Small Ruminant Repro Management Flashcards
What does it mean that small ruminants are seasonally polyestrous?
They have multiple estrous cycles restricted to a certain period of the year
- they are short day breeders and the onset and length of the breeding period is variable according to photoperiod, latitude and climate, food availability, breed, presence of a male, breeding system, physiological stage
T/F: the closer to the equator sheep are the longer their breeding season will be
True
Describe the physiology of the seasonal estrous cycle
When in season, eye detects decreased light, which decreases firing of retinal nerves and excitation from superchiasmic nucleus–> inhibition of pineal gland resulting in increased melatonin
- increased melatonin generates GnRH, FSH and LH pulsatility to initiate cycling
-opposite in the mare
What factors influence the start of puberty in small ruminants?
Age, nutritional status, season, breed, exposure to male
What age do rams/bucks usually go through puberty? Does? Pigmy goats? Ewes?
Rams/Bucks: 4-6 months
Does: 6-8 months
Pygmy goats: 3 months
Ewes: 6-9 months
At what percent of adult body weight should a small ruminant be prior to breeding?
60-70%
Why are ewes usually bred via laproscopic AI?
They have a very tortuous fibrocartilaginous cervix
- they have 6-8 cervical rings vs goats that have 4
How long is the cycle of goats and sheep? How long is estrus?
Sheep: 14-19 days (average 17), estrus 30-36 hrs
Goats: 18-22 days (average 21), estrus 24-48 hrs
- pigmy goats can vary from 18-24 days
T/F: Goats and sheep have an increased frequency of short cycling (silent heats) in the middle of the breeding season
False- more common at beginning and end, as well as postpartum
-more commonly seen in goats than sheep
-influenced by photoperiod or nutrition
What is the theory behind why small ruminants have the short cycle?
Thought to synchronize the group and bring them all into heat around the same time
How many follicular waves do sheep tend to have during each cycle?
3-4, compared to the 2-3 in cattle
How long after the LH surge does ovulation occur in small ruminants?
20-26 hours after LH surge
What are some of the estrus signs in small ruminants?
Swollen vulva, mucoid discharge turning cloudy, tail flagging, mounting/immobilization reflex
What are some of the indications for estrous cycle manipulation in small ruminants?
-induction of estrus in transition periods and during winter anestrous
-allows for distribution of milk and meat production throughout the year (breed selection is important)
-allows for synchronization within the season (labor saving for breeding and kidding)
What are some of the ways the estrous cycle can be manipulated in small ruminants?
-adapted nutrition
-photoperiod manipulation (artificial lighting, melatonin implants)
-hormonal treatments (most drugs are not approved for use in the US on goats)
-male effect
-combo of all of these
Describe the male effect.
After 30 days of no contact with the male he is reintroduced which will induce a silent heat and a visible heat during the next cycle
How can you manipulate the cyclicity of sheep during the breeding season? during the transitional season? Out of breeding?
Breeding season: Prostaglandins or progestin source for 14 days (CIDR)+/- gonadotropin (GnRH agonist)
Transitional season: Ram effect, progestin source for 8-14 days + gonadotropin up to 48 hours before removal, progestin source for 8-14 days + ram effect at removal
Out of season: progestin source for 8-14 days + gonadotropin up to 48 hours before removal, manipulation of lights, melatonin administration
How can adapted nutrition aid in fertility of female small ruminants?
Flushing females before breeding increases nutrition, which can increase ovulation rate and lambing/kidding rate
-affected by age, body condition, time of year
-best response with marginal body condition (2.5-3/5)
-supplement with 0.14-0.45 kg og a 10-12% crude protein grain/head per day starting 2 weeks pre breeding until 2-3 weeks into breeding season
What body condition should male small ruminants be when entering breeding season?
3-4/5
- will lose 10-12% of condition during season
-should feed concentrated energy protein supplement 4-6 weeks before breeding
-may need to supplement with concentrate to help them regain condition after breeding season
-DO NOT OVERCONDITION- negative effects on semen quality
How can you manipulate daylight to encourage cycling?
Begin with long days to prepare for the stimulatory effect of short days (if trying to
- decreasing daylight will trigger melatonin release from pineal gland
-could try melatonin implants but these are unavailable in US
Describe some of the out of season synchronization protocols for sheep/goats
-progestins for >14 days plus PG600 the day of or 24-48 hours before progestin removal
-artificial lighting programs (mimic long days for 60 days followed by short days for 60 days)
Describe the hormone treatments that can be used in small ruminants
-Prostaglandins lyse the CL. Can do single injections or double 11-12 days apart. Initiates estrus in 24-72 hours. MUST BE CYCLING
-Progestins: mimics luteal phase. estrus shown 24-96 hours after withdrawal
-eCG/PMSG- FSH like activity, acts directly on the ovary to stimulate ovulation
-GnRH agonists: act on the anterior pituitary to stimulate LH/FSH activity
For natural breeding, what should the ram to ewe ratio be?
