High Milk Somatic Cell Count Research Articles

Associations of sole ulcer at claw trimming with reproductive performance, udder health, milk yield, and culling in Swedish dairy cattle

The association between sole ulcer found at routine claw trimming 2–6 months after calving and reproductive, health and productive traits in the same lactation, was investigated in an observational study of 2368 dairy cows in 102 Swedish herds. The data were analysed by mixed multivariable linear-, logistic- and Poisson-regression modelling at the cow level, accounting for clustering within herd. Associations were found between sole ulcer and first-service conception risk in the first study year (OR 0.59), calving interval (2% longer), treatment for anoestrus (OR 1.61), and 305-day milk yield (479 kg ECM higher). No associations could be shown between sole ulcer and first-service conception risk in the second study year, the number of services per conception, clinical mastitis, high milk somatic-cell counts or culling.

Hydrolysis of bovine caseins by cathepsin B, a cysteine proteinase indigenous to milk

The presence of the lysosomal cysteine proteinase cathepsin B in milk has been demonstrated recently. The potential significance of this enzyme to proteolysis in milk and dairy products was evaluated by the study of its proteolytic specificity towards the caseins. Bovine cathepsin B (1.4 units mL−1) was added separately to β-casein or αs1-casein (5 mg mL–1, in 100 mm Na acetate buffer, pH 6.0, containing 1.5 mm dithiothreitol). Samples were taken over a 24 h period and analysed by urea polyacrylamide gel electrophoresis and RP-HPLC; peptides were identified by N-terminal sequencing and mass spectrometry. Cathepsin B cleaved β-casein at 32 sites and αs1-casein at 35 sites, extensively hydrolysing both proteins. Thus, cathepsin B has a very broad specificity against the caseins, with an apparent preference for bonds incorporating the amino acids Leu, Val, Gln, Pro and Ser. Cathepsin B cleaved some bonds in common with chymosin (including the Phe23–Phe24 bond of αs1-casein), plasmin and the cell envelope-associated proteinases of Lactococcus, suggesting that it could be involved in proteolysis in dairy products, particularly if manufactured from high somatic cell count milk.

Effect of Somatic Cell Count on Proteolysis and Lipolysis in Pasteurized Fluid Milk During Shelf-Life Storage

The general goal of this research was to provide fluid milk processors with data to enable them to estimate the economic benefits they might derive from longer fluid milk shelf-life or new marketing opportunities due to a reduction in raw milk SCC. The study objectives were: 1) to measure the time in days for pasteurized homogenized 2% milk to achieve a level of lipolysis and proteolysis caused by native milk enzymes present in milks of different somatic cell count (SCC) at 0.5 and 6°C that would be sufficient to produce an off-flavor, 2) to determine whether milk fat content (i.e., 1, 2, and 3.25%) influences the level of proteolysis or lipolysis caused by native milk enzymes at 6°C, and 3) to determine the time in days for milks containing 2% fat with different SCC to undergo sufficient lipolysis or proteolysis to produce an off-flavor due to the combination of the action of native milk enzymes and microbial growth at 0.5 and 6°C. In experiment 1, pasteurized, homogenized milks, containing 2% fat were prepared from raw milk containing four different SCC levels from <100,000 to >1,000,000 cells/ml. Each of the four milks was stored at 0.5 and 6°C for 61 d. In experiment 2, pasteurized, homogenized milks containing 1, 2, and 3.25% fat were prepared starting from two raw milks containing two different SCC levels, one <100,000 and the other >1,000,000 cells/ml. In experiment 3, pasteurized, homogenized 2% fat milks were prepared starting from raw milks containing two different SCC levels, one <100,000 and the other >1,000,000 cells/ml. For experiments 1 and 2, all milks were preserved with potassium dichromate to prevent microbial growth but to allow the activity of native milk proteases and lipases during storage. For experiment 3, one set of milk was preserved with potassium dichromate to prevent microbial growth but to allow the activity of native milk proteases and lipases, and a second set of milk was unpreserved during storage at 0.5 and 6°C for 29 d. Based on previous work, an off-flavor due to proteolysis was detected by 50% of panelists when the decrease in casein as a percentage of true protein (CN/TP) was>4.76%. Our data indicated (assuming 50% of consumers would detect an off-flavor when CN/TP decreases 5%) that pasteurized milk containing 2% fat would develop an off-flavor at a time long after 61 and at 54 d for the low SCC milk, and at about 54 and 19 d for the high SCC milk, at 0.5 and 6°C, respectively. Previous research reported that 34% of panelists could detect an off-flavor in milk containing 2% fat due to lipolysis at a (free fatty acid) FFA concentration of 0.25 meq/kg of milk. Based on these results, it was estimated in the present study that 34% of panelists would detect an off-flavor in a 2% fat pasteurized milk with low SCC at a time long after 61 and just after 61 d at 0.5 and 6°C, respectively, while for milk with high SCC, an off-flavor would be detected by 34% of panelists at slightly longer than 61 and 35 d at 0.5 and 6°C, respectively. The combination of low SCC milk and low storage temperature when coupled with processing technology to produce very low initial bacteria count in fluid milk could produce fluid milk that will maintain flavor quality for more than 61 d of storage at temperatures<6°C.

