Bovine Nutrition and Metabolic Disease 1 - Feedstuffs, Feeding Systems and Feed Intake

Question 1

Main aims of feeding cows.

Answer 1

Good rumen health.
- turns non-protein nitrogen sources and fibre into microbial protein which they can digest.
Good cow health.
Efficient production and sustainability.
- reduce greenhouse gases.
- fertiliser use.
– legumes that fix nitrogen from the atmosphere will reduce need for artificial fertilisers, reducing risk of environmental contamination and waste.
- soil health.

Question 2

1. What is a forage?
2. What are supplementary feeds?
3. What does NDF content mean?

Answer 2

1. e.g. grass, silage, straw, maize, turnip tops.
   Provides largest proportion of diet volume and fibre.
   - quality important.
2. e.g. wheat, soya, maize gluten.
   Balance out nutrients in the forage and increase nutrient density to ensure cow receives all nutrients needed within DMI.
3. Neutral detergent fibre content.
   - fibre left when treated with a neutral pH detergent.
   - forage >50%.
   - supplementary feeds <50%.
   – more nutrient-dense.

Question 3

Neutral detergent fibre (NDF).

Answer 3

Cell wall content.
- cellulose, hemicellulose and lignin.
High NDF:
- straw.
– high rumination, high rumen fill, high salivation (rumen pH buffering), low energy density, high acetate production, low cost.
Low NDF:
- wheat.
– low rumination, low rumen fill, high salivation, high energy density, low acetate production, high cost.

Question 4

Why do we consider acetate?

Answer 4

Acetate is the precursor for milk fat.
So need to increase dietary fibre to increase milk fat.

Question 5

1. Fresh forages.
2. Conserved forages.

Answer 5

1. Grass.
   Forage crops (e.g. rape/kale).
2. Ensiling (e.g. grass/maize silage).
   Drying/wilting (e.g. hay/straw).

Question 6

1. What does amount and quality of grass depend on?
2. What does grazing intake depend on?

Answer 6

1. Soil type and rainfall.
   Variety +/- clover.
   Fertilisers.
   Sward quality.
2. Access time.
   Sward height and density.
   DM content.

Question 7

1. Why does intake per day decrease as the year goes on?
2. What must be done to ensure adequate intake?
3. Main objectives of grazing strategies?

Answer 7

1. Because the grass becomes less palatable and more fibrous as the year goes on. Is lower in nutrients too.
   - higher in proteins and sugars, low in DM earlier in the year so easier to eat.
2. Increase hours spent grazing in the day.
   Supplementary feeding.
3. Maximise DMI and minimise damage to pasture.

Question 8

1. Main reason to house cattle in UK?
2. Types of grazing strategy?

Answer 8

1. Protect the fields and soil.
2. Continuous.
   Rotational (“paddock”).
   Strip.
   Zero.
   Extended.

Question 9

Conserving grass.

Answer 9

Silage:
- clamp.
- big bale.
Haylage.
Hay.
As move down this list, become more mature, increase DM, increase NDF, decrease energy and protein, decrease moisture.

Question 10

Round bale vs clamp silage.

Answer 10

Round bale reduced labour compared to clamp.
Round bale reduced cost compared to clamp.
Round bale reduced power compared to clamp.
No clamp required with round bales.
Reduced quality in round bale compared to clamp.
Increased chop length for round bale compared to clamp.
Round bale increased spoilage risk compared to clamp.

Question 11

Other silages.

Answer 11

Maize silage.
- v popular (dairy).
- increased energy and protein.
- increased yield and milk quality.
Whole crop cereals.
- e.g. wheat and barley.
- fermented whole crop vs Alkalage.
- decreased energy, increased protein, increased milk quality.

Question 12

Silage making.

Answer 12

Primary fermentation.
- anaerobic.
- lactobacilli –> lactic acid.
- pH <4.5.
- rapid pH drop produces a stable silage.
Increased water soluble carbohydrate (sugars) (minimum 30g/kg fwt).
- early season (~May).
- wilting – remove moisture to concentrate sugars, less water means fewer hydrogen ions to reduce pH and less effluent wastewater running out of the crop (toxic).
- afternoon cropping.
Increased DM.
- dry, windy weather.
- wilting.
- appropriate maturity.

Question 13

Secondary fermentation.

