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AN SC 472 > 11 Calf Lecture Final > Flashcards

11 Calf Lecture Final Flashcards

1
Q

Highest percent of calf mortality occurs at what stage? Related to…

A

Preweaned (4.5-5%)
Related to diarrhea

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2
Q

How long do calves stay solely on liquid feeds?

A

First two weeks of life

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3
Q

Calves on dam consume how much milk per day? What is the conventional methodology for holstein calves? Why?

A

On dam 6-12 kg of milk per day

Holstein calf liquid feed restricted 10% of BW (typically around 4L of milk at birth)
Promotes starter intake which promotes rumen development

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4
Q

Pros and cons of conventional milk feeding

A

Pros: smoother transition from milk to solid feed = reduced BW loss at weaning
Cons: lower pre-weaning gains, increased morbidity, animal welfare (hunger)

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5
Q

Alternatives to conventional milk feeding

A

Intensive milk feeding aka high plane of nutrition

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6
Q

Conventional milk feeding aka

A

Low plane of nutrition

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7
Q

What is intensive milk feeding? Pros and cons

A

Milk intake 6L per day for ~ 8 weeks
Reasoning: closer to “natural”
- pros: higher pre-weaning gains, normal beh, lower morbidity
- cons: lower starter intake, higher incidence of diarrhea? Higher costs?

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8
Q

Between conventional and intensive milk feeding, which had higher fecal score, days with loose stool, age at puberty and weight at puberty

A

Fecal score = intensive
Days with loose stool = intensive
Age at puberty = conventional
Weight at puberty = conventional

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9
Q

Why is lower age at puberty with intensive milk feeding beneficial?

A

Can be bred sooner, calve earlier, lactate earlier

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10
Q

Does conventional or intensive promote more starter intake?

A

Conventional (starter intake earlier)

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11
Q

Which had higher body weight from birth to weaning (int vs conv)

A

Intensive

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12
Q

Which had higher ADG to weaning and 305 day milk yield (int or conv?)

A

ADG = intensive

305d my: intensive

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13
Q

Increased levels of milk feeding are associated with…

A
  • greater milk yields in first lactation
  • earlier calving without being heavier
  • greater mammary parenchymal mass without fat deposition
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14
Q

A key goal for calf rearing is…

A

Development of the ruminal epithelium

To reach puberty, calves need to grow, and to grow, calves need to be able to digest and absorb nutrients from solid feeds

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15
Q

How does grain (calf starter) stimulate rumen development

A

Carbohydrates in calf starter are fermented into short-chain fatty acids (acetate, propionate, butyrate)

Butyrate has several biological properties that influence rumen development:
- increased gene expression
- cell cycle regulation
- energy source for rumen cells

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16
Q

What does higher rumen development mean?

A
  • more papillae
  • larger papillae
  • larger rumen
  • thicker epithelium
  • more vascularization

More VFA absorption = more energy = higher growth/efficiency

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17
Q

Why do we not feed hay in the conventional approach

A
  • calves cannot break down the hay
  • hay feeding has decreased starter intake (gut fill)
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18
Q

What benefits did hay feeding on a high plane of nutrition provide?

A

Had much higher rumen pH (ability to buffer rumen pH)

19
Q

Benefits of hay feeding with intensified feeding

A
  • does not affect daily gain
  • reduces risk of rumen acidosis at weaning
  • eases a smoother weaning transition
20
Q

Results of study supplementing butyrate in calf start to increase rumen development

A
  • protected butyrate had higher intake and body weight than unprotected
  • protected and unprotected butyrate affected fermentation profiles similarly
  • control and protected calves had similar growth performance

Slides 21,22

21
Q

When is a calf’s health most vulnerable? how do we manage it

A

In the first three weeks of life
Managed through appropriate nutrition, vaccination, and colostrum

22
Q

Two approaches to milk feeding

A

Conventional: low amounts of milk, promotes grain intake
- but can be stressful, hungry calves, low preweaning weights

Intensive: higher nutrient density, important pre-weaning weight gain
- more natural? less hunger? more diarrhea?

