Margarit Iliev’s scientific contributions

This study aimed to investigate the genetic polymorphisms in Agouti signaling protein (ASIP) and melanocortin 1 receptor (MC1R) genes and their association with coat color in native Bulgarian sheep breeds. A total of 247 individuals belonging to 7 native sheep breeds from 38 herds were genotyped for the ASIP and MC1R genes. Five single nucleotide polymorphisms (SNPs) were de-tected in the MC1R gene and three haplotypes representing MC1R ED and E+ alleles were identified among the studied sheep breeds. It was found that the dominant ED allele of MC1R is absent in the breeds - Patch-faced Maritza and Dubenska. The most common haplotype (h3) of the domi-nant ED allele was associated with either black or brown coat color in native Karnobatska, Kara-kachanska and Cupper-red Shumenska breeds, respectively. We can infer that haplotype 3 alleles could be a possible result that could interpret the mechanisms of black wool colour manifestation in the native Karnobatska sheep breed, which has formed the genetic pool of this sheep breed.

Subject of the study were 301 animals of the Karnobat fine-fleece breed from the flock of the Institute of Agriculture, Karnobat, born in the period 2013-2018. The purpose of the study was to analyze the weight development of sheep from the Karnobat fine fleece breed depending on the age and year of birth. The live weight trait was analyzed at weaning (at 90 days), at 9 months, 1.5, 2.5 and 3.5 years depending on year of birth. The necessary primary information for the study was taken from the Pedigree Book of the farm, kept at the Institute of Agriculture, Karnobat. The data were obtained according to the standard methods and guidelines defined in the Instruction for Control of Productive Traits (2011) of the Association for Breeding of Fine fleece sheep in Bulgaria. The data were processed using the method of variational statistics. It was established that the animals of the Karnobat fine fleece breed had an average live weight of 25.31 kg at 90 days, 42.37 kg at 9 months, 53.63 kg at 1.5 years, 58.39 kg at 2.5 years and 60.62 kg at 3.5 years. It was established that with age the change of this trait was in a positive direction, but at different rates depending on the effect of the year of birth, respectively and of production. Key words: Sheep, the Karnobat fine-fleece breed, live weight, age, year of birth

The Booroola Merino Breed, developed in Australia, is a valuable genetic resource for increasing biological fecundity in sheep worldwide. The purpose of this study was to summarize information about the Booroola Merino breed and its use worldwide and in Bulgaria for increasing the reproductive potential of Merino sheep and other breeds. The positive effect of the introduction of the FecB gene for high fecundity in sheep has been confirmed by a number of authors over a period of over 30 years. It has been established that crosses with Booroola achieve up to 30% higher ovulation rates and 20% more lambs after weaning compared to the purebred animals. The positive effect of introducing the FecB gene from Booroola in the Bulgarian fine-fleece breeds of sheep was established in terms of increasing the ovulation rate and the number of lambs born, with an insignificant negative impact on weight development and wool productivity. Negative effects can be reduced by choosing appropriate crossing schemes. Achieving a balance between benefit and risk in the introduction of the FecB gene from Booroola is an important condition for increasing the economic effect of animal husbandry and creating sustainable production in sheep farms.

2013-2019 година. Контролирани са някои основни продуктивни признаци на 316 овце: живо тегло от отбиване до 4.5 годишна възраст, вълнодобив и дължина на щапела до 4.5 години, рандеман на вълната и чисто влакно на 1.5 и 2.5 години. Установено е, че овцете от Карнобатската тънкорунна порода на 2.5 години тежат средно 59.090 kg живо тегло и дават средно 6.540 kg вълна с дължина на щапела средно 11.43 cm, среден рандеман на вълната 64.42 % и чисто влакно-4.220 kg. Нивата на всички проучвани продуктивни признаци са в зависимост от средовите фактори и годината на раждане оказва статистически значимо влияние, а линейната принадлежност дава достоверен ефект върху добива на вълна и количеството чисто влакно, получено от овцете на 2.5 години. Резултатите, получени за признаците на вълнодайната продуктивност са по-високи от стандартите за породата и показват добра изравненост в стадото и по възрасти. Данните за живото тегло са в норма и потвърждават скорозрелостта на Карнобатската тънкорунна порода овце. Ключови думи: Карнобатската тънкорунна порода овце; живо тегло; вълнодобив; дължина на щапела; рандеман; чисто влакно

