Immune responses induced with helminth parasites have been extensively studied, but there is limited information on those to Fasciola hepatica, especially on the subtype of T cell induced with this parasite. We investigated the local and systemic T cell responses of different strains of mice following oral infection with doses of metacercariae from F. hepatica. Spleen cells from BALB/c and 129Sv/Ev mice given a low-dose (5 metacercariae) infection exhibited a Th2 response, producing high levels of the cytokines IL-4 and IL-5, and low levels of IFN-gamma and IL-2. In contrast, C57BL/6 mice showed a mixed Th1/Th2 response. A more marked polarization to a Th2 response was observed in BALB/c, 129Sv/Ev exposed to a high-dose (15 metacercariae) infection and the C57BL/6 mice also exhibited a clear Th2 response. IL-4 defective (IL-4-/-) C57BL/6 mice infected with 5 metacercariae produced less IFN-gamma and more IL-5 compared to their wild-type C57BL/6 counterparts, suggesting that IL-4 is important in establishing the Th2 type response in murine fasciolosis. However, the secretion of IFN-gamma and IL-2 was completely suppressed in the high-dose infection and this was also observed in IL-4-/- mice. Thus, liver flukes may secrete molecules that downregulate Th1 responses. T cell responses in the mesenteric (MLN) and hepatic lymph nodes (HLN) were also examined since newly excysted juveniles infect through the intestinal wall of their host before migrating to the hepatic tissue. Cells from both MLN and HLN secreted higher levels of IL-4 and IL-5 compared to spleen cells. We also observed a difference in cytokine profiles secreted by the MLN and HLN, which may reflect responses to antigens liberated by newly excysted juveniles and hepatic stage parasites, respectively.

The influence of various factors on the concentrations of polymorphonuclear neutrophilic leukocytes (PMN) in milk samples from bulk tanks and individual cows was investigated. While somatic cell counts (SCC) and PMN level were in both cases significantly correlated, lower correlation coefficients were found between SCC and PMN for samples of bulk tank milks than for milk samples from individual cows. Furthermore, plots of PMN concentrations versus SCC showed great variability in PMN in milk samples of similar total SCC. One factor that may lead to variability in bulk tank PMN levels was shown to be increased proportions of high SCC milk in the bulk tank mixture, which result in relatively high PMN levels without excessive elevation of total SCC. In milk samples from individual cows, it was found that there was also a significant seasonal influence on milk PMN content, with milk from cows calving in the spring having, at SCC > 160,000 cells/ ml, higher proportions of PMN in the total milk SCC than milk from autumn calving cows. The results of this study suggest that the concentration of PMN may be a useful indicator of herd status in bulk tank monitoring schemes.

During the manufacture of Swiss-type cheese varieties, such as Emmental, Gruyère and Comté, a high scald temperature is used, which inactivates the added coagulant, decreasing the primary proteolysis of αs1-casein during ripening and resulting in the development of the rubbery texture characteristic of this type of cheese (Kosikowski & Mistry, 1997). Swiss-type cheese may be made from raw, thermized or pasteurized milk, depending on the type of manufacture and the country (Beuvier et al. 1997).The suitability of milk for cheesemaking is often assessed from the somatic cell count (SCC) of the raw milk, with increased milk SCC being linked to impaired cheesemaking properties and cheese yield potential (Barbano et al. 1991; Auldist et al. 1996). Late lactation milk, which often has elevated SCC, also yields poor quality cheese (Lucey, 1996). High SCC milk has elevated levels of the milk alkaline proteinase plasmin (EC 3.4.21.7), but its activity is not generally considered to be detrimental during cheese ripening (Farkye & Fox, 1992; Bastian & Brown, 1996). Milk somatic cells are themselves also associated with a number of proteolytic enzymes of differing properties, the activities of which are ill-defined in dairy products (Verdi & Barbano, 1991), with the exception of the acid proteinase cathepsin D, which has a chymosin-like activity towards αs1-casein (McSweeney et al. 1995). Preliminary evidence of cathepsin D activity in Swiss cheese during ripening has been reported (Igoshi & Arima, 1993; Beuvier et al. 1997).In the present study the effect of milk SCC on the ripening of Swiss-type cheese was examined. Of particular interest was the role of polymorphonuclear leucocytes (PMN), the predominant cell type in high SCC mastitic milk (Heegaard et al. 1994) and late lactation milk, when the frequency of milking varies (Kelly et al. 1998). PMN possess a range of proteolytic enzymes, including cathepsin D (Verdi & Barbano, 1991) and plasminogen activators (PA; Heegaard et al. 1994). The experimental strategy chosen was to examine the effects on the quality and proteolysis during ripening of Swiss-type cheeses of adding high SCC milk, whose cell population is mostly PMN, to creamery milk.

The effects of reducing the frequency of milking of cows in late lactation on milk somatic cell count (SCC), polymorphonuclear leucocyte (PMN) content, chemical composition and proteolytic activity were investigated. Intermittent milking is frequently practised by Irish farmers in late lactation, and the objective of this study was to determine whether this procedure could be linked to altered quality of milk. Seventeen Holstein Friesian cows in late lactation (>215 d in milk) were assigned to two treatment groups, and were either milked twice a day until drying-off (control group) or milked intermittently as the yield fell (test group). Milk composition and enzymic characteristics were measured on two occasions. At the first sampling, day 7, test cows were on once daily milking and at the second, day 15, the test cows were being milked every second day. Milk yields were significantly lower in test than control animals and decreased between days 7 and 15 in both groups. Milk SCC and PMN levels were increased on reducing milking frequency and, at day 15, the increase was not linked to decreased milk yield. Milk lactose levels were significantly decreased and pH, α-lactalbumin levels, plasmin activity and plasminogen activity significantly increased by reducing milking frequency. In conclusion, reduced frequency of milking in late lactation leads to the production of milk that is abnormal in character and this may be linked to reduced quality of dairy products manufactured from such milk.

The effects on milk composition and processing characteristics of varying grass supply by changing stocking density and of offering a concentrate supplement were investigated. The experiment was conducted over 28 weeks of the lactation (April–October) using 48 spring-calved Friesian–Holstein cows. Three herds each of 16 cows were offered a restricted grass supply, a standard grass supply and a standard grass supply with a supplement of 3 kg concentrate/d. Treatment groups were grazed separately with a residence time of 3 d/paddock. Milk production, composition and processing characteristics such as renneting properties, ethanol stability and plasmin activity were measured weekly. Increasing stocking density above the standard system resulted in significant reductions in milk fat and protein yields, the concentrations of total protein, casein and whey proteins, and a deterioration in most processing characteristics. Imposing concentrate supplementation on the standard system increased total protein, casein and whey protein concentrations but generally did not improve processing characteristics except for ethanol stability. These results suggest that the standard grass supply in a rotational grazing paddock system can support efficient production of quality milk, and concentrate supplementation will not improve processing characteristics when an adequate supply of good quality herbage is available.