Lecture 4: Bovine estrous cycle and synchronization

Estrous

cycle

Estrus

a portion of the cycle

How long is Estrus

Day 0

How long is Metestrus

Day 1-4

How long is diestrus

days 4-18

How long is proestrus

Day 19-behavioral estrus

What is the term for the sexual receptivity of the female bovine?

Estrus

What is the most definitive sign of estrus in cows?

Standing to be mounted

What occurs during follicular maturation in the bovine estrus cycle?

Peak Estradiol levels

What indicates that a cow is in estrus through vaginal discharge?

Clear vaginal mucus discharge

What behavioral changes are observed in cows during estrus?

Increased restlessness and bellowing, decreased rumination, appetite, and milk production

What is the stage of the estrus cycle characterized by the formation of the early corpus luteum?

Metestrus

What happens during ovulation in the bovine estrus cycle?

Final follicular maturation

What is secreted by the early corpus luteum after ovulation?

Progesterone

What is the term for the bleeding that may occur 1-3 days after estrus?

Bleeding off

What is the state of the uterus during diestrus?

Not toned (flaccid)

What hormonal changes occur during proestrus in the bovine estrus cycle?

Progesterone levels decreasing and Estradiol levels increasing

What must happen for ovulation to occur in the bovine estrus cycle?

Progesterone levels must drop

What is the average age of puberty for male bovines?

11 months (range 7-18 months)

What is the average age of puberty for female bovines?

11 months (range 9-24 months)

What is the average age of puberty for male ovines?

7 months (range 6-9 months)

What is the average age of puberty for female ovines?

7 months (range 4-14 months, seasonal effect)

What is the average age of puberty for male porcine?

7 months (range 5-8 months)

What is the average age of puberty for female porcine?

6 months (range 5-7 months)

What is the average age of puberty for male equines?

14 months (range 10-24 months)

What is the average age of puberty for female equines?

18 months (range 12-19 months)

What is the average age of puberty for male caprines?

6 months (range 4-8 months)

What is the average age of puberty for female caprines?

6 months (range 8-12 months)

What is the average age of puberty for canines?

6-12 months on average (range 4-24 months, breed and size effects)

What is the average age of puberty for felines?

5-9 months on average (range 4-18 months, breed and photoperiod effects)

What is the average age of puberty for llamas?

2-4 years of age, generally do not breed until ~3 years old

When does puberty generally occur in heifers?

When the heifer reaches 50-65% of her adult body weight.

What influences the onset of puberty in heifers?

Genotype

How does inbreeding affect the onset of puberty?

Inbred heifers have a later onset of puberty.

How does cross-breeding affect the onset of puberty?

Cross-bred heifers have an earlier onset of puberty.

Which breed reaches puberty earlier, Bos Taurus or Bos indicus?

Bos Taurus

What is the relationship between bull scrotal circumference and heifer puberty onset?

Heifers from bulls with large scrotal circumference go into puberty earlier.

What is the influence of body weight on puberty?

The onset of puberty appears to be dictated by it

How does nutrition affect puberty?

Underfed individuals experience delayed puberty.

Do heifers on different planes of nutrition reach puberty at the same age?

Heifers on various planes of nutrition will reach puberty at different ages, but at similar relative stages of physical development.

What type of estrous cycle do bovines have?

Non-seasonal polyestrus

What is the average length of the bovine estrous cycle?

17-24 days

What is the average length of the estrous cycle in cows?

21 days

What is the average length of the estrous cycle in heifers?

20 days

How long does estrus (receptivity) last in beef cattle?

20 hours

How long does estrus (receptivity) last in dairy cattle?

15 hours

How long does estrus (receptivity) last in Zebu cattle?

When does ovulation occur in relation to the end of estrus in bovines?

2-20 hours after the end of estrus (average ~10 hours)

What is the primary breeding method used in most beef herds?

Most bull bred

When do beef herds typically want calves to be born?

early mid Spring

What is a key goal for beef herds regarding calving intervals?

Desire light intervals

What do beef herds aim to maximize during light calving intervals?

