4 Nutritional Management 2 Flashcards
Energy balance at peak lactation affects:
- milk production
- reproduction
- general animal health
A 1 kg increase in peak milk yield leads to…
a 200 kg increase in milk yield for the entire lactation
Energy intake (Mcal/d) =
Diet energy density (Mcal/kg) x dry matter intake (kg/day)
Why doesn’t increasing dietary energy density = increasing energy intake
Because an animal will likely decrease intake
Three dietary factors and how they affect DMI
Fat: excess feeding decreases DMI
Starch (grain): excess starch decreases DMI, increases risk of rumen acidosis
Fibre (forages): excess fibre decreases DMI (physical fill)
How do cows communicate with us using DMI
Tells us how good or bad the diet formulation is, how good or bad the environment is
Management factors that affect DMI
Provide enough geed to ensure some feed refusals next day? Yes = increased yield
Push the feed to ensure feed is within reach of cows? Yes = increased yield
Feed availability, water intake, consistency, cow comfort
Three sources of milk fat
- de novo fatty acid synthesis (mammary gland synthesizes f.a. from acetate and butyrate from rumen fermentation)
- non-esterified f.a. from adipose (cows in negative E balance mobilize NEFA)
- fatty acids in the diet
When are cows most likely to mobilize NEFA?
After parturition (high fat content in milk right after calving)
Why does milk fat depression occur?
Feeding unsaturated f.a. at a low rumen pH (excess fermentation, lack of physically effective fiber)
= trans-fatty acids = milk fat depression
Slide 17*****
What fatty acid can increase milk fat yield?
Palmitic acid
How does feeding TMR with sufficient particle size affect milk fat content
Increases rumination time, therefore salivary buffer secretion, so increases rumen pH therefore milk fat content
How does feeding frequency affect milk fat content?
Feeding once per day = uneven feeding behaviour, more fermentation earlier in the day
Feeding three times a day = cows eat evenly, ferment throughout the day = higher milk fat
Strategies for reducing TMR sorting
- feed TMR more frequently
- push-up more often
- add less long hay
- chop hay finer
- higher quality hay
- add water
- add liquid molasses
What happens when cows are fed unsaturated f.a.
Fatty acids from diet increase, so de novo f.a. synthesis in the mammary gland decreases = less milk fat
Three factors causing milk fat depression
- Feeding unsaturated f.a.
- Low rumen pH
- Sorting
Milk urea Nitrogen is an indicator of…
wasted N
Slide 34*
What is milk urea nitrogen
Nitrogen not used for productive purposes
Why use milk-urea nitrogen over blood-urea nitrogen?
- Representative values accounting for diurnal variation
- Non-invasive collection
- Low cost
MUN increases with…
- excess N feeding
- excess ammonia absorption in the rumen
- imbalanced AA supply
What is the benchmark for MUN
14 mg/dL
What do you do if MUN is less than 10 mg/dl
Can feed more protein without negative effects
If production is optimized, no need to worry
If MUN is greater than 16, what does this mean? what do you do
Excess rumen degradable protein and/or insufficient organic matter fermentation
Dietary protein is not efficiently utilized
Decrease dietary protein content, increase OM fermentation in the rumen
If MUN is greater than 20, what happens?
Negative effects on reproduction (decreases uterine pH)
Look at graphs & slides
Do it
