Effects on fertility and litter traits under accelerated lambing scheme in crossbreeding between Finnsheep and an Alpine sheep breed

Analyses were conducted on data from 217 litters produced by mating Finnsheep (F) and Lamon (L) rams, a local Alpine Italian breed, to F, L, F × L and L × F ewes, with the aim of estimating breed direct, breed maternal, individual heterosis and maternal heterosis effects on litter traits and ewe productivity. Most differences between F and L were for maternal genetic effects, whereas differences in additive genetic effect were not significant for most traits. Finnsheep maternal effect improved pregnancy rate, particularly at synchronized estrus (+46%, P < 0.05) and litter size both per ewe lambing (+0.86, P < 0.05, and +0.60 at birth and at weaning respectively) and per ewe mated (+1.04, P < 0.05, and +0.67, P < 0.10, at birth and at weaning, respectively). Even though F maternal effect decreased average lamb weight at birth (−2.5 kg, P < 0.01) and at weaning (−1.6 kg), higher prolificacy of F derived ewes induced heavier litter per ewe mated (+6.7 kg, P < 0.10). Nearly all heterosis estimates were positive and relevant. Individual heterosis affected pregnancy rate, particularly at synchronized estrus (+17%,P < 0.05), and litter viability (+12%, P < 0.10). Individual and maternal heterosis improved litter size at birth and at weaning, especially on a per ewe mated basis (respectively +0.30, P < 0.10 and +0.28 for litter size at weaning), and their effects on litter weight at weaning per ewe mated were substantial (respectively +4.4 kg, P < 0.05, and +2.3 kg). In conclusion the highest improvement of saleable lambs from crossbreeding of Italian Alpine meat sheep with Finnsheep can be obtained by the adoption of mating schemes which allow to exploit the genetic potential of Finn as maternal line and heterosis effect on lambs (individual heterosis) and on ewes (maternal heterosis).