2The nutrients presented to the cow or steer by the rumen are Feed InVFAMicrobial ProteinVitaminsThe nutrients presented to thecow or steer by the rumen arevery different than those enteringthe rumen as feed.
3Digestion Fermentation All CHO must pass through Pyruvate to become VFA
4Some Basics Pyruvate Lactate VFA, H+ Nonstructural polysaccharidesStructural polysaccharidesPyruvate LactateVFA, H+Rumen pH must be defended in the face oforganic acids and H+ production to preventacidosis.
5Rumen papillae epithelium performs at least 3 majorfunctions:protectionmetabolismabsorptionVFA are absorbed passively; thus,the concentration gradient from lumento blood supply must be maintained.Metabolism of some VFA within thecells of the papillae help ensure agradient.
6Some Basics II. Rumen Development A. Newborns are not functional ruminants1. Lack sucrase2. Limited amylase3. Lactase: galactose, glucose4. Ability to digest non-starch polysaccharides precedes that for starch
7Some Basics B. Rumen Development Begins Early 1. Depends on: a. fibrous dietb. inoculationc. VFA stimulation
9Some Basics C. Inoculation occurs by: 1. Feed 2. Inter-animal contact (saliva)3. Manure, soil*occurs with isolation, but much slower and less completely
10Ruminants.... N metabolism vs. Protein metabolism... The quality and quantity of protein (amino acids) fed to the rumen is very different from that delivered to the small intestine because microbes within the rumen fix nitrogen and modify in coming proteins.
20CO(NH2)2 O C Ammonia enters the rumen from multiple sources... NH2 NH2 Urease produced by SOME rumenmicrobes adhered to the rumenepithelium cleaves amino nitrogenfrom blood urea and releases it asfree ammonia. The ammonia in theacid conditions of the rumen isionized (NH4+) and trapped.CNH2NH2Urease
21Ammonia enters the rumen from multiple sources... Trapped ammonia-N exits the rumen as protein, or ammonia for recylingNH3As microbialprotein<Absorption byrumen wall>>Flushing toomasum
22Ruminants.... Ruminants do not require amino acids in their diet Instead they require NThis N can come from amino acids or non-protein N (NPN) sources such as urea
23Rumen undegradable proteins... One of the challenges in formulating ruminant diets is that the AA ratio fed does not reflect the AA profile available to the animalTherefore, there is interest in “Rumen Undegradable Proteins” (RUPs, RBPs)
24Rumen undegradable proteins... RUPs cannot be degraded by the microbes in the RumenTherefore, the amino content of the RUP represents what is being presented to the small intestine of the animal