Thermoregulation and Reproductive Performance of Grazing Desert Ewes (Ovis aries) as Influenced by Concentrate Supplementation
Mohammed E. Elnageeb,
Abdalla M. Abdelatif
Sharaf Eldin A. Makawi
Twenty sexually mature Desert ewes were used to study
the effects of concentrate supplementation on thermoregulation and reproductive
traits. The ewes were divided into two equal groups, control and supplemented;
the supplemented group received daily 500 g of concentrate mixture (crushed
sorghum grain and cotton seed cake). In both groups, oestrus was synchronized
with hormonal method and the ewes were naturally inseminated. Pregnancy
was diagnosed by the ultra-sonography technique. Dietary supplementation
resulted in a shorter time of oestrus onset, higher rates of conception,
lambing and a significant decrease in gestation length. The fertility
and fecundity of ewes were also improved. Supplementations also increased
significantly the pre-and post lambing weight of ewes and the birth and
weaning weights of the lambs. The body weight, rectal temperature and
respiratory rate increased significantly with the advance of pregnancy
in both groups of ewes. These indices decreased significantly with the
progress of lactation. The supplemented ewes maintained higher values
of these indices during pregnancy and lactation.
Under tropical conditions where the bulk of sheep population is maintained,
nutrition constitutes a major factor that influences thermoregulation
and reproductive performance of ewes. Drought conditions, especially in
areas that have been overgrazed, can have deleterious effects on the reproductive
cycle of sexually mature animals because of malnutrition.
Pregnancy and lactation may influence the thermoregulation responses
of mammals. Also the level of food intake affects metabolic heat production
and thermoregulation in ruminants (Abdelatif and Ahmed, 1992; Brosh et
al., 1998). Moreover, a close relationship between the level of food
intake and the rate of metabolic heat production has been established
in Merino sheep (Olthoff et al., 1989). Freetly and Ferrell (1997)
reported an increase in energy requirements of ewes during pregnancy;
approximately 60% of the increase in heat production was associated with
the gravid uterus. Laburn et al. (1992) showed that the ewe`s body
temperature declined before and at parturition. Variations in the body
temperature of mother and foetus in animals are presumably associated
with heat dissipation capacity of the utero-placental circulation and
heat generation by the foetus (Faurie et al., 2001).
The reproductive performance of the ewe which is considered as the major
component of sheep productivity is usually determined by traits as age
at first lambing, conception rate, lambing rate, gestation length, lamb
birth weight and lamb weaning weight. The reproductive capacity of ewes
can be promoted by the supra-ovulation and increase of conception rate.
Follicle populations are very sensitive to nutritional input and folliculogenesis
and ovulation rate can be increased by nutritional manipulation (Scaramuzzi
et al., 2006). Ovulation rate is dependent on short-term improvement
of nutrition during the breeding season (flushing) in ewes which are within
the intermediate range of body condition (Gunn, 1983). Flushing may also
increase the lambing rate in ewes (Sulieman et al., 1990; El-Hag
et al., 1998). Moreover, copious supplementary feeding of ewes
during gestation and lactation may reduce considerably the morbidity and
mortality rates of lambs (Charring et al., 1992; Binns et al.,
2002). In tropical areas, animal owners have limited knowledge regarding
the energy and protein requirements of the various classes of livestock
and their role in expression of genetic potentials. In addition, the formulation
of livestock diets is based on information derived from studies conducted
in temperate regions. These values may not necessarily apply to indigenous
breeds of animals and the prevailing climatic conditions.
Therefore, studies on the nutritional requirements of sheep are needed
so that feeding systems which satisfy the actual requirements can be established.
Sheep in Sudan play an important economic and social role and constitute
valuable resource for local and export purposes. They provide a popular
source of meat for local consumption and an important source of foreign
currency. During dry summer conditions they may be exposed to shortage
of food which influences their energy budget and reproductive performance.
