Effect of parity (PA), stage of lactation (SL) and interaction of PA x SL on daily milk yield (DMY), composition (contents of total solids, fat, total protein and lactose) and quality (somatic cell and bacteria counts) of organic sheep milk were evaluated using 20 ewes of East Friesian which were reared on an organic farm in Habří. Ewes were on the 2nd (n = 10) and 3rd (n = 10) lactation. During the experiment ewes were reared on permanent pasture. The milk records and samplings were carried out on average 75th, 132th and 190th day of lactation. All parameters were determined by standard methods. The PA had a significant effect only on somatic cell count (SCC). On the other hand, SL had a significant effect on daily milk yield (DMY), contents of total solids (TS), total protein (TP) and lactose (L). The SL also had a significant effect on total bacteria count (TBC), psychrotrophic bacteria count (PBC), total coliform count (TCC) and SCC. The interaction of the PA x SL had a significant effect on DMY, TS and TP contents and PBC. Positive and significant correlations were found among the SL and contents of TS and TP. Significant and positive correlation was observed between the PA and SCC, but on the other hand, significant and negative correlation was found between the SL and SCC.

The aim of the study was to evaluate the eff ect of diff erent crossbreeds (CB) of Lacaune (LC) and East Friesian (EF) breeds (LC 50 EF 50, LC 75 EF 25 and LC 87.5 EF 12.5) on daily milk yield (DMY) and basic milk composition (contents of total solids (TS), fat (F), protein (P), casein (C) and lactose (L) for the whole lactation. The evaluation of the interactions between CB and parity (PA) and between CB and litter size (LS) on above mentioned indicators was also an integral part of this study. The study was carried out on the organic farm in Valašská Bystřice. The factor of CB had a signifi cant eff ect only on DMY and contents of P and C for the whole lactation whilst the higher proportion of LC breed in genotype, the higher DMY and the lower P and C contents. The CB x PA had a signifi cant eff ect on all indicators except for the lactose content when in all CB the DMY increased with the increase of the lactation number. On the other hand, in all CB the contents of TS, F, P and C were relatively very variable depending on the parity. Lastly, as for the interaction between CB and LS, the ewes with twins produced signifi cantly more milk compared to ewes with singles and these ewes had also signifi cantly higher contents of P and C and not signifi cantly higher contents of TS and F.

Evaluation of milk yield, composition and quality of organic milk of crossbreeds of Lacaune (L), East Friesian (EF) and Improved Wallachian (IW), (n = 10, L 50 EF 43.75 IW 6.25) during lactation was carried out on organic farm in Valašská Bystřice in 2007. All sheep were on the third lactation and during study they were reared on permanent pasture. The stage of lactation (SL) had a highly significant effect on milk yield (MY) and contents of total solids (TS), fat (F), protein (P), casein (C), lactose (L) and urea (U). The SL had also a highly significant effect on pH and titrable acidity (TA), whereas on rennet clotting time (RCT) the SL had a significant effect. On the other hand the SL had not a significant effect on somatic cell counts (SCC) and rennet curd quality (RCQ). The highest contents of TS, F and C were found at the end of the lactation, whereas their lowest contents were found on the 120th day. Between the second and the last sampling the lactose content decreased. The content of U and RCT were the most variable indicators whithin the frame of our study. On the other hand SCCs were, during the whole lactation, very well-balanced and relatively low. Between pH and SCC was found positive correlation. TA gradually increased and RCT gradually prolonged with advanced lactation.