Effect of CO2 Addition to Raw Milk on Proteolysis and Lipolysis at 4°C

Fresh raw milks, with low (3.1×104cell/ml) and high (1.1×106cells/ml) somatic cell count (SCC), were standardized to 3.25% fat, and from each a preserved (with 0.02% potassium dichromate) and an unpreserved portion were prepared. Subsamples of each portion were carbonated to contain 0 (control, pH 6.9) and 1500 (pH 6.2) ppm added CO2, and HCl acidified to pH 6.2. Milk pH was measured at 4°C. For the preserved low- and high-SCC milks, two additional carbonation levels, 500 (pH 6.5) and 1000 (pH 6.3) ppm, were prepared. Milks were stored at 4°C and analyzed on d 0, 7, 14, and 21 for microbial count, proteolysis, and lipolysis. The addition of 1500ppm CO2, but not HCl, effectively delayed microbial growth at 4°C. In general, in both the low- and high-SCC unpreserved milks, there was more proteolysis and lipolysis in control and HCl acidified milks than in milk with 1500ppm added CO2. Higher levels of proteolysis and lipolysis in the unpreserved milks without added CO2 were related to higher bacteria counts in those milks. In preserved low- and high-SCC milks, microbial growth was inhibited, and proteolysis and lipolysis were caused by endogenous milk enzymes (e.g., plasmin and lipoprotein lipase). Compared with control, both milk with 1500ppm added CO2 and milk with HCl acidification had less proteolysis. The effect of carbonation or acidification with HCl on proteolysis in preserved milks was more pronounced in the high SCC milk, probably due to its high endogenous protease activity. Plasmin is an alkaline protease and the reduction in milk pH by added CO2 or HCl explained the reduction in proteolysis. No effect of carbonation or acidification of milk on lipolysis was observed in the preserved low- and high-SCC milks. The CO2 addition to raw milk decreased proteolysis via at least two mechanisms: the reduction of microbial proteases due to a reduced microbial growth and the possible reduction of endogenous protease activity due to a lower milk pH. The effect of CO2 on lipolysis was mostly due to a reduced microbial growth. High-quality raw milk (i.e., low initial bacteria count and low SCC) with 1500ppm added CO2 can be stored at 4°C for 14 d with minimal proteolysis and lipolysis and with standard plate count <3×105cfu/ml.

Lameness and Udder Health in Swedish Dairy Herds, as Influenced by Housing Changes

