Genetic variability of�six�French meat sheep breeds in�relation to�their genetic management

Abstract

-Some demographic parameters, the genetic structure and the evolution of the genetic variability of six French meat sheep breeds were analysed in relation with their management. Four of these breeds are submitted to more or less intense selection: the Berrichon du Cher (BCH), Blanc du Massif Central (BMC), Charollais (CHA) and Limousin (LIM); the other two breeds are under conservation: the Roussin de La Hague (RLH) and Solognot (SOL). Genealogical data of the recorded animals born from 1970 to 2000 and of their known ancestors were used. The most balanced contributions of the different flocks to the sire-daughter path was found in the SOL. In the BCH, a single flock provided 43% of the sire-AI sire path, whereas the contributions of the flocks were more balanced in the BMC and LIM (the only other breeds where AI is used to a substantial amount). The distribution of the expected genetic contribution of the founder animals was found to be unbalanced, especially in the BCH and LIM. The effective numbers of ancestors (founders or not) for the ewes born from 1996 to 2000 were equal to 35 (BCH), 144 (BMC), 112 (CHA), 69 (LIM), 40 (RLH) and 49 (SOL). Inbreeding was not analysed in the BMC, due to incomplete pedigree information. From 1980 on, the rates of inbreeding, in percentage points per year, were +0.112 (BCH), +0.045 (CHA), +0.036 (LIM), +0.098 (RLH) and +0.062 (SOL). The implications of the observed trends on genetic variability are discussed in relation to the genetic management of each breed. The need for a larger selection * Corresponding author: verrier@inapg.fr 638 M. Huby et al. basis in the BCH, the efficiency of the rules applied in the SOL to preserve the genetic variability and the need for a more collective organisation in the CHA and RLH are outlined. genetic variability / inbreeding / selection schemes / conservation programmes / sheep

Combining microsatellite and pedigree data to estimate relationships among Skyros ponies

“…This parameter is often considered as the best criterion to characterize the quality of the pedigree information Baumung and Sölkner 2003). The geq was computed for each animal as the sum of (1/2) n , where n is the number of generations separating the individual from each known ancestor (Huby et al 2003 (Dimsoski 2003).…”

Lack of relationship between Visna/maedi infection and scrapie resistance genetic markers

“…Differences in the genotype frequencies between these studies could be due to the small sample size in the study by Acín et al (2004) and may also reflect variability in implementing the scrapie selection criteria in the flocks studied. Moreover, variability of certain characters or genes may not be easily comparable between populations (Huby et al, 2003). The distribution of the PRNP genotypes (or haplotypes) varies between the different Aragon sheep breeds and therefore, we can only compare our data with those reported for the Rasa Aragonesa breed (Acín et al, 2004).…”

Impact of strong selection for the PrP major gene on genetic variability of four French sheep breeds(Open Access publication)

“…80%, before the PrP selection programme started. It was also the breed with one of the worst situations in terms of genetic variability due to the very limited size of the selection nucleus, the lack of management of the genetic variability and the intensity of the selection processes [8]. The CDL breed had the lowest initial ARR frequency (15%), and strong efforts to select for scrapie resistance were made, due to the high prevalence of the disease in its breeding area.…”

“…The CHL breed showed the highest evolution of PrP frequencies among the French sheep breeds considering both the VRQ and the ARR alleles. This breed was also characterised by a large population size, weak selection procedures and favourable genetic variability criteria as defined by Huby et al [8], although no specific rules for managing the population were applied. The MTR breed had a low initial ARR frequency (16%) and the highest prevalence of scrapie.…”