The aim of the study was evaluated the effect of chosen factors (sex, litter size, year of the study) on the growth of lambs crossbreeds with using Suffolk (Sf) in the sire position. In the mother position there were used following genotypes: Charollais (Ch), Sf 50 Ch, Improved Wallachian (IW) and IW 50 Sf. The evaluation was carried out during two successive years (2004–2005) on the farm Růžďka and involved altogether 141 lambs. The growth of lambs was evaluated in the following crossbreeds: Ch 50 Sf (n = 38), Sf 75 Ch (n = 40), IW 50 Sf (n = 29) and Sf 75 IW (n = 34). All lambs were born indoor in the period from January until the end of first decade of February. Lambs were kept indoor till the end of the study. Genotype had significant effect (P ≤ 0.01) only on birth weight. The highest daily gain (DG) from birth to 100 days of age (201 g) and the highest body weight (BW) at 100 days of age (24.26 kg) were found out in IW 50 Sf. Effect of sex had highly significant effect (P ≤ 0.01) only on birth weight and significant effect (P ≤ 0.05) only on BW at 100 days of age. Litter size was the most important factor that influenced the growth of lambs whereas this factor highly significantly (P ≤ 0.01) influenced all parameters under study excerpt the DG between 70 and 100 days of age. Monitoring year had highly significant effect (P ≤ 0.01) on BW at 100 days of age and on daily gains between 70 and 100 days of age and between birth and 100 days of age.

The main aim of the study was the evaluation of the growth, meatiness and fattiness in vivo in lambs (n = 122) of chosen breeds (CH: Charollais and T: Texel) and crossbreeds (CH x Sf (Suffolk), CH x T, EF (East Friesiane) x CH and EF x T. Whithin the frame of this study were also evaluated the effects of sex (S), litter size (LS), age of the dams (AD) and year of the observation (YO) on aforementioned indicators. The study was carried out on the farm in Kunčice pod Ondřejníkem during the years 2004 and 2005. Within the scope of evaluation of meatiness and fattiness in vivo in lambs the following ultrasound measurement were carried out: area (Am.l.l.t., in cm2) and depth (Dm.l.l.t., in mm) of musculus longissimus lumborum et thoracis (m.l.l.t.) and fat thickness (FT, in mm). Genotype had a significant effect on body weight at birth and on daily gains (DGs) from 30 to 100 days of age and from birth to 100 days of age. Sex had a significant effect on most of body weights under study and on DGs from birth to 30 days of age, from 30 to 70 days of age and from birth to 100 days of age. The LS, AD and YO had a significant effect on most of growth indicators under study. Genotype had a significant effect on Am.l.l.t. at the age of 70 days, Dm.l.l.t. and FT at the age of 100 days. The S had a significant effect on Dm.l.l.t. and Am.l.l.t. at the age of 70 days and on Am.l.l.t. at the age of 100 days. The LS and YO had a significant effect on most of indicators of meatiness and fattiness in vivo under study. On the other hand only the AD had not significant effect on all parameters of meatiness and fattiness.