Traditionally, tie-stalls have been the predominant housing system for dairy cattle in northern Europe. In Sweden, tie-stalls are either long-stalls (approx. 2.20 m) or short-stalls (approx. 1.70 m). In long-stalls the cows are normally closed out from the feeding table when the herdsman is not in the barn, while in short-stalls they have always access to the feeding table. Loose housing has been recommended and increases with new facilities. Presently, one fourth of the Swedish dairy cows are loose-housed. Very few observational studies of possible animal health effects of a transition from one housing system to another have been performed. The aim of the present study was to assess effects of changes in housing system on the occurrence of veterinary-treated foot and leg disorders, clinical mastitis, teat injuries and of high milk somatic cell counts (MSCCs). The objective was to improve the basis for farmers' decisions in connection with structural changes in milk production. Monthly herd disease incidence rates or prevalences in 194 Swedish commercial dairy herds from 1988 to 1995 were collected retrospectively from the official milk recording scheme and merged with county administrative and farmers' data on housing and management. The studied herds constituted approximately one third of all dairy facilities approved for rebuilding in the selected counties during the same time period. The most common changes of housing systems were going from long-stalls to short-stalls (61 herds), remaining in short-stalls (41 herds) and going from short-stalls to cubicles (33 herds). Predominant breeds were the Swedish Red and White (SRB) and the Swedish Holstein breed (SLB). Mean herd size was 34.6 cows for long-stalls, 39.2 for short-stalls, 62.7 for cubicles and 55.8 for straw yards. The records were either from 1 to 45 months before building start (mean 10.7 months) or from 0 to 59 months after building finish (mean 11.4 months). All data from the actual building period were discarded. Four Poisson regression models were applied to the data (5982 to 7026 herd-month records), using the GEE method and the GENMOD procedure in SAS. Monthly observations were treated as repeated measures within herds (autoregressive correlation structure). There were significant transitory increases in the incidence of clinical foot/leg disorders when changing from tie-stalls to cubicles (RR=3.2-4.7) and decreases in the incidences of clinical mastitis (RR=0.20-0.77) and teat injuries (RR=0.13-0.60) when changing from tie-stalls to loose housing. Effects on foot/leg health generally lasted for less than 18 months after building finish, while udder health improvements persisted beyond 18 months. Reductions in the incidence of clinical mastitis were not accompanied by any clear changes in the prevalence of high MSCCs. Later than 18 months after rebuilding, herds that shifted from long-stalls to short-stalls had less foot and leg lesions than those remaining in long-stalls. It is concluded that a change in dairy cow housing from tie-stalls to loose housing deteriorates foot/leg health temporarily and improves udder health. 236 Abstracts – Oral presentations at 11th ICPD

Foot/leg and udder health in relation to housing changes in Swedish dairy herds

Monthly herd disease incidence rate or prevalence estimates in 196 Swedish commercial dairy herds from 1988 to 1995 were collected retrospectively from the official milk-recording scheme and merged with county administrative and farmers’ data on housing and management. To study the effects of changes in housing system on the occurrence of veterinary-treated foot/leg disorders, clinical mastitis, teat injuries and high milk somatic cell counts (MSCCs), four marginal Poisson or negative-binomial regression models were applied to the data (6011–7063 herd–month records), using the generalized estimating-equations method. Monthly observations were treated as repeated measures within herds. There were significant transitory increases in the incidence of clinical foot/leg disorders when changing from tie-stalls to cubicles and decreases in the incidences of clinical mastitis and teat injuries when changing from tie-stalls to cubicle or straw-yard systems. Effects on foot/leg health generally lasted for <18 months after building finish, while udder-health improvements persisted >18 months. Reductions in the incidence of clinical mastitis were not accompanied by any clear changes in the prevalence of high MSCCs.

Treatment of acute Escherichia coli mastitis in cows with enrofloxacin: effect on clinical signs and chemiluminescence of circulating neutrophils.

We have studied the effect of treatment with enrofloxacin on local and general clinical signs and chemiluminescence of circulating polymorphonuclear leucocytes during experimentally induced Escherichia coli mastitis in cows immediately afer parturition. Twelve cows were infected with 10(4) cfu Esch. coli P4:032 into both left quarters. Six cows received an intravenous injection of 5 mg enrofloxacin/kg at 10 h after infection and a second enrofloxacin treatment administered subcutaneously at 30 h post infection. The other six cows were controls that received no treatment. General clinical signs (fever, tachycardia, loss of appetite, reduced rumen motility and depression) were similar in both groups. Local clinical signs, such as swelling, pain and firmness of the inflamed mammary quarters, were less severe in the treated cows. We saw no difference in the appearance of the milk: flecks and watery or purulent milk were observed in both groups. The beneficial effects of treatment with enrofloxacin were mainly on milk production and composition. The decline in milk production and the changes in milk concentrations of lactose, Na+ and bovine serum albumin were less pronounced in the treated cows. Treatment with enrofloxacin accelerated the clearance of bacteria from the infected quarters, but had no effect on the chemiluminescence response of isolated polymorphonuclear leucocytes. The changes in the number of circulating leucocytes and the appearance of immature neutrophils in the circulation of the treated cows indicated possible beneficial effects on migration of neutrophils into the inflamed glands. Higher milk somatic cell counts in the treated cows supported this hypothesis. The results of this study indicated that treating cows that have been experimentally infected with Esch. coli mastitis after parturition with enrofloxacin reduced the severity of the disease, especially the decline in milk production and the changes in milk composition.

