Non-genetic factors affecting litter size, age at first lambing and lambing interval of Romanov sheep in Croatia

Abstract

Reproductive traits are of paramountimportance in an efficient lamb production system. In Croatia, values of reproductive traits of Romanov sheep are below the average expected for this breed, indicating the need for improvement of these traits to exploit the breed’s full reproductive potential. This study was conducted on 260 Romanov ewes located at a commercial Romanov sheep farm in Croatia. All ewes were kept under similar conditions, and reproductive management was based on accelerated lambing with continuous mating. Linear models with fixed effects were used to estimate the influence of year of birth/lambing, season of birth/lambing, ram, parity and litter type on litter size (LS), age at first lambing (AFL) and lambing interval (LI). Average LS was 2.11 ± 0.71, while the year of lambing and parity were the most important factors affecting this trait. The smallest litters were recorded after 1st parity (1.77 ± 0.06), and the largest after 5th parity (2.21 ± 0.08). AFL averaged 388.5 ± 72.4 days. All investigated non-genetic factors had a significant (P<0.05) influence on AFL, with year of birth as most important. The average LI was 241.2 ± 70.8 days. A significant (P<0.05) influence of all factors on LI was observed. Ewes lambing in spring (200.2 ± 7.9 days) or summer (190.5 ±6.6 days) had a significantly (P<0.05) shorter LI than ewes lambing in autumn (227.7 ± 8.3 days) or winter (237.2 ± 6.7 days). The longest LI was observed after the first parity (284.0 ±5.5 days). Average values for reproductive traits in the examined population of Romanov sheep were higher than those reported in the official Croatian database for breeding sheep. Non-genetic factors have a significant influence on the variation of reproductive traits of Romanov sheep, and therefore should be considered when assessing ewes’ reproductive performance.

Estimate the effect of non-genetic factors on the reproductive traits of Afec-Assaf strain in Bani Naim Farm, Palestine

“…After the second and third parities, the LI that was reported as being the longest (250.80±4.5 and 251.56±6.15 days) was significantly longer than the LI that was recorded after the fourth parities in Table 3. This is in agreement with the findings of (Vlahek et al 2022) in Romanov sheep, (Ahmed & Abdallah 2013)in Afec-Awassi and improved Awassi, (Tera et al 2021) in Bonga sheep and (Jalal et al 2015) in Rajshashi sheep. (Ahmed & Abdallah 2013) informed non-significant P>0.05 differences in the first, second and third LI of Afec-Awassi ewes with different parities.…”

“…This finding is comparable to those obtained by (Sodiq et al 2011), in which the litter size of Batur sheep at the time of birth was 1.55 and 1.36 lambs after they were weaned. Vlahek et al (2022) recorded an improvement in LS from 1.77 in 1st parity ewes to 2.21 in 5th parity ewes, whereas, in Afec-Awassi in Palestine, LS continually expanded gradually to 5th parity. (Ahmed & Abdallah 2013) Similar trends were observed in Romanov (Murphy et al 2020), Batur (Sodiq et al 2011), Rajshahi (Jalal et al 2015), Awassi (Al-Najjar et al 2022), Bonga (Tera et al 2021), Pelibuey (Canché et al 2016) and Romanov crossbred sheep (Freking & Murphy 2021).…”

“…This should be economically appealing given the significant increase in the price of lamb over the past few years. Models for LS analyses frequently incorporate lambing year (Canché et al 2016;Al-Najjar et al 2022;Vlahek et al 2022). In the current investigation, the total impact of lambing season on LS was found to be statistically significant P<0.05 in Table 2.…”

“…Assuming a 60-day ideal post-lambing oestrus interval, a 90% first-service conception rate, and a gestational period of 150 days, the ideal time between lambing is approximately 210 days. It is possible to double the number of sheep produced in the country in just over one and a half years if the lambing interval can be shortened by optimizing the breed, age, parity, and management practices used in this study (Vlahek et al 2022). It was hypothesized and discussed that a higher rate of milk production in multiparous ewes might be one of the factors contributing to the longer LI in ewes that have had more than one litter.…”

“…Litter size, lamb survival and lambing interval have been the objective of many studies. (Canché et al 2016;Deribe et al 2021;Tera et al 2021;Kabalin et al 2022), most notably in regions where traditional methods of husbandry are still widely used. Therefore, the aim of this study is to evaluate the reproductive performance of the Afec-Assaf strain, specifically focusing on traits such as litter size, litter size at weaning, and lambing interval.…”