FAC31: Diet Assessment in Dairy Cattle Flashcards Preview

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Flashcards in FAC31: Diet Assessment in Dairy Cattle Deck (22):

What are the metabolic diseases?


Milk Fever

Ruminal acidosis

Displaced abomasum

Fertility problems (esp. in high yielding cows)


How do we assess if a diet is working properly?

Milk production - yield changes, peak yields

Milk quality - butterfat and protein

Body condition score and weight change

Poor fertility - weak heat signs, returns


Define Peak Yield as a percentage of Total Lactation Yield

Peak Yield = 0.5% of Total Lactation Yield

Peak yield x200 = Total Lactation Yield


How much does milk yield decline after 100 days?

1.5-2% per week

8-10% per month


What two things determine butterfat quality?

Acetic fermentation and dietary fibre


What three things determine milk protein?

Microbial protein from rumen bacteria, dietary energy, DUP


How do cows maintain a well-buffered rumen environment for optimum microbial growth with a stable pH of between 6-7?

  • Consume up to 20 meals
  • Spend up to 9 hours ruminating
  • Chew, crush, and fragment forage using 30-50,000 jaw movements
  • Produce up to 180 litres of saliva containing 3.5kg bicarbonate
  • Lie resting for up to 14 hours


How do vets assess the adequacy of a diet

  • Dry matter intake
  • Feed quality
  • Faecal consistency
  • Observing cows when undisturbed for cow comfort and welfare
  • Milk production
  • Body condition scoring
  • Milk quality
  • Disease


When should cows be blood sampled to assess diet and why?

May or June when grass is of optimum quality and availability (provides baseline for comparison later on in the year)

July or August since grass growth and quality are unpredictable and variable

Autumn grazing period (identify potential problems resulting from an overestimation fo the nutritional contribution from autumn grass for recently calved cows) 

Winter feeding period (gives a good indication of the balance of the total diet and make adjustments)

After major management or feeding change


When should you time the blood sampling for diet assessment?

Allow 203 hours to elapse after the cow has had a major intake of concentrate feed

This delay is less important when small feeds are provided regularly or when a large proportion of the concentrate is fed mixed with forage


 When is the greatest energy gap in the cow's yearly cycle?

2 weeks post calving


What determines faecal consistency?

Influenced by water and fibre content


You are looking for presence of long fiber and undigested grains


What is the optimum body condition score for a dairy cow after calving?



Why are fat cows after calving bad?

They eat less after calving, suffer more metabolic disease, are harder to get back in calf


What is rumen fill dependent on?

DM intake, ration composition, rate of passage of feed


What are the biochemical measurements for energy? protein? minerals?


  • B-hydroxybutyrate (BOHB)
  • NEFA
  • Glucose


  • Urea
  • Total protein
  • Albumin Globulin


  • Calcium
  • Magnesium
  • Phosphorous
  • Copper
  • Selenium


What does BOHB measure and from sample do you obtain it?

stable ketone body

Can be measured in blood, urine, or milk


What does NEFA measure?

fat mobilistation


What does a high BOHB and/or NEFA indicate?

Increased risk of LDA, RFM, or metritis


What are the rules for blood sampling?

Timing of blood testing

Stage of production cycle (early-, mid-lactation group, or close up transition cow group)

Group size

Selection of cows for testing

Use of background information


What are the parameters for early lactation group when sampling? mid lactation group? Dry cow group?

Early lactation group = 10-20 days calved

Mid lactation group = 80-150 days calved

Dry cow group = last 10 days of pregnancy


How do you choose which cows to sample?

  • Not an individual cow test
  • Do not choose unusual cows to sample
  • Sample 5-10 cows in the group
  • However, stage of lactation is the critical selection criteria for cows to sample

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