Answer 13

Clostridial spp.
- butyric acid / protein degradation.
- decreases palatability which decrease DMI.
- reduces nutritional content.
Fungi and fungal toxins, mycotoxins.
Other bacteria and toxic products.

Question 14

How can secondary fermentation be reduced?

Answer 14

Good primary fermentation.
- stable at pH<4.5.
Anaerobic conditions.
- chop length.
- consolidation.
- sheeting.
Long, narrow, deep pit.

Question 15

Silage additives.

Answer 15

Acids or acid salts (e.g. formic/sulphuric) - reduce pH.
Sugars (e.g. molasses).
- increase soluble CHO.
- increase palatability.
Inoculants - start fermentation.
Enzymes - release CHO.

Question 16

Hay.

Answer 16

Dried grass.
Cut later.
Left on the ground/turned for longer.
Needs good, sunny, dry conditions for ~1w.
If not dry enough, can heat, ferment and even spontaneously combust.

Question 17

Straw.

Answer 17

“Stalks” of cereal crops (by-product).
Dry at time of harvesting.
Very high DM (~85-90%) but extremely fibrous and reduced nutrient density (~6MJ ME/kg DM, ~3% CP).
Price very variable.

Question 18

Supplementary feeds.

Answer 18

Grains, beans.
Fed to make up for deficits in forages.
Straights.
Compounds.
Premixed blends.

Question 19

Straights.

Answer 19

Primary feeds.
- e.g. soya bean meal, wheat, maize gluten, sugar beet pulp.
By-products.
- e.g. Brewers grains, apple pomace, biscuit waste.
“Energy” or “protein” feeds.

Question 20

Compounds.

Answer 20

Mixture of straights milled and pelleted.
Formulated to specification.
- e.g. 18% CP (often on least cost basis).
Contents may vary.
Matched to silage.

Question 21

Premixed blends.

Answer 21

Similar to compounds but not pelleted.
Formulated to a specification.
+/- milled.
Dusty and absorb water.
Can “see” what’s in them if NOT milled.

Question 22

Voluntary feed intake.

Answer 22

Appetite.
The 1st rate limiting step when feeding cows.
- i.e. can only get energy and protein from the food they eat!

Question 23

Cow factors of VFI.

Answer 23

Size - increased size = increased VFI.
– e.g. Holstein vs Friesian.
Yield - increased yield = increased VFI.
– even in 2 identically sized animals.
BCS - increased BCS = decreased VFI.
– rumen size and drive to eat.
Pregnancy stage:
- pre-calving – foetal size.
- post-calving – rumen size / adjust to new diet.
Presence of other animals.
Familiarity of environment.

Question 24

Feed factors of VFI.

Answer 24

Palatability.
- quality.
– increased NDF means increased time to digest means increased rumen fill meaning lower VFI.
- moisture content.
– VFI reduced if too wet or too dry.
- taste.
– select for sweet, avoid sour/bitter.
- chop length.
– VFI increased if short chop length.
- complete diet / mixed forages means increased VFI.
– improved rumen function.
– improved taste.
– Balanced nutrient intake.
Little and often.
- generates interest and stimulates eating.

Question 25

External factors of VFI.

Answer 25

Access.
- truly ad lib – 24hr access, 5% remaining.
- bullying.
- space – minimum 70cm trough per animal.
Day length - artificial light in winter.
Water - constant free access.
Ambient temperature - heat stress.

Question 26

On what basis is VFI calculated?

Answer 26

On a dry matter basis.
- i.e. convert wet weight intake in kg into dry matter by multiplying by dry matter content.
e.g. if intake is 44kg silage (27% DM) and 10kg concentrate (87% DM).
Actual DMI = (44x 0.27) + (10 x 0.87).
= 20.58kg DM/day.

Question 27

Predicting DMI.

Answer 27

Rule of thumb:
- 2.5% bwt +10% of yield (both in kg).
- 3% bwt (at BCS 2.5, mid lactation and not in calf) (less commonly used).
Computer programs.
Tables.

Question 28

1. What prediction does a correction factor of >1 suggest?
2. What prediction does a correction factor of <1 suggest?

Answer 28

1. The cow is likely to eat more than her predicted DMI.
   - e.g. complete diet/TMR, Holstein, parlour feeding, mixed forages.
2. The cow is likely to eat less than her predicted DMI.
   - e.g. heifers grouped with cows, self feed silage, poorly preserved silage, electric fence at silage face, week of lactation.