4Y Bovine oestrus cycle and physiology 2021 - Tagged.pdf

Bovine Oestrous Cycle Prof Robert Smith Why do cows need to get pregnant? • What do you think? • Level dairy contracts • No. cows needed to calve per month • Calves? • Not enough heifers for replacement? • Sexed semen as a solution PREPARES UTERUS FOR PREGNANCY Brain (Hypothalamus) GnRH Pitu...

Bovine Oestrous Cycle Prof Robert Smith Why do cows need to get pregnant? • What do you think? • Level dairy contracts • No. cows needed to calve per month • Calves? • Not enough heifers for replacement? • Sexed semen as a solution PREPARES UTERUS FOR PREGNANCY Brain (Hypothalamus) GnRH Pituitary Gland FSH LH Small follicle (containing egg) Progesterone Corpus Luteum Corpus Luteum Grows Egg Ovary Follicle produces Oestrogen SIGNS OF HEAT OVULATION: follicle bursts & egg released Regressing corpus luteum Pre-ovulatory follicle Post-ovulation Corpus haemorrhagicum Mature corpus luteum Frozen section Control of Follicular Development PRIMORDIAL FOLLICLE POOL FOLLICLE GROWTH INITIATED Antrum forms GONADOTROPHIN RESPONSIVE GONADOTROPHIN DEPENDENT OVULATORY FOLLICLE OVULATION Energy Stress Photoperiod ‘Brain’ Neurotransmitters Hypothalamus GnRH Anterior Pituitary LH FSH Ovaries Oestradiol ‘Brain’ Feedback +ve and -ve Neurotransmitters Hypothalamus GnRH Anterior Pituitary LH FSH Ovaries Oestradiol & Inhibin Webb et al 2004 Return of ovarian activity after calving Progesterone/ CL diameter Follicles size Oestradiol 0 7 14 Day postpartum/season 21 28 Emerg Select DominanceAtresia Sheldon Stages of cycle: progesterone and follicular waves Proestrus Dioestrus P4 concentration Follicle diameter (mm) OestrusMetoestrus 15 10 5 0 0 2 4 6 8 10 12 14 Day of oestrous cycle 16 18 LH FSH, LH, progesterone & follicle waves FSH Progesterone 0 2 4 6 8 10 12 Day of oestrous cycle 14 16 18 © Mark Crowe. UCD Oestrous cycle – 2 wave Oestradiol/ Follicle sizes 0 2 4 6 Progesterone/ CL diameter 8 10 12 Day of oestrous cycle 14 16 18 © Mark Crowe. UCD Examples of different numbers of follicular waves per cycle Dairy cows Legend P4 concentration Follicle diameter (mm) LH Small follicles (< 5mm) 15 10 5 0 0 5 10 15 20 25 30 35 40 45 5 10 15 20 25 30 35 40 45 Medium follicles (5-9 mm) Dominant follicle (>9 mm) Atretic follicles Ovulation LH pulse pattern Progesterone profile P4 concentration LH Follicle diameter (mm) Suckling Beef or cows in negative energy balance/disease 15 10 5 0 0 Days post-partum 50 55 60 65 70 Crowe Reprod Domest Anim, 2008 Reproductive parameters in the early postpartum period of dairy, and beef cows (suckling calves) Dairy Cow Beef Cow Emergence of 1st follicle wave (days postpartum) 5-10 5-10 % cows that ovulate 1st DF 50-80 20-35 Days to 1st oestrus 25-45 30-130 Nature of 1st ovulation Silent Silent % short cycles after 1st ovulation >70 >70 Regulation of LH pulse • declining NEB • declining NEB frequency • BCS at calving• BCS at calving • DM intake • suckling • disease state • calf presence • disease state Crowe et al., RDA 2008 Success of AI depends on - use of proven/fertile sires - reliable oestrus detection Oestrus detection Peters & Ball, 1995 times per oestrus Occurrence of Oestrus Behaviours 50 45 40 35 30 25 20 15 10 5 0 flehmen 47% sniffing 100% chin resting be mounted mount 100% 56% 89% mount head stand 22% Occurrence in % of bulling periods (Roelofs et al) 58% Behaviour around heat steps/hr 700 600 500 400 300 200 100 0 85 Sniffs another cow (76 times) Sniffed by another cow (31 times) Chin rests on another cow (45 times) Chin rested by another cow (52 times) Mounts rear of another cow (9 times) Did not stand when mounted (1 and 9 times) Stand and was mounted (12 times) pedometer Heatime activity weighted 86 Days after calving 87 88 Duration of Standing heat (n=50) 60 50 % 40 30 20 10 0 3 6 9 12 15 18 duration Standing heat Roelofs et al 21 24 Hunter, 1994 Number of cows in estrus one two three Hurnik et al., 1975 duration 10.2 17.8 23.8 mounts 11.2 36.6 52.6 Look at right time Effect of