Cortisol response to stress appears to differ between lactating and non- lactating animals. Lactating (14 d post partum) and non-lactating sheep were fitted with probes so that drugs and hormones could be infused directly into the posterior pituitary and paraventricular nucleus of the hypothalamus. The animals were also fitted with instruments to allow monitoring of heart rate, body temperature and blood cortisol levels. Their reactions to a source of acute stress (a barking dog) were then followed, with or without drug and hormone manipulation. Results in both lactating and non-lactating animals indicated shortcomings in the use of cortisol as a stress indicator. Infusing prolactin and oxytocin into either the posterior pituitary or the paraventricular nucleus of the hypothalamus suppressed cortisol responsiveness to stress in both lactating and non-lactating animals (the latter to a greater extent). In the absence of drugs, lactating animals had a slightly higher basal level of cortisol and a lower cortisol response to stress than their non-lactating counterparts. Despite suppression of cortisol responses, with or without drugs, other indicators of stress still changed with the presence of a barking dog, suggesting the complexity of control involved in stress responses.

Experiments were undertaken to validate a method (using adrenaline injection) for determination of the size of cisternal and alveolar compartments in the udder, to use this method to determine the pattern of milk accumulation in the udder over time and to determine the relationship between the size of the alveolar and cisternal compartments and tolerance of once daily milking. Cows received intrajugular injections of adrenaline (3 mg) immediately before milking, to block milk ejection and allow harvesting of the cisternal milk fraction. This was followed by removal of the alveolar fraction 30 min later after intrajugular oxytocin (5 i.u.) injection. Results obtained were similar to those obtained by catheter drainage. The alveolar compartment was 90% full at 16 h post milking while the cisternal compartment filled more slowly and was only 70% full at 24 h post milking. At full capacity (measured at 40 h), the volumes of milk contained in the cisternal and alveolar compartments were similar. In a further experiment involving identical twin cows, it was shown that the greater the degree of filling of the cisternal compartment at 24 h, the lower was the production loss on once daily milking. This suggests that the freedom of the alveoli to drain was an important factor in the production loss on once daily milking. Although there were significant correlations within twin sets for milk yield and the size of udder compartments, the relationship within twin sets for yield loss on once daily milking was not statistically significant.

The acid-soluble ribonucleotides of cow's, goat's and sheep's milks were measured by enzymic and ion-exchange chromatographic procedures at different stages of lactation. Colostra and milk from ruminant species contained orotic acid and 13 well-identified nucleotides: AMP, CMP, GMP, UMP, UDP, GDP, UDP-glucose, UDP-galactose, UDP-N-acetyl-glucosamine, UDP-N-acetyl-galactosamine, UDP-glucuronate, GDP-mannose and GDP-fucose. Cow's, goat's and sheep's colostrum contained significant amounts of nucleotides, which increased in amount from the moment of parturition, to reach a maximum 24–48 h later. The nucleotide concentration decreased thereafter with advancing lactation. Cow's milk contained substantial amounts of orotic acid, which increased during lactation, whereas in goat's and sheep's milk no increase took place. The cytidine and adenosine derivatives in ruminants' milk did not change significantly during lactation. The UDP-glucose/UDP-galactose ratio was measured in ruminants' milk at different stages of lactation.

Two polysaccharides produced concurrently by Lactococcus lactis subsp. cremoris strain LC330 have been identified. One had a high molecular mass (> 1 × 106 Da) and was neutral. The second was smaller (∼ 10000 Da), charged and had a high phosphorus content. Sugar composition also differed. In chemostat culture the neutral polysaccharide was influenced by temperature and by nitrogen limitation. This polysaccharide was branched with terminal galactose moieties and contained galactose, glucose and glucosamine. The phosphopolysaccharide was more complex with glucose, rhamnose, galactose and glucosamine in an approximate ratio of 6:5:4:1.

