A16: Origin and domestication of small ruminants (sheep and goat), their species characteristics.

Question 1

What is the line of descent of sheep

Answer 1

Exact line of decent btw domestic sheep to their wild ancestors is presently unclear.
The most common hypothesis: Ovis aries is jointly descended from the European (O.musimom) and Asiatic (O.orientalis) species of mouflon.

Question 2

Is ovis aries completely domesticated?

Answer 2

yes.
Ovis aries: Entirely domesticated animal, dependent on man for it’s health & survival (neotenic).

Question 3

What are the explanations regarding significant genetic differences between European and Asian breeds of sheep?

Answer 3

1) there exists a currently unknown species or subspecies of wild sheep that contributed to the formation of domestic sheep.
2) This variation is the result of multiple waves of capture from wild mouflon, similar to the known development of other livestock.

Question 4

Order
Family
Subfamily
Genus
Species group

Answer 4

Order: Artiodactyla (even hoofed)
Family: Bovidae(Ruminants)
Subfamily: Caprinae
Genus: (Ovis and Capra)
Species group: Ovis(sheep)

Question 5

What is the Chromosome number sheep?

Answer 5

in domestic sheep (Ovis aries): 2n=54,
wild sheep: 2n=54-58
Mediterranean wild sheep (moufflons): 2n=54,
Oriental(Asiatic) sheep: Urial-58,
Arkal-56

Question 6

What is the Chromosome number of goat

Answer 6

in all goat species: 2n=60; interspecific crosses are successful.

Question 7

When did domestication occur?

Answer 7

8 - 10,000 BC

Question 8

Is de-domestication possible?

Answer 8

De-domestication: (returning to wild life) rarely or unable (evolution is too far, but goat returns easily to nature).
Feral sheep populations are on islands (the isolated feral Soay sheep on island of Hirta).

Question 9

Is crossing btw wild & domesticated sheep possible?

Answer 9

Crossing (hybridization) of wild & domesticated sheep is possible (despite different chromosome number).
In wild and domesticated goats is also successful.

Question 10

Is interspecies hybridisation possible?

Answer 10

Intersp.-hybridization of sheep and goat arises with some problems:
-> ram x doe possible,
-> buck x ewe never

Interspecific hybrid: ram x doe occurred naturally.

Question 11

What are typical characteristics of sheep breeds?

Answer 11

relative lack of aggression,
manageable size,
early sexual maturity,
social nature,
high reproduction rates

Question 12

Alterations due to domestication (microevolutionary consequences): phenotype -> body, shape, form, conformation.

Answer 12

o Range of heights & weights according to breed -growth rate is a heritable trait (used in breeding selection).
o Typical weight: Ewes 45-100kg, Rams 45-160kg.

Question 13

Alterations due to domestication (microevolutionary consequences): coat and wool

Answer 13

domestication changes are seen in coat characteristic:
-> appearance of wool(secondary hair follicles),
-> continuous hair growth,
-> fibre length is increased,
-> diameter is decreased.

Question 14

Alterations due to domestication (microevolutionary consequences): wool colour

Answer 14

Initial breeding programs involved the selection for white fleeces which could be more easily dyed.

Question 14

Alterations due to domestication (microevolutionary consequences): tail length

Answer 14

-> Long, short, fat-tailed (Karakul, Awassi,Chios).
-> fat-rumped (Gissari, Somali, Romanow, Finnish Landrnace, many North-African breeds).
-> in goat: NO changes.

Question 15

Alterations due to domestication (microevolutionary consequences): horns and polledness

Answer 15

-> May be polled, have horns in one sex or both sexes (wild sheep).
-> Also variability in size & shape of horns (if present).

Question 16

Alterations due to domestication (microevolutionary consequences): ears

Answer 16

High variability: long, hanging, drooping, lop, less and well developed ears.

Question 17

Alterations due to domestication (microevolutionary consequences): reproduction, prolificacy.

Answer 17

o variations from Mono🡪polyoestrus.
o Increased testicular size.
o Higher fertility and Seasonal polyoestrus.

Question 18

Alterations due to domestication (microevolutionary consequences): milk production.

Answer 18

Udder size & form.
significant changes in goat!!

Question 19

Alterations due to domestication (microevolutionary consequences): muscle hypertrophy.

Answer 19

in sheep: callipyge.

Question 20

Alterations due to domestication (microevolutionary consequences):

Question 21

Alterations due to domestication (microevolutionary consequences): teeth

Answer 21

-> Mature sheep have 32 teeth (dental formula: I:0/4 C:0/0 P:3/3 M:3/3).
-> 8 incisors in the lower jaw and bite against a hard, toothless pad in the upper jaw; picking off vegetation.
-> NO canines: instead there’s a large gap btw the incisors and premolars.
-> Until 4 yrs (when all adult teeth have erupted) can tell age of sheep by teeth: 1 pair incisors/yr.
-> Front teeth gradually lost as sheep age-hinders their health and productivity 🡪 for this reason domestic sheep on normal pasture start to decline from 4 yrs.
-> Avg. life expectancy; sheep and goats=10-12 yrs although some sheep may live up to 20yrs.

Question 22

Alterations due to domestication (microevolutionary consequences): sensory organs.

Answer 22

-> Sheep have v. good hearing.
-> Pupils are horizontally slit-shaped-good peripheral vision, can see behind them without turning head.
-> Excellent sense of smell-have scent glands just in front of eyes and interdigitally on the feet.

Question 23

Differences between sheep & goats:
preferred environments

Answer 23

Sheep: temperate and lowland areas, steppes, savannah, varied soils, medium rainfall.

Goat: tropics, highlands and forest areas, sandy well-drained soils, low rainfall.

Question 24

Differences between sheep & goats: Nutrition.

Question 25

Differences between sheep & goats: body characterisitcs.

Answer 25

Sheep:
-> More uniform horns
-> No split in upper lips
-> Woolly
-> Tails hang downwards
-> no male caudal scent gland
-> less susceptible to stress
-> water economy moderate

Goats:
->Mobile, split upper lip
->Hairy
->Tails point upwards
-> Highly intelligent
-> Beards common
-> water economy is good and dehydration resistant
-> stress susceptible

Question 26

Differences between sheep & goats: horns

Answer 26

Sheep breeds are often naturally polled,but naturally polled.
goats are rare (many artificially polled).

Question 27

Differences between sheep & goats: intelligence and behaviouyr.

Answer 27

Sheep 🡪Flocking instinct
Goats 🡪 No flocking instinct, docile, intelligent

Question 28

Differences between sheep & goats: reproduction

Answer 28

Twinning common in both.
sheep: increasing fertility and prolificacy.

Question 29

Differences between sheep & goats: fibre

Answer 29

Sheep are bred for wool 🡪 fibre quality of fleece is important

Question 30

Differences between sheep & goats: milk production

Answer 30

Goat milk is more commonly produced.
sheep less common and efficient.