The production characteristics of Sudan desert sheep may reflect the seasonal
nutritional status and husbandry system (El-Hag et al., 2001).
Accordingly the objective of this study was to evaluate the effect of
long term supplementation with a concentrate mixture rich in energy and
protein on thermoregulation and some reproductive traits of desert ewes.
MATERIALS AND METHODS
Animals and management: Twenty sexually mature multiparous Desert
ewes were used in this study during January 2006-January 2007. The ewes
were 2½-3 years old with an average body weight of 35.2 3.6 kg
at the beginning of the study. They were selected from the breeding stock
of the Sheep Research Unit at Khartoum University Farm (latitude 15°40`
north, longitude 32°32` East and 380 m above mean sea level). The
animals were apparently healthy. However, the ewes were subjected to quarantine
measures for one month and were thoroughly examined to eliminate sick
animals and to ascertain that they were fertile and free from reproductive
abnormalities. The ewes were periodically dewormed with anthelmintic (Ivomec,
Anupco-England: l mL/50 kg BW) and they were given prophylactic antimicrobial
treatment (Sulphadiamadin pyrimidine, Richter-pharma, Austria: 1 mL 10
kg BW). The ewes were identified individually using ear-tags and were
randomly assigned to two experimental groups. Group A served as control
and was kept on grazing only while group B was supplemented with a concentrate
mixture. The ewes were kept in open shed with adequate ventilation to
facilitate the dissipation of sensible heat and disposal of water vapour.
The housing system was provided with appropriate facilities for feeding
Feeding: Normal nutrition of experimental animals (groups A and
B) was provided by grazing harvested residues before being irrigated for
regrowth or ploughed for the next sowing season. All animals were put
on pasture and allowed to graze daily on the residues of sorghum (Sorghum
bicolor) and grasses (Cyndon dactylon) for 6 h (from 8:00 am
to 2:00 pm). The ewes in group B were offered a supplemental concentrate
mixture composed of a high energy source and a source rich in protein.
Each animal in group B received daily at 7:00 am. A mixture of 250 g of
crushed sorghum grain and 250 g of cotton seed cake. Salt blocks (macro-minerals,
micro-minerals and vitamin D) were also provided to the supplemented group
in the animal pens. Tap water was available all the time in the shed.
Table 1 shows the chemical composition of the components
of the concentrate diet.
Body Weight (BW), rectal temperature (Tr) and Respiration
Rate (RR): During the experimental period, the ewes and their lambs
were weighed to the nearest±0.05 kg using a spring balance (Salter-England).
The measurements of rectal temperature (Tr) of experimental
animals were made to the nearest±0.1°C using a certified mercury-in-glass
clinical thermometer (Wilson-Supreme, Japan). The thermometer was inserted
into the rectum to a depth of approximately 8 cm in ewes for 2 min. before
the reading was obtained. The Respiration Rate (RR) of ewes was measured
visually by counting the flank movements with the aid of a stopwatch.
The values were taken for one minute of regular breathing with the animal
Synchronization of oestrus, insemination and pregnancy diagnosis:
The synchronization of oestrus in ewes was performed by the hormonal method
as described by Greyling et al. (1997). The intravaginal progesterone
release devices (CDIR, Inter Ag-UK: 300 mg/ewe) were inserted in the ewes
for 2 weeks. After withdrawal, ewes were injected with pregnant mare serum
gonadotrophin (PMSG, Intervet Ltd. UK: 500 IU/ewe).
During the breeding period, subgroups of the ewes were accommodated in
4 separate pens for 5 days to facilitate oestrus detection and insemination.
Each pen accommodated 5 ewes. During this period, oestrus was detected
visually by monitoring the signs of heat 3 times daily. Four fertile Hamari
breed rams were introduced (at the time of withdrawal of the device),
each for a subgroup of ewes. The ewe which showed signs of oestrus (mucus
discharge and male seeking behaviour) was allowed to be mated.
