The Estrous Cycle Physiology and Endocrinology Terminology Estrus

The Estrous Cycle Physiology and Endocrinology

Terminology • Estrus is a noun. – The cow is displaying estrus. • Estrous is an adjective. – The length of the estrous cycle is 21 days. • Oestrus and Oestrous – British and European spellings • Estrus and Heat are synonymous

Terminology (cont. ) • Anestrus – When the female is not having repeated estrous cycles. • Polyestrus – repeated estrous cycles • Seasonally Polyestrus – repeated estrous cycles only certain times of the year • Monoestrus – only one cycle per year

Average Reproductive Cycles Species Length of Estrous Cycle Length of Estrus Ovulation Length of Pregnancy cow 21 days polyestrus 18 hr 11 hr after end estrus 282 days ewe 17 days seasonal (fall) 29 hr near end estrus 148 days sow 21 days polyestrus 48 -72 hr 35 -45 hr after start estrus 115 days 4 -8 days 3 -6 day of estrus (1 -2 days before end of estrus) 335 days mare 21 days seasonal (spring) polyestrus

Variation in Cycle Types Example Type of Cycle Follicular Development Ovulation & CL Formation CL Function Cow, ewe, sow, mare Long Spontaneous rats, mice, hamsters Short (4 days) Spontaneous Induced (prolactin) rabbit, cat, mink, ferret, otter, alpaca Induced Spontaneous Induced (LH surge) Induced

Estrous Cycle q Length of the estrous cycle q Average 21 days (range 18 to 24 days) q Estrus (standing heat) q 12 to 18 hours (range 8 to 30 hours) q Ovulation q Approximately 30 hours after the beginning of standing heat (or 12 to 18 hours after the end of standing heat) 2

Estrous Cycle q Major structures on the ovary are … q Follicle … a blister-like structure containing the egg (referred to as oocyte); produces hormone “estrogen” q High amount of estrogen causes “standing heat” and “ovulation” q Corpus luteum (referred to as “CL”) … looks like a hard yellow structure and produces hormone “progesterone” that is responsible for maintenance of pregnancy 3

Phases in oestrous cycle 1. 2. 3. 4. Proestrus Estrus Metestrus Diestrus

Follicular Phase Proestrus • follicle enlarges • estrogen increases • vascularity of the female reproductive tract increases • endometrial glands begin to grow • estrogen levels peak

Follicular Phase Estrus • allows male to mount • estrogen decreases • LH surge occurs • ovulation 24 -48 hr after surge of LH • uterine motility high with contractions moving toward oviduct • sperm transport is optimal • cervical mucus volume increases

Luteal Phase Metestrus • estrogen low • ovulation in cow • corpus hemorrhagicum present • uterus Øcontractions subside Øendometrial glands continue to grow and become coiled Øin cattle bleeding occurs • FSH increases Øtriggering growth of follicles

Luteal Phase Diestrus • progesterone high • FSH Ø Increases at some point to cause growth of ovulatory follicle • Uterus Ø secrets fluid but volume gradually decreases Ø contraction stop Ø CL regresses at the end of this period if female is not pregnant due to PGF release

Characteristics of Estrous Cycles Cow Ewe Sow Mare Estrous cycle (days) 21 17 21 21 Proestrus (days) 3 -4 2 -3 Estrus Metestrus (days) Diestrus (days) 12 -18 hr 24 -36 hr 48 -72 hr 4 -8 days 3 -4 2 -3 2 -3 10 -14 10 -12 11 -13 10 -12

Estrus phase is the shortest phase in the estrous cycle, but the most important one…. !! Why…. ?

