Effects of ventilation rate and of dietary protein level in an intensive dairy sheep system on the features of Canestrato Pugliese cheese were studied. Cheeses were manufactured from the bulk milk obtained from ewes subjected to four different experimental treatments: (1) low dietary crude protein (CP) of 13% in dry matter (DM) at a low ventilation rate (23·5 m3/h per ewe) (LPLV); (2) low dietary CP at a moderate ventilation rate (47 m3/h per ewe) (LPMV), (3) moderate dietary CP of 16% DM at a low ventilation rate (MPLV); and (4) moderate dietary CP dietary at a moderate ventilation rate (MPMV). Bulk milk and cheeses (at 1, 15, 45 and 90 d of ripening) were analysed for chemical composition, N fractions and plasmin-plasminogen activities. The pH 4·6-soluble and insoluble N fractions were analysed by urea-PAGE. Bulk milk from ewes receiving the low CP diet displayed higher casein and lower urea contents. Ewes subjected to the low ventilation rate displayed a higher plasminogen activity in milk, whereas no differences emerged among treatments in the conversion of zymogen to plasmin. During ripening the plasmin-plasminogen system in cheese did not display significant changes across treatments. At 90 d of ripening, the cheese produced with milk from ewes receiving the low CP diet and exposed to the low ventilation rate displayed more markedly stained bands in the area of γ-caseins in pH 4·6-insoluble N fraction. As from 15 d of ripening, the pH 4·6-soluble fraction showed a greater number of bands in the LPMV and MPMV than in the LPLV and MPLV cheeses. The results showed that Canestrato Pugliese cheese manufactured with milk from ewes fed the low CP diet and exposed to the moderate ventilation rate was characterized by higher protein and casein content in the fresh cheese and by a greater proteolysis after 90 d of ripening.

The influence of three different ventilation regimens on air pollution in sheep houses and on the quality of ewe milk and of Canestrato Pugliese cheese was investigated during the summer season. The experimental treatments were low ventilation regimen (VR=35 m3/h per ewe) split in 30-min ventilation cycles (LOV-30); moderate ventilation regimen (VR=70 m3/h per ewe) split in 30-min ventilation cycles (MOV-30); moderate ventilation regimen (VR=70 m3/h per ewe) split in 60-min ventilation cycles (MOV-60). The LOV-30 milk had higher microbial load and bulk milk somatic cell count (BMSCC) and resulted in a weaker casein matrix in the curd compared with the MOV-30 and MOV-60 treatments. At 45 d of ripening, the LOV-30 cheeses had a lower casein content and higher non-casein nitrogen (NCN) and water-soluble nitrogen (WSN) contents than the MOV-30 and MOV-60 cheeses. Urea-polyacrylamide gel electrophoresis (urea-PAGE) of the pH 4·6-soluble N extract showed that the MOV-60 cheeses had fewer bands derived from casein (CN) hydrolysis than the LOV-30 or MOV-30 cheeses, despite its having exhibited the highest plasmin (PL) activity levels. Our results suggest that the ventilation regimen is critical in dairy sheep housing for optimizing the hygienic quality of ewe milk and the proteolytic processes occurring in Canestrato Pugliese cheese during ripening.

A total of 120 milk samples were collected from Comisana ewes throughout lactation. The ewes were ranked into two somatic cell count (SCC) categories: normal milk (N Milk) with SCC lower than 5·00×105/ml and high somatic cell milk (HSC Milk) with SCC higher than 1·00×106/ml. Milk samples were analysed in triplicate for pH, fat and protein contents, renneting parameters, and plasmin and plasminogen activities. The peptide profile due to total proteolytic activity (endogenous and exogenous enzymes) on α- and β-CNs were determined using urea-PAGE on sodium caseinate (pH 8·0 and pH 5·0) incubated at 37 °C for 4 d after sampling. The peptide profile due to non-plasmin enzyme activities at pH 5·0 was also determined using urea-PAGE. Plasmin activity was higher in the HSC milk than in the N milk throughout the study period. A decrease in plasmin activity was observed in the N milk during mid-lactation, which was probably related to decrease in pH, and in the HSC milk during late lactation, which may be ascribed to an enhanced influx of plasmin inhibitors from the blood stream. Proteolytic patterns in Comisana ewe milk were mainly affected by plasmin activity that increased with the SCC in milk. Also non-plasmin proteolytic activity was strongly enhanced by elevated SCC and resulted in a higher degradation of α-casein than of β-casein. In general, plasmin activity did not increase with the advancement of lactation and exhibited a different trend in HSC and N milk, suggesting that physiological factors did not play a key role in regulating the plasminogen-plasmin system in ewes' milk. Plasmin activity, detected with the colorimetric assay was consistent with proteolytic activity on sodium caseinate shown in urea-PAGE electrophoregram.

Fifty-six Holstein dairy cows from a commercial dairy herd in the Northern part of Greece were used to determine the effect of vitamin E supplementation on immune parameters, milk composition and milk quality. Cows were assigned to one of two experimental groups: control (no vitamin E supplementation) and vitamin E supplementation. Supplementation of vitamin E started 4 weeks prior to and continued up to 12 weeks after parturition. Supplementation included daily oral administration of vitamin E at 3000 i.u./cow prepartum and was reduced to 1000 i.u./cow post partum. Blood samples were collected weekly for 8 weeks starting 4 weeks before parturition, neutrophils were isolated and the following parameters were determined in neutrophils activated by phorbol myristate acetate: total cell-associated and membrane-bound urokinase plasminogen activator (u-PA) activity and superoxide production. Milk samples were collected weekly and fat, protein, lactose, somatic cell count (SCC), plasmin and plasminogen-derived activity were determined. Activated neutrophils isolated from cows that received supplemental vitamin E had higher (P<0·01) total and membrane-bound u-PA activities during the first 3 weeks after parturition and higher (P<0·01) superoxide production during week 1 prepartum and week 1 post partum compared with the corresponding values of activated neutrophils isolated from control cows. Vitamin E supplementation had no effect (P=0·28) on plasminogen-derived activity in milk. Milk obtained from cows that received supplemental vitamin E had SCC lower by 25% (P<0·05) and plasmin lower by 30% (P<0·01) than corresponding values in milk obtained from control cows. The reduction in plasmin as a result of vitamin E supplementation is very beneficial to the dairy industry because plasmin reduces the cheese-yielding capacity of milk, affects the coagulating properties of milk and its overall ability to withstand processing during cheesemaking. In conclusion, vitamin E supplementation had positive effects on the function of bovine neutrophils and milk quality in a commercial dairy herd.