THE COMPARISON BETWEEN REPRODUCTIVE PERFORMANCE IN SYNCHRONIZED AND SPONTANEOUS ESTRUS SHEEP

Access Open ABSTRACT Purpose: The objective of the present study was to compare the reproductive performance in synchronized and spontaneous estrus sheep raised under farm conditions. Subjects and Method: Two hundred Karadi and Two hundred Awassi were used in this study. Of each breed, 100 ewes were allowed to come in estrus spontaneously and the other 100 ewes were synchronized using intravaginal sponges (ESPONJAVET, HIPRA, Amer, Girona, SPAIN). Ewes were injected with intramuscular injection of 500 IU of PMSG when sponges were removed on day 14. Results: This study revealed that estrus synchronization had a higher rate of lambing (P=0.014), twining (P<0.001), dystocia (P=0.024), and barrenness (P=0.012) in Karadi ewes. Estrus synchronization also had a significantly higher rate of lambing (P=0.018), twining (P=0.017), abortion (P<0.001), barrenness (P=0.012) and productivity (P=0.010) in Awassi ewes. the result of the current study shows that the barrenness rate was higher in spontaneously ovulated ewes compared to synchronized Awassi ewes. The result of the current study shows that the abortion rate was higher in spontaneous ewes compared to synchronized ewes. The twinning rate was higher in synchronized compared to spontaneous Karadi ewes. Conclusion: In both breeds, synchronized ewes had higher reproductive efficiency compared to ewes that had spontaneous estrus.


INTRODUCTION
Recently, there has been an increasing interest in the understanding of the influence of some factors on productivity efficiency in sheep. Therefore, to maintain high reproductive performance in Karadi and Awassi sheep flocks under traditional conditions, identifying factors that influence reproductive efficiency is critically important (Juma & Alkass, 2005;Lafi et al., 2009;Zebari et al., 2018). Karadi and Awassi are the local breed of sheep in the Kurdistan region and Iraq (Alkass & Abdulkareem, 2004), and are considered the most important sheep breed in the semi-arid regions of the near east countries (Galal et al., 2008). The local breeding season starts as early as April and lasts through September (Oramari et al., 2014). The reproductive performance of Kardi and Awassi sheep has been low (Juma & Alkass, 2005).
During the breeding season, intravaginal progestogen sponges, followed by pregnant mare serum gonadotropin (PMSG) injection were applied to ewes to synchronize estrous (Mutiga & Mukasa-Mugerwa, 1992) and to improve the ovulation rate (Tetsuka et al., 1988). Intravaginal progestogen sponges are usually inserted over a period of 12-14 days followed by injection of PMSG, especially during the non-breeding season in sheep (Wildeus, 1997;Ungerfeld & Rubianes, 2002). The factors that influence the fertility of Karadi and Awassi are unclear (Zebari, 2020). In the reproductive planning of sheep, spontaneous versus synchronized estrus ewe are factors that have a great effect on fertility results (Buckley et al., 2003). Conception rate (Alkass & Abdulkareem, 2004;Zebari, 2019), litter size or percentage of lambs born to ewe lambed (Abdulkareem & Eidan, 2014), the number of ewe lambed, abortion, parturition dystocia and mortality rate after birth are considered the main aspects in sheep reproductive performance (Evans, 2003).
In general, productivity and profitability can be determined by the reproductive performance of sheep. Fertility in sheep is influenced by hormonal status (Taha & Alkass, 2011) and breeding programs; spontaneous versus synchronized estrus (Crosby et al., 1991). There are limited studies that reported the effect of the breeding programs on the reproductive efficiency in Iraqi native sheep (Zebari, 2020). However, there is also a paucity of published information on the factors that influence reproductive performance in Karadi and Awassi sheep raised under farm conditions. Therefore, the present study was designed to investigate whether the reproductive performance of Karadi and Awassi sheep raised under farm conditions are affected by spontaneous versus synchronized estrus ewes

METHODOLOGY
The experiment was undertaken between June 2020 and July 2021 at three traditional sheep farms in Sharmin, Akre, Duhok Governorate. The Animal Production Department Research Ethics Committee approved the research protocol in the College of Agricultural Engineering Sciences, University of Duhok.

