1165 BAP Exam 2 Study Set - Dairy Cattle

How much of the American diet is made of dairy products?

10%

What are the trend in fluid milk, cheese, and butter consumption in the US currently?

Liquid milk consumption is decreasing while cheese and butter product consumption is greatly increasing

Where does the US rank in terms of total milk production?

3rd globally

What percent of the dairy products produced in the US are consumed here?

85%

What percent of the dairy products produced in the US are exported?

15%

Who are the top 5 dairy product trade countries?

Mexico, Canada, China, Philippines, South Korea

How many dairy cows are in the US?

9.4 million

Top 3 states with the most cows?

1- California
2- Wisconsin
3 - Idaho

Which state has the fastest growing diary industry?

Texas

What's the average herd size in the United States?

317 cows

Top 3 states in # of head per farm?

1 - New Mexico
2 - Arizona
3 - Colorado

Average annual milk production per cow:

23984 lbs/head/year (7.6 milk gallons per day)

Top 3 states with the highest producing cows?

1. Wisconsin
2. Colorado
3. Wyoming

Why do grass fed dairy produce less milk?

Their diet of grass consists of 90% water, so it's very low energy

Does low milk production per cow = low profitability per cow on grass fed dairies?

Grass fed products can be marketed and sold at higher prices so not necessarily

What breed of cow makes up 95% of America's dairy industry?

Holstein
known for producing high volumes of milk

What's the other pure bred of cow used commercially?

Jersey
known for high concentrates of milk fat and protein

What is a "hojo"?

Holstein x Jersey crossbred
known for hardiness, health, and longevity

Who was "Old Jo"?

Dairy cow in. Missouri 1910
produced 8.6x the milk of the average cow
put Mizzou on the map for dairy science

Which cow holds the current milk production record?

Wisconsin cow Aftershock #3918
produces 3x the average cow or 30 milk gallons per day

Stress:

the amount of force applied to the object

Strain:

the movement or adaptation of the object to the stress

How can we reduce the strain on dairy cattle?

Genetic selection and high levels of comfort

What are the two highest genetically tested species?

1. Humans
2. Dairy cattle

Genex ICC:

Ideal Commercial Cow Index
high producing, trouble free, feed efficient, breeds on time, calves without assistance

Traditional US Dairies:

cows live in tie stalls, less than 100 cows per farm, cows are let outside once or twice per day, usually more family run

RFID's:

radio frequency ear tags
each cow has an electronic file based on it's RFID

Modern US Dairies:

cows live in freestall pens, feed is placed in bunks, much larger operations with a more commercial focus

Life cycle of a cow:

calf -> lactation 1 year -> dry 2 months -> lactation 1 year

Life cycle of a heifer:

puberty in 8-10 months -> cycles 4 months -> AI -> 1st pregnancy 9 months -> calf -> first lactation 1 year

When should first breeding and calving occur in a dairy heifer?

breed at 1 year 3 months, calve at 2 years of age

Replacement Heifers:

replace 30% of the herd annually
come into the hard at 2 years old after 1st parturition

Active Immunity:

your own body generates your antibodies - slow to develop but with long lasting results

Passive Immunity:

immunity through injection or ingestion of antibodies - immediate but short lived response

3 Q's of Colostrum

Quantity - 10% body weight within 10 hours of birth
Quality - high concentrations immunoglobulins
Quickly - feed within a few hours of birth

Colostrum:

first secretion from the mammary glands after parturition, contains antibodies and immunoglobulins that keep the calf alive, gives it strength

Conventional Calf Program:

feed less milk to maximize starter grain intake

Accelerated Calf Program:

feed more milk to maximize milk intake

What are the three methods of housing young calves?

calf hutches, group pens, paired housing

How long are calves housed in hutches?

until they are 60 days old

What are some issues of housing calves in group pen scenarios?

higher disease transfer, no individualized care, harder to track individual feed/milk/water intake

Heifer growth targets:

double weight in hutches, 2lbs/day after that
55% mature weight @ first breeding
85% mature weight @ first calving

Oviduct:

'highway' taken by the egg to get from the ovary to the uterus, site of fertilization

Where does natural breeding deposit semen?

Vagina

Where does AI deposit semen?

uterine body

Where is the site of fertilization?

the oviduct

Progesterone:

- produced by the CL
- used to maintain pregnancy
- targets the uterus to quiet uterine myometrium and stimulate the synthesis of nutrients in the uterine body
- is a steroid

Estradiol:

- produced by the follicle
- initiates heat and ovulation (GnRH + LH surges)
- targets the hypothalamus and uterus
- is a steroid

Primordial follicles:

eggs that have not started development yet, heifers are born with 100,000 of them

What are the 5 stages of follicular development?

1. Primordial
2. Primary
3. Secondary
4. Tertiary
5. Preovulatory

Hormone:

a chemical produced by an endocrine gland that travels through the blood and exerts an effect on a target organ

FSH (follicle stimulating hormone)

- initiates development of follicles/follicular waves
- produced by the anterior pituitary
- targets the follicles
- directly under the control of GnRH

LH (luteinizing hormone)

- targets follicles - stimulates ovulation
- produced by the anterior pituitary
- directly under the control of GnRH

GnRH (gonadotropin-releasing hormone)

- produced by the hypothalamus
- short sequence of peptides - amino acid
- impacts ability to get and maintain pregnant

PGF2a (prostaglandin F2 Alfa)

- produced by the uterus
- causes the CL to regress
- is an eicosanoid - derived from fatty acids

When does a heifer reach puberty?

first ovulation (approx. 8 months)

What is ovulation?

rupture of an ovarian follicle and release of the egg or female gamete into the oviduct

Phases of a follicular wave:

Recruitment - multiple follicles gather on ovary
Selection - follicles compete for dominance
Dominance - single follicle is chosen to ovulate
Atresia - death of follicle if not fertilized

How long is a bovine follicular wave?

