FULL TEXT - World Rabbit Science

WORLD RABBIT SCIENCE,
VOL
10 (3), 103-112
NON GENETIC FACTORS AFFECTING RABBIT REPRODUCTION
IN ALGERIA
BELHADI S., BOUKIR M., AMRIOU L.
Université Mouloud Mammeri, Département d’Agronomie, Faculté des Sciences de l’Ingénieur,
B.P. 17, 15000 - TIZI-OUZOU. Algérie.
ABSTRACT: Environmental variability of reproductive traits has
been investigated on a pool of 51 does of different origin in a rabbit
breeding unit in Tizi Ouzou region. The objective was to estimate
the effects of different factors such as kindling season, parity,
physiological state of does, and number born alive on characters
such as acceptation rate, conception and kindling rate by female,
total born alive, stillborn, litter size at weaning, pre-weaning and
post-weaning mortality and weekly litter weights from birth to
weaning. Mean bunny weight at birth, at weaning and 70 days of
age, litter weight at 70 days of age and total litter gain during
lactation have also been considered. Results show that kindling
season affects only litter size at weaning with favourable effect of
autumn and spring (7.8 vs 6.6). Highest mean weights at birth are
recorded in autumn (16.2 g more than others) and highest litter
weights at weaning during the three seasons other than summer
(700 g more). The highest mean weight at 70 days is obtained in
winter (1.9 Kg). For parity effect, we have recorded the greatest
conception and kindling rates at the beginning of reproductive life
(98.7 and 96.03% respectively). Other performances did not vary
according to this factor. Lactating females at mating had the same
acceptation, conception and kindling rate and similar litter sizes
as no lactating; however, superior values were obtained for non
lactating does for litter size. Moreover, differences due to effect of
number born alive on weekly mean weights were significant.
However this effect however fades down at 70 days of age.
RÉSUMÉ: Facteurs non génétiques affectant la reproduction
du lapin a l’Algérie.
Une étude de la variabilité des caractères de reproduction a été
réalisée dans un élevage cunicol de la région de Tizi-ouzou
(Algérie) sur un effectif de 51 femelles. L’objectif étant de mettre
en évidence la variation due aux facteurs de l’environnement
(saison de mise bas, ordre de portée, état physiologique de la
femelle au moment de la saillie et le nombre de nés vivants). Les
caractères étudiés sont les taux de réceptivité, de fertilité et de
mise bas par femelle, les nés totaux, nés vivants, nombre de sevrés
et de vivants à 70 jours d’âge, la mortinatalité, mortalité présevrage
et post-sevrage, les différents poids de portées hebdomadaires
de la naissance au sevrage ainsi que les poids moyens du lapereau
à la naissance, au sevrage et à 70 jours d’âge et le gain total de la
portée en présevrage. Les résultats montrent que la saison de
mise bas affecte la taille de portée au sevrage en faveur des
naissances automnales et printanières (7.8 vs 6.6). Aussi, en
automne, on a enregistré les meilleurs poids moyens à la
naissance (116.2 g de plus par rapport aux autres) et les poids
des portées au sevrage les plus élevés pendant les trois saisons
par rapport à l’été (700 g de plus). Le meilleur poids moyen à 70
jours d’âge est obtenu en hiver (1.9 Kg). Pour l’ordre de portée,
nous avons enregistré les meilleurs taux de fertilité et de mise
bas en début de carrière (98.7 et 96.03% respectivement). Les
autres performances ne varient pas selon le rang de mise bas.
Les femelles allaitantes au moment de la saillie ont les mêmes
taux de réceptivité, de fertilité et de mise bas et les mêmes tailles
de portée que les non allaitantes; néanmoins des valeurs
supérieures sont obtenues chez les non allaitantes pour la taille
de portée. Aussi, des différences dues à l’effet du nombre de
lapereaux nés vivants sur les différents poids moyens et
hebdomadaires sont observées avec de meilleurs poids moyens
au sevrage pour les portées inférieures à 4 par rapport surtout
aux portées avec un effectif compris entre 8 et 13 lapereaux (183
g). Cet effet toutefois s’atténue à l’âge de 70 jours.