The accuracy of methods that utilize the colour-forming reaction between pyridine, acetic anhydride and citric acid for the determination of citric acid in milk and milk sera has been examined. A method based on that of Saffran & Denstedt (1948), in which a trichloroacetic acid (TCA) filtrate is used, gave values 3–5% low for the citric acid content of both milk and milk ultrafiltrate. The method of Merier & Boulet (1958), in which aqueous samples are analysed, gave an accurate value for the citric acid content of milk. The same technique but applied to aqueous-NaOH samples (Marier & Boulet, 1960) gave values about 7% high for the citric acid content of milk and about 3% high for the citric acid content of ultrafiltrate. However, a method using the technique of Marier & Boulet and TCA filtrate gave accurate values for the citric acid content of both milk and milk ultrafiltrate.

Two experiments were carried out to determine the effect on milk yield, milk composition and composition and physical properties of milk fat of giving full fat soyabeans (FFS) and full fat rapeseeds (FFR) to dairy cows. In both experiments grass silage was provided ad lib. and constituted over 50% of the dry matter (DM) intake of the cows. In experiment 1, cows received 7·25 kg/d of a concentrate mixture containing 240 g/kg of extruded FFS or 7·25 kg/d of a mixture without soyabeans. Cow performance was not significantly affected by the inclusion of FFS but fatty acid composition of the milk fat was greatly altered. The contents of C8:0 to C16:0 were significantly reduced (P < 0·001) while the contents of C18:0, C18:l and C18:2 were significantly increased (P < 0·001). Milk fat produced during feeding on FFS concentrate had a significantly lower content of solid fat at temperatures between 0 and 25 °C compared with milk fat produced when FFS was not given. In experiment 2, cows received concentrate mixtures containing either no whole rapeseed, 150 g/kg of whole unground FFR or 150 g/kg of ground FFR. Milk yield was significantly higher and silage DM intake significantly lower with the ground FFR concentrate compared with the other two diets but milk composition was not significantly different among treatments. FFR inclusion, either ground or unground, reduced diet digestibility. Changes in fatty acid composition of the milk fat were similar to those observed with FFS inclusion but the effect was larger with ground FFR compared with unground FFR. Nuclear magnetic resonance analysis showed a lower solid fat content when the FFR diets were employed with the effect being greatest with ground FFR.

There is considerable interest in the possibility that diet-derived isoflavonoids may help in protection against a number of chronic diseases common in Western society. Based on animal studies, however, concerns have been raised that consumption of isoflavonoids by infants and young children may be undesirable. Clover contains isoflavonoids and therefore may represent, via milk, a source of isoflavonoids in the human diet. In this study the concentrations of daidzein (7, 4′-dihydroxyisoflavone), genistein (5, 7, 4′-trihydroxyisoflavone) and equol (7-hydroxy-(4′-hydroxyphenyl)chroman) were measured using HPLC in cows' milk samples obtained from 76 farms in three Australian states. In addition, concentrations were measured in samples collected from one South Australian factory both before and after pasteurization. Concentrations in all samples were found to be extremely low. The mean daidzein concentration was <5 ng/ml. Mean genistein concentrations ranged from just detectable (∼2 ng/ml) in Victorian samples collected during summer to 20-30 ng/ml in samples from all states collected during spring when isoflavonoid-containing clover is most dominant in pasture. Mean equol concentrations ranged from 45±10 ng/ml in Victorian farm samples collected during summer to 293±52 ng/ml in Western Australian samples collected in spring. The mean concentrations of genistein and equol in post-pasteurization samples collected in spring were approximately double those for samples collected in autumn. Pasteurization had no effect on isoflavonoid concentrations. We conclude that the concentrations of isoflavonoids in Australian cows' milk are low and are therefore unlikely to have any pronounced biological effects in human consumers.

