Reproduction Flashcards
what is the advantage of having Christmas lambs?
better lamb price at easter market
what is the advantage of spring lambs?
easy management due to better grass growth and weather
how is seasonality of sheep triggered?
light enters the eye, triggers the optic nerve which sends impulses through the hypothalamus to the superior cervical ganglion which then reaches the pineal gland, this then does/doesn’t produce melatonin depending on the day length which then leads to GnRH release
how does light effect melatonin production?
light blocks melatonin production
how does melatonin effect GnRH?
low melatonin release leads to low GnRH
is melatonin secreted more during light or darkness?
darkness
how long is the oestrus cycle of a sheep?
roughly 16 days
how many follicular waves do sheep have?
2-5 waves
how many ewes should you have per ram?
30
how is most commercial artificial insemination of sheep carried out?
laparoscopically into the oviduct with sedation
what are some ways reproduction can be modified in sheep?
genetics
ram effect
day length
nutrition
ram and day length
melatonin implants
pharmacological
what determines the fecundity of a ewe?
bone morphometric protein signalling in the ovary
what is the ram effect?
introduction of a novel male or after 2 weeks of male absence to inducing cycling in ewes
how does the ram effect alter the oestrus activity of ewes?
some ovulate silently after ram is introduces
those who didn’t have a silent heat ovulate around day 19
day 25 silent heat ewes ovulate again
why would a teaser ram be used for achieving the ram effect?
don’t won’t ewes mated on their first silent heat
how can seasonality be manipulated in sheep?
exposure to artificially shortened/lengthened days
what is an easier way of manipulating the seasonality of ewes than altering the day length of all the ewes?
just do it for the rams then use the ram effect to bring on the ewes
how can melatonin be given to ewes?
implant into ear (regulin)
what is the programme for using melatonin implant to manipulate the seasonality of ewes?
30 weeks before chosen lambing time remove ewes from sight/smell of ram (day 1)
put melatonin implant on day 7
introduce ram 30-40 days after implantation
use teasers for first 14 days to get a tighter lambing block
what are the two effects of flushing?
short term on the growing follicular waves
long term to bring them out of seasonal fertility trough sooner
what is the static effect of flushing?
ewes with a greater BCS have a higher ovulation rate
what is the dynamic effect of flushing?
ewes with an increasing live weight gain have a higher ovulation rate