Monitoring nutrition on farm

Question 1

Which diseases are we trying to avoid?

Answer 1

• ketosis and NEB
• hypocalcaemia

Question 2

NEB - when are cows at risk?

Answer 2

• just after calving
• at peak lactation

Question 3

Effects of subclinical ketosis/NEB

Answer 3

• reduced milk quality
• decreased fertility
• impaired immune function (-> metritis/RFM, mastitis)
• role in other dz (e.g. LDA)

Question 4

BCS - key targets

Answer 4

• no change over dry period
• max decrease of 0.5 between calving and peak lactation
• aim for 2.5-3 at calving, esp avoid >3

Question 5

Metabolic profiles

Answer 5

• Blood sampling a random selection of cows at specific stages
• Usually “transition” cows (e.g. 21-7d pre-calving) and fresh calvers (e.g. 10-25 days in milk)

How many samples?
- Varies a bit with size of group (e.g. number of dry cows)
- 8-12 samples/group often appropriate

Interpreting results
- Target prevalence of high BHB or NEFA <10-20%
- Usually means any abnormal results suggest a problem
- >=3/12 abnormal results taken to indicate herd problem

Question 6

Key indicators of energy balance

Answer 6

BHB (beta-hydroxy butyrate)
– Ketone body
– Current energy supply/demand
– Esp useful in fresh calvers

NEFA (non-esterified fatty acids)
– Transport form of fat
– Indicator of fat mobilisation
– Esp useful for transition

Question 7

Using milk parameters

Answer 7

• Many approaches – BF:Pr ratio (FPR) most common
• None have good research evidence for UK situation, but common in practice
• 1.4 is the cut off for normal BF:Pr for what is thought of as abnormal - may have NEB.
• Easy “first step”, then investigate further with BCS/bloods?

Question 8

How does NEB affect BF:Pr ratio?

Answer 8

• milk protein tends to be lower, and butterfat tends to go up (more circulating fat, some tends to leak into the milk)

Question 9

How does increased yield affect BF:Pr ratio?

Answer 9

• will dilute the constituents out more so have lower protein and butterfat

Question 10

How does increased fibre affect BF:Pr ratio?

Answer 10

• same protein, increased butterfat

Question 11

Ration analysis

Answer 11

• Assess feed intake (“DMI”)
• Calculate ration energy density and therefore daily energy intake
• Compare to cow requirements
• Specialist software available

Question 12

NEB - effect on transition/calving

Answer 12

• poor DMI
• excess BCS/overfeeding

Question 13

NEB - effect on early/peak lactation

Answer 13

• poor DMI
• low ration energy density

Question 14

Rough target DMI for transition (late dry period) cow

Answer 14

> 12kg/d

Question 15

Rough target DMI for high yielding cow

Answer 15

> 23kg/d

Question 16

Measuring DMI

Answer 16

• DMI = (kg fed per head – kg leftover refusals per head) * DM% of ration
• or compared to what the ration sheet (“recipe”) says

Question 17

Improving dry matter intake

Answer 17

• Minimise (impact of) group changes
• Easy access, trough space per cow
• Avoid over-conditioned cows (especially at calving)
• Maximise ration palatability
• Manage environment appropriately (temp, humidity, comfort)
• Especially important around calving – “natural” drop in DMI

Question 18

Ration formulation (& why it can go wrong)

Answer 18

• Diet usually carefully formulated by nutritionist
• Almost always using software which flags “problems”

Why might it go wrong?
- Something “wrong” with calculated ration?
- Not being mixed or fed correctly?
- An element of the diet has changed
– e.g. silage changes in quality as the clamp is fed

Question 19

Why can’t we just increase the diet energy density?

