Effect of somatic cell count on ewe's milk composition, its properties and the quality of rennet curd

The evaluation of the effect of somatic cells count on ewe’s milk composition, its properties and on the quality of rennet curd was carried using milk samples obtained from a total 10 ewes F112 crossbreeds of Lacaune (L), East Friesian (EF) and Improved Wallachian (IW), reared on a ecological sheep farm in Valašská Bystřice. All ewes were on the 1st  lactation, in good nutritive condition and clinically healthy. The sampling was carried on 47th, 81st, 123rd, 152nd and 189th day of lactation. The analysis involved a total of 50 milk samples, which were categorized into 5 different SCC groups: 1st group (≤ 10 000 SC/ml), 2nd  group (11 000–50 000 SC/ml), 3rd  group (51 000–100 000 SC/ml), 4th  group (101 000–200 000 SC/ml), 5th  group (≥ 201 000 SC/ml). Milk composition and milk properties were determined by standard methods. For the evaluation of the quality of rennet curd (class quality) was used following scale: 1st  class – very good and hard curd, 2nd  class – good curd, 3rd  class – bad curd, 4th  class – very bad curd, 5th class – no or invisible flocculation of casein. Recorded data were statistically analyzed using the classical least squares method (SAS; PROC GLM variant ss4). The SCC had a significant effect on all components of milk under study. The lowest contents of total solids (TS), fat (F), solids non-fat (SNF), protein (P) and casein (CN) were found in the group with the highest SCC (5th group). On the other hand, the highest contents of all above-mentioned milk components were found in the group with the lowest SCC. The significantly lowest content of lactose (4.42 %) was found in the group with the lowest SCC. The SCC had also significant effect on pH and titrable acidity. However on the other hand SCC had not a significant effect on rennetability and rennet curd quality (RCQ). The highest value of pH was found in the 5th group (the highest SCC). Titrable acidity has decreased from 10.10 °SH to 8.66 °SH depending on growth of SCC. The longest rennetability (257 s) was found in the group with the highest SCC. The best RCQ (class: 1.90) was found in the group where SCC per1 ml of milk ranged from 51 000 to 100 000. On the other hand the worst RCQ (class: 2.28) was found in the group with the lowest SCC.