PHYSIOLOGY OF REPRODUCTION Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 PHYSIOLOGY OF REPRODUCTION REPRODUCTIVE CYCLES Part I By Dr. Abdul samik, M.Si.,Drh

The Reproduction Cycles Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 The Reproduction Cycles Phenomena : Puberty and sexual maturity The breeding season The estrous cycle Postpartum sexual activity Aging and fertility

Regulation of Reproductive Cycle Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Regulation of Reproductive Cycle Environmental Genetic Physiologic Hormonal Behavioral Psychosocial

Events of Reproduction Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Events of Reproduction Puberty- Age at which reproductive organs become functional Female- Reproduction process occurs within Estrous cycle- Repetitive cycle occurring when pregnancy does not Estrus- “Heat” or receptivity to mating Fertilization- Egg & Sperm unite Only real male contribution is the sperm Gestation- Length of time of pregnancy Parturition- Act of giving birth

Age of Puberty Cattle: 6 to 12 Months Sheep: 5 to 7 Months Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Age of Puberty Cattle: 6 to 12 Months Sheep: 5 to 7 Months Swine: 4 to 8 Months Horses: 12 to 15 Months Humans: 9 to 16 Years

What influences the onset of puberty in heifers? Physiological events leading up to puberty Endocrine and morphological events in peripubertal heifers are similar to the resumption of cyclicity post partum in mature cows. Decreased negative feedback of oestradiol Maturation of the hypothalamus Increased frequency of release of LH pulses Enhanced development of ovarian follicles Enough oestradiol produced to induce behavioural oestrus and a preovulatory surge of gonadotrophins Puberty is attained with the first behavioural oestrus that is accompanied by ovulation and development of a corpus luteum with a typical life span What influences the onset of puberty in heifers? Factors that can influence the pubertal rise in release of LH pulses are: genotype season of year when pubertal age is attained growth or nutritional intake social cues treatment with exogenous hormones

Endocrine mechanisms of puberty

The Estrus Cycle When Heifer becomes sexually mature Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 The Estrus Cycle When Heifer becomes sexually mature ovaries function in a cycle activity estrus period cycle 17-24 days (21 days) Estrous cycle – period of time from one estrus to the next

Breeding Season Monoestrous : dog, cat Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Breeding Season Monoestrous : dog, cat Polyestrous (cycle throughout year) : cattle, goat, sheep, swine Seasonal polyestrous (Decreasing light, Fall) : sheep, goat Seasonal polyestrus (Increasing daylight, Spring) : horse

Length of Estrus Cycle Cattle: 19 to 23 Days Sheep: 14 to 19 Days Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Length of Estrus Cycle Cattle: 19 to 23 Days Sheep: 14 to 19 Days Swine: 19 to 23 Days Horses: 10 to 37 Days

Duration of Estrus Phase Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Duration of Estrus Phase Cattle: 6 to 27 Hours Sheep: 24 to 36 Hours Swine: 48 to 72 Hours Horses: 3 to 8 Days

Luteal phase. A corpus luteum is formed under the influence of pituitary LH. The function of the corpus luteum is to secrete progesterone, which reduces the amount of the hormone oestrogen produced. As long as the corpus luteum is functional, oestrogen is unable to trigger formation of the follicle (a large fluid-filled sac containing the egg). By day 18 the corpus luteum degenerates due to prostaglandin (released from the uterus) and goes through a regression phase. Associated with corpus luteum regression is a decline in progesterone

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Follicular phase Following the decline in progesterone, an increase in oestrogen (mainly oestradiol-17β) takes place and peaks before the onset of oestrus. Oestrogen stimulates the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. GnRH stimulates the release of FSH and LH from the pituitary gland. LH rises to a peak at the beginning of oestrus. FSH and LH stimulate the development of follicles in the ovary.

The follicle ruptures and releases the egg (ovulation). Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 One follicle predominates which secretes oestrogen and triggers a wide range of anatomical and physiological changes in the cow All the changes ensure that if the cow is mated, the sperm will stay alive until one of the spermatozoa will effect fertilisation. The follicle ruptures and releases the egg (ovulation).

Stage of heat Proestrus Estrus Diestrus Metestrus Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Proestrus Estrus Stage of heat Diestrus Metestrus

Stage of heat A. Proestrus day 19 -21 Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Stage of heat A. Proestrus day 19 -21 period for preparation of sexual activity

Stage of heat B. Estrus (heat, sexual desire) Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Stage of heat B. Estrus (heat, sexual desire) period of sexual activity, female permit mating duration : 6 - 30 hrs (heifer 15, cows 18hrs)

Signs of Estrus Primary Sign of Estrus Stands immobile when mounted. Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Signs of Estrus Primary Sign of Estrus Stands immobile when mounted.

