Assessing the genetic diversity in small farm animal populations.

Genetic variation is vital for the populations to adapt to varying environments and to respond to artificial selection; therefore, any conservation and development scheme should start from assessing the state of variation in the population. There are several marker-based and pedigree-based parameters to describe genetic variation. The most suitable ones are rate of inbreeding and effective population size, because they are not dependent on the amount of pedigree records. The acceptable level for effective population size can be considered from different angles leading to a conclusion that it should be at least 50 to 100. The estimates for the effective population size can be computed from the genealogical records or from demographic and marker information when pedigree data are not available. Marker information could also be used for paternity analysis and for estimation of coancestries. The sufficient accuracy in marker-based parameters would require typing thousands of markers. Across breeds, diversity is an important source of variation to rescue problematic populations and to introgress new variants. Consideration of adaptive variation brings new aspects to the estimation of the variation between populations.

Variation in direct and maternal genetic effects for meat production traits in Egyptian Zaraibi goats.

Multi-trait analyses were carried out to quantify the (co)variation in meat production traits in Zaraibi goats. The data were obtained from a research station. There were birth weight records on 6610 kids, of which 5970 and 5237 had also pre-and postweaning gain record, respectively. The kids were progeny of 115 bucks and 1387 does, which had altogether 3603 litter size and milk yield records in different parities and which were daughters of 109 sires and 721 dams. Single-trait analyses were carried out as preliminary to a three-trait (litter size, birth weight, early growth) and five-trait (litter size, milk and growth traits) analyses. The analyses containing birth weight data required the highest number of iteration rounds in estimating the variance components using AI REML. The maternal genetic component was important for the genetic variation of birth weight and preweaning gain. In general, direct heritability was low (0.03-0.12) for growth traits, possibly due to the low-input environment. The estimates on genetic correlation between direct and maternal effects within these traits indicated mostly favourable relationship. Genetic antagonism was found between birth weight and early growth. Heritability (repeatability) for 90-day and total milk yield was 0.16-0.23 and 0.23-0.24 (0.28 and 0.39-0.40), respectively and 0.04-0.05 (0.10-0.11) for litter size. The genetic correlation between 90-day (total) milk yield and litter size was 0.45 (0.22). The correlation between the milk yield and the maternal genetic effects for the preweaning gain was very high (0.94). Selection schemes aiming to improve meat (litter size and growth) and milk production simultaneously are feasible. The increased milk production serves also for the acceleration of early growth in kids.

Genetic diversity in Egyptian and Italian goat breeds measured with microsatellite polymorphism.

Seven microsatellite markers were used to study genetic diversity of three Egyptian (Egyptian Baladi, Barki and Zaraibi) and two Italian (Maltese and Montefalcone) goat breeds. The microsatellites showed a high polymorphic information content (PIC) of more than 0.5 in most of the locus-breed combinations and indicated that the loci were useful in assessing within- and between-breed variability of domestic goat (Capra hircus). The expected heterozygosity of the breeds varied from 0.670 to 0.792. In the geographically wider distributed Egyptian Baladi breed there were indications for deviations from random breeding. Analysis of genetic distances and population structure grouped the three Egyptian goat breeds together, and separated them from the two Italian breeds. The studied Mediterranean breeds sampled from African and European populations seem to have differentiated from each other with only little genetic exchange between the geographically isolated populations.