Follicular Development During Estous Cycle

Ovarian Structure

4 Follicle Development Follicular Wave Regression Dominance Growth Selection Recruitment Next Recruitment q Follicle development occurs as a wave-like pattern consisting of “Recruitment”, “Selection”, “Growth”, “Dominance”, and “Regression” phases q Usually 2 to 4 follicular waves occur during the estrous cycle in cattle

5 Follicle Development Follicle Stimulating Hormone (FSH) Regression Next Recruitment FSH q FSH precedes recruitment of follicles (causes follicles to start growing) q FSH is the same hormone used for superovulation and embryo transfer in cattle

6 Follicle Development Luteinizing Hormone (LH) Dominance Regression Growth Selection LH pulses q LH promotes further follicle growth and maturation of egg

Follicle Development and Ovulation Luteinizing Hormone (LH) and Estrogen Ovulation Dominance Estrogen Growth Selection Estrus LH Surge q LH stimulates follicle growth and a growing follicle produces high levels of estrogen q High levels of estrogen, in turn, cause estrus and surge release of LH that triggers ovulation 7

Follicle Development During the Estrous Cycle 8 Example for 3 Follicular Waves Ovulation 0 Estrus Ovulation 2 4 6 8 10 12 14 16 18 20 0 Day of the Estrous Cycle q Length of the estrous cycle in cattle with 3 follicular waves is typically 20 to 24 days

Follicle Development During the Estrous Cycle Example for 2 Follicular Waves 0 Estrus Ovulation 2 4 6 8 10 12 14 16 18 20 0 Day of the Estrous Cycle q Length of the estrous cycle in cattle with 2 follicular waves is typically 18 to 20 days, slightly shorter than the estrous cycle with 3 follicular waves 9

Endocrinology During the Estrous Cycle 10 Follicle Stimulating Hormone (FSH) 0 Estrus Ovulation FSH 2 4 6 8 10 12 14 16 18 20 0 Day of the Estrous Cycle q Example shown for cattle having 3 follicular waves during a 21 -day estrous cycle

Endocrinology During the Estrous Cycle 11 Luteinizing Hormone (LH) Ovulation LH Surge Estrus LH Surge LH pulses 0 2 4 6 LH pulses 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Example shown for cattle having 3 follicular waves during a 21 -day estrous cycle

Endocrinology During the Estrous Cycle 12 Estrogen 0 Estrus Ovulation Estrogen 2 4 6 8 10 12 14 16 18 20 0 Day of the Estrous Cycle q Example shown for cattle having 3 follicular waves during a 21 -day estrous cycle

13 Corpus Luteum (CL) Growth and Regression Estrus Growth 0 2 4 6 Regression 8 10 12 14 16 Day of the Estrous Cycle 18 20 Estrus Ovulation 0 q Corpus luteum develops from the ovulated follicle and takes approximately 10 days to reach mature size

14 Corpus Luteum (CL) Progesterone 0 Estrus Regression Estrus Growth Progesterone 2 4 6 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Corpus luteum produces progesterone q Progesterone is responsible for maintenance of pregnancy after conception occurs

15 Corpus Luteum (CL) Regression Prostaglandin F 2 (PG) 0 Estrus Regression Estrus Growth PG 2 4 6 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Late in the estrous cycle, uterus produces PG which causes regression of corpus luteum q PG is the same or similar hormone in “Lutalyse ®”, “Estrumate®”, “Prosta. Mate®”, and “In Synch®”

Corpus Luteum (CL) Maintenance 16 When cow becomes pregnant … Growth Estrus Maintenance 0 Embryo 2 4 6 PG 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Presence of embryo blocks uterus to produce PG late in the estrous cycle which causes maintenance of corpus luteum and production of progesterone for pregnancy

Progesterone regulates LH Pulses Luteinizing Hormone (LH) 0 LH pulses LH Surge Estrus LH pulses Progesterone 2 4 6 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Progesterone regulates secretion pattern of LH pulses and hence, follicular development 17

Endocrinology of the Estrous Cycle PG 0 Estrus Estrogen Progesterone 2 4 6 8 10 12 14 16 18 20 0 Day of the Estrous Cycle q Relationships among estrogen, progesterone, and PG during the 21 -day estrous cycle 18

0 19 Estrus Physiology and Endocrinology of the Estrous Cycle 2 4 6 8 10 12 14 16 Day of the Estrous Cycle 18 20 0 q Relationships among structural and hormonal changes during the 21 -day estrous cycle (example shown for cattle having 3 follicular waves)

Time to breed LABORATORIUM REPRODUKSI TERNAK FAPET UB 35

Presence of Offspring Pregnancy Causes of Anestrus Season Pathology Nutrition Stress

