W10 L1 Manipulating domestic animal reproduction 1 Flashcards
Effect of starvation in animal
– anovulation (no egg release in period)
– inability to maintain pregnancy
– inability to maintain lactation
– suppressed sperm production
– altered behaviour
Effect of intense excercise in animal
amenorrhoea (absence of menstruation)
Effect of obesity in animal
– inhibition of ovulation
– inhibition of sperm production
– behavioural modification
– altered fetal nutrition
– parturition issues
Nutrition on animal reproduction
-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)
Sheep and nutrition example
-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
resumption of cycle after calving and subsequence pregnancy rate
§ 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
Micronutritent
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.
Nutrient factor effect on female
§ 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
Nutrient factor in male
§ 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
Why do we manipulate breeding season
-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
Some method for manipulating breeding season
photoperiod, melatonin implants, pheromones
Ram effect
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
Artificial insemination
- 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)
Semen collection for AI
-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)
Improving heard genetic
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
Pros and Cons of AI
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
synchronisation of Oestrous: prostaglandin
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
Synchronisation of oestrous: progestin
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
synchronization of oestrous GnRH/hCG/eCG (PMSG)
ovulation inducers
§ Ensure timing relative to artificial insemination, embryo recovery
Combinational hormonal use: prostaglandin + CIDR
- 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
Use of Prostaglandin, CIDR and GnRH
- 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
Reasons for Synchronisation
- 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
why do we induce ovulation of animal
- Facilitate synchronisation of oestrus
- Multiple embryos for pregnancy recovery
- Increase twinning/multiple offspring rate
method for ovulation induction
– Stimulation- e.g. FSH, GnRH
– Inhibition- Immunisation with androstanedione-7-HSA
(fecundin), inhibin etc
Induction parturition
- Facilitate tighter calving/lambing interval
- Dexamethasone
- Increasing fazed out- ethical implications
