Dairy sheep farming relies on the capacity to maximize milk yield and solids output concurrently with excellent fertility parameters. However, productive and reproductive performances are known to be antagonistically correlated from a genetic point of view, suggesting that selecting only for yield output can potentially decrease the genetic merit for fertility over time. Therefore, the aim of the present study was to identify sources of phenotypic variation and to estimate genetic parameters for fertility traits in two Italian dairy sheep. Data were collected between 2015 and 2020 in the ASSONAPA nucleus herd of Comisana and Massese breeds located in Asciano (Siena, Italy). The following phenotypes were investigated: the number of total born lambs, born-alive lambs, stillborn lambs, weaned lambs as well as stillbirth (stillborn lambs/total born), and survival (weaned lambs/total born). Data were analysed separately by breed and within breed by physiological status (primiparous and multiparous ewes). Fixed effects included in the linear mixed model were age and year at first lambing (only primiparous), lambing order and year of lambing (multiparous). Season of lambing fixed effect was included only for Massese (lamb) ewes. Additive genetic, permanent environment (for ewes), and the residual were fitted as random terms. Inbreeding coefficients were computed for each individual from pedigree data. Heritability estimates in lamb ewes ranged from 0.03 (Massese stillborn lambs) to 0.06 (Comisana born-alive lams). Heritability of ewe fertility traits was greater, varying from 0.07 (Massese weaned lambs) to 0.15 (Comisana total born lambs). Inbreeding coefficients were below 0.10 in almost all individuals for both breeds. Although the magnitude was not very large, genetic variation does exist for almost all fertility traits. These results suggest the inclusion of reproductive performance in an aggregate selection index for Comisana and Massese breeds.
V. Floridia, G.B. (2022). Genetic and nongenetic variation of fertility parameters in Comisana and Massese sheep. EAAP scientific committee.
Genetic and nongenetic variation of fertility parameters in Comisana and Massese sheep
G. Buonaiuto;L. M. E. Mammi;G. Visentin
2022
Abstract
Dairy sheep farming relies on the capacity to maximize milk yield and solids output concurrently with excellent fertility parameters. However, productive and reproductive performances are known to be antagonistically correlated from a genetic point of view, suggesting that selecting only for yield output can potentially decrease the genetic merit for fertility over time. Therefore, the aim of the present study was to identify sources of phenotypic variation and to estimate genetic parameters for fertility traits in two Italian dairy sheep. Data were collected between 2015 and 2020 in the ASSONAPA nucleus herd of Comisana and Massese breeds located in Asciano (Siena, Italy). The following phenotypes were investigated: the number of total born lambs, born-alive lambs, stillborn lambs, weaned lambs as well as stillbirth (stillborn lambs/total born), and survival (weaned lambs/total born). Data were analysed separately by breed and within breed by physiological status (primiparous and multiparous ewes). Fixed effects included in the linear mixed model were age and year at first lambing (only primiparous), lambing order and year of lambing (multiparous). Season of lambing fixed effect was included only for Massese (lamb) ewes. Additive genetic, permanent environment (for ewes), and the residual were fitted as random terms. Inbreeding coefficients were computed for each individual from pedigree data. Heritability estimates in lamb ewes ranged from 0.03 (Massese stillborn lambs) to 0.06 (Comisana born-alive lams). Heritability of ewe fertility traits was greater, varying from 0.07 (Massese weaned lambs) to 0.15 (Comisana total born lambs). Inbreeding coefficients were below 0.10 in almost all individuals for both breeds. Although the magnitude was not very large, genetic variation does exist for almost all fertility traits. These results suggest the inclusion of reproductive performance in an aggregate selection index for Comisana and Massese breeds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
