dairy Flashcards
why is there an increase in jersey cows and other breeds in recent years?
there has been a cultural shift from drinking fluid milk to eating cheese products
how long is the lactation cycle
305 days
how long is a cow’s gestation period?
283 days
what are the 60 days before calving referred to as?
drying
what is the purpose of drying?
to renew the udder for lactation with the calf
what are the parts of an internal udder structure
lobules (containing the alveolis) –> duct system -> gland system –> gland cistern –> teat cistern –> streak canne
internal alveoli structure
epithelial cells (responsible for milk synthesis and secretion)
lumen (responsible for milk components and water)
myoepthelial (responsible for milk ejection)
capillary system (responsible for supplying milk components)
how are grades of milk determined
somatic cell count and bacterial count
grade a means
scc < 100,000 –> likely not an infection
<1,000,000 bacteria/ml
grade b means
scc > 250,000 –> likely an infection
> 1,000,000 bacteria/ml
classes of fluid milk
- fluid milk
- soft products (yogurts, ice cream, sour cream)
- cheese
- butter
what is pasteurization
rapid heating and cooling to kill bacteria
what is homogenization
separating the fat into smaller equal sized pieces so that it doesn’t rise to the top
what are the percentages of average milk composition
water –> 87.7%, fat –> 3.6%, protein –> 3.2%, lactose –> 4.8%, ash/minerals –> .7%
what is mastitis
the inflammation of the udder, caused by an infection
what are the types of mastitis
clinical –> with visible symptoms
subclinical –> without visible symptoms
what is the main test used in diagnosing mastitis?
CMT (california mastitis test)
combine milk with reagent and swirl, it should become very thick and bright purple
what is butter
water in fat
what is buttermilk
fat in water
how is yogurt made
bacteria ferments the milk
what is the DHIA and what is it for
Dairy Heard Improvement Association
serves as a record system
what is a sire summary
explains the genetic disposition to specific traits (mother and grandmother have higher or lower milk production than the average of the population)
why is sexing semen important
can get female sperm because females are more desired
what is the average herd size in the US
115
where are the most dairy herds located in the US
Wisconsin - 11,000 herds
Who produces the most milk in the US
California - 1,500 herds
what has been relationships of herd size to production?
herd size is decreasing while production is increasing
what are the main trends of milk products
fluid milk consumption has decreased while cheese consumption has increased
how has dairy trends affected herds
Holstein herds have decreased, while jersey herds have become more favored bcs of cheese production. crossbreeds are becoming more common
what are the steps in milk processing?
pasturization and homogenization
how does milk let down occur?
oxytocin is responsible for it
touch of udder is a nerve impulse
calf/milking machine releases oxytocin
key events in a lactation cycle
early lactation, mid lactation, late lactation
what aspects are contributing to success in dairy industry
AI, trait selection, maximizing production, DHIA
when are calves first bred?
15 months
at what age do heifers give birth for the first calf?
24 months
after the first calving, when are the cows rebred
at day 80
what is the repro cycle of cows
1st calving, 80 days later rebreeding, gestation is 283/5 days, 60 day drying period (365 days)
when does early lactiation occur
0-50/60 days in milk
when does mid lactation occur
60-175/180 days in milk
when does late lactation occur
180-305 days in milk
what are the alveoli responsible for
milk synthesis and secretion – houses the epithelial cells
lumen
collects milk components and water
myoepithileial cells
milk ejection
capillary system
supply milk components
how is cheese made
coagulation and separation of curds and whey
add rennet, which is a coagulation enzyme
remove whey (H2O, lactose, whey protiens)
low fat milk
1-2% milk fat
skim milk
0% milk fat
whole milk
3-4.5% milk fat
1/2 & 1/2
18% milk fat
heavy cream
35% milk fat