Secondary Signs of Estrus Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Secondary Signs of Estrus Behavioral Bellowing Increased Activity Walking the fence line Charging Butting Licking Sniffing Flehmen posture (inverted nostrils) Circling Chin-resting Mounting

Physical Signs of Estrus Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Physical Signs of Estrus Manure on flanks Roughened tailhead Loss of hair on tailhead Abrasions on tailhead Red vulva Swollen vulva Clear mucus discharge from vulva

Miscellaneous Signs of Estrus Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Miscellaneous Signs of Estrus Depressed appetite Depressed milk production Frequent Urination Metestrus bleeding : 35-45 hours after estrus; too late to breed

Stage of heat C. Metestrus (after heat) day 1-5 of cycle Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Stage of heat C. Metestrus (after heat) day 1-5 of cycle not permit mounting 50% cow , 90% heifer - metestral bleeding corpus luteum begins to develop

Stage of heat D. Diestrus (between heat) day 5 - 19 Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Stage of heat D. Diestrus (between heat) day 5 - 19 complete lack of sexual desire

LH and FSH During the Estrous Cycle Progesterone Hormone Concentration FSH 5 10 15 Estrus Days Relative to Estrus Estrus

The Estrous Cycle in Cattle LH 1st Progesterone 2nd Wave Wave Hormone Concentration Estradiol FSH 5 10 15 Estrus Days Relative to Estrus Estrus

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Mechanisms of luteolysis during the oestrus cycle of cows Luteolysis starts between days 16-17 post oestrus in the cow. Bovine luteal tissue is usually not responsive to PGF2-alpha until after day 4 post oestrus Two major mechanisms of luteolysis have been suggested: 1. Reduction of the blood flow in the corpus luteum (CL) A rapid decrease in luteal blood flow has been recently proposed as one of the main luteolytic actions of PGF2-alpha. It was demonstrated that the reduction in luteal blood supply 8 hours after prostaglandin injection was coincident with the onset of structural luteolysis, the first significant decrease in CL volume was seen.

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 2. Direct action on luteal cells A direct action of prostaglandin on the luteal cells, resulting from both the decrease in cAMP synthesis normally produced in response to LH and the inhibition of the steroidogenic action of cAMP. These effects would be further amplified by a reduction in the number of receptors for LH. This theory is further supported by the result of a study that demonstrated that a prostaglandin-induced decrease in plasma progesterone concentrations occurs before a detectable decrease in both the volume of the CL and the luteal blood flow.

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009

Follicular development in cattle Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Follicular development in cattle Ovarian follicular growth and development in ruminants is characterised by two or three consecutive follicular waves per oestrous cycle. Each wave involves the recruitment of a cohort of follicles and the selection of a dominant follicle. The dominant follicle continues to grow and mature to the preovulatory stage while others undergo atresia.

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009

Recruitment of follicular waves Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Recruitment of follicular waves The growth of follicular waves is initiated by a rise in circulating FSH. All follicles growing as a cohort contain specific receptors for FSH and depend on this gonadotrophin in their growth. At this stage the growing follicles do not have a sufficient population of LH receptors to respond to a LH-like stimulation. For this reason this stage of follicular growth is sometimes called FSH-dependent.

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 For reasons not yet properly understood only one dominant follicle is selected from among the cohort recruited by the small rise in FSH. A defining characteristic of the dominant follicle appears to be its greater capacity for estradiol production. Selection of the dominant follicle is associated with a decrease in FSH, FSH is maintained at basal levels. The selected future dominant follicle acquires LH receptors which allow it to continue growth in the environment of low FSH and increasing LH levels.

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 It seems that by decreasing the FSH support, the selected follicle depletes subordinate follicles from their vital growth stimulant while it benefits from both the low FSH and growing LH stimulation

Department of Veterinary Reproduction Faculty of Veterinary Medicine Airlangga University 2009 Selected dominant follicle and ovulation Following its selection, DF growth, oestrogen activity and lifespan are controlled by the LH pulse pattern. In response to maximum concentrations of oestrogens produced by the dominant follicle a massive LH release takes place. It is called a pre-ovulatory LH surge or peak and acts as the direct stimulation of ovulation