The subject of the study were 617 sheep from the Northeast Bulgarian Fine-Fleece Sheep Breed (NBFF)-Shumen inter-breed type, born from 2013 to 2018 and bred in the Scientific Center for Agriculture-Targovishte. The biological prolificacy trait at different ages has been investigated. There were 1839 observations of biological prolificacy from the first to the fifth lambing. The influence of the factors-breeding line, type of mating and year of birth was researched. The variance was analyzed on the basis of a multifactorial linear statistical model for each study age (consecutive lambing). The linear affiliation has a significant effect on biological prolificacy up to the third lambing. The type of mating has a significant effect on biological prolificacy at first lambing only. Sheep from the line No. 61 with FecB gene from Booroola Merino are superior in prolificacy the purebred and the lines with Australian Merino genes up to 4.5 years. The biological prolificacy increaseed by the second lambing and was highest at 3.5 years (117%).

In order to evaluate the levels of some main productive traits in sheep of the Karnobat Fine Fleece breed, raised in the flock of the Institute of Agriculture - Karnobat, a study was conducted for the live weight and wool productivity of animals born in the period 2013 - 2019. Some main productive traits of 316 sheep were controlled: live weight from weaning to 4.5 years of age, wool yield and staple length up to 4.5 years of age, clean wool yield and clean fiber at 1.5 and 2.5 years. It was established that the sheep of the Karnobat Fine Fleece breed at 2.5 years weigh an average of 59,090 kg live weight and give an average of 6,540 kg of wool with an average staple length of 11.43 cm, an average clean wool yield of 64.42 % and clean fiber – 4,220. The levels of all studied productive traits depended on environmental factors and the year of birth had a significant effect. Linear affiliation gave a significant effect on wool yield and the amount of clean fiber obtained by sheep at 2.5 years. The results obtained for the wool productivity traits are higher than the breed standards and show a good evenness in the flock and by ages. Live weight data are within the norm and confirm the early sexual maturity of the Karnobat fine fleece sheep breed.

The purpose of the current study was to establish the dynamics of weight development and growth capacities until weaning in lambs from the Karnobat Fine-fleece breed in both sexes and different types of birth. The subjects of the study were 15 female and 15 male lambs. The study was conducted in the flock owned by Institute of Agriculture – Karnobat, during the 2020 lambing season. Four groups were formed, equalized according to the method of analogues by type of birth (singles, twins), gender (male, female), age and live weight. Live weight was recorded at birth, at 10 days, at 30 days, at 70 days and at 90 days. It has been established that the Karnobat Fine-fleece sheep breed is characterized by a good intensity of offspring growth until weaning, with female lambs reaching an average of 29.233 kg, and male lambs, respectively, 30.835 kg at 90 days. The average daily gain of lambs from the Karnobat Fine-fleece breed ranged from 0.236 kg to 0.344 kg for females by periods and from 0.242 kg to 0.367 kg for male lambs. Lambs of both sexes achieved the highest growth in the period 30-70 days. The results of the study indicate good compensatory abilities in the weight development of lambs born as twins from the Karnobat Fine-fleece sheep breed. The total gain reached by twin lambs at 90 days was close in value to singles of both sexes, being 1.97% lower in female lambs and 4.77% lower in male offspring. The Karnobat Fine-fleece breed has a good genetic potential for meat production, which is an advantage for sustainable development against the background of competition from specialized meat-producing sheep breeds in Bulgaria.

