Production, reproduction, and some adaptation characteristics of Romanov sheep raised under humid temperate climate

2.1 Ethical approval

All experimental procedures and animal management were performed according to the Animal Care and Use Guidelines of Ondokuz Mayis University of Local Ethical Committee. (Process number: 2021/18).

2.2 Material and location

The study was carried out with sheep of Romanov breed (thought to be pregnant) brought from Ukraine and given to three private sheep breeders in Giresun province in 2019, with the coordination of the Ministry of Agriculture and Forestry and Giresun Province Breeding Sheep and Goat Breeders' Association. The study could only be carried out in three private farms due to the intention of most breeders who have taken Romanov sheep to dispose of their animals. The study was carried out at two farms in the first year and with a breeder who bought sheep from other farms where Romanov sheep were distributed in addition to these farms in the second year. The first farm (n = 31, 45 for years 1 and 2, respectively) in the Ucarlı village of Bulancak district (coordinates of 40° 55′ 17.8032″ N and 38° 14′ 43.494″ E and altitude of 75–150 m) where summer and winter and grazing was in an area with a radius of 600 m from a bird's eye view. The second farm (n = 44, 34 for years 1 and 2, respectively) was in Kuzkoy village of Bulancak district (40° 49′ 27.1452″ N and 38° 12′ 5.2992″ E) coordinates and 500–650 m altitude at sea level and where winter grazing was in an area with a bird's eye view of 1,200 m radius. In summer, the Bektas plateau (40° 40′ 8.0868″ N and 38° 12′ 48.4884″ E), and at 1800–2050 m at sea level and where grazing was in an area with a radius of 1250 m from a bird's eye view. The third farm (n = 32 in year 2) was in Yivdikci village of Kesap district of Giresun province where sheep were grazed in winter (coordinates of 40° 51′ 21.69″ N and 38° 34′ 18.6198″ E, and altitude of 600–750 m) and grazed in an area with bird's eye view of 1200 m radius. The third farm's herd in summer, Cakrak and Cikrik plateaus were grazed in an area with a radius of 1250 m from a bird's eye view at the coordinates of (40° 30′ 51.0258″ N and 38° 36′ 30.1824″ E) and at sea level 1900–2250 m. In the second and third farms, rams were randomly left next to the ewes in July and August, and on the other farm, the rams were left in the herd throughout the year.

According to the nearest meteorological (Gresun Province Tamdere) station data, the air temperatures varied from min − 14.5°C and max 30.0°C, average min − 5.7°C max 16.2°C, and relative humidity values varied from min 13.9% and max 100% average 65.0% and 90%; monthly total precipitation varied from average min 16.70 and 301.90 mm, kg/m² and annual total precipitation 1227.10 mm, kg/m²) for 2020, and the air temperatures varied from min − 14.0°C and max 31.4°C, average min − 7.3°C and max 18.9°C, and relative humidity values varied from min 9.0% and max 100% average 63.0% and 96.0%; monthly total precipitation varied from average min 18.80 and 284.10 mm, kg/m² and annual total precipitation 1190.30 mm, kg/m² for 2021 respectively. The abundance of plant species diversity and the length of the vegetation period (Aydin et al., 2019), and therefore the length of the grazing period, were considered when selecting the humid study site.

All the herds in the study were reared under an extensive semi-nomadic production system from early May to late October. During this period, herds were housed in simple sheep pens maintained against the harsh winds and with the ground laid with Pteridium aquilinum plants. From November to April, the remainder of the period, herds were housed near the sea to avoid snow conditions, permit grazing, and provide better shelters with straw-bedded birth pens.

In the shelters, at least two square meters of space per animal was provided to allow for adequate access to feeders and waterers.

2.3 Method

3.1 Reproductive parameters in ewes

In the study, sheep numbers, the number of lambs born, some reproductive values, and the number of dead ewes and lambs in Giresun province (in 2020, 2021) are given in Table 1. Fertility characteristics of young females (ewe lambs) who have given birth more than once and will give birth for the first time and survival rates in sheep and lambs are presented in Table 2.

The most decisive criteria that show the adaptation of a creature in a habitat other than its original habitat are its viability and reproductive ability in its new habitat (Dwyer & Lawrence, 2005). The study determined that the farms and years were insignificant in terms of the reproductive traits pregnancy rates, birth rates, abortion rates, singleton, and multiple birth rates.

