Digestive Disturbances in Feedlot Cattle

Question 1

What % of deaths in a feedlot do digestive upsets contribute?

Answer 1

Only a small amount of total mortality. ~ 5% from digestive disturbances.

Most deaths >90% are related to respiratory disease.

Question 2

By providing starch, once exposed to microbial population it is highly digestible. What are the main VFAs produced from this breakdown of starch?

Answer 2

Bacteria produce the VFAs

• Acetate
• Propionate
• Butyrate

–> major energy sources absorbed across the rumen wall in butyrate itelf in rumen wall or by acetate and propionate in the liver

High forage diets will produce more Acetate, high grain diets will produce more propionate –> gluconeogenesis

Question 3

What is classifed as subclinical (subacute) acidosis?

Answer 3

Episodes of rumen pH < 5.8

Question 4

What is classified as clinical or acute acidosis?

Answer 4

Constant pH < 4.8, lactic acid build up

Question 5

T/F: The amount of starch digestion in the rumen increases with the amount of processing of the grain.

Answer 5

True.

Question 6

T/F: The total tract digestibility is reduced with the amount of processing of the grain

Answer 6

False.

Low digestibility of whole coarse barley. Total digestibility is much higher (in the 90s) of processed grains.

Question 7

How can the effect of choosing different varieties based on their rates of digestion be lost?

Answer 7

By processing the grain.

Question 8

What is precision processing?

Answer 8

The roller is set to a certain thickness - to optimally process the grain (but there are things about the grain that can alter this - variation of kernel size). When the roller is set “optimally” for the large sized kernel or small sized? or somewhere in between does not process either “optimally” but does the best it can to find an inbetween.

Value for screening different partical size. Optimally process the small and large sized grain. —> blend it back together and then it is a optimally processed grain.

*good in feedlot cattle (~80% grain), not on dairy (45% grain)

Question 9

What is the effect of underprocessing barley grain?

Answer 9

decrease acidosis but decrease total tract digestibility of starch.

So the producers are decreasing the digestibility of barley for the 3-5% of the feedlot that would become acidotic but the other 95% are being fed underprocessed barley and will decrease total tract digestibility –> not performing to their maximum level.

Question 10

What was the trend in terms of time the pH < 5.2 in those cattle fed the gradual adaptation diet compared to those fed grain and rapidly adapted?

Answer 10

In the gradual adaptation the amount of time pH was below 5.2 was alot less than those on rapid adaptation

Question 11

Average Daily Gain (ADG): In the rapid digestion group of feedlot cattle they experienced “compensatory gain”. What is meant by this?

Answer 11

Gain less from days 1 - 34, then gain more than the gradual group from days 35 - 69.

But there is no significant change in overall Average Daily Gain between the groups. Adaptation had no effect on ADG as a whole.

Question 12

What is one method being addressed to aid acid utilisation in feedlot cattle and what is one problem associated with this technology?

Answer 12

Lactic acid utilisers and inoculate into feedlot cattle. Introducing bacteria into the animal usually done orally (a drench) although rumen bacteria are ANAEROBIC.

Competetive environment –> protozoa engulfing bacteria aswell.

Question 13

Where are the VFAs absorbed?

Answer 13

Across the rumen wall.

Question 14

What can effect absorbtion of VFAs?

Answer 14

• Reduced SA –> VFAs absorbed across rumen wall
• High osmolarity (in rumen)
• Keratinisation –> change in structure
• Reduced blood flow –> affects transport
• Transport mechanisms

Question 15

Why is there low levels of glucose inside the rumen?

Answer 15

Microbes love to use sugar, when they digest plant cell walls they produce enzymes to break down plant cells wall to sugars e.g. xylose or glucose –> sugars are used for energy and break down to VFA’s.

Use propionate for gluconeogenesis.

Question 16

What system was used to determine how feedlot cattle eat/consume feed and likelihood of developing acidosis?

Answer 16

Behavioural.

A transponder and antennae that lines feed bunk –> records the animals ID and broadcasts it. Although cannot tell how much they ate.

Question 17

T/F: Animals fed high forage diets take longer to consume feed?

Answer 17

True.

Question 18

If an animal was defined as sick, the ration was less. What are some illnesses in the feedlot?

Answer 18

Subclinical or clinical acidosis.

Resp disease: Lung lesions

Question 19

What system actually measured intake of feed in feedlot cattle?

Answer 19

Growsafe Systems - Intake System

Through wireless communication –> downloaded, use the same transponder system (in cattle ear), antennae in bunk itself, Load cells (now we know how much feed there is in the bunk)

Cons of this system: Costly, Changing behaviour (only one animal can feed at a time), Competition

Question 20

What is the purpose of the glycocalyx in the biofilm?

Answer 20

Bacteria exist in a complex biofilm, they live together in a community that carry out digestion of the feed. The glycocalyx is used to attach to the feed - apart of the biofilm.

Question 21

Feed Components: What are the primary fermenters that help digest Starch?

Answer 21

Ruminobacter amylophilus

Streptococcus bovis

Question 22

Feed Components: What feed components are first broken down by Primary Fermenters?

Answer 22

Starch, Cell Wall Polymers and Protein

Question 23

Feed Components: What is protein broken down into by Primary fermenters?

Answer 23

Carbon Skeletons

Question 24

Feed Components: What are starch and cell wall polymers broken down to by Primary Fermenters?

Answer 24

Sugars

Question 25

What is the by-product formed from the breakdown of protein by Primary Fermenters?

Answer 25

NH3 (ammonia)

Question 26

Feed Components: Simple sugars and Carbon Skeletons are broken down by Primary and Secondary Fermenters to form what?

Answer 26

Volatile Fatty Acids:

Acetate + Propionate + Butyrate + H2 +CO2

Question 27

Feed Components: What is H produced from the digestion of Starch; cell wall polymers & protein used for?

Answer 27

to reduce CO2 to Methane (CH4).

If H accumulates, NADH accumulate in rumen and bacteria lack ability to derive ATP from the production of VFAs. H has to go somewhere.

Question 28

What is bloat?

Answer 28

There are 2 types: Feedlot Bloat and Pasture Bloat

Bloat is when the rumen swells up because is can no longer rid gas from fermentaion (not only CH4 but also CO2 (which is greater than CH4 production) Gas must be removed by eructation

Question 29

There are 2 types of Feedlot Bloat;

Answer 29

1. Free gas bloat
(usually no free gas bloat seen in pasture system)
rumenal contractions inhibited (often due to damage of vagus nerve) In this case animals will bloat with no froth in rumen.

2. Frothy Bloat

Froth builds up in cardia (nxt to oesophagus) - senses detect if there is liquid there —> if there is fluid can move up to the oesophagus and down the trachea into the lungs and leads to pneumonia (suppress eructation —> gas build up) animal swells on the left hand side.