5 Maataloustieteellinen A ikakauskirja Vol. 60: 511—514, 1988 Effect of Finnsheep crossbreeding on Lamon sheep performance: in vivo traits' G. BITTANTE and E. PASTORE Istituto di Zootecnica Universitä di Reggio Calabria P.zza S. Francesco. 7 89100 REGGIO CALABRIA (Italy) Istituto di Zootecnica Universitä di Padova Via Gradenigo, 6 35131 PADOVA (Italy) Abstract. The objective of this trial was the comparison of the in vivo traits of Lamon (L), a local meat breed of the Eastern Italia Alps, and Finnsheep X Lamon (F x L) fattening lambs. Forty-one lambs (25 L and 16 F x L) of both sexes were weaned at 8 weeks of age and fattened for 14 weeks. The diet (11,6 MJ/kg d.m. M.E.) consisted of maize silage ad lib., 200 g/d of dried sugar beet pulp, 150 g/d of soybean meal and 30 g/d supplement. F x L lambs grew slightly more than L lambs (197 vs 176 g/d; P < .1) during the suckling period but not during the fattening period (207 vs 203 g/d; n.s.), reaching a slightly higher slaughter weight (36.9 vs 35.5 kg; n.s.). Crossbred lambs consumed, during fattening, slightly more d.m. (75.9 vs 73.1 g ■ d-' • kg-> • L.W. 75) and M.E. (.88 vs .85 MJ • d-' • kg- 1 ■ L.W. 75). D.M. conversion was not different (4.24 vs 4.16; P > .1) while M.E. requirements for growth, esti- mated assuming a maintenance requirement of .44 MJ • d~' ■ kg-' ■ L.W. 7S, resulted higher (+7 %) for Fx L than for L lambs (2.18 vs 2.04 MJ • kgDG • kg-1 • L.W. 75 ; P < .1). The ram-lambs showed superior growth potential and feed efficiency in respect to the ewe-lambs. In conclusion it appears that crossbreeding with Finnsheep is not detrimental to the in vivo performance of fattening Lamon lambs except for a slight increase of the energy requirements for growth. Index words: Finnsheep, Lamon, crossbreeding, fattening performance, growth, feed efficiency Introduction Among the Italian sheep breeds, the Lamon (L) breed belongs to the Alpine group. It is characterized by large size (wither height: Reasearch project founded by Regione Veneto. 80—85 cm for the rams and 70—75 cm for the ewes; live weight: 100—120 and 65—70 kg, respectively for males and females), medi- um prolificacy (1.2 —1.6), high birth weight (singletons 4—6 kg, twins 3—5 kg), good growth potential during suckling (200—250 511 JOURNAL OF AGRICULTURAL SCIENCE IN FINLAND g/d) and during fattening (from 200 g/d with diet with a moderate energy concentration to 350 g/d with all concentrate diets), low at deposition rate and average muscularity of the carcass (2, 6,7, 11). Crossing with Finnsheep (F) has shown to be an effective method of increasing the prolificacy of L ewes, the average value of the crossbred ewes is 2.4 lamb per parturition (3), but concern has been expressed about growth potential, feed efficiency and slaughter traits of crossbred lambs (5). The objective of this preliminary trial is to compare the in vivo performance of purebred L and crossbred F X L lambs. Malerial and methods The trial was carried out at the »Legnaro» Experimental Farm of the Padua University on 41 lambs (singletons) born in January 1987 from L ewes bred to 4 L rams (25 lambs-L) or 4 F rams (16 lambs—F X L); 17 of the lambs were males (9 L and 8 F x L) and 24 were females (16 L and 8 F x L). The lambs were suckled by their mothers for 57 ± 6 days and had no access to creep feed. During this phase the ewes and lambs were maintained in confinement in an open barn and the ewes’ diet consisted of maize si- lage ad lib. plus a limited amount of wheat straw (250 g/d), ensiled brewers grains (1000 g/d), soybean meal (150 g/d) and a vitamin mineral supplement (60 g/d). At weaning the lambs were placed in wood- en cages 1.2 x 1.4 m in a closed barn and offered 200 g/d of dried beet pulps, 150 g/d soybean meal, 30 g/d vitamin-mineral supple- ment and maize silage ad lib. The feedstuffs offered and orts were weighed daily and sam- pled weekly for chemical analysis (table 1) car- ried out according to the A.O.A.C. (1) methods. The metabolizable energy (M.E.) content of the feedstuffs was estimated on the basis of the proximate analysis, and of the digestibili- ty coefficients of feedstuffs obtained at the Experimental Farm (2) by applying the equa- tion of Hoffmann and Schiemann (8). The M.E. requirement for growth was estimated by subtracting from the M.E. daily intake the maintenance requirement which was assumed to be .44 MJ/kg L.W. 75 (10), and was ex- pressed as MJ of M.E. per kg of weight gain per kg of metabolic weight (L.W. 75 ). The fattening phase ended after 14 weeks with the slaughtering of lambs. The daily gain was calculated on the basis of the fortnightly weighings of the animals. All experimental data except birth weight were analyzed according to the following lin- ear model (SPSS/PC): Y ijk =H+Gi + Sj + GSu + b(A W ijk-AW) + E iJk where: Yijk = experimental datum; p = general mean; G| = fixed effect of the i,h geno- type (1 = L; 2 = F x L) Sj = fixed effect of the jth sex (1 =