Reproduction, Growth and lactation:

what is a dogs cycle timing for her oestrous cycle

- can cycle any time of year, often just once

what is a cows cycle timing for her oestrous cycle

cycles all year round

what is sheep's cycle timing for her oestrous cycle

cycles during autumn (short day breeder)

what is a horses cycle timing for her oestrous cycle?

cycles during spring / summer

(long-day breeder)

What hormone drives maturation and ovulation of the dominant follicle, as well as development of the corpus luteum (CL)?

LH , or Luteinizing Hormone

What does polyoestrus, spontaneous ovulator mean?

cycles are continuous throughout the year, does not need mating to induce ovulation.

e.g. cow

what does monoestrous mean?

will have one oestrous cycle then go into anoestrus

- e.g. dog

When does blood oestrogen concentration peak in the bitch?

late proestrus - as late tertiary follicles start to mature

When does blood progesterone concentration start to rise in the bitch?

late proestrus / early oestrus

what does seasonal breeder and an induced ovulator mean?

- can either be long day (oestrus cycles only in spring/summer) or short day breeder (cycles in autumn)

- will have a period of anoestrus when not breeding season

- needs to be mated to induce ovulation

What hormone is released if the female is bred several times during oestrus?

LH

- to induce ovulation of follicles

what is the main structure of the ovary in proestrus and hormone involved?

developing follicles and FSH (Follicle-Stimulating Hormone)

what is the main hormone and structure of the ovary in oestrus?

dominant follicles and oestrogen

what is the main structure of the ovary in diestrus?

CL (Corpus Luteum) and progesterone

what is the main structure of the ovary in anoestrus?

small inactive follicles and no hormones

when is an animal receptive to mating?

oestrus only

- may show interest in males during proestrus but will not be receptive.

what are the stages of the oocyte from when ovulated to movement into uterine horn?

oocyte - ovulated and fertilised

morula - multiple cell fertilised oocyte

blastocyst - cell will differentiated cells that moves into uterine horn

what are the events that lead to the formation of a zygote (sperm)

1. capacitation

2. acrosomal reaction

3. sperm fusion with oocyte membrane

4. fertilisation

5. formation of zygote

what are the main stages of labour and the main features?

stage 1: contractions of myometrium to dilate cervix

stage 2: delivery of the fetus(es) through strong myometrium contractions

stage 3: delivery of the placenta(s) seperate it from uterine wall

where does fertilisation take place?

in the uterine tube

What stage of development is the embryo normally at when it enters the uterus?

blastocyst

how does the ruminant supply glucose to the fetus during late pregnancy?

no glucose net absorption by the gut due to fermentative digestion

- makes VFAs

- use propionate for gluconeogenesis

- blood glucose of dam drops as going to fetus.

- make ketone bodies from fat stores

- can lead to ketosis.

Which cells of the mammary gland secrete milk?

Alveoli

What are the two main hormones that promote milk production?Where are they produced, and what signal drives their release?

prolactin and growth hormone

Both produced from the anterior pituitary into the blood.

• suckling results in impulses along sensory afferent nerves to hypothalamus leading to secretion of these hormones.

Why is colostrum important for newborn animals in the first 24 hours of life?

important source of nutrition and supplies a method (the only way in ruminants) of passive transfer of maternal antibodies to the offspring, providing them with protection against disease until there own immune system is protective.their

Mammals are born with a sterile digestive tract, which means ruminants are born without a population of microorganisms in their fermentative chambers. How do newborn ruminants obtain energy?

new born ruminants don't need micro-organisms right away - it will establish through ingestion when suckling, licking things, mother licking their face etc.

the oesophageal groove ensures that milk bypasses the reticulorumen so it can be digested in the small intestine for nutrition and energy.

How do long bones continue to grow in length?

grow from the growth plates at each end of the bone, cartilage is formed first by cartilage cells, the cartilage is then replaced with bone by the osteoblasts. the cartilage cells stay ahead of the osteoblasts so the bone continues to lengthen until puberty where the osteoblasts catch up with cartilage cells and the bones stops elongating

what animals are seasonal breeders? (large animals)

ewe, mare, nanny goat

what animals are non-seasonal breeders? (large animals)

cow and pig

What best describes the reproductive seasonality of the queen who is kept indoors?

non-seasonal breeder

- loose reproductive seasonality and have cycles all year round if they are kept indoors / under lights

what animals are monoestrus?

bitch

what animals are polyoestrus?

cow, ewe, mare, nanny goat, queen, sow

what does monotocous mean?

1 oocyte is released = 1 offspring at a time e.g. mares or cows (usually)

what is a spontaneous ovulator?

A species that needs no external stimulus to ovulate

how is the oestrus cycle divided into 2 phases by structures on ovary?

- follicular phase

- luteal phase

how is the oestrus cycle divided into 2 phases by behaviour?

- oestrus

- diestrus.

