Prof. dr George Yakimov Dimov
(CV, Research summary, Summary of some results, List of publications)





To participate in a joint research project in the field of dairy sheep genetic evaluations.


Permanent position:

Associate professor -  Bioinformatics and Population Genetics


Professional experience:

- Genetic evaluations in dairy sheep, cattle and buffaloes - genetic parameters and breeding values, formulation/construction of breeding criteria.

- Study of factors influencing the production traits, methods of their accounting.

- Construction of selection systems for obtaining a better genetic gain.



Ph.D. - Agricultural Academy, Sofia, Bulgaria. 1979

Major:  Sheep Breeding

Dissertation: Comparison of methods for predicting breeding values of rams for milk yield.


M.S. Agricultural Academy, Sofia, Bulgaria. 1975

Major: Animal Genetics.

Dissertation: Effect of inbreeding level on heritability and genetic correlations in silkworm (Bombix mori).


Agricultural Academy student (zootechnics) 1970 – 1974

5-th Sofia secondary scientific school. 1966 - 1968


Research activity:

Research interests: Genetic analyses of animal breeding data, studying new traits in dairy sheep, constructing of breeding plans, building FORTRAN programs for analyses of variance components, BLUP breeding values and selection indices, fifteen years experience in PC computer programming. Modeling of genetic gain in different systems of selection and methods for breeding values estimation. Systems of selection in a big number small sized herds. Implementation of the understanding for genetic values in the herd breeding practice. Implementation of extension service in animal husbandry.

Research activity: International scientific meeting and conferences attended - 15; research support grants - 3; scientific papers in the field of sheep, cattle and buffalo breeding, sheep physiology and reproduction - 50 (see appendix).

Computer skills: statistics, computer programming (FORTRAN).


Teaching experience:

Advisor of four Master of science post graduate students in sheep breeding - 1985 - 1990


Other experience:

- FAO International Project for Red Cattle Breeds comparison in Bulgaria. 1982 - 1984

- Standardizing methods for ram genetic evaluation in Eastern Europe, coordinator. 1988 - 1989

- FAO project “Strengthening Agricultural Policy-making and Economic Services Capability” in Bulgaria. TCP/BUL/ 2352(A). National consultant. 1994 - 1995

- Experience in working in international teams.


Study, research trips and employment abroad:

- Agricultural University of Norway. “Systems of selection in dairy cattle”. 1981.

- Lincoln University - Missouri, USA. ”Extension Service Activity in Cattle and Sheep Farming, Breeding and Marketing”. 1991

- University of Nebraska - Lincoln, USA. Employed as a Post Doc in the project: “Sire by Herd Interaction for Yield Traits in Holsteins”. 1992 - 1994  



Bulgarian  (mother thong).

English - read, speak, write - very good.

Russian - read, write, speak - very good.


Other skills and hobbies:

swimming, skiing, bridge.


Personal history:

Born - 23 April 1950 in Sofia.

Citizenship at birth and present - Bulgarian.


 Prof. dr George Yakimov Dimov




Findings and areas of interest in the field of sheep breeding.

1. The influence of duration of period from lambing to first test day on yield traits of dairy sheep.

2. Dairy sheep information is summarized for over 70 000 lactations for the period of 1980-87.

3. A new trait in dairy sheep is formulated - type of lactation curve. Factors influencing it, its inheritance and connections with the other traits were the aim of an enhanced study.


Classification of the research


1. Influence of nongenetic effects on traits

      1.1. Traits

Sheep - milk yield, lactation period, maximum daily yield, persistency of lactation, type of lactation curve;

      1.2. Factors

Year, farm, herd, month of lambing, duration of first control period, type of lactation curve.

      1.3. Correction of nongenetic effects

Additive and multiplicative corrections which are performed before the genetic evaluation. (ANOVA1)

      1.4. Simplifying of milk recording in dairy sheep

Prediction of milk yield for complete lactation or commercial yield (after weaning, e.g. for milking only period) based on two test day records. Breed differences, season and age effects.


