The effect of genotype and lactation on yield and physicochemical properties of ewe milk

Two genotype of sheep have been utilized in the conduct of the experiment composed of 60 ewes from Pirot x Virtemberg as genotype 1 and 60 ewes of Improved Pirot as genotype 2. All the ewes were reared under identical conditions and without any differences in nutrition and management during the whole period under study. The collection of Milk sampling was done in morning and evening during periods (1, 2, 3) of lactation duration. The average lactation duration and average total milk of the two genotypes were very close and has a minimal difference of 0.467 day and 1.562 kg, in favor of genotype 2. The differences between genotypes were not significant (P>0,05). Regarding physical and chemical properties of milk for both genotypes, the difference were very minimal such as follows; viscosity Pa x s - 0.006, electrical conductivity ? - 0.018, density kg/m3 -0,001, freezing, t 0C - 0.013, LD number - 0.028 total solids, % - 0.014, fat,% - 0,026, protein,% - 0.085, lactose,% - 0.038, ash,% - 0,021, acidity, 0SH - 0.209. The results indicated that the properties of milk for both genotypes were very near to each other. It can be interpreted that the breeds utilized in the experiment were comparable due to similar characteristics perhaps. The effect of genotype was very significant only for the % protein of the milk. The lactation periods were highly significant in all physical and chemical properties of milk.