What is proestrus?

period leading up to oestrus

- period of growth in dominant follicle, increasing oestrogen production and signs of impending heat

What is metoestrus?

period after ovulation when the CL forms and progesterone production increase.

what stages of the oestrous cycle fall into the follicular phase?

proestrus and oestrus

what stages of the oestrous cycle fall into the Luteal phase?

Dioestrus and metoestrus

what is a traditional oestrous cycle?

These species have 2, 3 or even 4 follicular waves develop between two consecutive ovulations, and their luteal phase is long (about 70 to 80% of the length of the cycle).

what is the mares variation of a traditional oestrous cycle?

The mare's cycle is close to the traditional oestrous cycle, often with two follicular waves, but a long oestrus (5-7 days) and relatively shorter dioestrus (14-15 days).

what is the sows variation on the traditional oestrous cycle?

The sow is similar to the traditional oestrous cycle, but with no discernable follicular waves.

what animals have traditional oestrous cycles?

sheep, goats, (mares and sows)

what animals do not have traditional oestrous cycles?

bitch, queen and camelid.

what does the oestrous cycle of the mare look like?

- seasonally polyoestrous long-day breeder

- The oestrous cycle is normally around 21 days long

- long oestrus of 5 to 7 days (teasing behaviour)

Dioestrus lasts for around 14 days (negative behaviour)

what are some dioestrous behaviours seen in mare?

- clamping down tail

- biting or baring teeth

- ears back

- moving away

- agitated and nervous

what are some oestrous behaviours seen in the mare?

- clitoral winking

- ears forward

- nuzzling

- posturing and leaning

- quiet and calm

- raising tail

- urinating

what does the oestrus cycle of a ewe look like?

- seasonally polyoestrus short-day breeder

- oestrous cycle = 17 days ish

- oestrus = 30 hours ish

- ovulate more one or more oocytes per cycle

- behaviour = activly seek out ram and interact, wagging tail, females may mount other females (less than cows)

what does the oestrus cycle of a nanny goat look like?

- seasonally polyoestrus short-day breeder

- oestrous cycle = 21 days ish

- oestrus = 36 hours ish

- ovulate more one or more oocytes per cycle

- behavioural = more obvious in male presence, vocalising and similar behaviours as ewe.

what does the oestrus cycle of a sow look like?

- non-seasonal and polyoestrous

- oestrous cycle = 21 days

- oestrus = 2-3 days

- vulvar swelling and vaginal discharge.

- mounting behaviour, increased activity, vocalisation, and tilted ears

- standing reflex

- ovulate many oocytes each cycle.

What is puberty?

the period during which an animal first becomes able to reproduce

- In males puberty begins when mature spermatozoa are produced

- In females puberty starts when the first oestrus leads to ovulation

what does puberty require?

secretion of Gonadotrophin releasing hormone (GnRH) at the appropriate frequency and appropriate quantities to stimulate gonadotropin release from the pituitary.

what do Gonadotropins do?

promote development of gametes, steroid hormones and the development of reproductive organs toward their adult shape and size.

what is sexual maturity?

- when a male can successfully bred and deliver a suitable number of spermatozoa to fertilise an oocyte

- when a female can successfully carry a pregnancy to term.

what do trophic hormones do?

stimulate growth, development and function of specific organs or tissues (usually endocrine glands)

- regulate secretion of other hormones by these glands.

What gonadotrophins does GnRH stimulate the secretion of? Where do these gonadotrophins act?

GnRH stimulates secretion of FSH and LH from the anterior pituitary

FSH and LH bind to cell receptors in the gonads.

how old are alpacas at puberty? (M/F)

M = 2-3 years

F = 1 year

how old are bovine at puberty? (M/F)

M = 11 months (7-18)

F = 11 months (9-24)

how old are canine at puberty? (M/F)

M = 9 months (5-12)

F = 12 months (6-24)

very dependant on breed.

how old are equine at puberty? (M/F)

M = 14 months (10-24)

F = 18 months (12-19)

how old are feline at puberty? (M/F)

M = 9 months (8-10)

F = 8 months

how old are ovine at puberty? (M/F)

M = 7 months (6-9)

F = 7 months (4-14)

how old are porcine at puberty? (M/F)

M= 7 months (5-8)

F = 6 months (5-7)

what are some factors that modulate age at puberty?

- Body size and composition

- Genetics and breed

- environmental factors

why can body size and composition effect age of puberty?

- The onset of puberty normally requires a threshold body size and body composition

- puberty is delayed in animals that don't reach the target body size for their breed and species; this may be due to undernutrition.

why can genetics and breed effect age of puberty?

Breeds that are larger at maturity are older and heavier when they reach puberty

what environmental factors can effect age of puberty?

Photoperiod is important for timing of puberty in seasonal breeders

The presence of a male, and social interaction with the male, may influence the timing of onset of puberty in females of some species.

what are the pubertal changes of the female?

Oestrogen stimulates sexual receptivity in females

- start showing behavioural signs of oestrus

- increased vocalisation, activity, mounting behaviour, clear mucus at vulval lips and some udder development

what information can farmers use to predict when animals achieve puberty?

