Lecture 18: Dairy Nutrition 2 (Exam 2) Flashcards
What is a transition cow
3 weeks before calving or 3 weeks after calving
What is unique about the transition period
- The body changes, displaced rumen risk, & weight loss
- B/c of adjusting to more energy (grains)
What lab measurement estimates digestibility of fiber
ADF
What factors influence DMI
- Stage of lactation
- Digestibility of fiber in the diet
- Envi conditions
What is the DMI % for dairy cattle
3.5 to 4.5% (3.7%)
What factors are involved in the regulation of DMI
- Affected by rumen fill (eating decreased digestible food leads to rumen staying full longer & animal doesn’t want to eat)
- Affected by level of production (lactating dairy cows; energy needs)
- Affected by energy content of feed (dry dairy cows)
How do cows budget there time/energy each day
- 3 to 5 hours eating (9 to 14 meals)
- 10% of energy is used for chewing
- 30 mins drinking
- @ least 7 to 10 hours ruminating (the min)
- Needs @ least 10 Hs of lying/resting
- 2 to 3 Hs milking
What are the benefits of resting/lying down
- Rumination
- Increase in eating
- Reduced stress on feet leading to a reduction in lameness
- Increases blood flow to the udder
What happens if they rest < 10 H/d
Mild production decreases
What is perching
- Cows standing w/ front feet in stall hind feet in alley or cows laying partially in the alley
- Can be an indication of lameness, uncomfortable surface or short beds
Why is the standard recommendation 18 to 30 inches of bunk space
B/c it allows about 70% of cows to eat @ one time
What happens if there is decreased feeding space
- Increased aggression
- Cows eat for shorter periods of time
- Eat faster
- Eat more @ night
For every additional 1 lb of DM eaten how many lbs more of milk is produced
2.5 to 3 lbs
List the major VFAs produced in the rumen
- Acetate
- Propionate
- Butyrate
Describe propionate
- Mainly from NFC (mostly starch)
- Main glucose precursor
- Undergoes gluconeogenesis constantly
Describe acetate
- Mainly from structural CHO
- Main precursor for fat (adipose & milk)
- Makes 50% of milk fat
What is butyrate a precursor for
beta-hydroxybutyrate
What are the fiber recommendations for proper rumen functions
- Early lactation NDF from forage = 20 to 24% DM
- Dry cows NDF from forage = 25%
Fill in the ?s: Cows need a min of ? % of forage particles to be over 1.5 inches long to stimulate rumination to provide physically effective NDF they need at least ? % peNDF
15 to 20%; 22%
What helps the rumen pH stay stable
- VFAs are rapidly absorbed by papillae on the rumen wall
- Bicarbonate in saliva buffers the rumen pH
Describe subacute rumen acidosis (SARA)
- More common in dairy
- Prolonged periods of decreased rumen pH (5.2 to 5.6)
- VFAs are accumulating but no persistent lactic acid accumulation
- Physiological response to restore pH after many hours
- Seen mostly in transition cows
Insufficient physically effective NDF reduces salivary production of buffer (less rumination)
What happens if SARA is detected
- Neg effects on rumen fat metabolism which leads to milk fat depression
- Reduced feed intake
- Reduced cud chewing
- Mild diarrhea
- Poor appetite
- Reduced milk production
- Poor body condition
- Laminitis
What is the normal pH fluctuation of the rumen in a 24 H period
0.5 to 1 pH
What does the pH of the rumen depend
- Intake of fermentable carbs
- Buffering capacity of the rumen
- Rate of VFA absorption from rumen