Effect of somatic cell count and polymorphonuclear leucocyte content of milk on composition and proteolysis during ripening of Swiss-type cheese.

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 &amp; 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 &amp; Fox, 1992; Bastian &amp; 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 &amp; 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 &amp; 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 &amp; 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.

Effects of Somatic Cell Count on Quality and Shelf-Life of Pasteurized Fluid Milk

Milk was collected from eight Holstein cows four times before and four times after intramammary infection with Streptococcus agalactiae. Postinfection milk had significantly higher somatic cell count (SCC) (849,000 cells/ml) than preinfection milk (45,000 cells/ml). High SCC raw milk had more lipolysis and proteolysis than low SCC raw milk. Pasteurized, homogenized, 2% fat milks from pre- and postinfection periods were stored at 5°C and analyzed for lipolysis, proteolysis, microbial quality, and sensory attributes at 1, 7, 14, and 21 d post processing. During refrigerated storage, the average rates of free fatty acid increase (i.e., lipolysis) and casein hydrolysis in high SCC milk were, respectively, three and two times faster than those in low SCC milk. In general, standard plate counts, coliform counts, and psychrotrophic bacterial counts of both the high and low SCC milks remained low (<100,000 cfu/ml) during 5°C storage. Low SCC milk maintained high organoleptic quality for the entire 21-d shelf-life period. However, for high SCC milk, between 14 and 21 d, sensory defects were detected, which resulted in low overall quality ratings. The sensory defects mainly included rancidity and bitterness and were consistent with higher levels of lipolysis and proteolysis. Hence, mastitis adversely affected the quality of pasteurized fluid milk. It is recommended that the fluid milk industry consider implementation of premium quality payment programs for low SCC milks.

Correlation Between Bovine Milk Somatic Cell Count and Polymorphonuclear Leukocyte Level for Samples of Bulk Milk and Milk from Individual Cows

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.

Effects of Milk Somatic Cell Count on Cottage Cheese Yield and Quality

Eight Holstein cows in midlactation were selected for low milk somatic cell count (SCC) and the absence of the pathogens that cause mastitis. Milk collection and cottage cheese manufacture from low SCC milk were replicated on each of 4 d (control period). Each cow was infused with 1000 cfu of Streptococcus agalactiae. One week after infusion, milk from the same eight cows was collected and commingled. On each of 4 d, cottage cheese was made from milk with high SCC (treatment period). A mass-balance protocol, accounting for protein and total solids, was used to determine recoveries in whey, wash water, and uncreamed curd. Actual yields, yields adjusted for composition, and theoretical yields of uncreamed curd were calculated. Mean milk SCC for the periods with the low SCC (control) and the high SCC (treatment) were 83 × 103 and 872 × 103 cells/ml, respectively. The recovery of protein in the uncreamed curd was higher during the low SCC period than during the high SCC period (75.85% vs. 74.35%). High SCC and the associated higher proteolytic activity caused higher protein loss in the whey and wash water and more curd fines. The percentage of total solids recovery in uncreamed curd was higher for high SCC milk because the lactose content of the high SCC milk was 0.27% lower than that of the low SCC milk. The moisture content of the curd was higher for the high SCC milk (82.75% vs. 83.81%). Proteolysis during refrigerated storage was faster in cottage cheese made from high SCC milk. The yield efficiency of uncreamed curd, adjusted for composition based on 81% moisture, was 4.34% lower for the cottage cheese curd made from high SCC milk.