23
Q

Three main goals of management during weaning

A
  1. Wean calves off milk and onto calf starter
  2. Limit stress -> limit weight loss
  3. Reach target intakes and weight gain
24
Q

Changes to calf management during weaning transition

A
  • diet: higher consumption of solid feeds, less nutrients from milk (pre-ruminant -> ruminant)
  • housing: individual to group (sometimes), to another farm after weaning (heifer raising, feedlots)
25
Q

How do calves get energy during weaning transition

A

Calf starter and hay ferment in the rumen -> SCFA
SCFAs are used as energy sources
Gluconeogenesis from SCFA in the liver becomes primary E source

Slide 27 TCA cycle

26
Q

Protein in weaning transition

A

Protein from the diet is degraded by microbes -> microbial protein

Digestion and absorption of microbial protein in SI

27
Q

Why are calves at a higher risk of rumen acidosis at weaning transition?

A

When we remove milk, calves must consume starter/grain to meet their nutrient requirements

Increased starter intake = increased intake of rapidly fermentable carbohydrates
- increased production of SCFAs -> reduction in ruminal pH

28
Q

What is ruminal acidosis

A

Fermentation disorder in the rumen characterized by a lower-than-normal ruminal pH, reflecting an imbalance between microbial production, microbial utilization and ruminal absorption of SCFAs

29
Q

Why is the threshold for acidosis in cattle? What is interesting in calves? Avoid going below what pH in calves?

A

pH 5.8

Calves spend a lot of time below acidotic threshold (threshold might be lower in calves, ability to rebound better)

Avoid pH below 5.2 because it damages rumen tissue

30
Q

Describe weaning systems and milk strategies

A
  • calves fed low plane (10% BW) and weaned at 3, 4, 5, 6 weeks of age = no diff in health or performance
  • calves fed high plane of nutrition weaned at 6 vs 8 weeks of age = no significant differences in health and performance
31
Q

Research shows calves weaned at 8 weeks tend to…

A

have less abrupt changes in microbiome (fewer dips in performance)

32
Q

Calves weaned at 8 weeks of age had higher…

A

Calves weaned at 8 weeks of age had higher starter intake, ME intake, average daily gain, oat straw intake after weaning

33
Q

Abrupt weaning had negative effects on…

A

milk replacer intake, starter feed intake, ME intake

34
Q

Slide 43

A

Table; confusing

35
Q

Nutrition transition in weaning

A

Milk -> calf starter -> forages/TMR

36
Q

Appropriate age of weaning depends on…
More abrupt the transition, the…

A

depends on plane of nutrition

higher likelihood of having reduced gain

37
Q

Three main goals of heifer management

A
  1. optimize growth
  2. stimulate sound mammary development
  3. minimize cost
38
Q

Goals of heifer calf management after rearing

A
  1. optimal growth for calving at around 22-24 months of age (BCS between 3 and 3.5)
  2. minimize inputs (25% of dairy’s cost goes into heifer rearing, 50% is feed)
  3. minimize nutrient loss through manure
39
Q

Appropriate growth rate depends on…

For holsteins to calve at 24 months, BW gain should be…

A

desired age and estimated body weight at calving

BW gain should be 0.8 kg/d from birth to calving

40
Q

Inadequate gains in heifers =

A

extended breeding and calving ages, increased feed costs

41
Q

Higher rates of gain in heifers could allow for target ages or earlier, but…

A
  • excess gain, especially adipose tissue, could increase the risk of dystocia and metabolic diseases
  • excess gain between 3-10 months of age = fat deposition in mammary (displaces milk cells)
42
Q

When does mammary gland growth begin? What is key to its development?

Describe mammary growth from birth to puberty, puberty onwards

A

After birth (parenchymal cells not detected at 2d after birth)
Calf nutrition is key to mammary development

Birth to puberty = allometric growth

Puberty onwards = isometric growth

43
Q

What is allometric growth? Isometric growth? How can we change plane of nutrition to enhance milk production using this knowledge?

A

Allo: mammary gland grows at a faster rate than the rest of the body in pre-pubertal stage

Iso: after puberty, mammary grows at same rate as rest of body

Intensive pre-pubertal plane of nutrition may enhance milk production, excess post-pubertal gains may decrease yield

44
Q

Effects of overfeeding heifers

A

Brings on a feed cost and may also decrease output per cow (long term costs)

AN SC 472 (13 decks)

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