The diagnosis of pregnancy was performed one month following natural
insemination in order to determine the number of ewes that conceived.
Pregnancy was diagnosed by the ultrasonography technique using a standard
device (550 Trioga PIE Medica-Netherlands).
Determination of reproductive traits: The reproductive traits
were evaluated according to the method of Charring et al. (1992).
The conception rate (the percentage of ewes which conceived and got pregnant
out of the total number of ewes exposed to the ram) based on non-return
rate following the double insemination, was determined 60 days after natural
insemination. The lambing rate was determined by calculating the percentage
of ewes that gave birth to lambs out of those which conceived. The fertility
rate (number of ewes lambing out of those inseminated) was calculated
by the following formula: (lambing ewes/ewes inseminated)x100. The fecundity
rate (number of lambs born out of number of ewes inseminated) was calculated
by the following formula: (lambs born alive/ewes inseminated)x100.
Statistical analysis: The student (t) test was used to compare
the reproductive traits of control and supplemented groups of ewes. For
the effects of physiological state of each group of ewes on rectal temperature
(Tr) Respiration Rate (RR) and Body Weights (BW) the data were
subjected to appropriate General Linear Model (GLM) procedure of statistical
analysis using the SAS package (1988). The SAS was used to perform Analysis
of Variance (ANOVA) to evaluate the effects of physiological state on
these parameters. The data considered were at the end of each of the experimental
periods: initial (IN), mating (MT), Early Pregnancy (EP), Mid-Pregnancy
(MP), Late Pregnancy (LP), parturition (PR) and at the end of the first,
second and third month of lactation (L1, L2 and
L3, respectively). Also the student (t) test was used to compare
the control and supplemented group at each of the physiological states
The climatic data (Table 2) indicate that during the
experimental period the highest mean value of ambient temperature was
measured in May 2006, during dry summer, while the minimum mean value
was recorded during January in 2006 and 2007, during winter. Also the
minimum mean value of RH (%) was measured in April 2006 during dry summer,
whereas the highest mean value was recorded in July and August 2006, during
the rainy season.
||The ambient temperature (Ta) and Relative Humidity (RH)
during the period January 2006-January 2007 at the experimentation
||Effect of dietary supplementation during different physiological
states on rectal temperature (Tr) of ewes
Rectal temperature (Tr): There was no significant difference
e in the initial values of Tr of the ewes before supplementation
of group B animals (Fig. 1). During flushing period,
the values of Tr fluctuated in both groups of ewes. There was
a significant (p<0.05) increase in Tr values in both groups
of ewes during pregnancy to reach maximum values at parturition. During
the first and second month of lactation, there was a significant (p<0.05)
decrease in Tr of the control ewes, but there was a significant
(p<0.05) increase by the end of the third month. The supplemented group
showed a progressive significant (p<0.50) decrease of Tr
throughout three months of lactation. During the first and second month
of lactation, the supplemented ewes showed significantly (p<0.01) higher
Tr compared to the control. However, the difference in Tr
between the 2 groups during the 3rd month of lactation was not significant.
||Effect of dietary supplementation during different physiological
states on Respiration Rate (RR) of ewes
||Effect of dietary supplementation during different physiological
states on Body Weight (BW) of ewes
Respiration Rate (RR): There was no significant effect of supplementation
on the initial values of RR of the ewes (Fig. 2). Starting
from beginning of supplementation, both groups of ewes showed a progressive
significant (p<0.05) increase in RR to reach peak values in mid gestation.
Thereafter, RR showed a significant (p<0.05) decrease during late gestation
and at parturition. Both groups showed progressive significant (p<0.05)
decrease in RR during lactation period. The supplemented ewes showed significantly
higher RR values during mid gestation (p<0.001) and at parturition
and lactation (p<0.01).
