ABSTRACT
The aim of the present study was to evaluate variability and haplotype structure of twenty-eight single nucleotide polymorphisms (SNPs) at myostatin (MSTN), insulin-like growth factor 1 (IGF1), and bone morphogenetic protein 2 (BMP2) genes. Association between the polymorphic SNPs and morphometric traits was performed on a population of 263 Tunisian goats. The SNPs analyzed were all polymorphic (except one), and the three genes had different haplotype structures. Significant association of SNPs at MSTN with head length was highlighted in the Tunisian goats. The variability at IGF1 gene was associated with body length, ear length, tail length, and chest depth. For BMP2, significant association was revealed with chest depth. Significant association was also detected between linkage disequilibrium (LD) block 2 at IGF1 with body length. These findings might play a potential role in gene-assisted programs.
Subject(s)
Goats , Insulin-Like Growth Factor I , Animals , Insulin-Like Growth Factor I/genetics , Goats/geneticsABSTRACT
This study was conducted to (1) estimate Wood's incomplete gamma function parameters (a, b and c) for individual registered Tunisian Holsteins in the 3 first lactations; (2) estimate persistency (Per), peak time (PT), peak yield (PY) and 305-day lactation milk yields (Y305); (3) estimate the genetic parameters of the predicted traits and (4) evaluate the genetic trend of the most heritable traits. Pedigree data and 380,709 test-day milk records of 20,758 Holstein cattle collected from 2008 to 2018 in 33 herds were analyzed. Initially, Wood's incomplete gamma function parameters were determined and subsequently along with some production characteristics (Per, PT, PY and Y305). Each estimated trait was subjected to a single trait animal model to estimate genetic parameters using MTDFREML program (Boldman et al. 1995). Multivariate animal model was used to estimate genetic and phenotypic correlations between the most heritable traits and their breeding values (EBVs). Genetic trends were defined using BREEDPLAN multi-trait EBVs by averaging the EBV of all animals born by year of birth. The resulting heritability estimates varied from 0.04 to 0.06 for Per, 0.01 to 0.02 for PT, 0.08 to 0.16 for PY and 0.09 to 0.16 for Y305. The greatest heritabilities were within the first lactation for PY and Y305 traits. Genetic and phenotypic correlations were very high between the most heritable two traits (0.91 and 0.83, respectively). Heritability estimates of PT and Per were close to zero indicating that these traits are more influenced by the management and the environment. The regression coefficients, relative to the genetic trend graph, mark an overall rate of increase of 13.18 kg/year and 0.056 kg/year in Y305 and PY, respectively, over 16-year period. A number of policies should be developed by the Tunisian government to attend better genetic progress.
Subject(s)
Lactation , Milk , Animals , Cattle/genetics , Female , Lactation/genetics , Parturition , Phenotype , PregnancyABSTRACT
This study analyzed the genetic variability, inbreeding and population structure of the Tunisian-North African dairy sheep breed, the Sicilo-Sarde (SS), created by crossing the Sarda and Comisana dairy breeds. The level of variability in the SS, considered as an endangered breed after a dramatic decrease, was assessed using 17 microsatellite markers by analyzing the two breed populations sampled from their respective cradles: SS of Beja (SSB, n = 27) and SS of Mateur (SSM, n = 25). High levels of genetic diversity in SS were revealed, with a total of 212 alleles, a high mean number of alleles (12.47 ± 4.17) and a high average polymorphism information content (PIC) (0.81 ± 0.10). The observed heterozygosity was considerable in SSB and SSM (0.795 and 0.785, respectively). The inbreeding level measured by the population inbreeding coefficient FIS is higher in the SSM population (0.121) than in the SSB population (0.090). The higher genetic diversity level detected in SSB reflected the effect of new Italian Sarda genes introduced by intra-uterine artificial insemination recently practiced in this population. The Wilcoxon test and the mode-shift distribution indicated that the SS breed is a non-bottlenecked population. The structural analysis reflected the historical miscegenation practiced during the breed creation and highlighted further ancient miscegenation, which could date back to the first waves of sheep introduction to the western Mediterranean region. Microsatellite markers were successfully applied in the assessment of the genetic variability of SS and should be used in monitoring this variability during the application of conservation strategies.
