11 Calf Lecture Final Flashcards
Highest percent of calf mortality occurs at what stage? Related to…
Preweaned (4.5-5%)
Related to diarrhea
How long do calves stay solely on liquid feeds?
First two weeks of life
Calves on dam consume how much milk per day? What is the conventional methodology for holstein calves? Why?
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
Pros and cons of conventional milk feeding
Pros: smoother transition from milk to solid feed = reduced BW loss at weaning
Cons: lower pre-weaning gains, increased morbidity, animal welfare (hunger)
Alternatives to conventional milk feeding
Intensive milk feeding aka high plane of nutrition
Conventional milk feeding aka
Low plane of nutrition
What is intensive milk feeding? Pros and cons
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?
Between conventional and intensive milk feeding, which had higher fecal score, days with loose stool, age at puberty and weight at puberty
Fecal score = intensive
Days with loose stool = intensive
Age at puberty = conventional
Weight at puberty = conventional
Why is lower age at puberty with intensive milk feeding beneficial?
Can be bred sooner, calve earlier, lactate earlier
Does conventional or intensive promote more starter intake?
Conventional (starter intake earlier)
Which had higher body weight from birth to weaning (int vs conv)
Intensive
Which had higher ADG to weaning and 305 day milk yield (int or conv?)
ADG = intensive
305d my: intensive
Increased levels of milk feeding are associated with…
- greater milk yields in first lactation
- earlier calving without being heavier
- greater mammary parenchymal mass without fat deposition
A key goal for calf rearing is…
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
How does grain (calf starter) stimulate rumen development
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
What does higher rumen development mean?
- more papillae
- larger papillae
- larger rumen
- thicker epithelium
- more vascularization
More VFA absorption = more energy = higher growth/efficiency
Why do we not feed hay in the conventional approach
- calves cannot break down the hay
- hay feeding has decreased starter intake (gut fill)
What benefits did hay feeding on a high plane of nutrition provide?
Had much higher rumen pH (ability to buffer rumen pH)
Benefits of hay feeding with intensified feeding
- does not affect daily gain
- reduces risk of rumen acidosis at weaning
- eases a smoother weaning transition
Results of study supplementing butyrate in calf start to increase rumen development
- 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
When is a calf’s health most vulnerable? how do we manage it
In the first three weeks of life
Managed through appropriate nutrition, vaccination, and colostrum
Two approaches to milk feeding
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?
Three main goals of management during weaning
- Wean calves off milk and onto calf starter
- Limit stress -> limit weight loss
- Reach target intakes and weight gain
Changes to calf management during weaning transition
- 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)
How do calves get energy during weaning transition
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
Protein in weaning transition
Protein from the diet is degraded by microbes -> microbial protein
Digestion and absorption of microbial protein in SI
Why are calves at a higher risk of rumen acidosis at weaning transition?
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
What is ruminal acidosis
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
Why is the threshold for acidosis in cattle? What is interesting in calves? Avoid going below what pH in calves?
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
Describe weaning systems and milk strategies
- 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
Research shows calves weaned at 8 weeks tend to…
have less abrupt changes in microbiome (fewer dips in performance)
Calves weaned at 8 weeks of age had higher…
Calves weaned at 8 weeks of age had higher starter intake, ME intake, average daily gain, oat straw intake after weaning
Abrupt weaning had negative effects on…
milk replacer intake, starter feed intake, ME intake
Slide 43
Table; confusing
Nutrition transition in weaning
Milk -> calf starter -> forages/TMR
Appropriate age of weaning depends on…
More abrupt the transition, the…
depends on plane of nutrition
higher likelihood of having reduced gain
Three main goals of heifer management
- optimize growth
- stimulate sound mammary development
- minimize cost
Goals of heifer calf management after rearing
- optimal growth for calving at around 22-24 months of age (BCS between 3 and 3.5)
- minimize inputs (25% of dairy’s cost goes into heifer rearing, 50% is feed)
- minimize nutrient loss through manure
Appropriate growth rate depends on…
For holsteins to calve at 24 months, BW gain should be…
desired age and estimated body weight at calving
BW gain should be 0.8 kg/d from birth to calving
Inadequate gains in heifers =
extended breeding and calving ages, increased feed costs
Higher rates of gain in heifers could allow for target ages or earlier, but…
- 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)
When does mammary gland growth begin? What is key to its development?
Describe mammary growth from birth to puberty, puberty onwards
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
What is allometric growth? Isometric growth? How can we change plane of nutrition to enhance milk production using this knowledge?
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
Effects of overfeeding heifers
Brings on a feed cost and may also decrease output per cow (long term costs)