- information on normal age

- weight and targets

- body condition and targets

what are the pubertal changes of a male?

testosterone secreted by leydig cells increases greatly

- promote diffusion into sertoli cells and seminiferous tubules where it stimulates spermatogenesis

- also stimulates growth of internal and extrenal organs,

- possible agressive behaviour towards other males may start

- increased bone and muscle growth

what is sexual receptivity?

when they display specific behaviours and will stand to be mounted and bred by a male

what does sexual arousal in the male involve?

a cascade of endocrine and neural events resulting in penile erection and mounting of the sexually receptive female, intromission and ejaculation.

what does erection involve?

specific neural and biochemical events that result in vasodilation of the penis.

Ejaculation

is a reflex initiated by stimulation of the glans penis

what are common courtship behaviours?

- Sniffing of the vulva by the male

- Urination by the female and postural changes to show she is receptive.

- Flehmen response

- Vocalisation

what does the method of breeding depend on?

on the species, and the breeding objective.

what is live cover breeding?

where the male physically breeds the female

- can be any male with any female

- one animal can be bought to one female (in-hand breeding.)

what is Artificial insemination? (AI)

semen is harvested using artificial vagina, semen is diluted and is inseminated into the female reproductive tract using a pipette or catheter

what are the potential benefits of AI in a breeding program?

- reducing risk of injurt to animals and people involve in in-hand breeding

- allow 1 sample to be used for multiple females

- can know what the concentration and motility of sperm is like.

- don't need to own animals to get their genetic merit.

What types of males can be used as teaser animals to detect heat?

small males - restrained by a handler or pen

vasectomised males - have testies, remove portion of deferent duct

surgically altered males - done historically not now

what are the ways we can detect heat without males?

- visual observation of mounting behaviour or other oestrus behaviours

- tail paint

- heat mount detectors

- electronic heat detection

- veterinary transrectal ultrasound examination (mares)

Why do you think oestrous cycles are detected by methods that don't involve a bull in dairy herds?

AI is widely used - no bulls on farm to use

- bulls can be very dangerous to people

what events happen to the spermatozoa before fertillisation?

1. Capacitation

2. acrosome reaction

3 fusion of sperm-oocyte membranes

what is Capacitation?

where the tail of the spermatozoa develop a whip-like movement which enables them to swim towards the oocyte

What is the acrosome reaction?

- where the sperm membranes change

- allowing penetration of the zona pellucida

What is a zygote?

fertilized egg cell (single cell embryo)

what is a morula?

solid ball of cells that starts to develop a fluid pocket as the surrounding cells continue to divide

what is a blasocyst?

a spherical structure with two distinct cellular populations:

1. An inner cell mass that will develop into an fetus.

2. A thin, outermost layer of trophoblast cells that develop into the extra-embryonic (fetal) membranes.

what is the amnion?

the membrane surrounding the fetus and creating a cavity (the amniotic cavity) in which the fetus develops.

- The fluid in the amniotic cavity protects the fetus from mechanical impact.

What is the chorion?

grows rapidly to envelop the amnion and fetus, and together with cells from the endometrium, forms the placenta.

what is the allantois?

a sac-like structure that functions as a reservoir for waste products. Eventually it fuses with the chorion.

What ovarian structure produces progesterone?

corpus luteum

What hormone kills off (lyses) the CL?

prostaglandin

when does Maternal recognition of pregnancy occur?

- occurs when a signal prevents luteal regression, allowing the corpus luteum to persist and continue to secrete progesterone to maintain pregnancy

what is MRP (Maternal Recognition of Pregnancy) in ruminants

- signal comes form embryo (Interferon-tau)

- Prevents expression of oxytocin receptors in the uterus, so the is no secretion of prostaglandin F2-alpha (PGF2α) by the uterus, so the corpus luteum is retained and not lysed.

what is MRP in the mare?

- signalled by physical stimulation of the endometrium by the spherical embryo traveling between both uterine horns and the uterine body

- Prevents expression of oxytocin receptor in the uterus, blocking uterine synthesis of PGF2α, so the corpus luteum is retained and not lysed.

what is MRP in the sow?

- signalled by Oestradiol secreted by at least two embryos, one in each uterine horn

- The oestrogen redirects the PGF2α synthesis towards the endometrial lumen (exocrine) rather than diffusing into the blood (endocrine), so it does not reach the ovaries. The corpora lutea are retained and not lysed.

what is the key event that transforms a "normal luteal phase" into a "pregnancy"?

Maternal recognition of pregnancy.

what is the difference about the maternal recognition of pregnancy in dogs?

- dogs are not polyoestrus and have only a single cycle oestrous cycle once or twice a year, separated by anoestrus periods.

- Following ovulation, the pattern of progesterone secretion is essentially the same for the pregnant and non-pregnant bitch, so there is no need for maternal recognition of pregnancy.