The influence of somatic cell count on the heat stability of bovine milk plasmin activity

Abstract The heat stability of bovine milk plasmin activity and the role of plasminogen activators in milk of low and high somatic cell count (SCC) were examined, with or without KIO3 addition. The inactivation of plasmin was a first-order reaction and Arrhenius plots showed two-stage inactivation kinetics. Plasmin was more heat stable in high SCC milk than low SCC milk after low temperature treatments such as thermisation and pasteurisation, but less stable in high SCC milk under UHT-range thermal treatments. The addition of KIO3 to low SCC milk before heating resulted in considerably greater heat stability of plasmin at all heating temperatures. The activation energy, Ea, for the inactivation reaction in the temperature range 63–110°C was estimated as 52.75 and 74.44 kJ mol-1 for low and high SCC milk, respectively. The Ea for inactivation of plasmin in the temperature range 110–138°C was estimated as 22.03 and 24.70 kJ mol-1 for low and high SCC milk, respectively. The high SCC milk containing KIO3 showed evidence of considerable plasminogen activator activity, apparently leading to activation of plasminogen during the heating process itself. Overall, without the inactivating influence of denatured β-lactoglobulin, plasmin activity is extremely heat stable in native milk systems and plasminogen activators derived from somatic cells appear to be likewise very heat stable and active during heating processes.

Proteolysis and storage stability of UHT milk as influenced by milk plasmin activity, plasmin/β-lactoglobulin complexation, plasminogen activation and somatic cell count

Little residual plasmin activity was found in both low and high somatic cell count (SCC) milk which had been subjected to indirect ultra-high temperature (UHT) treatment (138 °C × 2.4s) and subsequently stored at 20 °C. Milk with elevated SCCs showed definite sedimentation after 150 d storage but did not gel. Addition of potassium iodate to the milk before UHT treatment led to considerably increased plasmin activity during subsequent storage, indicating the protective influence of potassium iodate on the thermal stability of plasmin. These milk samples underwent significant decrease in pH on storage, did not gel, and urea-PAGE electrophoresis showed them to have almost complete breakdown of β-casein but incomplete hydrolysis of αs1-casein. When plasminogen was added to milk immediately after UHT treatment, it was readily activated to plasmin. Activation occurred more rapidly in the high SCC milk, suggesting the presence of cell-associated heat-stable plasminogen activators. UHT milk with added plasminogen showed definite gelation at 150 and 180d storage and gelation was more pronounced in the high SCC milk. Samples to which plasmin was added immediately after UHT treatment showed proteolysis patterns similar to those with added potassium iodate and showed slight gelation. Low levels of proteolysis appeared to be linked to the onset of gelation.

Associations between health disorders during two consecutive lactations and culling in dairy cows

Data from an observational study, carried out from 1986 to 1990, were used to quantify the effects of 15 main health disorders during two consecutive lactations on the risk of culling in the latter one. The study population consisted of 47 commercial Holstein herds from western France, comprising 4123 cows. Logistic regression was used to assess the relationship between health disorders and culling within and after 45 days post-partum. Adjustments were made for year, month of calving, parity, breeding value for milk, best of the two first milk production records and reproductive performance. Effects of interactions were investigated. Herd effect was accounted for using random effect models. Few diseases from the previous lactation were related to culling in the current lactation. Non-traumatic udder disorders, teat injuries, mastitis, high milk somatic cell count, abortion and metritis from the previous and current lactations were dominant with respect to culling within and after 45 days post-partum. The risk of being culled within and after 45 days post-partum increased with higher parity and lower breeding value for milk. Lower previous 305-day milk production and poor reproductive performance increased the risk of culling within and after 45 days post-partum respectively.

Origins, interpretations and uses of high milk somatic cell counts

Origins, interpretations and uses of high milk somatic cell counts

Properties of Proteases from Milk Somatic Cells and Blood Leukocytes

Proteolytic activity of proteases associated with somatic cells isolated from high SCC milk and proteases associated with leukocytes isolated from bovine blood was assayed at pH 6.6 and 5.2 in a model system consisting of a -casein (.96%) substrate in Jenness/Koops buffer. Intact β-casein and casein proteolysis products were measured by densitometric analysis of SDS-PAGE gels. Relative proteolytic activity was expressed as percentage degradation of β-casein after 24h at 37°C per 1 × 106 cells/ml. Proteolytic activity associated with somatic cells isolated from bovine milk was 27.5 and 13.6% at pH 6.6 and 5.2, respectively. Proteolytic activity associated with leukocytes isolated from bovine blood was 16.0 and 8.4% at pH 6.6 and 5.2, respectively. Proteolytic activity at pH 6.6 was significantly higher for the somatic cells isolated from milk than for leukocytes isolated from blood. The reason for the difference in proteolytic activity of leukocytes isolated from blood of a healthy cow versus somatic cells isolated from milk produced by a cow with mastitis is not known. Further work is needed to determine whether the difference may be caused by a higher proportion of activated macrophages in somatic cells isolated from milk produced by cows with mastitis than in the leukocytes isolated from blood of healthy cows.