Body Weight (BW) of ewes: Figure 3 shows the
effects of dietary supplementation at different physiological states on
the mean BW of the ewes. There was no significant difference between the
mean BW of the groups before supplementation of group B. In both groups
of ewes, there was a significant (p<0.05) increase in the mean BW after
mating and during different stages of pregnancy. After parturition, the
mean BW of both groups of ewes decreased significantly (p<0.05) to
reach lower values by the third month of lactation. Also it was noted
that the mean BW of supplemented ewes was significantly (p<0.05) higher
compared to control ewes during different stages of pregnancy and lactation.
The pre-lambing and post-lambing weights of ewes were significantly (p<0.001)
higher in the supplemented ewes compared to the control.
||Effects of dietary supplementation on reproductive performance of
|Paired means within the same row bearing different superscripts
(small) are significantly different at p< 0.05, Paired means within
the same row bearing different superscripts (capital) are significantly
different at p<0.001
Reproductive performance: Table 3 indicates
that the initial numbers of animals used in the studies were 10 ewes for
control (kept on grazing only) and 10 ewes maintained on similar grazing
conditions and supplemented with concentrate mixture before breeding and
throughout the periods of gestation and lactation.
There was no significant difference between the two groups of ewes in
the oestrus response to the synchronization, but the time of oestrus onset
was shorter in supplemented ewes compared to the value measured for the
control group. The pregnancy diagnosis test indicated that the conception
rate was higher in the supplemented group compared to the control (7 ewes
for control vs 10 ewes for supplemented). Dietary supplementation decreased
the gestation period significantly (p<0.05); the mean values for the
control and supplemented group were 155.7±0.3 and 152.8±0.4
days, respectively. The supplementation also increased the percentage
of ewes lambing, which was 70% for control and 100% for the supplemented
group. The percentages of fertility rate and fecundity were higher in
Table 3 also indicates that the birth weight was significantly
(p<0.001) higher for lambs born to supplemented ewes compared to those
born to the control group. The lambs born to the supplemented ewes also
had significantly (p<0.001) higher weaning weight with a mean value
of 19.89±0.6 kg compared to a mean weaning weight of 14.93±0.8
kg for lambs born to the control ewes.
Thermoregulation in ewes was influenced by pregnancy, lactation and dietary
supplementation. Figure 1 and 2 indicate
that there was a significant increase in rectal temperature (Tr)
and Respiration Rate (RR) during pregnancy in both groups of ewes. The
increases in Tr and RR are attributed to increase in metabolic
heat production. The results are in line with previous studies that have
reported an increase in metabolic heat production during pregnancy in
ewes (Gilbert et al., 1985; Freetly and Ferrell, 1997). Furthermore,
Rattray et al. (1974) reported that the extra heat production that
occurs in pregnant ewes is primarily foetal in origin. The foetus loses
its heat via the foetal circulation and uterine wall (Schroeder et
al., 1988), foetal heat production represents an extra thermal load
on mother heat production. The increase in RR during gestation could be
related to the fact that pregnancy limits the excursion of the diaphragm
during inspiration and when expansion of the lungs is restricted, adequate
ventilation is maintained by increased frequency.
The results showed a significant increase in Tr of ewes at
parturition. This is presumably attributed to the process of labour (i.e.,
hormonal effects) and muscle contraction during parturition. Marx and
Loew (1975) reported that the stress of labour and myometrial contraction
may produce sufficient heat in the active tissues that will increase body
temperature. The present results support the findings of Laburn et
al. (1994), who reported that the body temperature of ewes rose at
0.7°C h-1 in the final stage of labour. The decrease in
Tr (Fig. 1) and RR (Fig. 2)
after lambing and during lactation may be attributed to decrease in uterine
blood flow and elimination of heat dissipation from the foetus as a result
of delivery. Foetal lambs lose about 85% of their body heat via transfer
to the placenta and 15% through the uterine wall (Shroeder et al.,
1988). The progressive decrease in Tr and RR during lactation
is related to metabolic adjustment and hormonal changes associated with
change in milk yield. The relatively higher values of Tr and
RR during lactation in the supplemented group is a reflection of the higher
plane of nutrition and concomitant rise in milk yield. Gunn and Gluckman
(1983) and Laburn et al. (1992) reported that the daily peak in
Tr in ewes was influenced by the heat increment of feeding;
both feeding and postural changes can affect Tr in ewes.