Gestational Anestrus • Progesterone during pregnancy – negative feedback • After parturition anestrus continues – progesterone exposure during pregnancy – hypothalamus • Lacks estradiol positive feedback • allows time for uterine involution

Seasonal Anestrus • just like entering puberty • silent ovulation

Silent Ovulation Anestrus Estrus

Lactational Anestrus

Lactational Anestrus • Suckling • Other offspring factors – visual encounter – olfactory encounter – auditory encounter • Prolactin – inhibits Gn. RH release – major infertility problem in women who are not lactating

Nutritional Anestrus

Terima kasih…

20 Estrus Synchronization

21 Effective Estrus Synchronization Programs q Shorten the AI breeding season q Cows or heifers are in estrus during a predictable interval that facilitates AI q Reduce time and labor required to detect estrus q Result in more cows and heifers becoming pregnant early during the breeding season q Progestin-based programs can induce estrous cyclicity in anestrous cows and prepubertal heifers (For example: MGA, or CIDR)* * Progestins are progesterone-like compounds that act like progesterone

22 Effective Estrus Synchronization Programs q Result in older and heavier calves at weaning q Will have beneficial effects on the next breeding season q More cows and heifers calve early q More days postpartum at the next breeding season q Replacement heifers will be older

23 Effective Estrus Synchronization Programs q Consider what happens during a restricted breeding season, based on the average 21 -day estrous cycle: q If cows or heifers are cycling when an estrus synchronization treatment is implemented and they exhibit estrus during the synchronized period, they would have 3 opportunities to conceive during a 45 -day period or 4 opportunities during a 65 -day period q If cows or heifers are cycling but no estrus synchronization treatment is implemented, then they have only 2 (45 -day) or 3 (65 -day) opportunities to conceive q If cows or heifers are not cycling at the beginning of the breeding season, they have even less opportunity to conceive

Points to Consider When Using Estrus Synchronization 24 q Estrus synchronization is never a substitute for: q Nutrition q Herd health q Proper management q Estrus synchronization should not be used as a crutch for poor management q When administered appropriately, estrus synchronization is an effective reproductive management tool that can be used to facilitate AI

Points to Consider When Using Estrus Synchronization q Determine which females would make the best candidates before beginning estrus synchronization q Successful application of estrus synchronization is easier to accomplish with heifers (no calves to work with) 25

37 Selecting Heifers for Estrus Synchronization q Heifers should be of adequate age (cycling or close to reaching puberty) q Heifers should be of adequate weight q Developed to 65 % of projected mature weight q Do you know the mature weight of your cows? q Utilize reproductive tract score (RTS) to assess reproductive maturity

38 Timing of Puberty in Heifers q Target weight: Heifers reach puberty at approximately 65% of their mature body weight q Determine your desired weight at breeding, calculate the gain needed to meet that weight, and feed to meet it

39 Management Considerations for Heifers q DO NOT use growth promoting implants in replacement heifers q Implants may disrupt or impair normal development of reproductive organs q Developing uterus is especially sensitive to growth promoting implants

40 Management Considerations for Heifers q Reproductive Tract Scores (RTS) are determined by rectal palpation of the ovaries and uterus q The RTS should be performed approximately 6 to 8 weeks prior to breeding season and/or approximately 2 weeks prior to beginning an estrus synchronization treatment

41 Reproductive Tract Scores (RTS) Ovarian Measurement (mm) Ovarian Length Height Width Structures RTS Uterine horns 1 Immature < 20 mm diameter No tone 2 20 -25 mm diameter No tone 3 20 -25 mm diameter Slight tone 22 4 30 mm diameter Good tone 30 5 > 30 mm diameter 15 18 > 32 Description 8 No palpable follicles Infantile 10 8 mm follicles Prepubertal 15 10 8 -10 mm follicles 16 12 10 12 20 15 (more than 30 days to puberty) Peripubertal (within 30 days to puberty) Cycling > 10 mm follicles (Follicular Phase) CL possible CL present Cycling (Luteal Phase) Adapted from Anderson et al. , 1991