Experimental Animal, Housing and Management
Four hundred Karadi and Awassi sheep (200 Karadi and 200 Awassi) with parity 2.7 ± 1.3 were used at three traditional sheep farms in Akre, Duhok Governorate. At the start of the study, the sheep (Ewe and Rams) were submitted for detection of any abnormalities of the reproductive tract. Sheep were kept with the main flock. The sheep were housed in a free-stall yard during night and sheep were put out to graze during the day (06:00 to 20:00) in the summer months and continuously housed during winter. During housing, total mixed ration (TMR; hay, barley and wheat barn) was provided daily, sufficient for ad libitum availability. Water was also provided ad libitum from water troughs at the free stall yard and pasture during the summer.

Estrus Synchronization
Each Karadi and Awassi ewes were randomly divided into two groups. The first group (n=100 Karadi and n=100 Awassi ewes) were allowed for coming into estrus spontaneously. The second group (n=100 Karadi and n=100 Awassi ewes) were synchronized using intravaginal sponges composed of polyurethane sponge soaked with 60 mg of medroxyprogesterone acetate/sponge (ESPONJAVET, HIPRA, Amer, Girona, SPAIN). The sponges were introduced with the aid of an applicator which was disinfected before each use. The sponge remained in the vagina of the ewe for 12 to 14 days then the sponges were removed at day14 of the anestrus stage. Ewes were injected with intramuscular injection of 500 IU of PMSG (ESPONJAVET, HIPRA, Amer, Girona, SPAIN). The injections were carried out on day14 after the withdrawal of the vaginal sponges. The active fertile rams were introduced to ewe 48 hrs after the removal of sponges (ram to ewe ratio; 1:15).

Spontaneous Versus Synchronized Estrus
Each Karadi and Awassi ewes were randomly divided into two groups. The first group (n=100 Karadi and n=100 Awassi ewes) were allowed for coming into estrus spontaneously. The second group (n=100 Karadi and n=100 Awassi ewes) was synchronized using intravaginal sponges according to ESPONJAVET-HIPRA company. These were used to analyze the effect of spontaneous versus synchronized estrus on the reproductive performance of ewes.

Statistical Analysis
Statistical analyses were performed using the Genstat statistical software package (Genstat 18th edition, 18.1.14713, VSN International Ltd, UK). All of the data sets analyzed were normally distributed. Chi-Square tests were used to compare reproductive parameters (0/1) of the fertility rate, conception rate, abortion rate, dystocia rate, lamb mortality rate from birth to weaning, barrenness and productivity between synchronizes versus spontaneous estrus ewes. Chi-Square tests were also used to compare reproductive performance (1/2) of litter size, laming rate and twining rate between synchronizes versus spontaneous estrus ewes. Differences were reported as significant at P<0.05 and trends were reported when P is between <0.1 and >0.05

Spontaneous vs synchronized Karadi ewes
As expected, the result of the current study shows that the lambing rate was more in synchronized Karadi ewes compared to spontaneous Karadi ewes. Similarly, Abdulkareem and Eidan (2014) and Quintero-Elisea et al. (2011) found lambing rate in synchronized ewes (100%) higher than spontaneous ewes (66.7%). The lambing rate in synchronized Karadi ewes of the present study is within the range (97-123%) reported by Abecia et al. (2007) in three sheep breeds in Spain raised under farm conditions. The result of the current study was higher than that found by Crosby et al. (1991) who recorded a 72% of lambing rate in synchronized ewes using progesterone treatments. In addition, the result of the current study lambing rate was higher than that recorded by Berhan and Van Arendonk (2006) of 81% vs 76% in Menz and Horro, respectively. However, the result of the present study lambing rate in spontaneous Karadi ewes of this study is lower than that reported by Taha and Alkass (2011) of 86.5% spontaneous Karadi ewes. The lambing rate in spontaneous Karadi of the present study also is lower than that found by Binns et al. (2002) of 96% in UK sheep breeds.
In addition, the results of the present study found that the twinning rate was higher in synchronized compared to spontaneous Karadi ewes. This finding is consistent with those found by Abdulkareem and Eidan (2014) of twinning rate (18.75% vs 6.66 in synchronized and spontaneous, respectively) in Iraqi native sheep. The result of the present also agrees with the report by Quintero-Elisea et al. (2011) who found that the twinning rate was higher in synchronized 30% compared to spontaneously ovulated ewes (22%). Alongside with higher lambing rate and twinning rate, the productivity rate in synchronized ewes was also trended to be higher compared to spontaneous Karadi ewes. Higher lambing and twinning rate in synchronized ewes may be due to the persistent dominant follicle was regressed during progestogen treatment and a new follicle was ovulated at progesterone withdrawal (Gazal et al., 1998). This will lead to a higher ovulation rate and ovum quality (Abdulkareem & Eidan, 2014).
Furthermore, the result of the present study revealed that the rate of dystocia was higher in synchronized ewes compared to spontaneous Karadi ewes. Similarly, Rawlings and Howell (1988) and Sánchez et al. (2008) found that dystocia rate in synchronized ewes was higher than that of the spontaneously ovulating sheep. The result of the present study of synchronized ewes is within the range (3.53-10.58) as found by Mandal et al. (2007) Muzaffarnagar sheep. A higher percentage of dystocia in synchronized ewes may be due to a higher rate of twinning in synchronized ewes compared to spontaneous ewes (Mandal et al., 2007). According to the Australian report, twin lambs effect on dystocia rate and there is a positive relationship between the twinning rate and the rate of dystocia in sheep (Hailat et al., 1997).
However, in the present study, the rate of barrenness ewes was recorded more in spontaneous Karadi ewes compared to synchronized Karadi ewes. These results are in agreement with those reported by Abdulkareem and Eidan (2014) of barrenness rate (21.4% vs 7.55% in synchronized and spontaneous, respectively) in Iraqi native sheep. Lower barrenness rate in synchronized ewes than spontaneously estrus ewes may be due to more strength of estrus in synchronized ewes of sustained growth of the largest follicle at day 14 after the withdrawal of the vaginal sponges which lead to subluteal level induced by the exogenous treatment and an increase in LH concentration (Leyva et al., 1998;Quintero-Elisea et al., 2011).

