Some Genetic and Non-Genetic Factors Influencing Fertility of Different Sheep Breeds In Highland of North-Shewa, Ethiopia
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Shenkute Goshme. (30/6/2018). Some Genetic and Non-Genetic Factors Influencing Fertility of Different Sheep Breeds In Highland of North-Shewa, Ethiopia.
Abstract
Small ruminant specially, sheep are important for the subsistence, economic and social
livelihood of small holder farmers in the developing countries and those residing in highlands
of Ethiopia are no exception (Solomon et al., 2013; Mueller et al., 2017).Traditionally the
sheep were/are selected for their adaptive traits which compromised with their productive,
reproductive functions and existing environment (Solomon et al., 2008; Kosgey and Okayo,
2007). The overall improvement of the livestock is best sustained through within breed
selection (Kosgey and Okeyo, 2007; Solomon et al., 2009, 2011; Philipson et al., 2011).
However, the genetic improvement through within breed selection are a slow and tedious
process and the other method of improvement can be through crossing them with some
improved breeds (Solomon and Tesfaye , 2009; Tesfaye et al., 2013, 2016).
Crossbreeding by using fast growing temperate sire lines has been suggested as rapid ways of
breed improvement and such programs have been initiated in the past in many parts of the
tropics and Ethiopia being no exception. These projects were initiated to improve the
production and reproduction traits among the indigenous genotypes. However over the years
several attempts of crossbreeding have not met with their appropriated goals as the introduced
breeds were not adapted to the prevailing agro climate/s (Philipsson et al., 2011). The
performance of the crossbreds at the farmers end are much below what was obtained on
station studies , the traits which are adversely influenced were those associated with fertility
(Tesfaye et al., 2013). In Ethiopia several exotic sheep breeds have been introduced over
decades and Debre Birhan Agricultural Research Station had been established as the focal
station for sheep research. Awassi breed was among the sheep breeds which were introduced
from Israel in the year 1980, 1984 and 1994. They were introduced with an aim to improve the body weight of the Menz sheep (Rummel et al., 2005). Studies by Tesfaye et al., (2016) have
indicated that the fertility among the Awassi rams reared in Ethiopia was lower than those
reported from many Middle Eastern countries (Galal et al., 2008). Findings of a study by
Solomon et al., (2007) indicated that there are around 14 breeds of sheep in Ethiopia, with
within breed variations for most of the economical traits. The nicking ability of the Menz and
Wollo ewes with those of Awassi rams have being studied (Solomon and Tesfaye, 20009;
Tesfaye et al., 2013, 2016). Menz and Wollo ewes are small sized besides that they are poorly
prolific (Solomon &Tesfaye, 2009; Tesfaye et al., 2013).
The aim of selecting the Menz sheep was to access the within breed variations for improving
their body weight (Solomon et al., 2008, 2009). The selection of the rams was based on their
fitness which in turn is influenced by inbreeding, fertility and survival related traits among the
closed nucleus flock (Solomon et al., 2013). The major challenges in the process of selection
include identification of the genetically superior breeding stock (rams and ewes) and
estimating the response to selection based on their breeding values of the trait of importance
(Solomon et al., 2011). However, the underlying bottlenecks of the same are the difficulties
associated with recording of the performance and reproduction related parameters of the
animals themselves or their ancestors or progenies (Tesfaye et al., 2013). Besides the pedigree
of these animals, which in most of the cases are not formally maintained by the reared or
sometimes are remembered through recall methods thereby compromising on the quality of
the data (Solomon et al., 2014). Studies by Petrovic et al., (2012) have indicated that the
fertility related traits are lowly heritable and hence can be improved only through improving
their management. Thus, in order to improve the weight of the Menz sheep raised in the
Central highlands of Ethiopia it was decided to upgrade them using Dorper (from South Africa) and Awassi (from Israel). The introduced sheep breeds were reared at two government
ranches, Debre Birhan Sheep Breeding and Multiplication Center (DBSBMC) and Amedguya
Sheep Breeding and Multiplication Center. Presently nucleus stock of Awassi sheep are being
maintained at these ranches with an aim to maintain the pure stock besides the crossbreeds are
also being developed with Menz ewes as dam lines. The performances of these crossbreds are
evaluated vis-a-vis those of the Menz sheep for traits such as yearling weight, survival and
fertility (Solomon and Tesfaye, 2009; Tesfaye et al., 2016). However, it has been recorded in
several studies that the fertility of the crossbred rams ( Awassi♂ x Menz♀) are/were lower
when compared to their Menz counter parts (Tesfaye et al.,2013,2016). However, it was also
recorded that the lambs born from the crossbreds Awassi ♂x Wolo ♀had better nicking abilities
and had heavier body weights vis-a-vis those of the dam lines (Tesfaye et al., 2013, 2016)
On farm and on station performances have indicated that the F1 (Awassi ♂x Menz♀) was much
below the expectations with respect to their fertility traits which varied across the studied
locations (Tesfaye et al., 2013). The values for the fertility traits for the Awassi rams were
significantly lower than those reported from the Middle Eastern countries (Mohammed et al.,
2006; Galal et al., 2008). Overall conception rate of the ewes are fallout of several hormonal
attributes of both the sexes. Among the functions associated with the conception of the ewes
are those associated with the semen related traits of the rams themselves besides several
genetic and non-genetic factors (Foote, 1964; Duguma et al., 2002; Al-Samarrae, 2009;
Tejaswi et al., 2016). Among the same are the various semen components viz. mass motility
or individual motility of the sperms, acrosome integrity, the size of head, mid piece, length of
the trail and other morphological functions associated with the same (Salhab et al.,2003,
Ababneh et al., 2017) .The overall component of the semen and their fertilizing capacity is influenced by several genetic and non-genetic factors the latter being more important as the
fertility traits are lowly heritable (Salhab et al., 2003; Mohammed, 2006; Casao 2010;
Babiker, 2010). Studies by Yavarifard et al., (2015) have indicated that the fertility is also
influenced by inbreeding among the flock, where the inbred rams have low fertility when
compared to their non-inbred counterparts. Findings by Shamir et al., (2010) have indicated
that inbreeding among Awassi sheep of the Ein Harod flock resulted in day blindness reared in
Israel. Evaluating the performance of the traits particularly those related to fertility of different
indigenous and exotic breeds of rams at each stage is impudent. Reproductive performance is
one of the factors which determine the efficiency of the production among the sheep flock/s in
the cool highlands of north Shewa, Ethiopia. In the region mentioned ahead sheep production
is important as a means of livelihood and thus selection of rams’ breeds on the reproduction
trait and pedigree record is essential in sheep breeding program.
