lecture 27: manipulating domestic animal reproduction 1

Question 1

What can we increase fertility?

Answer 1

manipulating reproduction

• breeding at younger ages
• advancing breeding season
• more frequent pregnancies
• synchronisation of ovulation
• induction of multiple ovulations
• genetic improvement
• artificial insemination
• improved pregnancy rate
• embryo transfer and associated techniques
• pregnancy testing
• control of birth timing

increasing economy, decreasing labour

Question 2

What is the relationship between nutrition, energy and reproduction?

Answer 2

• starvation
  
  • anovulation
  • inability to maintain pregnancy
  • inability to maintain lactation
  • suppressed sperm production
  • altered behaviour
• intense exercise
  
  • amenorrhea
• obesity
  
  • inhibition of ovulation
  • inhibition of sperm production
  • behavioural modification
  • altered foetal nutrition
  • parturition issues

Question 3

What is the influence of nutrition?

Answer 3

• influence HPG axis acute and chronic effects
• patterns of LH secretion in a rhesus monkey on a normal day of feeding, during a day of fasting, and during refeeding
• nutrition/stress interaction
  
  • LH surge
  • ovulation number and egg quality “flush feeding”
  • sex ration of offspring

Question 4

What is the relationship between nutrition and puberty?

Answer 4

• timing of breeding in sheep fed different diets to manipulate growth rate
• patterns of GnRH secretion in a rapidly growing (top) and in a slowly growing (bottom) lamb

Question 5

What happens with resumption of cycles after calving and subsequent pregnancy rate?

Answer 5

• 1st heat BUT then continued cyclicity affected
• conception rate - bell-shaped distribution
• leptin, kisspeptin, ghrelin and other hormones
• metabolic substrates
• direct effect of nutrients

Question 6

What is the role of micronutrients?

Answer 6

• e.g. vitamin E and selenium
• antioxidant - free radical scavenger
• deficiency causes infertility in both males and females but by different mechanisms and effects vary between species
  
  • reduced sperm motility and maturity
  • rats: normal ovulation/mating but foetal loss after day 7
  • cattle: silent heat, delayed conception, reduced fertilisation, cystic ovaries, retained foetal membranes, metabolic disorders
• goats (control vs selenium deficient)
  
  • conception rate: 93% vs 64%
  • infertile does: 7.4% vs 36%
  • weaned kids/doe: 0.89% vs 0.36%
  • milk fat (g/day): 41 vs 36
  • milk protein (g/day) 32 vs 28

Question 7

What is the impact of nutritional factors?

Answer 7

• impact on females
  
  • ovarian/oocyte
    
    • energy (fat) content/ratio of the oocyte or zona pellucida
  • uterine
    
    • sperm swimming/signalling - viscosity + pH “inhospitable”
    • modulated lumen histotroph (nutrients - glucose, proteins)
  • embryonic loss
    
    • glucose main substrate for embryo development
    • modulated embryo-maternal communication (MRP)
    • placentation failure - foetal reabsorption or abortion
• impact on males
  
  • testis development
    
    • hormone regulation altered
    • testicular mass and function
  • sperm
    
    • sperm fatty acid composition
    • characteristics - abnormal morphology

Question 8

What is manipulating the breeding season?

Answer 8

• why?
  
  • marketing - lambs
  • survival or young
  • convenience
  • to fit artificial constraints (e.g. horses)
• methods
  
  • photoperiod
  • melatonin-implants
  • pheromones

Question 9

What is the “ram effect”?

Answer 9

• pheromones from ram induce increased LH pulsatility in ewes
  
  • synchronisation of ewes and lambing
  • earlier breeding onset (seasonal) (varies with breed)
  • allows maximisation of use of valuable stud rams

Question 10

What is artificial insemination?

Answer 10

• first performed in 1800s
• widespread commercial use began in 1950s when semen freezing developed
• facilitates genetic improvement of herds
• global frozen genetics - avoids some quarantine restrictions for studs
• “insurance” against death or injury
• cost/benefit determines usage ($10-$100 straw)
• “heat” detection - timing
  
  • visual, tailpant, KAMAR, paedometer
  • e.g. cows are in heat for about 18h; best fertilisation rate after insemination 12 h after onset of heat

Question 11

What are aspects of semen to consider in AI?

Answer 11

• collection
  
  • artificial vagina; teaser
  • bull ~12 billion sperm per ejaculate
• evaluation
  
  • motility, morphology
• dilution
  
  • specialised media containing cryoprotectants, egg yolk, fructose etc
  • need 10-25 million sperm per straw
• pack in “straws” (~20 million sperm)
• cool and freeze
• store in liquid nitrogen
• thaw
• inseminate via cervix
• sexed semen (recently available)

Question 12

Are semen collection requiremnets all the same?

Answer 12

• no, semen collection requirements vary by species

Question 13

What is improving herd genetics?