In Romanov ewes, litter size per ewe lambing and litter size per ewes joined to rams were found to be 1.42 and 1.76 at birth, respectively. Corresponding litter size values at weaning were 1.29 and 1.56. The results obtained regarding the reproduction characteristics of winter-mated Romanov sheep in the present study are lower than the values reported by Kuchtík et al. (2012) and Đuričić et al. (2019) for autumn matings. However, in the present study, reproductive characteristic values were 42% higher than results for summer matings, as reported by the same researchers (Đuričić et al., 2019; Kuchtík et al., 2012). In addition, the number of lambs at birth was lower than the values of Kuchtík et al. (2012), Wolfová and Milerski (2011), and Đuričić et al. (2019, 2022) by 1.76 vs 2.86, and the number of lambs at weaning was lower than 1.56 vs 2.10.

The highest lamb yield in Romanov ewes was obtained from autumn matings and ewes in the fifth parity (Fahmy, 1989; Kuchtík et al., 2012; Đuričić et al., 2019; Gootwine, 2020). Schmidova et al. (2016) reported that the litter size of Romanov ewes is up to six (11.13% for singles, 35.88% for twins, 37.92% for triplets, 13.06% for quadruplets, 1.79% for quintuplets and 0.23% for sextuples). However, three offspring per litter size could be obtained in 2020 and 2021 in Giresun province, and lamb productivity (1.56 vs. 2.59) was found to be lower than those reported by (Schmidova et al., 2016; Wolfová & Milerski, 2011). Cam et al. (2017, 2018) also reported that the litter size of pure Karayaka ewes could go up to 1.59. The lower results for litter size of the current study may be due to lower ovulation rates (litter sizes) of first and second parous ewes compared with later parous ewes.

3.2 Reproductive performance in ewe lambs

In the Romanov herd of the first farm, where the rams were continuously kept in the herd, three of the 22 head of ewe lambs obtained from the matings in 2020 were mated at the age of 6 months, 11 of them 7 months old, four of them 8 months, and 1 of them 9 months old; three of them did not mate to the ram. Twenty-seven lambs were obtained from 19 ewe lambs that gave birth. Of ewe lambs, 11 gave birth to singletons (11/19 = 57.89%), and eight gave birth to twins (8/19 = 42.11%). Survivability in lambs from ewe lambs was 77.8% (21/27), litter size 1.42 (27/19) at birth, litter size at weaning 1.11 (21/19), fecundity at birth 1.23 (27/22), and fecundity at weaning 0.95 (21/22) (Table 1). These values of the reproductive performance reported for Romanov's ewe lambs were higher than those reported by Wolfová and Milerski (2011).

3.3 Vitality in ewes and lambs

Vitality is one of the most important criteria for an organism's ability to adapt in a region (Dwyer & Lawrence, 2005). Ricordeau et al. (1990) reported that the viability of Romanov lambs decreased with the increased number of litters, but relatively less compared with other breeds. Romanov ewes and lamb mortality rates are presented in Table 2 according to year, male, female, and birth types in lambs. In terms of mortality rates, there was no difference between years and sex, and birth types. While the mortality rate in sheep was 3.23% on average in 2 years, the mortality rates up to the 90th day in lambs was 12.55% in two years' mean (Table 2).

In this study, mortality rates in singleton lambs (14.10%) from birth to weaning were higher than the mortality rates of other twins (12.50%) and triplet (9.09%) lambs. However, the lamb average mortality rates are 12.55%, which is considered above the acceptable limit (8%) (Cam et al., 2017, 2018). It is noteworthy that the mortality rate in singleton lambs is higher than in other birth types, though not significantly (p > 0.05). On the other hand, in this study, Romanov lambs' mortality rates were lower than the average value reported by Maria and Ascaso (1999) and Wolfová and Milerski (2011), possibly because the present study recorded a lower litter size.

3.4 Body weight values

The live weight values recorded on Romanov lambs at birth and on days 30, 60, and 90 days after birth are presented in Table 3.

The average lamb BW was determined as 2.36 ± 0.02 kg in 2020 and 2.35 ± 0.02 kg in 2021. The effect of gender (M: 2.50 ± 0.020, F: 2.21 ± 0.014 kg) and birth type (single, 2.65 ± 0.018, twin, 2.44 ± 0.015, and triplets, 1.90 ± 0.030 kg) on lamb BW were found significant (p < 0.01).