number, time and duration of observations on heat detection rate van Vliet et al., 1996 Mount Detectors • Paint / chalk or Kamar/Ambic • A cow is detected only when stands to be mounted • • At least two cows in/near oestrus Not all animals show standing heat • Threshold is important • Easy to use, but maintance can be time consuming Other aids • Record keeping • 21 day diary actually 18 - 24 day cycle so start looking 18 days after the last oestus • • • • Teaser animals Chinballs Milk progesterone Activity meters – leg, neck, ear Heat Detection Aids Pedometers Activity 1200 800 400 0 05dec 07dec 09dec 11dec 13dec 15dec 17dec 19dec 21dec 23dec 25dec Activity Maatje et al., 1997 Heatime 7 day rolling Mean + 5 S.D. HeattimeTM same efficiency as farm staff But still ~40% heats not being detected Detection method % of possible heats identified % of heats detected correct Estrus Alert scratchcard 36 64 KaMaR 57 61 Pedometer 63 73 Farm staff (alone) 56 93 Heattime 59 93 75 92 TM Heattime + Farm staff TM Silent Herdsman • NMR marketing in UK • 3 dimensional movement • They say better than one dimensional products • No independent data Icetags - CowAlert • Alta Genetics marketing in UK • 3 dimensional movement • Lying time and “Icescore” mobility Moomonitors, Rescounter, Smartbow etc On the horizon? • Animal location • GEA - CowView • • • • Ultra wide band 2 dimensions? Find a cow in robot milking http://www.youtube.com/watch?v=n-QGwTyRsfo • Faire Systems • Ultra wide band • 3D • • • • • • • • Location tag - position within X cm? Speed of tag movement – mobility score Time lying and location preference – cow comfort / welfare Tag not moved in X hours – early illness detection Activity windows - Location and time – feedings opportunities Proximity to others - disease transmission and social group Social hierarchy and dominance One tag above another – reproductive behaviour! – more subtle behaviours How many sperm in an AI straw? 51 AI routine Things to consider if reduced pregnancy rates: • • • • • • • • • Has flask become empty and sperm thawed then refrozen? Have they used fingers rather than tweezers Thaw @ 37 deg. for 40 seconds Dry thoroughly Load gun, snip off end of straw Disposable sheath Keep warm Chilling once thawed bad! Thaw one at a time! • • • Get AI company to test some straws or do yourself (ideally warm microscope stage) Suggest retraining for ALL staff Natural service – bull management Why was AI introduced? 1. 2. 3. 4. Bulls are good at oestrus detection! Cows must be cycling and clean What are the problems with natural service / bulls on farm? What is the energy requirement for a bull? How many farms have a good bull pen and cubicles of the correct size for bulls in the cubicle building? Oocyte covered in sperm Post-Fertilisation Development Maternal mRNA Embryonic mRNA • first cleavage • embryonic genome activation • morula compaction • blastocyst formation Classification and Grading of Embryos Unfertilised Ova 16 cell embryo This stage on day 7 = degenerate Grade 1 Morula Grade 1 Early Blastocyst Progesterone crucial for embryo growth Low Progesterone Normal Progesterone Beltman, 2009 Luteolysis or maternal recognition of pregnancy Non-pregnant PGF2alpha (uterus) Progesterone + oxytocin OT-R Pregnant Interferon Tau (oTP1;trophoblast) Progesterone + oxytocin (CL) PGF2alpha Uterus Ovary Bursa Utero-ovarian blood Counter-current distribution Multiple sections through uterus Day 29 Day 55 From Kahn, 1994, Veterinary Reproductive Ultrasonography Plasma hormones in pregnancy Line below horizontal axis = pregnancy CL dependant Control of calving by CALF ? signal from brain Hypothalamus CALF pituitary ACTH Fetal adrenal Ablation causes prolonged pregnancy Infusion causes premature labour Placentome Cortisol (helps develop fetal lung phospholipids) Prostaglandin F2a increased Progesterone reduced The placenta during and after calving • Premature expulsion of the foetal placenta has been found in 12% of stillbirths (Mee,1991:Vet Rec. 128: 521)