improving fertility in ewes

Question 1

fertility importance

Answer 1

the most important limitation on sheep productivity

Question 2

how do you know how good your flock fertility is

Answer 2

the number of lambs born per ewe

Question 3

embryonic mortality

Answer 3

first 4 weeks of pregnancy is 20-30%

Question 4

fertility

Answer 4

-low heritability
-influenced by multiple genes
-the genetic relationships involving reproductive traits are seldom studied
-expressed in only one gender
-optimum phenotype at maturity

Question 5

phenotype=

Answer 5

genotype + environment

Question 6

main factors affecting ewe fertility

Answer 6

-genetics
-nutrition
-management

Question 7

nutrition for fertility in ewes

Answer 7

-poor nutrition causes:
-irregular estrus cycles in females
-reduced ovulation
-reduced multiple births
-fetal abortion (mummified fetus)
-weak offspring
-pregnancy toxemia

Question 8

nutrition for fertility in rams

Answer 8

-in males poor nutrition may reduce sperm quality and quantity and well as libito

Question 9

what is BCS associated with for puberty

Answer 9

initiation of puberty

Question 10

what does flushing do

Answer 10

-increased ovulation rates of ewes

Question 11

body reserves and food intake for reproduction

Answer 11

BR (long term) and food intake (short term) both contribute to nutritional stimulation of the hypothalamus (GnRH)

Question 12

how does amount of food and BCS influence birth weight of offspring

Answer 12

-correlated with lamb survival
-ewes with BCS <2.5 had 23.8% lambing mortality 0-2 days compared to 14-15% in ewes with BCS 2.5 or greater
-overfed ewes have difficulties lambing

Question 13

how does genetics/heredity affect fertility

Answer 13

-high fecundity breeds and normal or low fecundity breeds
-rideau arcott lambing precent=250% but merino=110%

Question 14

what can genetic mutations do to fertility

Answer 14

improve it:
-booroola gene
-inverdale gene

Question 15

although genetic mutations can improve fertility what else can it do

Answer 15

-give rise to abnormal developments in embryos
-inverdale gene

Question 16

genetic variants affecting litter size

Answer 16

-booroola gene (FecB)
-inverdale gene (FecX
-GDF9

Question 17

booroola merino

Answer 17

-typical merino lambing precent 70-110%
-booroola sheep station, aus
-booroola ewes: mean ovulation rate of 4.2 and mean litter size of 2.5

Question 18

booroola mutation

Answer 18

-increases ovulation rate and litter size
-single gene: imcomplete dominance with each occurrence having an additive effect
-on 6th chromosome
-BB 5-9ova 5lambs
-B+ 3-4ova 3lambs
-++ 1-2ova 2 lambs
-bone morphogenetic protein 1B receptor (BMPR-1B)
-A>G (single nucleotide polymorphism)
-amino acid change glutamine 249 arginine
-causes follicles to mature faster than normal so more follicles ovulate at once

Question 19

booroola gene discovery

Answer 19

-first major gene to be identified
-the most researched
-most research began in the late 1980s
-mutation identified by wilson
-originally though to have originated in booroola merino breed
-later evidence indicates that the gene originated in the garole sheepform india

Question 20

inverdale gene (BMP15)

Answer 20

-romney lambing precent is 90-130%
-the inverdale gene was discovered in a prolific flock that had a romney ewe with 33 lambs in 11 lambing
-located on x chromosome
-bone morphogenetic protein 15 (BMP15)
-C>T SNP
-glutamic acid 239 stop
-homo causes sterility
-ovarian hypoplasia (small nonfunctioning ovaries)

Question 21

what should you avoid breeding for the inverdale gene

Answer 21

-mating inverdale rams to inverdale ewes as homozygous ewe lams will be infertile
-XX 1/2 females affected

Question 22

mating a inverdale ram to a non-inverdale ewe

Answer 22

will result in the ewe lamb offspring to be inverdale carriers

Question 23

mating a inverdale ewe to non inverdale ram

Answer 23

1/2 males and 1/2 females will be inverdale carriers

Question 24

GDF9 gene

Answer 24

-appears to work in conjunction with the BMP15 mutation
-researchers are not yet clear on whether BMP15 itself affects litter size of if its the ratio BMP15:GDF9 that increases litter size

Question 25

negative effects of increased litter size

Answer 25

-decreases embryo survival
-increased lamb mortality
-low birth weight
-homozygous copies of mutation of the inverdale gene causes sterility