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 Fi nnsheep (F) and Lamon (L) rams, a local Alpine Italian breed, to F, L, F x L and L x F ewes, with the aim of estimating breed direct, breed maternal, individual heterosis and maternal heterosis effects on litte r traits and ewe productivity. Most differences between F and L were f or maternal genetic effects, whereas differences in additive genetic e ffect 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 (+.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). Ev en 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 der ived ewes induced heavier litter per ewe mated (+6.7 kg, P < 0.10). Ne arly all heterosis estimates were positive and relevant. Individual he terosis 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, espe cially on a per ewe mated basis (respectively +0.30, P < 0.10 and +0.2 8 for litter size at weaning), and their effects on litter weight at w eaning 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 la mbs (individual heterosis) and on ewes (maternal heterosis).