The results demonstrated that pregnancy had marked effects on the BW
of the ewes (Fig. 3). The mean BW increased significantly
with the advance of pregnancy in both groups of ewes. The increase in
BW after mating and during early gestation is related to the development
of conceptus, which was associated with increase in metabolism and body
weight gain and to an increase in food intake. An increase in voluntary
food intake has been reported to be associated with increase in BW of
RambouilletexColumbia ewes during early gestation (Lodge and Heaney, 1973).
However, in the present study, the increase in BW could be partly accounted
for by changes in the weight of the uterus and foetus. Lodge and Heaney
(1973) reported that at parturition, the weight of the contents of conceptus
exceeded live weight gain of ewes indicating a loss in BW of ewes during
the last quarter of gestation as a direct result of pregnancy, which is
also associated with BW loss during mid- and late stages of pregnancy
(Robinson et al., 1978). The higher BW of supplemented group of
ewes reported in the present study during pregnancy is clearly attributed
to the dietary factors. The results are in agreement with the findings
of Quirke (1979), who reported that in pregnant ewes, there was an increase
in BW with increase in the level of energy and protein intake. The rapid
development of the conceptus during mid- and late gestation results in
a marked loss of the maternal tissue and consequently in BW losses (Lodge
and Heaney, 1973). The significant decrease in BW of both groups of ewes
during lactation (Fig. 3) is associated with involution
of the uterus and increase in tissue catabolism as a consequence of biosynthesis
of colostrum and milk. The current result is in conformity with John et
al. (2000), who indicated that during early lactation the ewe is generally
unable to consume enough feed to meet the energy demands of high milk
production and she loses body weight mostly due to metabolism of fat stores.
The higher BW of the supplemented group of ewes during lactation indicates
that the concentrate provided sufficient nutrients to reduce the rate
of body weight loss. Since the nutrient demands for biosynthesis of milk
decreases with the advance of lactation, the rate of BW loss decreased
progressively. Hassan (1996) reported that the increase in body weight
gain in lactating desert ewes was associated with increase in intake of
The current results indicate that some of the reproductive traits of
the Desert ewes were improved by dietary supplementation. The data projected
in Table 3 indicate that there was no significant difference
between the 2 groups in oestrus response to synchronization. According
to the appearance of oestrus signs, however, the interval from the injection
of PMSG to the onset of oestrus was shorter in supplemented ewes (25.2
h) compared to the time recorded for the control (28. 3 h). The decrease
in the time of onset of oestrus is presumably attributed to the nutrition-induced
hormonal changes (gonadotropins, oestrogens). It has been established
that oestrogen, which is secreted from the mature follicles in the ovary,
is responsible for the signs of oestrus (Jainudeen and Hafez, 1993). Haresign
(1981) and Downing and Scaramuzzi (1991) reported that nutritional factors
(e.g., protein) might influence the development of growing follicles.
