Bovine Nutrition and Metabolism 4

Question 1

What is the expected DMI in dry cows?

Answer 1

~2% of bodyweight
10-15 kg/day

Question 2

List two physiological factors that reduce DMI in cows

Answer 2

Increase calf size
Increase BCS and reduce appetite

Question 3

What is the aim for BCS at drying off and calving?

Answer 3

2.5-3

Question 4

What are the energy requirements of cows in at drying off and near calving ?

Answer 4

At drying off ~(65+15) = 80MJ/day
Near calving ~(65+45) = 110MJ/day

Question 5

List three things that digestible undegraded protein is used for in the dry period.

Answer 5

Foetal growth
Increased milk yield and quality
Increased fertility

Question 6

What is an advantage of a single ration for dry cows?

Answer 6

Avoids sudden change in diet during early dry periods which may maintain better improved energy balance and reduced risk of LDAs.

Question 7

How would you offset the cost of a having a single ration dry cow diet?

Answer 7

+/- shorter dry periods to offset the cost

Question 8

What is the calcium requirements in lactation?

Answer 8

~2g per litre of milk

Question 9

List three methods to prevent milk fever

Answer 9

Calcium restriction
Magnesium supplementation
DCAD/DCAB manipulation

Question 10

What is the ideal amount of calcium in a dry cow diet to prevent milk fever?

Answer 10

<20g/day

Question 11

List three feeding strategies for calcium restriction

Answer 11

Grass/grass silage high in [Ca]
Dilute [Ca[ by increasing straw in ration
Tightly stock transition if at grass

Question 12

Which ion that you can supplement improves calcium mobilisation?

Answer 12

Magnesium

Question 13

List three feeding strategies of magnesium supplementation.

Answer 13

MgCl2 in TMR or drinking water
Can affect ration palatability
Will influence DCAD

Question 14

What is the equation to work out the dietary cation anion difference?

Answer 14

DCAD = ([Na+] + [K+]) - ([Cl-] + [S2-])

Question 15

What happens to cows who have diets with a low DCAD?

Answer 15

Metabolic acidosis in induced and more rapid mobilisation of Ca from body reserves around calving

Question 16

List 4 disadvantages for a full DCAD

Answer 16

Expensive
Unpalatable (reduces dry matter intake)
Very soluble so wash out in the rain
Relative pH instability in the face of variable DMI

Question 17

How would you feed a partial DCAD?

Answer 17

Manipulate feeds to reduce ration DCAD

Question 18

What are two forages you can feed with a low DCAD?

Answer 18

Maize/wholecrop wheat silage
Straw (lowest)

Question 19

What are two straights you can feed with a low DCAD?

Answer 19

Brewers grains
Wheat

Question 20

Briefly describe how peripheral insulin resistance works in cows

Answer 20

High BCS +/- excess ME in early dry period.
Reduce tissue response to insulin.
Reduce dry matter intake increases negative energy balance and increases fat mobilisation.

Question 21

Why is there fat deposition in the liver with a negative energy balance?

Answer 21

Lack of acetyl CoA leads to free fatty acid unable to eneter the TCA cycle.
Depletion of lipoproteins means the liver is unable to export fat.

Question 22

Briefly describe the difference between the two types of ketosis in cattle.

Answer 22

Type 1 - energy intake < output, seen in peak lactation
Type 2 - insulin resistance, fat infiltration of the liver, see around calving

Question 23

List two ways to prevent ketosis in cattle.

Answer 23

Minimise peripheral insulin resistance
Maximise DMI

Question 24

What is the rumen buffered by?

Answer 24

Saliva

Question 25

What causes acute rumenal acidosis?

Answer 25

High quantity of carbohydrate in a short timeframe

Question 26

What are the causes of ‘subacute rumenal acidosis’?

Answer 26

Chronic exposure to high starch levels
Lack of physically effective NDF
Herd level problem

Question 27

List 6 observations you may make of cows with SARA

Answer 27

Change in faecal consistency and incomplete digestion
Poor cow cleanliness
Tail swishing
Reduced DMI and increased sorting
Decreased rumination and increased dropped cuds
Ration assessment

Question 28

What is the maximum amount of feed the cows should get in the parlour?

Answer 28

4kg/feed

Question 29

List two ways to prevent SARA

Answer 29

Improve rumen function
Include buffers