2. Genetic parameters

      2.1. Methods

      - intraclass correlation, no computers, later on Becker’s (1968) methods on CPM and DOS type machines.

      - approaches - without correction for nongenetic effects, preliminary correction, simultaneously in the model - REML (single and multiple trait).

      - correlations among estimates of variances (additive, permanent environmental and residual) show a pattern of complementarity.


3. Selection indices

      3.1. Information from several traits

      Milk yield and persistency, weights as difference from the breeding goal. Weights does not influence the index, summation of standardized rams’ EPD rank them similarly.

      3.2. Information from several relatives for sex restricted traits

Empirical regressions of several relatives on rams’ progeny testing.

Theoretical study on increasing accuracy based on own phenotype when dams’ and paternal half-sib information is accounted for.

Accuracy of preliminary (at weaning) estimation of BV for milk yield, based on descendent and co-laterals.

Combining six types of relatives in a simulation MOET - ONBS study.


4. Study on breeding values

      4.1. Non genetic effects

Correlations between rams’ EPDs for milk yield dropped down to 0.48 when complex of fixed effects differ.

      4.2. Complex estimate on several traits

For dairy and merino rams standardized EPDs were combined with relative importance of four traits e.g. a simplification of selection index.


5. Developing of computer programs

      5.1. Non genetic effects – ANOVA

Allows an arbitrary number if cross-classified effects, or one nested within the main with several linear regressions. Direct inversion of design matrix. Tested with up to 1500 levels of a factor. Results - mean, SD, min. and max. of trait and regressions, F-test, LS-estimates, R2 (determination coef.), T-test.

Variant - ANOVA1. Additive correction for all/significant fixed effects; output - prepares an input file for H2RG.

      5.2. Heritability and genetic correlations - H2RG.

No restriction for sire number, allows missing data, based on Beckers’ methods, input file for selection index.

      5.3. Selection index SI.

Arbitrary number of traits.

      5.4. BLUP sires EPD program (sire model) - SOGO.

Progeny testing for unlimited number of rams and relatively small number of fixed effects.


6. Breeding programs

      6.1. Predicted generation/year genetic gain of cattle and sheep populations with different:

- proportion of population inseminated with young sires;

- number of progenies for estimation of breeding values;

- intensity of selection of young and progeny tested sires (bulls, rams).

6.2. Prediction genetic gain for buffaloes with progeny testing and with MOET without progeny testing.




1. Types of lactation curves in dairy ewes (Dimov, 1986).

Data: One year, 394 first and 355 second lactations, 9 herds, 25 sires, minimum № daughters - 12.


Table 1. Averages


Type of lact. curve

№ observ.

Milk yield in l

Mean (SD)

Lactat. period

Mean (SD)

Max. daily in l

Mean (SD)



170 (21)

236 (16)

1.16 (0.17)



175 (19)

229 (12)

1.26 (0.16)



169 (19)

236 (11)

1.17 (0.19)


Table 2. F-test




Type I

Type II

Type III

Lactat. number

df = 1



26.4 ***

28.0 ***

R2 %





df = 8


3.3 ***

14.8 ***

14.2 ***

R2 %









df = 24



2.0 **

1.9 **

R2 %





- 0.12





2. Non genetic effects on rams’ EPD for milk yield (Dimov, 1992).

Data: 2214 Pleven Black-head dairy ewes, 28 herds, only first lactation, years of birth 1982-85, month of lambing - December - March, minimum 9 daughters.

I c.p. - first control period, e.g. from lambing to I test day - n.s. in the model.

Average yield - 212,7 l (SD 37.6),  Lactation period - 225.7 days (SD 26.2), Yield for standard 200 days period - 200.5 l (SD 36.5).

