Teaming with Microbes (DVD)

Instructions: Discuss with a class partner each of the following questions for 2 minutes. Write down your notes and be prepared to share your thoughts with the rest of the class if/when called upon.

1. Why is the rumen mat so important for proper rumen function?

The large particles four in the rumen mat is the source of stimulation to make the cow chew. Chewing, in turn makes her produce saliva, which is rich in bicarbonate and phosphate buffers. The salivary buffers help neutralize luminal VFA and thus help maintain higher rumen pH. A pH near neutrality is important to optimize energy extraction from fiber (NDF) in the rumen and maximize the production and supply of bacterial protein to the host animal.

2. What are the three types of protozoa described in the movie and what do they feed on? Explain the consequences of having protozoa in the rumen?

The three types of protozoa described in the movie were: Entodinium (Flagellate); Isotrichia (ciliates), and Ophryoxolex

Protozoa can feed on feed particles (granule of starch for example) but the also act as “predators” of bacteria. In other words, they can feed on bacteria.

3. Explain some of the consequences of having protozoa in the rumen.
  • By ingesting granules of starch, the protozoa can have a “stabilizing effect” on rumen fermentation (for example slow down the rate of VFA formation be effectively “protecting” starch from rapid degradation by bacterial enzymes.
  • By predating on ruminal bacteria, protozoa in effect decrease the efficiency of microbial synthesis and supply to the small intestine because of internal “nitrogen recycling” within the rumen.
  • Finally some protozoa seem to live in symbiosis with methanogens (bacterial species that ferment fiber and produce methane). Methane is a loss of energy to the animal and when eructed contribute to greenhouse gas emission to the atmosphere (and thus contribute to climate change).

4. Describe the change in volatile fatty acid (VFA) pattern in the rumen of ruminants with a change in forage to concentrate ratio in the diet.

With increased concentrates (i.e., less forages and thus less fiber), one will observed :
  • higher total VFA (lower rumen pH)
  • Decreased proportion of Acetate (from 70-80 to < 50%)
  • Increased proportion of propionate (from 20 – 25 to > 50%)
  • Slight increased in proportion of butyrate (< 10 % to about 10-15%)

5. Both dairy and beef cattle are ruminants. A typical lactating cow diet contains approximately 30% NDF (more than 45% forage), but a typical finishing beef diet contains approximately 10% NDF (less than 15% forage), Why is there such a large difference in the proportion of forage (and thus concentrates) in the ration of a lactating cow and a finishing beef?

The need to maintain higher forage in the diet of dairy cattle come from the need to maintain a high fat test in the milk (which historically has been as the basis of milk component pricing system). Lowering fiber in the diet will results in low fat test.
In contrast the reason of such low fiber level in finishing beef cattle diet is because of the need to maximize animal growth by providing high energy diets that bring the steer to market weight in the minimum number of days (as a way to lower the overhead cost of maintenance.)

Keywords:Teaming with Microbes   Doc ID:66670
Owner:Michel W.Group:DS 414 Ruminant Nutrition
Created:2016-09-05 16:54 CDTUpdated:2016-09-13 11:34 CDT
Sites:DS 414 Ruminant Nutrition
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