The effects of heat treatment and subsequent acidification of milk on the distribution of proteins, Ca and Pi, between the serum and micellar phases were examined using ultracentrifugation. After heating milk at 85 °C for 10 min, and storing for 22 h at 4, 20 or 30 °C, there was a marked increase in the concentration of κ-casein in the serum. At 4 and 20 °C there was also slightly more β-casein in the serum from heat-treated milk than in that from the corresponding raw milk. The whey proteins were extensively denatured, and were almost equally distributed between the supernatants and micellar pellets. After storage for 22 h the distribution of Ca and Pi between soluble and colloidal phases in heat-treated milk was similar to that in raw milk. After acidifying heat-treated milk by the addition of glucono-δ-lactone and storing for 22 h at 4, 20 or 30 °C there was progressive solubilization of colloidal calcium phosphate with decreasing pH, and at pH 5·0 almost all of the Ca and Pi was present in the serum. At 20 °C, and even more so at 4 °C, serum concentrations of the individual caseins increased considerably with decreasing pH, reaching maximum levels of about 25 and 40% of the total casein at pH 5·7 and 5·5 respectively, and then decreasing rapidly at lower pH. Compared with raw milk, maximum dissociation in heat-treated milks stored at 4 and 20 °C occurred at higher pH, and the overall levels of dissociation of individual caseins from the micelles were lower. At 30 °C, the concentrations of individual caseins in the serum of heat-treated milk decreased steadily as the pH was reduced, and did not show the slight increase found previously for raw milk. The role of the denatured whey proteins in interacting with κ-casein and in promoting aggregation of the micelles on acidification is discussed.

In the present study newly calved cows were tentatively classified as moderate and severe responders to experimentally induced Escherichia coli mastitis based upon the reactive oxygen species (ROS)-generating capacity of their blood neutrophils before infection. The groups differed in blood and milk composition prior to infection. This initial classification was supported by the corresponding variation in clinical symptoms and in the changes in milk production and composition measured during mastitis. Responses of newly calved cows to Esch. coli challenge varied from mild to severe symptoms of inflammation in infected glands and differed in the intensity of systemic disturbances and general illness. Losses in milk yield and compositional changes were most pronounced in inflamed glands and in severe responders. In inflamed glands milk yield and composition did not return to preinfection level in either moderate or severe responders. The yields of lactose, α-lactalbumin, casein and fat followed the same pattern as milk yield. It is concluded that the severe and long lasting systemic disturbances observed in severe responders can be ascribed to absorption of endotoxin from infected glands into circulation, indicating the important role of endotoxin in the pathology of coliform mastitis in periparturient cows. Evaluation of the ROS-generating capacity of blood neutrophils and blood and milk composition before infection might help to predict the cow's sensitivity to Esch. coli mastitis.

We studied the effects of goat and cow milk fat on the digestive utilization of this nutrient and on some of the biochemical parameters that are related to the metabolism of lipids, using rats with a resection of 50% of the distal small intestine and control animals (transected). The fat content in all the diets was 10% but the lipid quality was varied: the standard diet was based on olive oil, while the other two diets included fat obtained from lyophilized goat milk and cow milk, respectively. The digestive utilization of the fat was lower in the resected animals than in the transected ones for all three diets studied. In both resected and transected animals, the apparent digestibility coefficient (ADC) of the fat was greater with the standard diet (olive oil) than with diets whose fat content was provided by goat or cow milk. The digestive utilization of the fat was greater in the transected and resected rats receiving a diet of goat's milk (rich in medium-chain triglycerides) than those given a cow-milk-based diet, and more closely approached the values obtained for olive oil. The consumption of goat milk reduced levels of cholesterol while levels of triglycerides, HDL, GOT and GPT remained within the normal ranges, for both transected and resected animals. The advantageous effect of goat milk on the metabolism of lipids with respect to cow milk suggests that the former should be included in the diet in cases of malabsorption syndrome.

Progressive changes in the concentrations of milk protein components were followed after infusions of Streptococcus agalactiae or bacterial endotoxin into different quarters of individual cows. Both types of infusion produced similar increases in somatic cell count and resulted in similar changes in milk proteins, although the effects of the endotoxin infusion lasted for a shorter length of time.

The treatments had little effect on α-lactalbumin and β-lactoglobin concentrations, but serum albumin and immunoglobulin (Ig) concentrations increased markedly. The greatest effect on serum albumin was after the endotoxin infusion and on Ig after the Str. agalactiae infusion. Changes in the individual globulins indicated that passive transfer of blood proteins to milk could not account for the observed increases in IgM and IgA.