Terms: Residual variance (MSE) x10-3, SD of EPD (SD epd). Assumed h2 = 0.25



Milk yield for lactation

200 days yield

Model №















Farm (F)















Herd (H)















Year (Y)















Month (M)















Lac. days











































































SD epd






























Correl. with [1]%















So, catch the accurate model. Better to account for lactation length, than to use normal lactation (up to 200 days), corresponding to 305 in cattle.


3. Genetic (co)variances between lactation milk yield and number of peaks of daily yield (Dimov, 1995).

Data: East - Friesian crosses ewes, 714 first and 523 second lactations.

Average yield is 172 l for 238 days and 176 l for 235 days correspondingly.

% of ewes with one peak 29 and 27.

Fixed part of the model - herd-year, month of lambing, number of lambs born, breed of ram (pure IF or IF-cross).

First and second lactations analyzed separately with MT MTDF AM.



First lactation

Second lactation







Milk yield

Peak 1

- 0.27

- 0.11

- 1.00


Milk yield

Peak 2




- 0.01

A tendency for increasing the yield when two peaks are observed.

Not enough data for a more precise study.


4. Persistency of lactation in Pleven Blackhead ewes

Data: 544 ewes.

Persistency = lactation yield/(max. daily yield x lactation period)


Heritabilities and correlations:






1. Lactation yield (LY)





2. Maximum daily yield (MY)





3. Lactation period (LP)





4. Persistency (P)





h2 - on diagonal; rp - above diagonal; rg - below the diagonal


5. Testing selection criterion for dairy rams - maximum lactation yield of the dam

Data: 248 ram lambs,  6245 ewes - relatives and their herdmates, born in 1978 - 1986.

Maximum uncorrected yield of the rams’ dam (MYD) was correlated with EBV based on corrected data for:

-  all lactations of dam,

- first lactation of paternal HS,

- dam and paternal HS,

- combined index - dam, maternal and paternal grandams, half-sisters of the ram, his dam and sire.

 assumed heritability 0.3 and repeatability 0.5.

All data were corrected for the significant (P<0.001) effects of herd/year, month of lambing, first control period and lactation period.


Correlations with MYD






- 0.047

Dam + HS


All six relatives




List of publications of George Dimov


1. Dimov, G. 1979. “Prediction of rams’ breeding value for milk yield. I. Comparison of different sources of information”. Bulgarian Journal of Anim. Sci. XVI, N8.

2. Dimov, G. 1980. “Prediction of rams’ breeding value for milk yield. II. Correlation and regression coefficients among different sources of information”. Bulgarian Journal of Anim. Sci. XVII, N1.

3. Dimov, G. 1980. “Dependence of heritability coefficient from the method of its estimation (for lactation yield in sheep)”. in “ Phenotypic and Genetic Parameters in Sheep”. Ministry of Agriculture. Sofia. 46-49.

4. Hinkovski Tz., A. Alexiev, G. Dimov, D. Nasev. 1982. Results from the red-and-white cattle breed comparison in the P.R. of Bulgaria. FAO-TAC Meeting, Leningrad, USSR.

5. Hinkovski Tz., A. Alexiev, G. Dimov, 1983. Results from the red-and-white cattle breed comparison in the P.R. of Bulgaria. FAO-TAC Meeting, Madrid, Spain.

6. Dimov, G. 1984. “Factors that influence the accuracy of breeding value for sex restricted traits”. Second international conference in Genetics. Bulgarian Academy of Science. Sofia.

7. Dimov G. 1986. Types of lactation curves in Pleven blackhead ewes. III International conference in genetics. Varna, Bulgaria. p.373-376.

8. Stojanov, A. and G. Dimov, 1988. Nutzung Einiger Deutscher Schafrassen zur Herausbildung Der Milchschafzucht in der VRB. In "Zuchtungsmassnahmen zur Leistungssteigerung in der Schafproduktion. Leipzig. Germany. 142-150.

9. Dimov, G. 1989. “Importance of different relatives for prediction of milk yield in dairy sheep”. In “Problems of technological renewal and labor organization in cattle and sheep breeding”. Agricultural Academy. Sofia. 205-210.