A ram per 30-50 ewes
-if really good libido and testicular size + semen characteristics, can breed 100 in 17 days
-ram lambs should only be expected to service 15-25
-lower numbers when out in range pasture
-with synchronized cycles, add a second male as they all will be in estrus at the same time
Describe some different options for producing teaser males
-teaser harness that blocks off prepuce, but still has marker for breeding detection (there is a risk of them getting it off)
-vasectomy or epididectomy- retains sexual behavior but there is a risk of venereal disease transmission
T/F: exposure to seminal plasma via copulation may improve AI rates
True!
In natural breeding, where is semen deposited?
Usually in the vagina
- a lot of the semen dies before it can reach the ovum
In which species- sheep or goats- can you inject frozen semen through the cervix?
GOATS
What are some of the advantages of laparoscopic AI?
Higher rates of successful pregnancy, less semen needed
When is transcervical AI okay to perform in sheep?
When using fresh semen
In what part of the horn should you deposit semen when doing laparoscopic AI?
In greater curvature where there are no blood vessels
- deposit 50% in each horn
What is the normal gestation length in sheep vs goats?
Sheep: 145-150 days
Goats: 147-155 days
Describe the timeline of pregnancy in sheep and goats?
Day 4- embryo enters uterus
Days 12-13: maternal recognition of pregnancy via interferon tau production
Day 16: implantation
Day 20: amnionic vesicle extends to contralateral uterine horn
What is the difference between maintenance of pregnancy in sheep and goats?
60-75 days: placental progestins take over and CL is no longer the primary P4 source IN SHEEP
IN GOATS CL IS ALWAYS THE PRIMARY PROGESTERONE SOURCE
Why do we perform pregnancy detection?
To determine if breeding was successful
- to determine if there is infertility issues, to rule out health problems, and make culling decisions
-to determine quantity (those with more babes are more susceptible to preg tox, singletons more prone to dystocia, important for nutritional management decisions)
If you are using serum progesterone for pregnancy detection, when should you pull the sample?
19-24 days
-not practical in most situations
What is a good blood test to use to detect pregnancy?
Pregnancy specific protein B
-can detect after 25 days
-cannot determine fetal viability
Whats the earliest you can detect pregnancy via ultrasound?
25 days with rectal probe
35 days with transabdominal probe
When can fetal sexing be done?
55-70 days
- more accurate with singletons, hard to do with multiples
When can radiography be used for preg detection?
after day 70
-accurate but pricey and annoying to set up
T/F: fluid in the uterus is diagnostic for pregnancy in small ruminants
False- you need to see at least a fetus or a placentome
- they can get hydrometra commonly
What is detectable on ultrasound on day 21? Day 25-35? Days 30-40? Days 40-90? After day 90?
21: placentomes visible as small echogenic areas on the surface of the endometrium (transrectal)
25-35: embryo readily visible. Hyperechoic fetus in fluid filled uterine horn. Amnion has a hyperechoic line that encircles the embryo at a distance of 1-2 mm
30-40: “C” shaped placentomes become visible
40-90: placentomes, umbilical cord readily visible. Hyperochoic fetuses surrounded by large amounts of hypoechoic fluid. Fetal organs/skeletal structures can be seen. After day 50 fetus starts to resemble a lamb/kid
90+: becomes difficult to count fetuses. Fetal body parts only partially visible but can still view placentomes. Ballotment useful at this stage. Can assess fetal heartrate.
How can you age fetuses via ultrasound?
-in the first 3 months, fetal size is not related to litter size and head diameters and length provide a good index of fetal development
-by third trimester not accurate as depends on amount of fetuses
What are some main considerations for repro management in small ruminants?
Know the breeding dates or mating periods to improve the accuracy of diagnosis
-speed and accuracy is important (can change technique, position of animal to improve. Fast from food for 12 hrs and water for 4 hours)
-assess the number and viability of fetuses optimally between 45-85 days
If the producers goal is simply to know if they are pregnant, when should you come out to assess the herd?
Wait 40 days after the ram/buck has been removed or after the last possible date of breeding
-this allows for balance between speed and sensitivity (while pregnancy can be confirmed in seconds, the diagnosis of pregnant/open takes up to a minute)
-makes it much easier to determine they are not pregnant
If the producers goal is to estimate gestational age or number of fetuses, when should you come out?
Wait 50-55 days after the ewes/does were first exposed to the ram/buck
-fetuses can be accurately counted until 90 days gestation, but counting fetuses is much faster and more accurate in early gestation
-this may mean more than one exam may be needed
What are some important considerations for late gestation nutrition in small ruminants?
-realize that 70% of fetal growth occurs in the last 6 weeks of pregnancy
-inadequate nutrition may increase periparturient diseases, cause low colostrum quality, low birth rates, lower energy reserves in newborns and increased death losses
-increase concentrate feeding in last 6 weeks due to increased metabolic demand and lower abdominal space