Answer 13

• desired improvements in productivity
  
  • milk, meat, wool production etc
• limited availability and high cost of top-quality sires
  
  • e.g. top-quality bull may be able to service 3-4 cows per day during breeding season
• proving Bulls for AI at genetics australia (progeny testing)
  
  • year 0-1 source best bulls and best cows, mate and rear bull calves
  • year 2 - and collect and distribute semen for test programme (500-1000)
  • year 3 - calves born
  • year 4 - daughters mated
  • year 5 - daughters start milking and sires obtain genetic ranking (BV)
  • year 6 - sires of best daughters chosen for use (~1 in 30)
• large numbers → more accurate genetic diagnosis
• faster time scale than with natural breeding

Question 14

What does AI with frozen semen make possible?

Answer 14

• makes careful genetic selection of sires possible

Question 15

What are pros and cons of AI?

Answer 15

• advantages
  
  • increased production e.g. need 3 rams per 100 randomly cycling sheep to maintain good pregnancy rates
  • disease control
  • sire availability (global)
  • safety (e.g. dangerous bulls)
  • long-term supply
• disadvantages
  
  • cost of semen
  • technical skill
  • can have lower success
  • potential for uterine injury or infection

Question 16

How can we get synchronisation of oestrus?

Answer 16

• prostaglandin
  
  • synthetic PGF2alpha - cloprostenol
  • induces luteolysis
  • one injection: oestrus 2-3 days after
    
    • CL only sensitive to PG after day 4 post-oestrus
  • two injections 11 (cow) or 9 (sheep) days apart – increased synchrony
• progestins
  
  • e.g. CIDR (controlled internal drug releasing device)
  • placed for 7-12 days then removed
  • animal on heat about 2 days after removal
• GnRH/hCG/eCG (PMSG)
  
  • ovulation inducers
  • ensure timing relative to AI, embryo recovery

Question 17

What is the normal oestrous cycle in a cow?

Answer 17

• use of
  
  • prostaglandin
  • CIDR (progestins)
  • ovulation inducers (GnRH/hCG/eCG)

Question 18

What is use of prostaglandin in cow oestrous cycle?

Answer 18

• can use any time after day 4 of cycle, when CL is responsive → luteolysis and synchronisation

Question 19

What is use of prostaglandin x 2 ?

Answer 19

• can use any time after day 4 of cycle, when CL is responsive → luteolysis and synchronisation
• 2nd treatment 11 days later: sensitive CL → luteolysis and = tighter synchrony

Question 20

What is use of prostaglandin and CIDR?

Answer 20

• can use an initial PGF2alpha injection
• insert CIDR in late luteal phase for 7-12 days
• PGF2alpha injection 1-2 days before CIDR removal → luteolysis = tighter synchrony
• heat observed and AI or time mated
• CL already regressed by PG injection, but high progesterone suppresses ovulations until CIDR removal

Question 21

What is use of prostaglandin, CIDR, and GnRH?

Answer 21

• CIDR and PGF2a injection = luteolysis
• injection of GnRH also synchronises timing of ovulation = very tight synchrony
• heat observed and AI or time mated

Question 22

What is a typical oestrus synchronisation programme?

Answer 22

• 0 days: insert CIDR
• 9 days: inject PGF2a (am and pm)
• 10: remove CIDR, + GnRH
• 11: heat check am, pm
• 12: heat check am, pm
• AI or natural mating
• or, embryo transfer on day 7 post-oestrus
• many synchronisation programmes
  
  • depends on species and country of use (legalisation)
  • depends on reason for synchronising
• references
  
  • bartolome JA et al. 2009, Theriogenology
  • Lmb GC et al. 2009, journal of animal science
  • Thatcher WW et al. 2006, theriogenology

Question 23

What are reasons for synchronisation?

Answer 23

• restart oestrous cycles after parturition
• synchronised ovulations/inseminations
  
  • e.g. if sheep flock ovulated on one day then almost all births will occur over a one week period
• easier to schedule supplementary feeding
• reduces time needed monitoring oestrous events
• cross-fostering much easier (lambs)
• treatments of young easier to manage together
  
  • e.g. castration, tail docking easier to do at optimum times
• marketing of young coordinated

Question 24

What is ovulation and parturition induction?

Answer 24

• ovulation
  
  • facilitate synchronisation of oestrus
  • multiple embryos for pregnancy recovery
  • increase twinning/multiple offspring rate
  • mechanisms
    
    • stimulation - e.g. FSH, GnRH
    • inhibition - immunisation with androstanedione-7-HSA (fecundin), inhibin etc
• parturition
  
  • facilitate tighter calving/lambing interval
  • dexamethasone
  • increasing fazed out - ethical implications

Question 25

What is decreasing fertility?

Answer 25

• why?
  
  • suppression of behaviour (e.g. male aggression)
  • management and stop in-breeding
  • improved growth rates, taste (Boar-taint)
    
    • androstenone and skatole in fat
• domestic, companion and wild animals
  
  • desexed e.g. castration
  • vaccination - GnRH, GDF-9/BMP-15
  • immunocastration
    
    • GnRH agonists (Deslorelin)

Question 26

summary

Answer 26

• why?
  
  • blanace economy and labour with increased productivity/income
  • number of offspring, generation time and genetics
• how?
  
  • nutrition
  • seasonal influences
  • pheromones - ram effect
  • artificial insemination
  • oestrus synchronisation
  • ovulation and parturition induction
  • immunocastration/vaccination