Reproduction (Tait)

Question 1

why do we manipulate the estrus cycle in sheep/goats?

Answer 1

to control the time of breeding/time of lambing to plan for marketing, effectively use labor and facilities, time mngment

Question 2

how can you synchronize the females in a sheep/goat group IN SEASON?

Answer 2

prostaglandin injection (estrumate or lutalyse) to cause CL regression=drop in progesterone=onset of estrus. this only works if animals are already cycling.

external progesterone: constant release of progesterone, preventing initiation of estrus, then when you remove it, the animal goes into estrus.

Question 3

explain the “two dose program” regarding prostaglandin injection to induce estrus?

Answer 3

on the first injection, only 70% of the animals will be in diestrus (they’ll have a CL), the other 30% will be in estrus and the injection wont work. So you inject everyone, then wait 11 days and give a second injection. After the second injection, the ones that were cycling will now be in diestrus and the injection will work, and the ones that were in diestrus will be on the NEXT cycle of diestrus. So it works on everyone and now they’re all synced up! :)

Question 4

what are the 2 main forms of external progesterone?

Answer 4

CIDRs (natural progesterone) and MGA (feed additive, synthetic)

Question 5

proper way to use CIDRs?

Answer 5

leave in for at least 10 days

stagger time of removal so that the ram has enough time to eff everybody

females come into heat 24-48 hrs after removal, can put the ram in a little before this

can use PMSG at removal for an extra ovulation boost, increase ovulation rate, tightens ovulation window. You have to use this if doing out of season breeding or AI/ET

Question 6

why are CIDRs more common than MGA?

Answer 6

MGA is a feed additive and expensive, it’s hard to know who is getting how much, and in order to add it into the feed it HAS to be pre mixed into a pellet, you can’t sprinkle it on top. It also requires enough bunk space. The results are also more variable than with CIDRs and are therefore not used often anymore.

Question 7

why is it beneficial to do out of season breeding?

Answer 7

high market price for lambs, efficient use of labor and facilities,

Question 8

what are some disadvantages to doing out of season breeding?

Answer 8

its difficult to get good conception rates, even with all the drugs to help you

you must use specific breeds with better genetic selection for our of season breeding

ram fertility will be lower no matter what you do

you have to keep replacement lambs from the ewes that lamb out of season to build your herd with desirable genetics

Question 9

what are the main strategies used to breed out of season?

Answer 9

progesterone and PMSG, and daylength manipulation

Question 10

what’s the first step to start stimulating females to start cycling out of season? Second step?

Answer 10

progesterone for at least 10 days! Need to trick the follicles into thinking there’s a CL making progesterone. This will stimulate wimpy little follicles to develop. They need a little extra kick with PMSG (mostly sheep, use GnRH in goats)

Question 11

how can you manipulate day legnth for out of season breeding?

Answer 11

you need an expensive barn with artifical lighting and multiple entrances and exits.

essentially you trick the females into thinking the days are getting shorter to simulate cycling. Long day light for 8-12 weeks, then short lay light for 8-12 weeks with min 6-8 hr difference.

rams need to be exposed to the same light cycle so that they will want to breed.

with this method you dont need injections or CIDRs

Question 12

how can you manipulate the transitional period?

Answer 12

we can initiate regular cycling 6 weeks before the normal start of the season by using the ram/buck effect. this is where you use a teaser buck/ram for every 50 females. This requires a breed of ram/buck with strong libido in the off season.

Question 13

proper procedure for the ram/buck effect

Answer 13

please the teasers, some females have silent heat, remove teasers and replace with in tact males, youll get some early heat and late heat

Question 14

advantages and disadvantages of the traditional breeding system (fall breeding, spring lambing)

Answer 14

advantages: it’s the most natural way, highest natural prolifacy, ideal time for AI/ET, better feed for lambs and kids
disadvantages: low market price for lambs, more parasite problems in lambs and kids

Question 15

advantages and disadvaatges of modified breeding system (spring or summer breeding and fall or winter lambing)

Answer 15

advanatges: higher market prices for lambs

disadvanatges: often more expensive due to synchronizing programs, more facility requirements (need indoor places to lamb in winter), decreased fertility and prolifacy

Question 16

why would you want to combine traditional with modified breeding systems?

Answer 16

can have multiple lambings per year but each ewe only lambs once. allows for better use of facilities, can spread the workload over the year, and spread the income from lamb and kid sales

Question 17

what is required if you want to do advanced breeding?

Answer 17

genetic selection for aseasonal breeds, high management skills, excellent nutrition all year, analyze costs constantly,

Question 18

why is pregnancy diagnosis a good management tool?

Answer 18

cull any open females while they still have lamb value or send them to market

can sort them into feeding groups

can better manage lambing and kidding time

Question 19

how is pregnancy usually diagnosed?

Answer 19

transbadominal ultrasound OR a teaser males (he breeds the open ones)

Question 20

what things should be included in a BSE for the males?

Answer 20

health and breeding history
BCS and conformation
scrotal exam/measurement/palpation
penis and sheath exam
semen collection + eval