INTRODUCTION
1979). Besides, genetic improvement of reproduction
traits becomes difficult because of their low
The productive and economic interest of
heritabilities (BASELGA et al., 1982; B ONNES et al.,
reproduction traits has been reported by several
1984).
authors (BONNES et al.,1984; B ASELGA and BLASCO ,
1989). They are main objectives in rabbit genetic
On the other hand, environment, that contributes
improvement for meat (B ASELGA et al., 1984; BASELGA
greatly to the variation of these characters, is the first
and BLASCO, 1989).
component to study in order to design an eventual
program of genetic improvement of medium or long
The study of reproduction is complex as it
term for our local populations of rabbits. The aim of
involves simultaneously the mother’s physiological
this paper is to quantify the effects of different
functions and their offspring (AURAN and SKJERVOLD ,
environmental and non-genetic factors on reproductive
103
BELHADI S. et al.,
traits of a population of local rabbits raised in Algerian
Concerning the factors of variation studied, the
conditions.
season of kindling was considered for litter size from
birth to 70 days, mortality, weekly weights and litter
weights. The summer effect was studied only on
MATERIAL AND METHODS
weights at weaning and litter size at birth and weaning.
The seasons considered were summer and autumn
The data came from 51 females (24 nulliparous
1999, winter and spring 2000. Two levels of parity
and 27 multiparous at the start of the experiment, but
order were taken into account for litter size and
some of them reached the 8 th parity) that are a sample
weights, the two first litters for the first level and from
of the rabbits commonly raised in Algeria with some
the 3 rd to the 8th for the second. The eight levels were
influence of New Zealand White and California. They
kept for acceptation, conception and kindling rate.
were housed in individual cages in an 80 m²
Another factor was the physiological state. Females
commercial farm that was naturally lit and ventilated.
are lactating when they accept bucks during 30 days
Humidity went beyond 80% in winter and reached 50%
after kindling; beyond, they are non lactating. Three
in summer.
classes, referred to as the number of born alive per
litter were considered for weights and litter total gain
during lactation. The first class included litters between
Females were first mated when they were 15-22
1 and 4 young, the second between 5-7 and the third
weeks and had a minimum weight of 2500 g. They
between 8-13. All factors were considered fixed in the
were re-mated 10-12 days after kindling and also
analysis.
forced if they refused. Bucks were used three to five
times/week. After mating, palpation was 12 or 14 days
Summarising, three different models were
later. Females were culled when they permanently
considered. The first one used for acceptation,
refused bucks and when their weights decreased .
conception and kindling rates was:
For the whole trial period (July 1999-June 2000),
Yijk=POi + PSj + eijk being,
animals were fed ad-libitum with a commercial feed
containing 4% soya, 42% alfalfa flour, 32.5% bran,
Y ijk, the kth observation of the trait carried out in the ith
16% barley, 0.5% feed blocks and 5% corn.
parity (POi) and the jth physiological state;
The traits recorded were acceptation rate (RA),
the second used for litter sizes was:
conception rate (CA), kindling rate (KR) per female,
litter size at birth, born alive and their weight (LSB,
BA, WWB) and weekly weights from birth up to
Yijkl= POi + PSj + SKk + eijkl being
weaning at 30 days (LW1, LW2, LW3, LW30) and 40
days after weaning the litter was weighted (LW70)
Y ijk, the lth observation of the trait carried out in the ith
and young were counted (N70). Stillbirths, pre-
parity (PO i), the j th physiological state and the k th
weaning and post-weaning mortality were also
season of kindling;
recorded. Some variables were deduced from some
traits: mean kit weights at birth, at 30 days and 70
and the third model used for litter and mean individual
days of age (MWB, MW30, MW70). Total litter gain
weights was:
during suckling (TLGb-w) was calculated from litter
weights at birth (LWB) and at 30 days (LW30).
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N ON GENETIC FACTORS AFFECTING RABBIT REPRODUCTION IN ALGERIA
Y ijkl= POi + CB j + SKk + eijkl being
season on litter size at weaning. It is possible that preweaning mortality is the main reason for these results.
K HALIL et al., (1987) indicated that kits in this period
Yijk, the lth observation of the trait carried out in the
are very sensitive to changes of external environment.
ith parity (POi), the jth class of number born alive and
However, AFIFI et al., (1989) did not find differences
the kth season of kindling;
related to this factor for the number of young at 30
days of age.
Statistical analyses were performed using the
least squares method implemented in the general
linear model procedure (SAS, 1987). Test of
Table 2 shows that autumn, winter and spring did
significance between levels of each factor were
not affect litter weight at birth, at one, two and three
carried out.
weeks of age, mean kit weight at weaning, litter weight
at 70 days of age and total litter pre-weaning gain.