The mean BWs of Romanov lambs are nearly 1 kg less than the mean BWs of the native Karayaka breed (Cam et al., 2017, 2018, 2021). As can be seen in Table 3, the average 90-day weaning weight of Romanov sheep lambs is around 12.58 kg. This value is similar lower than the 21.7 kg (Cam et al., 2017) and 17.64 kg (Akçapınar et al., 2002) for the local breed Karayaka lambs. In the study, body weight values of Romanov lambs obtained at birth and weaning were compatible with some literature reports (Dwyer & Lawrence, 2005; Fahmy et al., 1997; Kuchtík et al., 2012) and inconsistent with others (Al-Ksas et al., 2018; Dvalishvili et al., 2015; Emsen et al., 2012; Khattab et al., 2021; Murphy et al., 2020; Şen & Uğurlu, 2021).

Lamb BWs were found to be different between farms (2.32 vs 2.35 vs 2.39 kg; p < 0.001), but not different between years (Table 4).

3.5 Body measurements in Romanov lambs

The live weight and body measurement values measured at 30-day intervals from birth to 90-day weaning age in Romanov lambs are presented in Table 4–9. The data related to measurement values such as withers height, rump height, BL, CW, CD, and CC (which are the determinants of growth, body development, and breed-specific basic parameters) showed that the growth and development characteristics of lambs were low compared with those of lambs in other studies. In the present study, BW values of 2.36 kg in 2020 and 2.35 kg in 2021 (Table 4) were close to 2.90 kg in Al-Ksas et al. (2018) and 2.64 kg in Khattab et al. (2021) and 2.92 kg in Murphy et al. (2020). However, the BWs reported by Emsen et al. (2012) 3.9 kg, Şen and Uğurlu (2021) 3.31 kg, and Vlahek et al. (2023) 3.23 kg were found to be much higher than those in the present study.

Sheep breeders in the region compare Romanov sheep and lambs with the Karayaka sheep. For this reason, it will be helpful to compare the growth values of Romanov sheep obtained in the study with the growth measurement data of Karayaka sheep. The values determined for the live weight for 90 days in this study (Table 3) were lower than the native Karayaka (male 22.60 vs 12.90 kg, female 20.8 vs 12.27 kg) lambs of the Black Sea Region of Cam et al. (2017). This result is consistent with the reports of Fahmy (1989) and Kuchtík et al. (2012) that Romanov lambs reported low growth characteristics.

Different results can be found regarding the effect of gender on body weight and body measurements in lambs (Freitas-de-Melo & Ungerfeld, 2020; Yilmaz et al., 2007). In this study, when gender was considered for its effect on BW, it was determined that males were (p < 0.001) heavier than females (Table 5). The birth type affected the BW of Romanov lambs and the body weight values and body measurements in the following months. Triplets were born at significantly lower body weights than singles and twins.

Year affects the phenotypic values of animals as an environmental factor. The effect of the year on the phenotypic values may occur depending on the uncontrollable climatic features or the genetic structure of the animals that change from year to year or the way of breeding (pure, crossbreeding), and the differences in the care and feeding of the animals from year to year (Düzgüneş et al., 2012). In the present study, there was no year effect on live weight at birth and day 60 but lambs were significantly heavier in 2021 compared with 2000 on days 30 and 90 (Table 3).

It has been determined that there were differences in the growth and body sizes of Romanov lambs on different farms that may have resulted from the differences in the maintenance and feeding conditions of the enterprises (Tables 4, 6, and 8).

Various body measurements of Romanov sheep on the 30th, 60th, and 90th days according to year and farms, birth type, and sex are given in Tables 4–9). Wither height, rump height, CW, CD, and BL are widely used to define breeds' morphological and developmental characteristics (Cam et al., 2010, 2017). No data regarding the body measurements of Romanov lambs other than the studies of Şen and Uğurlu (2021) could be found.

The body measurement values found in our study were lower than those reported for the Romanov on 90th day (HH = 44.12, CD = 20.61, BL = 43.38 cm) by Şen and Uğurlu (2021). Body measurement values of Romanov lambs on the 90th day are compared to the 90-day measurement values of Karayaka lambs (Akçapınar et al., 2002), which is the dominant breed of the Black Sea Region (HH = 45.22, 43.94 BL = 46.18, 39.88 CD = 21.75, 17.84 CC = 57.52, 49.72 cm) which are relatively low. These results confirm the report of Kuchtík et al. (2012) and Maria and Ascaso (1999) that the growth rate of pure Romanov lambs is low.