Grasses, forages, and favorable environmental conditions

What breeding method is commonly practiced in dairy herds?

Most practice artificial insemination (AI)

Why are bulls not commonly used in dairy herds?

Not many bulls → Bezerk, which is dangerous

What is a characteristic of calving in dairy herds?

Year round calving

What rule do dairy herds follow for breeding based on estrus detection?

AM-PM rule for breeding

What formula represents the relationship between pregnancy rate, estrus detection rate, and conception rate?

PR = EDR x CR

At what age are heifers typically bred?

Heifers are bred at ~14-15 months of age.

What is important for proper heifer development?

Heifers must meet proper weights at proper times.

At what age do heifers typically calve?

Heifers calve at 22-24 months of age.

When do heifers enter the milking herd?

after calving.

What happens when a calf is born?

Calf is removed at birth.

What is the maternal instinct status in dairy cattle?

Maternal instinct is bred out.

What is the first food a calf receives?

Calf is fed colostrum.

How are calves raised in dairy farming?

Calves are hand-reared.

What happens to a cow after it enters the milking herd?

It undergoes a Voluntary Waiting Period (VWP).

What is the Voluntary Waiting Period (VWP) for dairy cows?

It is a time period after calving in which the cow will not be bred.

How long is the typical Voluntary Waiting Period (VWP)?

Typically 45-65 days.

What is the purpose of the Voluntary Waiting Period (VWP)?

It allows the uterus to heal.

What happens after the Voluntary Waiting Period (VWP)?

The cow enters the breeding group.

What is the voluntary waiting period in dairy cows?

It is the time period after calving in which the cow will not be bred.

What should be done once cows are past the voluntary waiting period?

Cows should be observed in heat, inseminated, and conceived efficiently.

What is the term for the time from heat detection to breeding in cows?

Days to first service.

How long is the typical days to first service after calving?

About 70 days.

What do days to first service give us?

gives us a picture of heat detection or anestrus

What does it mean if days to first service number is not increased?

animals are not cycling or not being detected cycling

what Is the conception rate on the first service?

should be 40% or greater

if both estrus detection and conceptions dates are adequate then few cows should have....

extended open days

Formula for pregnant rate

estrus detection rate x conception rate

Why is service rate poor

Inadequate estrus detection, Poor expression of estrus

Heat, concrete

Why is the conception rate poor?

High incidence of EED, estrus detection errors, semen quality, AI technique

What is the average duration of estrus for a cow milking 60 pounds a day?

14.7 hours

What is the average duration of estrus for a cow milking 70-80 pounds a day?

9.6 hours

What is the average duration of estrus for a cow milking 80-90 pounds a day?

6.3 hours

What is the average duration of estrus for a cow milking 90-100 pounds a day?

4.8 hours

What is the average duration of estrus for a cow milking 100-110 pounds a day?

5.1 hours

What is the average duration of estrus for a cow milking 110-120 pounds a day?

2.8 hours

What are some ways to enhance estrus detection

Separate into and observe small groups for heat, ensure all nutritional and welfare needs are met

What are some aids for estrus detection?

Tail-Head pressure monitors, Kymar, lotter tickets, tail paint, chalk, Heatwatch

What are estrus detector animals?

Animals used to detect estrus in other animals

What is a chin ball marker used for?

To mark animals during estrus detection

What are Gomer bulls?

Teaser bulls used for detecting estrus

What is a vasectomized bull?

A bull that has been surgically altered to prevent reproduction

What is an androgenized heifer or steer?

A female or castrated male that has been treated with androgens to exhibit male behaviors

What is pedometry?

A method that can be used as an adjunct for estrus detection

What happens to vaginal fluid electrical resistance during estrus?

It decreases

Is the use of vaginal fluid electrical resistance for estrus detection practical?

Not practical yet

how to improve service rate

Estrus Control or Synchronization

Is fertile estrus 'induced' in the strictest sense?

No, fertile estrus is not 'induced' in the strictest sense.

Can some treatment schemes reduce fertility during estrus synchronization?

Yes, some treatment schemes may reduce fertility.