αs1-Casein and β-casein concentrations were reduced and inversely related to somatic cell count during the immediate post-infusion period, and this was accompanied by an increase in para-κ-casein. Para-κ-casein was not detected in pre-infusion or post-recovery milk samples. The decrease in β-casein was greater than that of αs1-casein. Casein concentrations returned to pre-infusion levels 2 d and 5 d after the endotoxin and Str. agalactiae infusions respectively.

The possibility that proteolytic enzymes are partly responsible for the changes in casein concentration is discussed.

The objective of this study was to determine the effect of high pressure homogenisation (HPH) on alkaline phosphatase activity and plasmin and plasminogen-derived activities in raw whole bovine milk. Milk (approximately 4% fat) was treated by two-stage conventional homogenisation (18 MPa) or single or two-stage HPH at 50, 100, 150 or 200 MPa. Inactivation of plasmin and plasminogen-derived activities was evident in conventionally homogenised samples, and increased as HPH pressure increased. Two-stage HPH reduced both activities to a greater extent than single-stage HPH. Milk inlet temperature had a significant effect on residual plasmin and plasminogen activities of HPH-treated milk samples, especially those treated at 50 MPa. Inactivation of plasmin and plasminogen on HPH-treatment (150 MPa) of milk samples of varying fat contents (0–10%) was also investigated; there was a curvilinear relationship between residual plasmin and plasminogen-derived activities and fat content in the ranges 0–2% and 0–4%, respectively, with little additional inactivation at higher fat contents. Thus, indigenous proteolytic activity of milk is clearly affected by HPH. However, all homogenised milk samples retained active alkaline phosphatase, indicating that thermal conditions during HPH did not equate to that of conventional high temperature short time pasteurisation, and that the wide range of forces experienced by milk during HPH treatment does not inactivate the latter enzyme.

A subjective cow cleanliness scoring system was validated and used to assess the cleanliness score of dairy cows at different times in the year. A longitudinal study followed a number of farms from summer to winter, and a larger, cross-sectional study assessed a greater number of farms during the housed winter period. The scoring system was demonstrated to be both a repeatable and practical technique to use on-farm and showed that cows become dirtier in the transition from summer grazing to winter housing. Although farming system (organic or conventional) had no effect on cow cleanliness when cows were at grass, when housed in the winter, organic cows were significantly more likely to be cleaner. There was a link between cow cleanliness scores and milk quality, with herds having lower bulk tank somatic cell counts (BTSCC) tending to have a lower (cleaner) median cow cleanliness score; with this relationship strongest for the organic herds. There was no significant link between cleanliness score and Bactoscan (BS) count or clinical mastitis incidence. No major mastitis pathogens were cultured from bulk tank milk samples from the quartile of herds with the cleanest cows in contrast to the quartile of herds with the dirtiest cows, where significant mastitis pathogens were cultured. Based on this study, all farms, especially organic systems, should attempt to keep cows clean as part of subclinical mastitis control.

The properties of commercial directly and indirectly heated UHT milks, both after heating and during storage at room temperature for 24 weeks, were studied. Thermally induced changes were examined by changes in lactulose, furosine and acid-soluble whey proteins. The results confirmed previous reports that directly heated UHT milks suffer less heat damage than indirectly heated milk. During storage, furosine increased and bovine serum albumin in directly heat-treated milks decreased significantly. The changes in lactulose, α-lactalbumin and β-lactoglobulin were not statistically significant. The data suggest that heat treatment indicators should be measured as soon as possible after processing to avoid any misinterpretations of the intensity of the heat treatment.

A simple and rapid phosphatase test is described which is based on the use of p–nitrophenylphosphate as the substrate. Execution of the test requires few and easy operations: incubation of the milk at 37° C. with a buffered solution of the substrate, followed directly by a visual comparison of the intensity of yellow colour of liberated p–nitrophenol with that of boiled-milk standards containing known amounts of p–nitrophenol. The test permits the detection of minor processing faults with an incubation time of only 30 min. In this form it should prove of value in creamery control. A more searching, but equally simple test is obtained by increasing the period of incubation to 2 hr.