Chemical composition and biological protein value of milk of Tsigai sheep and their F2 cross-breeds of Chios

The composition of milk was studied from purebred Tsigai sheep and F2 cross-breeds with Chios breed from 4th to 6th month of lactation, raised on a mountain pasture. The chemical analysis samples were taken from each sheep in the period of April-June. The content of fat, protein and amino acids was determined in individual samples and total sample formed by the milk yield from all animals, proportional to the daily milk yield from each individual. There is a tendency for higher milk yield and content of total protein and casein in milk of F2 cross-breeds of Chios in comparison with Tsigai sheep. Milk sheep from F2 crossbreeds of Chios had higher content of Lysine, as well as glutamic acid, methionine and leucine, in comparison to that form Tsigai sheep, respectively: 0.458±0.011. 1.389±0.040. 0.084±0.005 and 0.572±0.013. The milk chemical index in both groups of sheep was comparatively low and it constituted respectively 38.3% in Tsigai sheep and 35.4% in F2 cross-breeds, as a result of low concentrations of methionine and cysteine in milk. Biological value of milk obtained from Tsigai breed sheep and F2 milk cross-breeds of Chios had close values - respectively 92.01 and 91.87%. Results showed that the sward composition and the vegetation stage had an influence over the essential amino acids content in purebred Tsigai sheep and their cross-breeds with Chios breed

**Original scientific paper

Abstract: Study of the skin histological structure in ewes fro

SHEEP BREED**

**Original scientific paper Abstract: The study was carried out during the grazing period (April-July) with a group of 5 local sheep of the Srednostaroplaninska breed in 3 rd lactation. The following system of animal raising was used: grazing on a mountain pasture (April and May), supplementation in April and alpine grazing on high-mountain pastures (June and July). Samples were taken every month during milking period (April-July). Chemical composition of milk and amino acid composition of protein were studied by ion exchange column chromatography. The objective of the study was to determine the chemical composition and biological protein value of milk from Srednostaroplaninska sheep breed. The amino acid content in milk protein, namely glutamic acid, proline, lysine, alanine, valine and serine, increased with advance of lactation period, whereas that of the limiting amino acid methionine decreased and subsequently increased till the end of the period. The protein of milk from the Srednostaroplaninska breed had an index of 35.35 % and a biological value of 90.8 %. The sward type and vegetation stage exerted an influence on the content of essential amino acids, biological value and chemical index of protein of sheep’s milk

Fatty acid composition of milk fat in milk of Tzigay sheep and their F2 cross-breeds with chios

The study was conducted on aggregate milk samples, which were taken every month during the milking period from Tzigay sheep and their F2 cross-breeds of Chios, raised in the conditions of the Central Balkan Mountain. The fat extraction of milk samples was done by the Rose-Gottlieb method. Fatty acid composition was determined on a gas chromatograph with flame ionization detector and capillary column. The aim of the study was to follow the changes in the composition of fatty acids in the milk fat of milk of Tzigay sheep and their F2 cross-breeds. The saturated fatty acids in milk of the two groups had high values during both consecutive years, as they varied from 67.05% in milk of Tzigay sheep in the second lactation up to 70.87% at their F2 cross-breeds. The content of myristic acid was correspondingly 8.22-8.88% at Tzigay sheep and 8.45-8.74% at their F2 cross-breeds. The total amount of polyunsaturated fatty acids in the examined milk for the two types of sheep was comparatively low with near concentrations (4.39-5.20%) in the period of the two years. The milk of the two groups had high values of the correlation SFA/PUSFA (15.71 and 13.17) and low values of PUSFA/SFA (0.06-0.08). Monоunsaturated fatty acids, represented mainly by the oleic acid (C18:1) varied during both periods from 21.92% to 25.32% and appeared as a substratum in the synthesis of CLA. The short-chain fatty acids (C4:0-C11:0) had higher values in Tzigay sheep in comparison with F2 cross-breeds of Chios. The long-chain fatty acids (C17iso-C25:0) maintained close concentration in the milk of Tzigay breed, while their content in the milk of F2 cross-breeds was increased