Determinants of high somatic cell count prevalence in dairy herds practicing teat dipping and dry cow therapy and with no evidence of Streptococcus agalactiae on repeated bulk tank milk examination

A series of least squares analytical models were developed in a cross-sectional epidemiologic study of observed variability in within-herd high milk somatic cell count (SCC) prevalence. The study population was restricted to Ohio (U.S.A.) dairy cow herds where post-milking antiseptic teat dipping and prophylactic dry cow antibiotic therapy of all cows were practiced. Additionally, no Streptococcus agalactiae was isolated from repeated bulk tank milk screening of these herds. The first analysis considered 12-month herd average high SCC prevalence as the dependent variable. The second analysis narrowed the herd average calculation to a 3-month or seasonal interval, while the third analysis included age adjustment of the 3-month rolling herd average high SCC prevalence. All of the models identified significant main effects and significant first order interactions of main effects. Milking order was a significant factor in all models, as were four interactions: washing teats only and rinsing teat cups between cows; washing with a common cloth or sponge and milking order; washing teats only and elapsed time between udder preparation and teat cup attachment; and elapsed time between udder preparation and teat cup attachment, and rinsing teat cups between cows.

Yield and Quality of Cheddar Cheese from High Somatic Cell Milk Supplemented with Retentate to Varying Concentrations or Directly Ultrafiltered

High somatic cell milk with a mean cell count of 2,235,000/ml was supplemented to 1.25:1 to 1.88:1 total protein with approximately 5.5:1 low somatic cell whole milk retentate of UF. Curd formation time of cheese milk decreased with increasing concentration of SCC. Supplemented milk concentrated to 1.65: 1 and 1.88:1 total protein displayed normal curd formation times: 34 and 31min, respectively. Also, cheese made from these mixtures had normal moisture, whereas the remaining cheeses had higher than normal moisture. Supplementation to 1.65:1 and 1.88:1 total protein increased cheese yield by 9.67% and 11.38%, respectively, and produced excellent quality cheese after 2 mo at 10°C.Direct UF of high SCC milk to 1.84:1 total protein improved cheese quality and increased yield over control milk cheeses but not to the same high level attained with retentate supplementation.

Influence of somatic cell count on the whipping properties of cream

SummaryCows were infused with Escherichia coli endotoxin to provide a pool of milks with high somatic cell counts (SCC). This was mixed with bulk tank milk obtained from either of two Institute herds, producing a range of milks containing 0, 10, 20, 30 and 100% high SCC (HCC) milk. Creams containing 38% fat were produced from these milks on nine separate occasions; five times from winter milks and four times from summer milks. The SCC of the milks, the free fatty acid concentration of the unwhipped creams and the whipping time, stiffness and overrun of the whipped cream were measured. Whipping time and stiffness increased and overrun (volume increase) decreased as the proportion of HCC milk in the mixture increased. However, these changes were statistically significant only when comparing the 100% HCC milk with the other treatments containing lower levels of HCC milk. Creams produced in the summer took less time to whip and were less stiff than winter creams but there was no change in overrun. The source of bulk milk supply affected the stiffness and overrun of the whipped creams. Free fatty acid concentration appeared to have no direct effect on whipping characteristics.

Effects of variations in somatic cell count on the rennet coagulation properties of milk and on the yield, composition and quality of Cheddar cheese

SummaryCheddar cheeses were prepared from low somatic cell count (SCC) milks and from milks containing 10, 20 and 30% added high SCC milk to give modestly elevated SCC. Increased SCO in the milk were associated with a reduction in the coagulum strength and an increase in moisture content of the cheeses. Cheese texture was affected significantly as judged both by the findings of an assessment panel and by instrumental physical measurement. The panel scores for flavour were also slightly altered. It was concluded that even a small increase in SCC is detrimental to cheese composition and quality, although no significant effects on yield were detected. Relationships between cheese yield, composition and properties, coagulation properties and composition of the milk were also studied. Yield was related to the total solids and fat in the milk but not to the coagulation properties or the flavour or texture of the cheeses. Coagulum strength, cheese composition and cheese texture were strongly interrelated.