Spontaneous vs synchronized Awassi ewes
The results of the present study found that lambing rate and twining rate were higher in synchronized Awassi ewes compared to spontaneous Awassi ewes. These findings are in agreement with those of Abdulkareem and Eidan (2014) who found lambing rate and twinning rate in synchronized Awassi ewes were higher in comparison to spontaneous Awassi sheep. However, the lambing rate in synchronized and spontaneously ovulated Awassi ewes of the present study were higher than those (82.9-100.0%) reported by Juma and Alkass (2005) in Awassi sheep. While the twinning rate in the present study of the spontaneously ovulated Awassi ewes was lower than those reported by Juma and Alkass (2005) of 12.3 to 13.7% in Awassi sheep. Higher lambing and twinning rate in synchronized Awassi ewes may be due to higher ovulation rate and ovum quality and consequently an increase in lambing and twinning rate in synchronized sheep (Gazal et al., 1998;Abdulkareem and Eidan, 2014). Different lambing and twinning rate in various studies may be due to the effect of environmental and management factors (Binns et al., 2002). Productivity was higher in synchronized Awassi ewes compared to spontaneous Awassi ewes. This finding is consistent with those found by Juma and Alkass (2005) and Abdulkareem and Eidan (2014). The higher productivity in synchronized ewes compared to spontaneously ovulated Awassi ewes may be due to the higher lambing rate and twinning rate in synchronized ewes.
In healthy sheep herds, the normal proportion of aborting ewes is generally between 2% and 5% (Menzies, 2011). The result of the current study shows that the abortion rate was higher in spontaneous ewes compared to synchronized ewes. These findings are in agreement with the finding of Beck et al. (1993) who found that the abortion rate was higher in synchronized ewes compared to spontaneously ovulated Awassi ewes (8% and 2%, respectively). The reasons of the higher abortion rate in spontaneously ovulated ewes compared to synchronized Awassi ewes are unclear and need more investigations. The abortion rate in the present study is within the range reported by (Mahboub et al., 2013) of 1-25% in three Egypt sheep raised under farm conditions.
As expected, the result of the current study shows that the barrenness rate was higher in spontaneously ovulated ewes compared to synchronized Awassi ewes. This result is consistent with that found by Abdulkareem and Eidan (2014) reported that the barrenness rate in synchronized (21.4%) was higher than spontaneously ovulated (7.55%) in Awssi ewes raised under farm conditions in the middle and south of Iraq. Lower barrenness rate in synchronized ewes than spontaneously estrus ewes may be due to sustained growth of the largest follicle at day 14 after the withdrawal of the vaginal sponges which lead to subluteal level induced by the exogenous treatment and an increase in LH concentration (Leyva et al., 1998). This leads to higher estrus activity in synchronized ewes which can be detected easily by rams during the breeding season and consequently an increase in pregnancy rate (Quintero-Elisea et al., 2011)

CONCLUSION
In both breeds' synchronized ewes had her reproductive efficiency compared to ewes that came into estrus spontaneously under traditional farm conditions.