10. Dimov, G., Ts. Dimitrov, D. Vassilev, 1990. Expected Genetic Progress Under MOET Buffalo Breeding Scheme. International Symposium on Buffalo Breeding. Shoumen, Bulgaria.

11. Dimov, G., T.Todorov, A.Ignatov. 1990. “Comparative Study of TRU-TEST milk-meters and traditional method for individual milk yield control in dairy cows”. Agricultural Technics. 27:N 8, 45-50.

12. Lazarov, V., G. Dimov. 1991. Multiple trait progeny testing of Bulgarian merino rams. Annual Meeting of EAAP. Berlin.

13. Dimov, G. 1992. “Influence of nongenetic factors on progeny testing of dairy rams for milk yield”. Genetics and Selection. 25, N1, 91-96.

14. Baransky, R., G.Dimov, St. Alexandrov. 1993. “Parameters of milk flow in Black -and White cows”. Bulgarian Journal of Anim. Sci. N5-6, 38.

15. Dimov, G., R.Baransky, St. Alexandrov. 1993. “Influence of level of production and stage of lactation on milk flow of cows, crosses of Black-and-White breed”. Bulgarian Journal of Anim. Sci. N5-6, 44.

16. Dimov, G., J. Keown, L.D.Van Vleck and D. Norman. 1993. Sire by herd interaction for milk and fat yield in California Holsteins. Annual Meeting of American Dairy Science Association. Beltsille. Maryland.

17. Dimov, G., L.D.Van Vleck and J. Keown 1994. Complementarity of variances for yield traits of Holsteins. Annual Meeting of the American Dairy Science Association. July 11-15, Minneapolis, MN.

18. Dimov, G. 1995. “Genetic covariances of lactation milk yield and type of lactation curve in East-Frieseian dairy sheep crosses”. Bulgarian Journal of Anim. Sci. N5-8.

19. Dimov,G., D.Georgiev. 1995. “Selection index of information from the relatives as a selection criteria for dairy ewes”. Bulgarian Journal of Anim. Sci. N5-6.

20. Dimov, G., L. Albuquerque, J. Keown, L.D.Van Vleck and D. Norman. 1995. Variance of Interaction Effects of Sire and Herd for Yield Traits of  Holsteins in California, New York and Pennsylvania with an Animal Model. J. Dairy Sci. 78: 939 - 946.

21. Albuquerque, L. G., G. Dimov, J. F. Keown and L.D. Van Vleck. 1995. Estimates Using an Animal Model of (Co)variances for Yields of Milk, Fat and Protein for the First Lactation of Holstein cows in California and New York. J. Dairy Sci.  78: 1591 - 1596.

22. Dimov, G., J. Keown, L.D.Van Vleck and D. Norman. 1996. Effect of Variance of Interaction Effects of Sire and Herd on Selection for Milk and Fat Yield. J. Dairy Sci. 79: 140 - 144.

23. Kolev,A., G.Dimov. 1996. Effect of semen receiving regime on ejaculate characteristics of Pleven black head dairy rams. Macedonian J. of Reprod. 2: (1), 65-73.

24. Dimov, G. 1995. Persistency as an element of breeding criteria of Pleven black head dairy sheep. 3-rd International conference for Sheep and Goat Production (KOK). Ohrid. Macedonia. 164-169.

25. Dimov,G., D.Vassilev. 1996. Effect of true vs approximate variances on selection for yield traits in Bulgarian Jersey-type Rhodopa cattle. INTERBULL Meeting. Holland. Intrrbull Buletin N 8, 60-65.

26. Dimov, G. 1996. “Persistency of lactation in Pleven Blackhead dairy ewes”. Bulgarian Journal of Anim. Sci. 33: N5, 20-25.

27. Kolev, A., G.Dimov. 1996. Ejaculate characteristics of dairy crosses rams at 7-19 months of age at three regimes of utilization. Bulgarian Journal of Anim. Sci. 33: N6, 25-30.