Measuring values of cannon circumference (CaC) in Romanov sheep according to year, farm, sex, and birth type are presented in Tables 4–9). Some morphological body measurements values such as live weight, withers height, rump height, CW, BL, CC, and CaC in animals can be used as determining criteria in adaptation to the environment and care-feeding conditions (Kutluca Korkmaz & Emsen, 2016). It is essential to evaluate the solid bone structure of animals, especially in uneven areas around the cannon. While the CaC measurements between years were not different at the 30th day (6.27 and 6.26 cm), they were different at the weaning age (7.22 and 6.68 cm). While there was no effect of gender and birth type in terms of CaCs of lambs at both the 30-day age and weaning age, the effect of the enterprise was found to be significant. The mean CaC value (6.92 cm) at the weaning age of Romanov lambs was found to be lower than the mean value (7.78) reported by Şen and Uğurlu (2021).

EL, EW, TL, TW, head length (HdL), and head width (HdW) values from birth to weaning in Romanov lambs were presented in Tables 5 and 10 according to the variables of year, farms, sex, and birth type. It was determined that the TL and the TW of Romanov lambs changed according to years and enterprises but did not change according to gender and birth type. In this study, it was determined that the year and farm environmental factors affect the TL of Romanov lambs. However, the mechanism of this remains to be solved.

EL and EW were found as 5.21 and 3.19 cm at birth, and 6.56 and 3.84 cm at weaning age. EL and EW, the angle of the ear with the connection point, that is, the position of the ear, may differ according to the breed. However, information on these features has yet to be found in the literature. Romanov TL was measured as 7.73 at 30 days of age, 9.42 cm at weaning, 2.91 cm at TW at 30 days of age, and 3.47 cm at weaning.

Although some of the fat accumulation around the subcutaneous and internal organs is collected in the tail (Cam et al., 2021), it is reported that the Romanov breed does not have a fat tail but produces genotypically less fatty meat than fat-tailed sheep, and other domestic breeds (Kuchtík et al., 2012). A literature search indicated a complete lack of information on tail characteristics of Romanov sheep and lambs.

The daily live weight gain in Romanov lambs increased by approximately 5 g in 2021 compared to 2020 (Table 10).

Although this difference is statistically significant, it is not small from a breeder's perspective. The difference could be attributed to changes in climate-related vegetative development, which may vary over the years.

In the study, the daily body weight gain of Romanov lambs of 113.6 g was similar to the body weight gains reported by Fahmy et al. (1997) 105.6 g, Al-Ksas et al. (2018) 115.50 g, and Şen and Uğurlu (2021) 92 g. However, it was lower than the values reported by Dvalishvili et al. (2015) 133 g and Murphy et al. (2020) 174.67 g. The daily gain reported by Kutluca Korkmaz and Emsen (2016) (303 g) is exceptional. The fact that the daily body weight gain of pure Romanov lambs reared in extensive conditions in Giresun province was lower than some literature reports can be attributed to the differences in raising conditions. However, the fact that the domestic Karayaka breed has higher daily live weight gain under breeder conditions may cause a problem convincing the sheep breeders to prefer the Romanov breed sheep.

3.6 Herd instinct and grazing behaviors of Romanov sheep

Herd instinct and grazing behavior of the Romanov sheep were compared with the native Karayaka breed. It has been observed that Romanov sheep breed can reach the places that the native Karayaka sheep cannot reach by grazing on the fenced garden edges. In addition, Romanov sheep breed is more diligent in overcoming the obstacles (fenced, excessively rough areas) that the native Karayaka breed does not try to cross. By overcoming obstacles, Romanov sheep can reach and consume nuts, cherry laurel, fruit saplings, and tree leaves like a goat. Although the region is mountainous, humid, and rainy, Romanov sheep always move faster than Karayaka sheep across the pastures. Romanov sheep graze separately from the Karayaka herd, but they can adapt to be dominant within their own breed and, over time, within the other breed. Most breeders and shepherds in the region do not prefer Romanov sheep in their flocks, as the Romanov sheep breed is fast and accelerates the other breed in the herd.

Romanov sheep attract the attention of breeders in different parts of the world due to their high breeding characteristics. Results of the current study suggest the Romanov breed may improve litter size to a small to moderate degree but low growth rates of the lambs and differences in grazing behavior, compared with the native Karayaka sheep, need to be considered by breeders before incorporating the new breed as part of their grazing system. That many environmental factors affect animals' economically important phenotypic values both inside and outside their original habitats should be remembered. Breeders should especially consider the new breed's adaptability and its product acceptability before attempting to substitute another race for breeds adapted to their production areas.