Reproductive and Maternal Behavior of Livestock - Genetics and the Behavior of Domestic Animals - page 170

Maternal Behavior in Sheep
In sheep, as in cattle, the selection of a proper birth site is crucial for the sur-
vival of the offspring. At the time of birth, the ewe and her lambs are in a
weakened state and reducing susceptibility to predators is of major importance
in certain areas. In wild Bighorn Sheep (Ovis canadensis), strong separation
behavior for parturition has been observed ( Bangs et al., 2005 ), whereas
Merino sheep tend to give birth wherever they are. With the initiation of labor,
progressive restlessness, pawing and stamping, and cessation of grazing may
occur ( Hulet et al., 1975 ). Much of the birth process occurs with the ewe in
recumbency, especially toward the end of the delivery process, even though
she may stand intermittently. The duration of labor is relatively short (often
less than 1 hour) and it has been shown that ewes respond to amniotic fluid
via licking and sniffing. Maternal responsiveness seems to be induced partly
by the release of progesterone and estradiol ( Dwyer, 2008; L´vy and Keller,
2009 ) although it appears that these steroids may have a priming role, allow-
ing the expulsion of the fetus ( Nowak et al., 2000 ). This mechanical action
seems to trigger maternal care in ewes. Once the first lamb is born, maternal
behavior develops rapidly and can be described in two phases ( Lindsay,
1996 ). During the first phase, which may last for 1 h or less, the ewe will
respond to any newborn. This has been termed the responsiveness phase.
Normal behavior during this phase includes cleaning, licking and nuzzling the
newborn. Ewes will start at the head and nose of the lamb, licking away any
fluids that may impede breathing and this action also stimulates peripheral
blood flow, promoting homeothermy within the new environment ( Darwish
and Ashmawy, 2011 ). In the second phase, the ewe develops a bond with a
specific lamb or lambs; a period termed the selectivity phase. The onset of the
selectivity phase varies from 4

12 hours after birth and it is influenced by
genotype, age, experience, and environmental factors. If, however, this second
phase is not achieved, a lasting bond is not developed between the mother and
young ( Poindron and Le Neindre, 1980 ) and lamb survival is compromised.
Therefore, both periods are often referred to as a “critical period” because sur-
vival is compromised if a good mother young bond is not established.

Sheep are classified as a follower species. Olfactory cues play a major
role in the development of the maternal bond ( Nowak et al., 2000 ) and it has
been shown that the odor of monozygotic twins is more similar than that of
dizygotic twins, thereby complicating discrimination between monozygotic
twins for ewes ( L´vy and Keller, 2009; Romeyer et al., 1993 ). Losses in
twins are usually greater than those of singletons, especially in breeds such
as the Merino, which is reputedly defective in its ability to care for twins
( Alexander et al., 1984 ). Mismothering can also occur in the form of lamb
“stealing” by ewes that have lost their lamb. Overall, pneumonia and mis-
mothering account for more than 30% of lamb losses ( Mandal et al., 2005 ).
Whately et al. (1974) observed that Merinos and Romneys in New Zealand