Subject of the study were 15 female and 15 male lambs from the Karnobat local sheep breed. The aim of the experiment was to monitor the weight development of offspring with different types of birth in the period before weaning. The study was conducted in 2020 with a flock owned by the Institute of Agriculture – Karnobat. There were 4 groups of lambs, equaled in type of birth (singles, twins), sex (female, male), age and live weight. The live weight trait was recorded at birth, at 10, at 30, at 70 and at 90 days. A total of 150 measurements of the live weight of the lambs were made, on the basis of which the average daily gain was calculated by periods for both sexes and for different types of birth. The data were processed by the method of variation statistics with the software MINITAB 16. It was found that the Karnobat local sheep breed is characterized by a good growth intensity of the offspring until weaning. Female lambs reached an average of 28,557 kg, and males respectively 30,233 kg at 90 days. The average daily gain ranged from 0.233 kg to 0.312 kg for female lambs and from 0.255 kg to 0.347 kg for male lambs. The highest growth was achieved by lambs of both sexes in the period 30 - 70 days. Lambs born as singles had a higher average live weight and daily gain until weaning, but with age the differences decrease, which shows good compensatory growth abilities of the twin lambs. Key words: Karnobat local sheep breed, live weight, average daily gain, sex, type of birth

Citation: Iliev, M., Staykova, G., & Tsonev, T. (2022). Dynamics of the selection traits milk yield and fertility in sheep from the Bulgarian dairy synthetic population. Zhivotnovadni Nauki, 59(2), 3-9 (Bg). Abstract The subject of the study were 254 ewes from the Bulgarian Dairy Synthetic population, owned by the Institute of Agriculture-Karnobat, born in the period 2013-2018. The aim of the study was to establish the dynamics of milk yield and fertility in sheep. The selection traits of milk yield of a standard 120-day period, duration of milking period and biological fertility by years of birth in animals of different ages have been studied and analyzed. The dynamic of milk productivity for 120 days was monitored from I to IV lactation, and biological fertility was monitored from I to IV lambing, until reaching 5.5 years. The data from the performed controls were processed by the method of variation statistics. It was established that the average milk yield for a standard 120-day period (108.6l), average daily milk yield (0.905 l) and duration of the milking period (140.6 days) were the highest during third lactation. Biological fertility of sheep increased from 134.2% to 154.1% during the time from the first to third lambing. The analyses of the obtained results indicate sufficient perspectives for increasing the potential and real productivity of sheep from the studied herd of Bulgarian Dairy Synthetic population. Резюме Обект на изследването са 254 овце майки от Синтетична популация българска млечна, собственост на Института по земеделие-Карнобат, родени през периода 2013-2018 година. Целта на проучването е да се установи динамиката на млечността и плодовитостта при овцете. СЕЛСКОСТОПАНСКА АКАДЕМИЯ • ЖИВОТНОВЪДНИ НАУКИ, LIX, 2/2022 4 Проучени и анализирани са селекционните признаци дойна млечност за стандартен 120-дневен период, продължителност на доен период, средна дневна млечност за доен период и биологична плодовитост по години на раждане при животните на различна възраст. Динамиката на дойната млечност за 120 дни е проследена от І до ІV лактация, а на биологичната плодовитост от І до ІV агнене до достигане на 5,5-годишна възраст. Данните от проведените контроли са обработени по метода на вариационната статистика. Установено е, че средната млечност за 120-дневен стандартен доен период (108,6 l), средната дневна млечност (0,905 l) и продължи-телността на дойния период (140,6 дни) са най-високи на трета лактация. Биологичната плодовитост на овцете се увеличава от първо до трето агнене от 134,2% до 154,1%. Анализът на получените рузултати показва добри перспективи за повишаване на потенциалната и реална продуктивност на овцете от проучваното стадо от Синтетична популация българска млечна. Ключови думи: Синтетична популация българска млечна, селекционни признаци, млечност, плодовитост