28. Dimov, G., J.Petrova. 1996. “Short cut method for milk yield control of dairy sheep crosses”. -  Bulgarian Journal of Anim. Sci.

29. Dimov, G. 1996.Testing three methods for simplified milk recording in dairy sheep.” II International Symposium on Sheep and Goats. Ohrid. Macedonia.

30. Kolev,A., G.Dimov, M.Semkov. 1996.Correlation coefficients between volume of ejaculate and some characteristics of sperm production of 9-15 months of age Pleven black-head rams depending on the season and regime of sperm collection”. IV Intrnational Symposium on Reproduction in Sheep and Goats. Ohrid. Macedonia.

31. Dimov, G. 1997. “Models for prediction of individual Breeding Value”. Bulg. J. Anim. Sci. №7-8, 111-115.

32. Kolev, À., G.Dimov. 1996. Morphological changes in ram sperms, stored in absence of germ plasma for 72 hours at 0-4 oC. Research conference. Kostinbrod, Bulgaria.

33. Dimov, G., D.Georgiev, G.Getov. 1999. Prediction of Lactation Yield of Pleven Blackhead Dairy Sheep by Multiple Regression. Bulg. J. of Agric. Sci. N5.

34. Dimov, G., D.Georgiev, G.Getov. 1999. Comparison of milk yield prediction by two and three test day records. Bulg. J. of Agric. Sci. N4.

35. Dimov, G. 1999. Correlation coefficients in milk yield of Pleven black head dairy sheep during suckling, milking and lactation periods. 7-th Conference for ovine and caprine production. Ohrid. 8-11 Sept.

36. Dimov,G., G.Getov. 2000. Influence of suckling period, level of production and age on correlation coefficients among the milk yields for suckling, milking only and lactation periods in Pleven Blackhead sheep. Research Conference. Trojan, Bulgaria. (in Bulgarian.)

37. Gorinov,Y., D.Vassilev, G.Dimov. 2001. Effect of separate test days on milk production of cows. Animal Sci. No.1. (in Blgarian.)

38. Djorbineva,M., G.Dimov. 2001. Influence of genetic and non-genetic factors on milk yield during suckling, milking only and lactation periods in local Stara Zagora sheep. Anim. Sci. No1. (in Bulg.)

39. Dimov, G., Y.Gorinov, D.Vassilev. 2001. Methodical approaches in assessment of test day milk yield of hafers. Animal Sci. No.2. (in Bulgarian.)

40. Vassilev, D., G.Dimov, T.Tsankov. 2002. Direct, maternal and uncorrelated (co)variances for gestation period in Pleven Warmblood mares. 7 World Congress GALP. 19-23 August, Montpellier, France.  05-10.

41. Dimov, G. 2002. Correlations between mixed model estimates of milk yield for suckling, milking only and whole lactation periods in Pleven Blackhead Dairy Sheep. 7 World Congress GALP. 19-23 August, Montpellier, France. 01-54.

42. Dimov,G., M.Djorbineva. 2003. Criteria for determination of first class limits in sheep breeding for milk yield during milking only period. Bulg. J. Animal Sci. No.1-2, 80-82. (in Blgarian.)

43. Dimov,G. 2003. Short cut method for control of milk yield during milking only period in sheep of some dairy breeds  Bulg. J. Animal Sci. No.1. (in Blgarian.).

44. Dimov, G. 2004. Methodical recommendations from INTERBULL for choice of model in assessment of breeding value of the productive traits in dairy cattle. J. Montaneous Agric. N1.

45. Gievski, M., G. Dimov, N. Pacinovski and B. Palasevski (2006) Possibilities for prediction of the test day milk yield based on only one individual test per day in Awassi sheep. 57-th Ann. Meet European Assoc. Anim. Prod., Antalia, Sept. 17-20, 2006. S14, P24


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