W10 L1 Manipulating domestic animal reproduction 1

Question 1

Effect of starvation in animal

Answer 1

– anovulation (no egg release in period)
– inability to maintain pregnancy
– inability to maintain lactation
– suppressed sperm production
– altered behaviour

Question 2

Effect of intense excercise in animal

Answer 2

amenorrhoea (absence of menstruation)

Question 3

Effect of obesity in animal

Answer 3

– inhibition of ovulation
– inhibition of sperm production
– behavioural modification
– altered fetal nutrition
– parturition issues

Question 4

Nutrition on animal reproduction

Answer 4

-Nutrition and feeding can affect HPG axis
LH secretion patterns in rhesus monkey:
§ Normal fed day (30 pellets) = normal LH pulses, fasted day = flatlines LH, refed day = large LH pulses (turning system back on)
§ 1 or 2 days of fasting sufficient in interfering with GnRH, changing repro function
* Cortisol released by stress interferes with LH surge (timing, frequency, amplitude)
* Flush feeding: burst of high nutrition 2-3 weeks before ovulation = ↑ovulation number + egg quality
§ Stimulates folliculogenesis to overcompensate
* High glucose/fat diet = more male offspring (affects composition of egg/sperm + uterine environment)

Question 5

Sheep and nutrition example

Answer 5

-Timing of breeding in sheep fed different diets to manipulate growth rate
- syncing growth with mating season, so sheep goes through puberty at the lowest weight does not waste extra time
§ Slow growing: body partitions nutrition away from reproduction = infrequent pulses of Gnhr
§ Fast growing: lots of energy towards reproduction = frequent GnRH pulses

Question 6

resumption of cycle after calving and subsequence pregnancy rate

Answer 6

§ Body condition scoring measures adipose tissue across skeleton (1.0 – emaciated, 10.0 – obese)
§ Lower body condition score at calving = longer to 1st heat (not enough energy reserves for reproduction – all invested in milk)
§ After first heat, continued to be cyclicity affected. More cycles after calving = more like to get pregnant (require a few cycles to get back into rhythm – egg quality, hormone levels)
Ø Leptin, kisspeptin, ghrelin + other nutrition hormones directly feedback on HPG Axis to trigger GnRH pulsatility = info on parturition + investing energy towards reproduction
§ Contraception rate: optimal condition ~4.0 body score

Question 7

Micronutritent

Answer 7

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.

Question 8

Nutrient factor effect on female

Answer 8

§ Ovarian/oocyte: energy (fat) content/ratio of oocyte/zona pellucida; can affect ability of oocyte to fertilise + develop
§ Uterine environment: sperm swimming/signalling (viscosity + pH), modulated lumen histotroph (nutrients)
§ Embryonic loss: glucose main substrate for embryo development, slow growing embryo = failure of maternal communication
(MRP) = prostaglandin clears foetus, placentation failure = foetal reabsorption/abortion

Question 9

Nutrient factor in male

Answer 9

§ Testis development: inappropriate/insufficient cholesterol impacts hormone regulation = testicular mass/function loss
§ Sperm: sperm fatty acid composition, various enzymes/minerals can change morphology of sperm

Question 10

Why do we manipulate breeding season

Answer 10

-cost (injections etc. at the same time), survival of young,
- convenience (husbandry tasks done once),
-to fit artificial constraints (racehorses all have same birthday = want horse born at start of breeding season

Question 11

Some method for manipulating breeding season

Answer 11

photoperiod, melatonin implants, pheromones

Question 12

Ram effect

Answer 12

Pheromones from ram induce increased LH pulsatility in ewes
* Synchronisation or ewes & lambing
* Earlier breeding onset (seasonal) (varies with breed)
* Allows maximisation of use of valuable stud rams
-place a vasectomised ram but still release pheromones into the herd

Question 13

Artificial insemination

Answer 13

• 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 and an animal can produce hundreds)
• “Heat” detection – timing (from animal behavior) to know which one is ready for mating/ AI (visual, tailpaint, kamar, paint)

Question 14

Semen collection for AI

Answer 14

-Collection with artificial vagina
-evaluation for motility and morphology
-dilute with specialised media and pack into straw (each with 10-25 million sperm per straw)
* Cool and freeze
* Store in liquid nitrogen
* Thaw
* Inseminate via cervix
* Sexed Semen (recently available)

Question 15

Improving heard genetic

Answer 15

desired improvements in productivity (milk, meat, wool production)
Ø Limited availability + high cost of top quality sires (one bull can only provide for 3-4 cow per day)
Ø Proving bulls for AI (progeny testing) takes 6 years

Question 16

Pros and Cons of AI

Answer 16

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 17

synchronisation of Oestrous: prostaglandin

Answer 17

Prostaglandin: synthetic PGF2a cloprostenol induces luteolysis (CL removed)
§ 1 injection: oestrus 2-3 days after, CL only sensitive to PG after day 4 post-oestrus
§ 2 injections: 11 (cow) or 9 (sheep) days apart = sensitive CL + luteolysis = ↑synchrony

Question 18

Synchronisation of oestrous: progestin

Answer 18

Progestins inserted (artificial progesterone) via CIDR (controlled internal drug releasing device)
§ Placed for 7-12 days + produces high levels of progesterone (acts as CL + lengthens cycle)
§ Animal in heat ~2 days after removal

Question 19

synchronization of oestrous GnRH/hCG/eCG (PMSG)

Answer 19

ovulation inducers
§ Ensure timing relative to artificial insemination, embryo recovery

Question 20

Combinational hormonal use: prostaglandin + CIDR

Answer 20

• Can use an initial PGF 2α injection
• Insert CIDR in late luteal phase for 7-12 days
• PGF 2α injection 1-2 days before CIDR removal  luteolysis = tighter synchrony
  CL already regressed by PG injection, but high progesterone suppresses ovulations until CIDR removal
• Heat observed and A.I. or time mated

Question 21

Use of Prostaglandin, CIDR and GnRH

Answer 21

• CIDR and PGF 2α injection = luteolysis
• Injection of GnRH also synchronises timing of ovulation = very tight synchrony
• Heat observed and A.I. or time mated

Question 22

Reasons for Synchronisation

Answer 22

• 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 23

why do we induce ovulation of animal

Answer 23

• Facilitate synchronisation of oestrus
• Multiple embryos for pregnancy recovery
• Increase twinning/multiple offspring rate

Question 24

method for ovulation induction

Answer 24

– Stimulation- e.g. FSH, GnRH
– Inhibition- Immunisation with androstanedione-7-HSA
(fecundin), inhibin etc

Question 25

Induction parturition

Answer 25

• Facilitate tighter calving/lambing interval
• Dexamethasone
• Increasing fazed out- ethical implications