carbohydrates and primarily produce propionate and butyrate) and fibrolytic bacteria (which digest fiber and primarily produce acetate). Young preweaned ruminants on high-concentrate starters will have increased proportions of amylolytic bacteria within the rumen. To effectively convert them to a diet with increased levels of fiber after weaning, it is important to increase the proportion of fibrolytic bacteria within the rumen. This can be accomplished by slowly ramping up the amount of fiber offered in the diet.
At the end of the day, animal response and performance should be the determining factor of what is or isn’t a successful feeding program. Trust the animals and don’t force a feeding decision just because it makes sense on paper or “that’s what we’ve always done.”
Dairy Goat Performance