B17: Reproduction features, most important genetic diseases of sheep

Question 1

What are the reproduction traits of sheep?
puberty
sexual activity
breeding deason
biostimulation

Answer 1

Puberty: 6-8 months.

• Sexual activity: is breed dependent, they are seasonally polyestrous.
• Breeding season: August -November, January – February (short period), Highest fertility September, October, November.
• Biostimulation: Role of sexual pheromones is important (e.g. teaser rams). Body condition plays important part in fertility e.g. flushing may be required –> increases rate of ovulation.

Question 2

Oestrus in ewes:
length
duration
symptoms
ovulation
heat detection
method of inducing oestrus

Answer 2

Length: Ewe 17-18 days, biphasic (follicular & luteal phase).

• Ovulation: Spontaneous, in the second part of the heat, 1-4 eggs per ovulation.

*sponging is a common practice in sheep breeding, it brings the ewes into heat at the same time thus synchronising lambing. sponges are impregnated with progesterone and a PMSG injection causes ovulation.

• Mating/ AI: Prior to ovulation. Artificial Insemination → Laparoscopic (low success rates).
• Twinning and multiple births are common desirable traits, fecundity genes.

Question 3

gestation in ewes:
length
location of fertilisaiton

Answer 3

• Pregnancy: 145-150 (147) days
• Fertilization occurs in Fallopian tube & migrates to uterus on day 3-4
• Implantation: Centric, early (14-15 days)

Question 4

methods of pregnancy detection

Answer 4

◦ Easy
◦ Abdominal palpation from day 90
◦ Ultrasonography
◦ Lactation: 100-180 in sheep

Question 5

mention 2 important reproductive disorders in sheep

Answer 5

• Persistent CL
• Heat & cycle disorders:
  ◦ Anovulatory cycle
  ◦ Inactive ovaries
  ◦ Prolonged cycles
  ◦ Perinatal mortality of lamb

Question 6

Important genetic disorders of sheep related to circulation and haemostasis?

Answer 6

• Hyperbilirubinemia I et II
• Glutathione-deficiency anaemia
• Haemophilia A (XL, factor VIII)

Question 7

Important genetic disorders of sheep related to metabolism (lysosomal storage disease)

Answer 7

◦ Ceroid lipofushinosis
◦ Gangliosidosis I
◦ Gaucher and Krabbe disease
◦ Mucopolysaccharidosis
◦ Glucogenosis II & V

Question 8

Important genetic disorders of sheep related to fat metabolism

Answer 8

yellow fat (recessive disorder)

Question 9

Important genetic disorders of sheep related to muscle

Answer 9

Muscular hypertrophy (callipyge)
Muscular dystrophy

Question 10

Important genetic disorders of sheep related to bones

Answer 10

Chondrodysplasia, achondroplasia
Spider lamb syndrome, SLS (black faced down, Suffolk, Oxford breeds)

Question 11

Important genetic disorders of sheep related to intersexes

Answer 11

XX males

Question 12

Important genetic disorders of sheep related to skin and hair

Answer 12

albinism
Dermatosparaxis (skin ashthenia)
Eptheliogenesis imperfecta