Increased nutritional level may result in increasing rate of degradation
of steroids and reduction in the inhibition of hypothalamic-pituitary
axis and consequently resulting in increased gonadotrophin secretion (Thomas
et al., 1987). Furthermore, high dietary protein level may increase
the responsiveness of the pituitary to Gonadotrophins Releasing Hormone
(GRH), resulting in high plasma level of luteinizing hormone (Jordan and
Swenson, 1979). In addition, the plane of nutrition may also influence
the ovarian response to circulating gonadotropins (Harrison and Randel,
1986; Cox et al., 1987). However, the change in nutrition can influence
ovarian activity by changes in circulating concentrations of metabolic
hormones, including insulin, IGF-1, growth hormone and Leptin (Webb et
The rates of conception and lambing were higher in supplemented ewes
compared to the control (Table 3). This is attributable
to the effect of improved nutritional status of the ewes and hence increases
in ovulation and embryo survival. These results are in line with previous
studies which reported that increasing the level of nutrition increased
the rate of ovulation in Border LeicesterxMerino ewes (Rizzoli et al.,
1976) and in Desert ewes (Sulieman et al., 1990). Furthermore,
Kenney et al. (1980) supplemented Border Leicester x Merino ewes
with lupin grains for two weeks prior to and during mating period and
they reported an increase in the rates of ovulation and lambing. Since
the fertility and fecundity of mammals are usually associated with conception
rate, lambing rate and litter size (Gunn, 1983), the present findings
suggest that dietary supplementation increased the rates of fertility
and fecundity of Desert ewes.
Earlier studies have shown that variation in gestation length in indigenous
breeds of sheep is negligible (Khalafalla and Sulieman, 1992). However,
the present study showed that dietary supplementation significantly decreased
the gestation length in Desert ewes (Table 3). This
is attributed to the rapid development and growth of the foetus associated
with maturity of the Hypothalamic-Pituitary-Adrenal (HPA) axis and improvement
of the live weight of the ewes. The foetal HPA axis plays a primary role
in determining the time of parturition by secreting increased amount of
corticosteroids (Thorburn and Challis, 1979; McLaren et al., 1996).
Hawkins et al. (1999) pointed out that modest restriction of maternal
nutrition (15%) during early pregnancy depresses HPA axis function in
the foetus in late gestation. Wallace et al. (1997) reported that
rapid growth rate of adolescent ewes was associated with decrease in gestation
In the present study (Table 3), the birth weight of
lambs born to supplemented ewes (4.67 kg) was higher compared to the birth
weight of lambs born to ewes kept on grazing only (3.97 kg). This is clearly
related to the high nutritional status and the improved body condition
of supplemented ewes during pregnancy. Ocak et al. (2005) pointed
out that maternal nutrition during pregnancy is a major extrinsic factor
that influences the birth weight in domestic livestock. In sheep, the
birth weight of lambs increased with increase of gestation live weight
of dams (Mukasa-Mugerwa et al., 1994).
The data indicate than the mean body weight of the lambs born to supplemented
ewes at weaning was significantly higher compared to the lambs born to
control ewes (Table 3). This could be attributed to
the influence of ewes` BW. Earlier studies indicated that there was a
positive correlation between birth weight and weaning weight of lambs
and the ewe BW (Farid and Makarechina, 1978; Ploumi and Emmanouilidis,
1999). The milk yield of dams was not measured in the present study. However,
it could be assumed that the higher plane of nutrition of supplemented
ewes was associated with higher milk yield. During the early weeks of
life, there is high correlation between growth rate of lambs and milk
yield of dams as lambs consume very little solid feed during this period.
Previous studies indicated that the growth of lambs was closely related
to the milk yield of ewes (Cowan et al., 1980; Snowder and Glimp,
1991). The growth rate of lambs is primarily determined by energy intake
relative to the live weight (Hassan, 1996).
The studies indicate that pregnancy and lactation influence thermoregulation
and body weight of Desert ewes. Dietary supplementation could influence
thermoregulation and improve reproductive performance of ewes, particularly
when it is maintained throughout gestation period. Further research is
needed to investigate the impact of summer thermal load on endocrine responses
and reproductive performance of Desert ewes.
We would like to thank the laboratory staff of the Department of Physiology,
Faculty of Veterinary Medicine for technical assistance. Also we acknowledge
gratefully the help rendered by Dr. K.A. Abdoun in presentation of the
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