Differences were significant (P<0.05) on mean kit
weight at birth and litter weight at weaning with the
RESULTS AND DISCUSSION
highest values in autumn (67 g ± 5 and 3482 g ± 149
respectively) with the summer the season with the
Season of kindling (Table 1) did not affect
lowest litter weight at 30 days (2600 g ± 240). This
significantly total born alive (TBA), born alive (BA).
effect was also significant on mean kit weight at 70
The effects of autumn, winter and spring on number
days with the highest values in winter (1989 g ± 50)
of kits alive at 70 days of age were non significant.
and the lowest in spring (1704 g ± 62) with a difference
For litter size at weaning (LSW), the greatest were
of 285 g between them. YAMANI et al., (1991) found
those related to temperate periods (autumn and
that high mean weights at birth are those pertaining to
spring, 7.92 ± 0.32 and 7.70 ± 0.34 respectively)
young born in autumn and winter which is similar to
having 0.86 more weaned kit than in winter. The
our results. It may be due to lower litter sizes during
lowest value was obtained in summer (6.25 ± 0.54).
these seasons compared to summer and spring. The
As it has been reported in literature, kindling season
drop obtained for litter weights at weaning in summer
is a factor that influences most performances,
is in agreement with findings of RAFEL et al., (1990).
through differences in temperatures, humidity,
Many authors (Y AMANI et al., 1991) justify these
photoperiod and other parameters (CHERIET , 1983).
results by a decrease in milk yield during this season
Our results are comparable with those of TORRES et
of birth. On the contrary to mean kit weight at weaning
al., (1992) who noted the negative effect of heat
Table 1: Least square means of season effect on litter size at birth (LSB), born alive
(NBA), litter size at weaning (LSW) and number of young (KIT) alive at 70 days/litter
(N70).
Season
LSB
NBA
LSW
N70
Summer
8.84 ± 0.70
8.29 ± 0.71
6.25 ± 0.54 a
_
Autumn
8.74 ± 0.40
8.87 ± 0.42
7.92 ± 0.32 b
5.38 ± 0.48
Winter
8.70 ± 0.40
8.33 ± 0.41
6.95 ± 0.31 ac
5.06 ± 0.40
Spring
9.43 ± 0.38
8.08 ± 0.40
7.70 ± 0.34 cb
5.40 ± 0.52
NS
NS
**
NS
Signification
a, b, c: means within columns that does not share any letter are statistically different (**P< 0.01; NS: no significant).
a, b, c: Within a column, means that does not share any letter are statistically different (**P< 0.01; NS: no significant).
105
BELHADI S. et al.,
Table 2: Least square means of season effect on different litter weights, mean weights and total litter
pre-weaning gain.
Season
Summer
Autumn
Winter
Spring
Signification
LWB
-
375 ± 40
308 ± 19
305± 16
NS
MWB
-
66± 5b
56± 2cb
53 ± 2c
*
LW1
-
735± 44
793± 37
771 ± 41
NS
LW2
-
1416 ± 76
1329 ± 71
1391 ± 78
NS
LW3
-
2204 ± 100ª
2068 ± 97ª
2069± 114a
NS
LW30
2600 ± 239ª
3482 ± 149b
3233 ± 158b
3327 ± 185b
*
MW30
569 ± 31
602 ± 19
626 ± 20
589 ± 24
NS
LW70
-
8721 ± 767
8326 ± 733
6801 ± 919
NS
MW70
-
1865 ± 51ª
1989 ± 50b
1704 ± 62c
**
TLGb-w
-
3381 ± 17
3643 ± 11
3402 ± 10
NS
LWB: Litter weight at birth (g); MWB: mean bunny weight at birth (g); LW1: litter weight at one week (g); LW2: Litter weight at two weeks
(g); LW3: Litter weight at three weeks (g); LWW: Litter weight at weaning(g); MW30: Meanbunny weight at weaning(g); LW70: Litter weight
at 70 days (g); MW70: Mean weight at 70 days (g); TLGb-w: Total preweaning gain (g).
a,b,c: means within rows that does not share any letter are statistically different ( *P<0.05;** P<0.01 ; NS: no significant).
which depends basically on does milk yield (ROUVIER,
according to season of kindling being autumn, winter
1978), at 70 days of age the trait is more affected by
or spring. Even if this factor had an effect, it would
season of kindling, despite our data for this trait has
be totally hidden by the mother-kit relationship
not observations in summer. Young born in winter are
(OUHAYOUN, 1978 ; V RILLON et al., 1979). It is to note
the heaviest in relation to spring and autumn. The
that the small number of observations of these traits
effect of season on mean weights appears therefore
could explain our findings in less agreement with the
stronger after weaning. BASELGA (1978) found the best
corresponding results reported in the literature.