7-10 days

When do follicular waves begin in cattle?

At a very young age (pre-puberty), just don't ovulate until the follicle/repro tract grows large enough to produce enough estradiol to begin ovulation cycles

Signs of estrus:

- standing while mounted by others
- restless walking/lower feed intake
- mucous secretion

How long is the bovine estrus cycle?

21 days, 4.8% of females coming into heat daily

Common estrus detection aids include:

- tail scratch patches
- walk and chalk method
- activity system collars
- milk testing for progesterone levels

What are two reasons a heifer may not come into heat?

1. she is already pregnant
2. she is a freemartin

What is a freemartin?

Sterile female calf born twin to a male calf.

1st wave dominant follicles:

- form in the first 10 days of the cycle
- typically doesn't ovulate because previous CL is still producing progesterone

2nd wave dominant follicles:

- surge in estradiol/pgf2a regresses the CL
- allows this follicle to successfully ovulate

What happens to the CL if the animal is pregnant?

it is maintained and continues producing progesterone to maintain the pregnancy and prevent ovulation

What hormone causes CL regression?

PQF2a, this is the same hormone used in estrus synchronization

Herd Navigator System (Delaval)

tests progesterone levels in the milk to track heat cycles and detect pregnancy, also tests for mastitis by measuring LDH (lactate dehydrogenase)

When does a bull reach puberty?

- defined as the capacity to get a cow pregnant (produces sufficient levels of sperm)
- occurs at approximately 1 year of age

Gamete production in bulls vs. cows

Cows: 1 gamete per 21 days
Bulls: 10,000 gametes per second

Which country uses fresh semen vs. frozen semen?

New Zealand

Who was Toy Story?

record setting dairy bull owned by Genex who had over 500,000 daughters

Advantages of AI:

1. no venereal disease (STD) transfer
2. reduced injury for cows + heifers
3. increased farmers safety

How many straws per ejaculate?

250-500 straws containing approx. 20 million sperm each (5-10 billion sperm per ejaculate)

What are bull studs?

farms that raise only bulls for semen collection to be used in AI

SNP?

single nucleotide position in a DNA sequence

Basics of genetic testing:

- costs $50 to test 50,000 SNP's
- certain SNP's are favorable to others
- genetics are used to determine phenotypic variability
- bovine genome consists of billions of base pairs

Genomic Sires:

bull studs whose worth is completely determined from a genetic test, start collecting semen at 1 year of age

How many years did it used to take to prove a bull?

6 years

How many years does it take to prove of bull today?

2 years thanks to genetic testing/chromosomal mating

Semen Evaluation:

1. progressive motility - greater than 30% mobile
2. morphology - greater than 70% is normal
3. concentration - 1200M/mL
4. volume - 5-10mL per ejaculate

Components of Packaging Semen:

- salts (ionic)
- buffer
- egg yolk or milk (protects during cooling)
- glycerol (protects during freezing)
- glucose (energy source for sperm)
- antibiotic (prevents bacterial growth)

What is semen frozen in?

liquid nitrogen

Why do we stain semen?

Darker sperm are carrying an X chromosome, lighter sperm are carrying a Y chromosome - used to sex semen

Disadvantages of sexed semen?

- lower fertility rates due to damage during sorting
- more expensive per straw

What is a flow cytometer?

a machine used to sex semen, can sort 90,000 sperm per second and one machine takes 15 hours to sort a single ejaculate

How many straws of sexed semen per ejaculate?

approx. 150 straws containing 4 million sperm each

What is "sire conception rate"?

the ability of a bull to get cows pregnant, how good is his semen in relation to other bulls, low SCR = no semen bought from this bull

What hormone is injected during estrus synchronization?

PGF2a

When will a PGF2a injection not bring a cow into heat?

if injected during the first 5 days of the estrous cycle

How long does it take heifers and cows to come into heat after a PGF2a injection?

Heifers: 2-3 days
Cows: 3-5 days

When should you AI to ensure the best chance of conception?

12-16 hours after she's been in heat - gives sperm time to capacitate and the egg time to travel down the oviduct

When does the fertilized embryo enter the uterus?

When it becomes a morula, 5 days post fertilization in the oviduct

Early cleavage states of the egg:

1, 2, 4, 8, 16, Morula, Blastocyst, Hatched Blastocyst, Spherical, Tubular

What are the parts of a blastocoel?

1. inner cell mass = embryo
2. trophoblast = future placenta

Structure of the uterus:

Uterine lumen: where the egg develops
Endometrium: glandular tissue where nutrients are synthesized and secreted into the lumen
Myometrium: muscle surrounding the uterus

What is interferon tau and how does it work?

molecule released by the tubular embryo to block the release of PGF2a by the uterus, therefore maintaining the pregnancy

What are cotyledons?

fetal placenta attachment points to the endometrium