42 RTS Measurements RTS No. of Heifers Weight (lb) Pelvic Height (cm) Pelvic Width (cm) Pelvic Area (cm 2) Estrous Response 1 61 594 a 13. 9 a 10. 9 a 152 a 54 %a 2 278 620 b 14. 1 a 11. 2 a 158 a 66 %b 3 1103 697 c 14. 5 b 11. 4 b 166 b 76 %c 4 494 733 d 14. 7 c 11. 7 c 172 c 83 %d 5 728 755 d 14. 7 c 11. 7 c 172 c 86 %d a, b, c, d = P < 0. 05 q Note the relationship between increasing RTS, weight, and skeletal development determined by pelvic area q Estrous response increased among heifers that were more reproductively mature at the beginning of estrus synchronization and/or breeding season Adapted from Patterson et al. , 1999 a

43 Relationship Between RTS and Pregnancy RTS No. of Heifers Pregnant Open Pregnancy Rate 1 53 31 22 58 % 2 762 610 152 80 % 3 3458 3014 444 87 % 4 3398 3006 392 89 % 5 2613 2331 282 89 % q Higher pregnancy rates at the end of the breeding season were achieved among heifers that were more reproductively mature at the beginning of estrus synchronization and/or breeding season Randle et al. , 2001

53 Prepubertal Anestrus q Timing of puberty is controlled by … q q Age Weight Breed Season Many factors involved q Develop heifers to approximately 65% of mature weight by the breeding season q This will help them to attain puberty at the right time

55 Nutritional Anestrus q Nutritionally stressed cattle will experience delays in return to estrus after calving q Can be “managed” through q Improvement in BODY CONDITION q Proper feeding management

Postpartum Anestrus 56 Induction of Estrous Cyclicity q Bull exposure q Prepubertal heifers Exposure of prepubertal heifers to sterile bulls (for example, vasectomized, epididyectomized … etc) for 60 to 80 days before the breeding season may hasten the onset of puberty (ranges from no effect to 70 days earlier) Izard and Vandenbergh, 1982; Berardinelli et al. , 1978; Mac. Millan et al. , 1979; Roberson et al. , 1991 q This procedure also shortens the postpartum period in anestrous cows however my concentration is on heifers Foote, 1974; Mac. Millan et al. , 1979; Zalesky et al. , 1984; Gifford et al. , 1989

Products Currently Utilized in Protocols to Synchronize Estrus *** Price may vary depending on suppliers *** 28 q Prostaglandin F 2 (PG) Lutalyse®, Estrumate®, Prosta. Mate®, In Synch® q Approximate cost is $3. 00/dose (range $2. 50 -$4. 00) q Gonadotropin-Releasing Hormone (Gn. RH) Cystorelin®, Factrel®, Fertagyl® q Approximate cost is $5. 00/dose (range $4. 00 -$6. 00) q Melengestrol Acetate (MGA® Premix) q Approximate cost ranges $0. 14 - $0. 40/day/head including carrier q 14 days ($2. 00 -$5. 60/head) or 7 days ($1. 00 -$2. 80/head) q EAZI-BREED™ CIDR® Cattle Insert (CIDR) q Approximate cost is $8. 00 (range $8. 00 -$10. 00) q Syncro-Mate-B® (off the market)

60 Prostaglandin F 2 (PG)

Prostaglandin F 2 (PG) 61 q PG causes CL regression q No effect on anestrous cattle q No induction of estrous cyclicity … No Jump-start q Only effective during Days 6 (6 days after estrus) to 16 of the estrous cycle Lauderdale, 1972

Prostaglandin F 2 (PG) PG regresses CL NO NO YES Estrus 0 2 4 6 8 10 12 Estrus 14 16 Day of the Estrous Cycle 18 20 0 62

Estrous Response Double Injection PG Program 77 Example shown is 14 -day interval for PG injections % of cows in estrus 50 2 x PG 40 30 20 10 0 PG 0 < 24 36 48 60 72 84 96 108 120 > 120 Hours following second PG injection Modified from Stevenson et al. , 2000

Single or Double Injection PG Programs $3. 00 or $6. 00 ($3. 00/one dose) q Advantages: q Cost effective ($3. 00 or $ 6. 00) q Easy to use q Good fertility 74