individual mean weights at 70 days in autumn and
winter. He assigned the result for the most part to
The parity effects on acceptation rate (AR),
modification of animals´ appetite. ROUVIER (1978) and
conception (CR) and kindling rates (KR) are showed
CHERIET (1983) noted that when young are under their
in Table 3. Females accepted bucks whatever their age
mother (before weaning), weight characters are more
and very high rates were noticed in the beginning of
dependent on maternal effects. Consequently, the
the reproductive life although even later, percentages
effects of external factors appear more important post
are high. The 8th litter showed the lowest value.
weaning. Our current results did not show differences
KEMOUCHE and OUYED (1998), RABIA and YACINI (1999)
on litter weights at birth, at one, two and three weeks
remarked that females accept better the bucks while
of age and also on total litter preweaning gain
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N ON GENETIC FACTORS AFFECTING RABBIT REPRODUCTION IN ALGERIA
Table 3: Least square means of parity effect on acceptation (AR), conception (CR) and
kindling rates (KR).
Parity order
Acceptation rate (%)
Conception rate (%)
Kindling rate (%)
1
99.41 ± 3.34a
98.72 ± 6.53a
96.03 ± 6.94ad
2
95.12 ± 3.04a
68.92 ± 5.95cb
64.24 ± 6.31bc
3
91.29 ± 3.43ab
73.98 ± 6.72cb
70.93 ± 7.13b
4
99.15 ± 3.72a
82.07 ± 7.28ab
78.33 ± 7.72ab
5
94.97 ± 4.18a
69.89 ± 8.19cb
57.50 ± 8.69bc
6
89.58 ± 4.55ab
69.02 ± 8.91bc
63.61 ± 9.46bc
7
98.93 ± 5.23a
84.62 ± 10.23ac
83.86 ± 10.86ab
8
78.97 ± 6.55b
47.24 ± 12.82c
36.50 ± 13.61c
Signification
*
**
**
a, b, c, d: means within columns that does not share any letter are statistically different (*P<0.05; ** P <0.01 ).
they are young in agreement with our results. The
Estimates of our results are not statistically different
parity effect was more important on conception and
but we can see the increase when females parity
kindling rate because the range of their values is wider
becomes superior to two; this agrees with findings of
than for acceptance rate. There is not a clear pattern
H ASSAN et al., (1994) and R ABIA and Y ACINI (1999). It
for the effect of parity order on conception and
might be due to good body condition and health while
kindling if the fact that the highest ratios were obtained
does were in middle of their production, to the fact
in the first parity. P OUJARDIEU and T HEAU -C LÉMENT
that sexual maturity was fully reached and to
(1995), R ABIA and Y ACINI (1999) noted this decrease
favourable intra uterine environment during gestation
from the second and the third litter.
development (AFIFI et al., 1989).
Table 4 sohws the effects of parity on litter size.
Parity effects were non significant for litter
According to several authors, AFIFI et al., (1989), RAFEL
weights and mean weights of young (Table 5).
et al., (1990), BRUN and SALEIL (1994), POUJARDIEU and
However, all values for parities posterior to the second
THEAU-CLÉMENT (1995), litter size is improved with
were a little higher than the corresponding estimates
the age of does. The maximum of this trait occured
for the 1 st and 2 nd parities. K HALIL et al., (1987)
between the third and the fifth parity for those authors.
indicated that litter size weight at birth increases until
Table 4: Least square means of parity effect on litter size at birth (LSB), born alive (NBA), number of
weaned (LSW) and litter size at 70 days (N70).
Parity
LSB
NBA
LSW
N70
1-2
8.79 ± 0.37a
8.25 ± 0.38a
6.83 ± 0.30a
5.05 ± 0.44a
3 to 8
9.06 ± 0.37a
8.53 ± 0.38a
7.58 ± 0.29a
5.50 ± 0.39a
a: means within columns that does not share any letter are statistically different.
107
BELHADI S. et al.,
Table 5: Least square means of parity effect on different weights and
on total litter pre-weaning gain.
