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
