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The aim of the study was to determine the effect of birth type and sex on lambs survival parameters of polish heath and żelazneńska sheep. The research included data, which was used to determine the prolificacy index, the percentage of live-born lambs and the lambs rearing index up to 100 days of age. A higher prolificacy index (P≤0.01) and a higher percentage (P≤0.01) of reared lambs were determined in the polish heath compared to the żelazneńska sheep. In the herd of the first breed, a greater proportion of twin and more numerous litters than singleton births were noted. Single and twin litters were dominant in the żelazneńskie sheep. The rearing rate of lambs from single litters was at a similar level in both observed breeds. However, in the herd of polish heath sheep, lambs from multiple litters shoved also high rearing rate. Single ram lambs were characterized by higher (P≤0.01) body weight at birth and at 56 days of age compared to twin born and ewe lambs, both in polish heath sheep and żelazneńska sheep. Statistical differences (P≤0.01) in body weight at birth and on 56th day of age were also recorded between twins and triplets in polish heath sheep. The analysis of the distribution of lambs' mortality during the rearing period has shown that the most critical is the first week of life of the born offsprings.

The aim of the study was to compare two mating systems and their impact on reproductive parameters in sheep of the synthetic WROBER line and to evaluate the profitability of lamb meat production. Sheep were raised at the Agricultural Experimental Station in Żelazna (Warsaw University of Life Sciences) in a traditional system with mating once a year and at the Werbkowice Experimental Farm (Institute of Soil Science and Plant Cultivation – National Research Institute) in an intensified system with a shortened lambing interval. The study confirmed the suitability of the WROBER line for intensive production of slaughter lambs. In this system, 0.5 more lambs were obtained per ewe (in all seasons) than in the traditional system. Due to the increased number of lambs produced, the WROBER line can become more profitable.

The aim of the study was to investigate the distribution of prion protein PRNP alleles in flocks of Polish Merino and Suffolk sheep. The research was conducted in 2012-2017 on ewes and rams kept in the Golina Wielka sheepfold (Greater Poland Voivodeship, Poland). All animals (264 ♀ and 64 ♂ Polish Merino; 98 ♀ and 73 ♂ Suffolk) were up to one year old. PRNP gene polymorphism was identified in the sheep. The frequency of scrapie alleles and genotypes was found to be highly significantly influenced by the breed and significantly influenced by the year in the case of Polish Merino sheep. Five alleles (ALRR, ALRQ, ALHQ, AFRQ and VLRQ) were detected in Polish Merino sheep, leading to the identification of 10 PRNP genotypes. In the Suffolk breed, three alleles (ALRR, ALRQ and ALHQ) and three genotypes were identified. In the Polish Merino breed, the frequency of the ALRR/ALRQ genotype was high and was the highest among all genotypes, followed by ALRR/ALRR. The level of genotypes containing valine at codon 136 was very low. In the Suffolk breed, the frequency of the ALRR/ALRR genotype was very high, and there were no alleles with valine at codon 136. In addition, in Polish Merino sheep, phenylalanine at codon 141 was detected only in the AFRQ allele, which appeared in two genotypes (in combination with ALRR and ALRQ).

The study was conducted on Polish Merino (143♀ and 39♂) and old-type Polish Merino sheep (176♀ and 61♂) in Brylewo flock (Wielkopolskie Province). The examined sheep were at the age of one year. Prion protein (PrP) genotype was determined in all animals. In both breeds four alleles (ARR, ARQ, AHQ, VRQ) were found. Highly significant effect of breed and insignificant impact of gender within breed was observed in regard to the frequency of occurrence of alleles and genotypes susceptible to classical scrapie in the sheep. Eight different PrP genotypes in Polish Merino and nine genotypes in old-type Polish Merino were identified. Very high frequency of ARR/ARR genotype in old-type Polish Merino and high frequency of ARR/ARQ genotype in Polish Merino were found, with relatively significant frequency of occurrence of the genotypes containing VRQ allele. In old-type Polish Merino, three animals (of both genders) had VRQ/VRQ genotype. Breeding work involving elimination of animals encoding valine at codon 136, and introduction of rams with ARR allele to the population increased the frequency of occurrence of ARR/ARR genotype and ARR allele in the population of old-type Polish Merino. To improve the distribution of the genotypes genetically resistant to scrapie in the flock of Polish Merino only rams with ARR/ARR genotype were left. This guarantees an increase in the frequency of occurrence of genotypes genetically resistant to scrapie in the offspring.

Appropriate level of bio-components in blood plasma of animals is associated with their concentration in soil and in green fodder. Cycling of elements in nature and their adequate level in animal organisms result in proper functioning of an organism as a whole (Khan et al. 68:279-284, 2007). Therefore, it is important to analyse soil and green fodder for these components. If some deficits are found, it is important to supplement components responsible for e.g. proper growth and development of a young organism, proper reproduction and, consequently, good quality of obtained product, which may affect human health (Minzanova et al. 134:524-533, 2015). The aim of the presented study was to demonstrate the effect of extensive grazing by sheep on vegetation and soil and to analyse the cycling of some elements important for animal health. The effects of vegetation season on the concentration of potassium in soil and differences in the concentration of some elements in soil, green fodder and animal blood were demonstrated.

The number of nematode eggs in the faeces was estimated in Polish Wrzosowka sheep, in the spring and autumn of 1993 and again in 1994. The sheep had been naturally infected. The dominant species were Haemonchus contortus and Teladorsagia circumcincta, but Trichostrongylus spp., Cooperia curticei, Nematodirus spp. and Chabertia ovina were also present. Anthelmintics were not used. Egg counts were skewed, with a range of 0–4100 eggs g−1 (EPG); most sheep had egg counts below 100 EPG. Egg counts were approximately four times higher in spring than in autumn. Repeatability values within a season were all significant and positive. The repeatability of egg counts between seasons was estimated from the correlation between the mean transformed value in spring and in autumn, and was 0.52 in 1993 (P < 0.001) and 0.41 in 1994 (P < 0.05). The results show that animals with higher than average values in spring are likely to have higher than average values in autumn, and suggest that similar mechanisms regulated egg counts in both seasons even though egg counts were much lower in autumn.