Parity
1-2
3 to 8
Signification
LWB
326 ± 21
339 ± 20
NS
MWB
57 ± 3
61 ± 2
NS
LW1
761± 38
771 ± 40
NS
LW2
1330 ± 67
1424 ± 75
NS
LW3
2079 ± 100
2149 ± 103
NS
LW30
3038 ± 142
3283 ± 163
NS
MW30
594 ± 18
599 ± 20
NS
LW70
7912 ± 778
7986 ± 767
NS
MW70
1898 ± 54
1807 ± 50
NS
TLGb-w
3434 ± 333
3516 ± 270
NS
LWB: Litter weight at birth (g), MWB: Mean weight of young at birth (g); LW1: Litter weight
at one week (g); LW2: Litter weight at two weeks (g); LW3: Litter weight at three weeks (g);
LW30: Litter weight at weaning (g); MW30: Mean weight at weaning (g); LW70: Litter weight
at 70 days (g); MW70 days: Mean weight of kit at 70 days (g); TLGb-w: Total pre-weaning
litter gain (g).
NS: no significant.
the sixth parity; and at weaning, YAMANI et al., (1991)
differences on conception and acceptation rates
and POUJARDIEU and THEAU -CLÉMENT (1995) showed
(HULOT and MATHERON, 1981; BOLET et al., 1990).
that mean weight of young was higher for the first,
second and third litters than for the fourth and fifth
The least square means of the physiological state
ones but the reverse was true for litter weight. They
for acceptation, conception and kindling rates (AR,
justify these results by an improvement of litter sizes
CR, KR) are showed in Table 6. The three traits were
at birth and weaning as the age advances. Our results
not significantly affected by the fact that females were
however did not reveal any effect during the whole
lactating or non lactating at the re-mating time,
period; they are in agreement with those of H ASSAN et
although we have higher values for lactating females.
al., (1994) who noted unaffected weights according
Similarly, some investigators have obtained such
to this factor. It is accepted that differences in mean
results (THEAU -C LÉMENT and P OUJARDIEU 1994); but
individual weight at weaning due to parity are mainly
previous studies show contradictory findings. THEAU-
explained by biological components and less by
C LÉMENT and R OUSTAN (1980, 1991) found greater
Table 6: Least square means of physiological state effect on acceptation,
conception and kindling rates (AR, CR, KR).
Physiological state
AR (%)
CR (%)
KR (%)
Lactating
95.14 ± 1.90
78.91 ± 3.73
74.71 ± 3.95
No lactating
91.72 ± 2.72
69.71 ± 5.33
63.04 ± 5.65
Signification
NS
NS
NS
NS: no significant.
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N ON GENETIC FACTORS AFFECTING RABBIT REPRODUCTION IN ALGERIA
Table 7: Least square means of physiological state effect on litter size at birth (LSB), number
of born alive (NBA), litter sizeat weaning (LSW) and litter size at 70 days (N70).
Physiological State
LSW
NBA
LSW
N70
Lactating
8.77 ± 0.31
8.20 ± 0.31
7.07 ± 0.25
5.40 ± 0.36
No lactating
9.78 ± 0.51
9.13 ± 0.53
7.76 ± 0.39
5.62 ± 0.51
Signification
NS
NS
NS
NS
NS: no significant.
conception rate when females are not lactating
(1984). RABIA and Y ACINI, (1999) also gave similar
comparing to lactating ones. It’s well known that
results in nearly the same conditions. Our results could
females accept bucks better just after kindling and
be related to limited experimental data.
become less receptive 3-5 and 10-12 days after
delivery than no lactating females (THEAU -CLÉMENT et
Only the mean kit weight at weaning (Table 8)
al., 1990).
was significantly affected by the classes of litter size.
The greater the litter size lower the weight at weaning.
It’s clear, as shown in Table 7, that physiological
The value for the class of 1-4 born alive was 698g ±
state had no significant effect on litter size during the
37 showing a difference of 183 g with the class 8-13.
whole period (0-70 days). Nevertheless, the best
The same trend, but not statistically significant, was
results were noticed at non lactating females. The same
observed for mean weight at birth and at 70 days.
conclusions have been reached by ESTANY et al., (1989)
Significant effects of the number of born alive were
who assigned the reason to competition between
observed for the different litter weights that increased
lactation and gestation, however a positive effect of
with the number of born alive, but this effects did not
lactation on ovulation rate has been noted by P LA ,
reach significance for total litter gain during lactation,
Table 8: Least square means of classes of number of born alive (NBA) effect on different litter weights,
mean weights and total litter preweaning gain.