Answer 19

• Energy densities of ingredients don’t vary all that much
• Need to maintain fibre intake to keep rumen healthy

Question 20

Additives/”treatments” to ration formulation

Answer 20

• Propylene glycol
• Protected methionine
  – Improves fat export from liver
• Linoleic acid
  – Fatty acid with less tendency to accumulate in liver
• Monensin
  – Antibiotic, changes rumen flora to aid energy balance - bolus for “at risk” cows
  – Most herds shouldn’t need to use Monensin

Question 21

Hypocalcaemia: Aetiology

Answer 21

• Calcium in milk&raquo_space;> circulating calcium pool
• Sudden increase in demand at calving (lactation)
• If stores (mainly bone) not mobilised quickly enough:
  – Circulating [Ca] falls
  – Clinical or subclinical “milk fever”

Question 22

Hypocalcaemia: Pathophysiology

Answer 22

decreased plasma calcium concentration -> decreased muscle activity

effect on skeletal muscle:
- clinical signs of milk fever (recumbency etc)

effect on smooth muscle:
- subclinical effects
- uterus -> increased uterine infection
- GIT -> increased abomasal dz, decreased DMI

Question 23

Hypocalcaemia: Diagnosis

Answer 23

Clinical milk fever:
- Characteristic clinical signs
- Blood sample shows low plasma Ca

Subclinical milk fever:
- More difficult
- Control restored within 2-3d of calving
- Can monitor
– Clinical case rate
– Using blood samples within 24-48hrs of calving
– Urine macrominerals

Question 24

Hypocalcaemia target rate

Answer 24

<5 cases/ 100 cows/ year is a common target

Question 25

Hypocalcaemia prevention

Answer 25

- Feeding in the final 2-3 weeks before calving is key to preventing hypocalcaemia

Question 26

DCAB

Answer 26

- Difference between concentrations of major cations (Na+, K+) and major anions (Cl-, S2-) in the diet -- i.e. it’s just a chemical property of a feedstuff or diet - DCAB = ([Na+] + [K+]) – ([Cl+] + [S2-]) (all in mEq/kg DM) - Diets with low DCAB (<0 mEq/kg DM) induce mild metabolic acidosis - metabolic acidosis means: -- Enhanced uptake of Ca from the GI tract -- Ca mobilisation from bone -- Higher rate of vitamin D3 activation per unit PTH -- Increased target tissue sensitivity to PTH and activated vit D3 -- So the cow is able to mobilise Ca from body reserves more quickly

Question 27

DCAB manipulation - "True" or "Full" DCAB

Answer 27

- Aim for diet DCAB around -100 mEq/kg DM - Likely to require use of anionic salts (e.g. MgCl2, MgSO4) -- anionic salts don't taste nice so large use will decrease DMI - Usually needs Ca supplementation too - Effective but more involved/ expensive

Question 28

DCAB manipulation - “Partial” DCAB

Answer 28

- Aim for diet DCAB around 0 to -50 mEq/kg DM - Often just by choosing lower DCAB feeds, may also use salts - Usually doesn’t require Ca supplementation - More common in lower yielding herds

Question 29

DCAB of grass silage

Answer 29

- can vary substantially, and may be >500mEq/kg DM

Question 30

Other methods of hypocalcaemia prevention

Answer 30

Ca restriction - “Conditions” homeostatic mechanisms to be more efficient at Ca uptake/mobilisation - Hard to get diet [Ca] low enough with normal feeds - Ca binding feedstuffs available -- Work well but moderate cost -- Becoming popular in UK Other methods - Mg supplementation -- Mg required for production of PTH -- Generally not very effective alone - Prophylactic treatment -- Ca boluses most appropriate -- Often targeted e.g. at older cows

Question 31

Why is dry cow feeding vital?

Answer 31

To: - Maintain DMI around calving, and prevent problems with early lactation negative energy balance - Prevent clinical and subclinical hypocalcaemia

Question 32

How to maximise DMI - the ration

Answer 32

* Increase palatability - Improve taste e.g. molasses - “Open” ration - Approximately 50% dry matter * Allow 10% refusals (left over) for true ad lib feeding * Remove left over feed * Make ration fresh daily * “Push up” regularly * Keep feed face/trough clean

Question 33

How to maximise DMI - feed face design

Answer 33

* Adequate feed face (length) * Ensure neck rail not pushing on neck * Shiny feed surface * Good access to feedface * Dividers to reduce bullying (must be comfortable)

Question 34

How to maximise DMI - other

Answer 34

* Ensure adequate water access * Maintain appropriate body condition * Maintain appropriate environment (e.g. avoid heat stress)

Question 35

Dry cow ration

Answer 35

* Dry cows are not lactating so require less energy * Maximising intakes is still important * The ration contains a much higher proportion of straw

Question 36

How to reduce sorting

Answer 36

* Cows may “sort” the ration * Compare before and after * Avoid with short chop length for long fibre