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.

Toll-like receptors (TLRs) play an important role in mediating the immune response against various microbes, such as bacteria, viruses, parasites, and fungi, in innate and adaptive immunity. Ten functional TLRs (TLR1 to TLR10) have been identified and mapped in cattle, with each TLR recognising specific pathogen-associated molecular patterns. The variation in genes controlling the immune response contributes to susceptibility or resistance to various infectious diseases such as mastitis, bovine tuberculosis, and paratuberculosis. Identifying TLR SNPs shows promising results for future marker-assisted breeding strategies, screening for disease risks, and improving the genetic resistance of dairy cattle. This article aims not only to review the research into susceptibility or resistance to infectious diseases and milk production traits in dairy cattle but also to discuss the limitations in current studies and the prospects in dairy cattle breeding.

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Abstract. This research aimed to analyze whether ewes' total reproductive performance up to the fourth year of life (RP4) can be predicted based on the data available at an early stage of a ewe's productive life. The RP4 of 133 Romanov ewes was measured in terms of the total number of lambs born per ewe (TNLE) and total birth weight of lambs per ewe (TBLE). Multiple regression was used to analyze whether early reproductive performance indicators (first litter size – FLS, age at first lambing – AFL, first lambing interval – FLI), ewe birth rank, dam age, and dam birth rank can be used as the predictors of RP4. Predicted R2 and 95 % prediction intervals were used as indicators of the precision of prediction. Average TNLE and TBLE at the end of fourth year of ewe life were 11.84 lambs and 37.96 kg, respectively. FLS and FLI significantly (P<0.05) influenced TNLE and TBLE, while AFL was not a significant (P>0.05) variable. Ewes with shorter FLI had significantly (P<0.05) higher TNLE (10.94 lambs) and TBLE (36.17 kg) than ewes with long FLI (TNLE = 9.12 lambs and TBLE = 28.05 kg). R2 predicted for TNLE and TBLE was 7.54 % and 11.49 %, respectively. The ewe's birth rank and the dam's birth rank significantly (P<0.05) influenced TNLE and TBLE. Ewes born as singletons and ewes from singleton-born dams had significantly (P<0.05) lower TNLE and TBLE than ewes born as triplets and ewes from triplet-born dams. R2 predicted for TNLE was 16.76 %, and 25.69 % for TBLE. FLS and FLI are better predictors of RP4 than AFL. The birth rank of ewe and dam also proved significant predictors of RP4. For both sets of predictors (early reproductive indicators and birth rank data), low values of R2 predicted indicate that precise prediction of RP4 cannot be made.

The relationship between growth rate and ossification is not consistent among fish. In some species, fast-growing individuals ossify earlier, while in other species, a trade-off between growth rate and ossification exists. This research was conducted to test the hypothesis about the existence of a trade-off mechanism in common carp offspring. For this purpose, specimens from two groups of common carp offspring (96 in total) with different growth rates were sampled at multiple time points between 5 and 29 days post-hatching. The standard length was measured and presented in correlation with the days post-hatching. To evaluate the skeletal system development, whole specimens were fixed in 10% neutral buffered formalin and stained for bone and cartilage. Particular emphasis was placed on the onset of ossification in the clearly visible bones of the head, vertebral column, and fins. According to our findings, larger, fast-growing specimens ossify earlier. The hypothesis on the existence of a trade-off between fast growth and the onset of ossification in common carp was not confirmed in our study.