Classes of NBA
1-4
5 -7
8 -13
Signification
MWB
60 ± 4
60 ± 2
57 ± 2
NS
LW1
385 ± 81a
840 ± 32b
1075 ± 25c
***
LW2
845 ± 153a
1507 ± 56b
1778 ± 43c
***
LW3
1467 ± 193a
2247 ± 85b
2628 ± 64b
***
LW30
2137 ± 289a
3225 ± 131b
4119 ± 109c
***
MW30
698 ± 37a
576 ± 17b
515 ± 14b
***
LW70
5267 ± 1543a
7910 ± 651a
10611 ± 434b
***
MW70
2052 ± 185
1844 ± 73
1752 ± 92
NS
TLGb-w
2803 ± 824
2921 ± 366
3864 ± 435
NS
MWB: Mean kit weight at birth (g); LW1: Litter weight at one week (g); LW2: Litter weight at two weeks (g); LW3: Litter weight at three
weeks (g); LW30: Litter weight at weaning (g); MW30: Mean kit weight at weaning (g); LW70: Litter weight at 70 days (g); MW70: Mean
weight at 70 days (g); TLGb-w: Total pre-weaning litter gain (g); a,b,c: means within rows that does not share any letter are statistically
different (***P< 0.001; NS: no significant).
109
BELHADI S. et al.,
Table 9: Season of kindling , parity and physiological state effects on mortality.
Factors of Variation
Stillbirths
Pre-weaning
mortality
Post-weaning
mortality
Season of kindling
***
*
NS
Parity
NS
NS
NS
Physiological status
NS
NS
NS
NS: no significant; * P0.05. *** P 0.001.
despite the estimated value of 3864 g ± 435 for the
sign of heat stress, heat stress that also causes poor
class 8-13, compared to 2803 ± 824 for the class 1-4.
weights gains, impaired feed conversion and increased
It is well known that when young are under the mother,
diseases incidence. Our results are similar to those of
their growth depends mainly on maternel effects
YAMANI et al., (1991) who noted that the effect of
(AURAN and SKJERVOLD, 1979; CHERIET , 1983). As we
season of kindling is due to temperature variations.
have pointed out before, mean weight at birth was not
Post-weaning, youngsters seemed to be less sensitive
significantly influenced by the number born alive in
to harsh climate and conditions of breeding although
spite of the high correlation between this trait and litter
it was during this period when the highest mortality
size. Mean kit weight at weaning, however,
took place (26.2% after weaning, 10.2% before
significantly decreased when the number born alive
weaning). A negative effect due to physiological state
increased. This influence of litter size has been
on mortality has been indicated by some authors
reported by several authors (R OUVIER, 1978; VRILLON
(RAFEL et al., 1990) which is associated with the more
et al., 1979; D ELAVEAU, 1982; MASOERO , 1982; ESTANY
important stress in lactating does. This is contrary to
et al., 1992). This effect appears mainly by the amount
our results that may be due to our re-mating interval
of milk offered to each kit. ROUVIER et al., (1973) and
(10-12 days after parturition), which gives better
B OLET et al., (1996) reported that the effect of this
performances. Several authors (ROUVIER et al., 1973;
factor along lactation persists sometimes beyond
HULOT and MATHERON, 1981; YAMANI et al., 1991) have
weaning. OUHAYOUN (1978) noted that effects on mean
been interested by parity effect on mortality. They
kit weight at slaughtering are the consequence of litter
justify the findings by the exhaustion of females with
size effect on weight at birth and during lactating
advancement of age but our results do not corroborate
period, but in our results, mean kit weight at 70 days
those as the effect was not significant
of age did not vary significantly according to litter
size, but the effect appeared on litter weight at this
CONCLUSION
age.
Concerning the effects of different factors on
Our results concern populations adapted to real
mortality the only trait exhibiting a clear trend over
local conditions in Algeria. Studied factors of variation
season of kindling was stillbirths (P≤0.001). A slight
did not affect in the same way the different
effect was observed on pre-weaning mortality
reproduction traits. Season of kindling influenced
(P≤0.05), but post-weaning mortality was not affected
significantly only litter size at weaning, mean weights
at all by the studied factors (P>0.05). According to
at birth and weaning and also mortality. Conception
some authors (KHALIL et al., 1987 ; Y AMANI et al.,
and kindling rate are mainly affected by parity
1991 ; HAMADÈNE, 1996), mortality is the most obvious
compared to other traits. However, physiological state
110
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characters.
The most considerable effect is revealed by litter
size at birth, which affected nearly all measured
weights.
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