Single or Double Injection PG Programs $3. 00 or $6. 00 ($3. 00/one dose) q Disadvantages: q No effect between days 0 to 4 or 16 to 21 of the estrous cycle q Improved effectiveness after day 10 of the estrous cycle q Require heifers and cows to have CL (cycling) q Require extensive estrus detection (minimum 7 days) q No induction of estrous cyclicity (No Jump-start) 75

Possible Outcomes 76 Single or Double Injection PG Programs q Estrous response: q Varies depending on the degree of estrous cyclicity in the herd and the stage of the estrous cycle of an individual animal q Single injection of PG … up to 40 to 60 % q Double injection of PG … up to 50 to 80 % q Timing of estrus: q Before PG injection to 7 to 10 days after PG injection q Peak response ranges from 48 to 96 hours after PG injection

98 Melengestrol Acetate ® (MGA ) MGA is a registered trademark of Pfizer Animal Health

99 Melengestrol Acetate (MGA) q Orally active progestin, administered as a feed additive q Blocks estrus and ovulation q Acts similar to progesterone from CL q MGA can induce estrous cyclicity in peripubertal (within 30 days to attain puberty) heifers and postpartum anestrous cows q Currently, MGA and CIDR are the only progestins commercially available in the U. S. Patterson et al. , 1989

100 Intake Considerations What type of carrier to use? q Mix with grain source (example: cracked or ground corn) For example: MGA with ground corn ($0. 15/day/head) q Top dressing does not work well q If cattle are on lush pasture, remove salt from pasture and include salt in MGA carrier 0. 5 oz. Salt per cow and MGA in carrier ($0. 30/day/head) q Pellet form (very palatable) For example: MFA Cattle Charge® with MGA ($0. 40/day/head)

101 Intake Considerations q Need to provide adequate bunk space (18 inches per heifer, and 24 inches per cow) q Make sure cattle come to bunk before start of feeding MGA q If cattle are not used to bunk feeding, 1 -2 weeks of warm-up bunk feeding is recommended q MGA should be fed one time per day at approximately the same time every day q Separate heifers from cows for MGA feeding q Late-term pregnant cows should not be fed MGA

• MGA can be combined with PG to improve results

106 Distribution of Estrus 3 -5 days 7 -10 days % of herd in estrus MGA-PG (for AI) MGA only (for Natural service) q Adding the PG injection to the MGA program results in a much tighter synchronization of estrus Adapted from Patterson et al. , 2000

Management Considerations Why Not Introduce Bulls Right After MGA Withdrawal? Less fertile estrus after 2 nd estrus for MGA 7 -10 days anestrous cows after short estrous cycle (more fertile) % of herd in estrus 107 2 nd estrus for most of cows (more fertile) Suggested timing of introducing bulls (see page 104 and 105) 0 5 10 15 20 25 Days after MGA feeding 30 q If bulls were introduced to the herd right after MGA withdrawal, they may be overworked during the less fertile estrous period after MGA withdrawal, but before cows express fertile estrus

Natural Service with MGA Program 109 $2. 00–$5. 60 (MGA cost) q Advantages: q Easy to use q Shortens the next calving season (ideal way to start AI program in the following year) q MGA can induce estrous cyclicity in postpartum anestrous cows (Jump-start) q Does not require cattle to be handled

Natural Service with MGA Program $2. 00–$5. 60 (MGA cost) q Disadvantages: q Must have adequate bull-power q At least 1: 15 to 20 bull: female ratio for 2 -year or older bulls q Yearling bulls … consider decreasing the bull: female ratio q Resulting calves may be of inferior quality and provide less genetic improvement for the herd compared to AI calves (depends on the genetic quality of the clean-up bulls) 110

Summation • Lots of programs – Many combinations of programs • Many prices • The numbers definitely show results – Earlier calving season – More time to return to Estrus – Increased opportunity to become pregnant • However due to expense and labor intensity this is not for everyone

Bibliography • “Guide to Estrus Synchronization of Beef Cattle” CD Freddie N. Kojima, Ph. D. and David J. Patterson, Ph. D. Department of Animal Sciences University of Missouri Columbia, MO 65211