Generally, ______ of the herd is in milk, while _______ of the herd is dry; if there are deviations in this, think...
85%; 15%; repro problem if too many cows are in milk (cows aren't getting bred back)
Define "momentum". Why shouldn't this be relied upon?
- calculated from historical information
- too much time goes into calculation, making changes difficult to detect
- reduced the impact of both positive and negative responses (this is why averages should be regarded with suspicion, since many values can be above and below the average and point out problems)
- between occurrence and measurement of the event
- time between when an event occurs and when it is measured
- prevents prompt response to problems or interventions (ex. she's dx pregnant but calving interval cannot be known until she calves)
Rolling herd average is not useful for ___________ because...
recognizing acute changes; it takes data over so many months, so data may look pretty good when some of the months are way off
Why is it necessary to examine the averages as well as the distribution of the data (on a graph for instance)?
a few values can skew the data (outlier cows can make the data look better or worse than it actually is)
____________ reduces the impact of both positive and negative responses and reduces the effectiveness of monitoring responses to intervention.
Momentum from historical intervention (with regard to rolling herd averages)
If you can increase peak milk by 1#,...
increase total lactation by 200-220# (MARGINAL MILK)
The typical holstein cow producing 80# of milk usually eats approximately...
50# of dry matter a day.
What non-nutritional factors can affect milk production? (5)
- herd DIM (repro problems--> DIM too high--> most cows are later in lactation--> lower milk)
- distribution of age for the herd (younger herd--> lower milk production)
- season of the year (summer heat--> lower milk)
- mastitis losses
- culling patterns
What should average DIM of the herd be at any given time (excluding seasonally calving herds)?
When average DIM for the herd goes up,...
- % of herd in milk goes up--> more stale cows in the herd in late lactation--> production is lower in late lactation--> lower production overall
- look at repro- are cows getting bred back?
If the herd is >200DIM on average, ...
repro problems (cows not getting bred back) or maybe a seasonally calving herd
What is mature equivalent?
mature milk production based on a 305 day lactation (305d is the length of a lactation with a perfect 12 month calving interval)
ME production is adjusted for what factors? (6)
- milking frequency
- season of calving
- geographical location
- age of the cow
The __________ should be the highest milk test (#) of the lactation.
second milk test (this will occur ~60-70DIM....PEAK MILK)
Define rolling herd average.
- average for he last 365 days
- Average daily production= totally yearly production/ total yearly cow day
- RHA= average daily production x 365
What are the "cow days" that are taken into account to calculate average daily production and RHA?
- how many days each cow was milked
- takes into account new cows coming in and cows being culled (cows that didn't produce for the entire year)
There is a lot of __________ in rolling herd average, so consider changes that occured 6 months ago.
Why is bulk tank milk (milk sold) lower than rolling herd average?
non-saleable milk: mastitis, antibiotics, fresh cow milk (don't sell milk until 3DIM), feeding some milk to calves
Rolling herd average will be ________ than ME and should be within _______.
Theoretically, if you're making genetic progress in your herd, _________ cows should have the highest Me production; in reality, usually _________ cows usually have the highest ME production milk because...
- first lactation; second lactation; because poor performing first lact heifers have been culled
- [second lactation is usually ≥500# greater than first lactation]
What might low ME of first lactation heifers mean? (3)
- poor freshening conditions
- poor genetic merit
- too much competition at the feed bunk
What might low ME in second lactation cows mean?
- [sophomore slump]
- first lactation cows not separated into their own group--> competition at the feed bunk--> lose body condition during first lactation--> start second lactation with poor body condition--> low ME
the 205-day actual production of first lactation cows should be within _________ of mature cows' production.
What is standardized 150-day milk?
- expected production at 150DIM, including cows 50-330 DIM (this skews the data because includes cows at peak and cows that are stale)
- adjusts milk yield using standard lactation curves
How is standardized 150-day milk used?
allows comparison of test-day yield per milking cow from month to month
Describe the accuracy of standardized 150-day milk.
- reasonably good for cows between 125-175 DIM
- overestimates production when DIM <125
- underestimates production when DIM > 175
What is persistency of the lactation curve?
- change in milk yield past peak milk (change per 30 days
- 1st lact drop 2.5#/ dat after peak (first lactation animals peak later and have slower slope downward)
- older cows drop 5#/ day after peak
What is summit milk?
- average of the 2 highest test-day milk yield of the first 3 tests in a cows lactation
- 3+ lact cows should have the highest summit milk
Peak milk should occur _______DIM, with most occurring at _________.
Heifers should peak at ________ of mature cows; heifers should peak at _________ of second lactation cows; second lactation cows should peak at __________ of mature cows.
75%; 80%; 90%
What are potential causes of low first lactation peaks? (3)
- small heifers with additional growth needed
- poor transition
- limited bunk space/ competition at the bunk with older/bigger cows
What are potential causes of low second lactation peak?
- [sophomore slump]
- low BCS and poor growth during first lactation
What are potential causes of low peaks in mature cows? (4)
- short dry period
- metabolic diseases
- low BCS
What 2 dairy breeds have the highest milk fat?
What milk test should have the highest fat and why?
- first milk test
- milk volume is lower right at freshening, and a higher percentage of fat is seen in milk
What drop can we expect milk fat percent to be at the first test day, and what might this mean if it is higher than expected?
- reasonable for milk fat to be ~4.5% at the first test day; if >4.5%, ketosis or other metabolic problems [there will be a drop to 3.2-3.5% at second test....too large of a drop causes fatty liver][if you have more than a 1% drop b/w first 2 tests...look for ketosis]
- normally about 50% of the fatty acids in milk are from de novo synthesis of fatty acids from precursor acetic acid from rumen fermentation—> in early lactation, right after calving, the cow is not eating a lot, so proportionally, more of the fatty acids in milk are coming from adipose tissue, increased mobilization of fatty tissue, NEFAs going up, go to mammary gland and are preformed fat that goes into milk
Describe the change in milk fat over the lactation.
- highest milk fat at first test day
- fat percent will decrease by ~0.5% at peak milk (second test day)
- fat will steadily increase past peak milk
What are causes of high milk fat percentage? (4)
- low milk yield
- higher fiber diet
- excessive weight loss
- feeding supplemental fat (to a degree)
What are causes of a lower than expected milk fat percentage? (5)
- acidosis (inadequate fiber, low effective fiber, excessive starch, sorting at the bunk)
- feeding excessive unsaturated fat
- feeding rumensin
- low BCS
- low DMI
A 1% increase in milk fat at first test day increased risk for _________ by _______.
Describe how the fat conc in milk compared between the fore-stripping milk, composite milk, and post-milking sample.
- fore-stripping has lowest milk fat
- composite sample represents the entire milking
- post-milking sample will have higher fat conc (milked out...more conc)
What is the difference between crude protein and true protein?
- crude protein is calculated by measuring nitrogen in feed and multiplying it by 6.25
- true protein is how milk is priced; this value is determined by infrared technology
- CP of milk can be calculated by %N x 6.38
- CP - TP (of milk) = 0.2
Causes of high milk protein. (4)
- low milk yield
- high SCC
- feeding protected animo acids
What are causes of low milk protein? (1)
nutritional factors (energy and/ or protein in feed)
In what group is milk fat: protein ratio inversion normal?
- normal for 15-20% of cows between 40-100DIM to be inverted
- bulk tank inversion or whole herd inversion is a major problem