The Chaco Pampean Plain of central Argentina constitutes one of the largest regions of high arsenic (As) groundwaters known, covering around 1×106 km2 (Smedley & Kinniburg, 2002; Farías et al. 2004).

The first stage in acid casein manufacture is the isoelectric precipitation of casein from skim milk. This stage controls the particle size of the casein curd which is important in the later washing, dewatering and drying stages. Casein was precipitated batchwise from 9% total solids skim milk using 0·3 M-H2SO4 at temperatures from 25 to 53 °C and at pH (measured in the whey) from 3·6 to 5·1. A wet sieving method has been developed for measuring the particle size distribution of the casein curd. Ferric ammonium sulphate was added to the curd/whey mixture to toughen the curd particles and to reduce their stickiness. For given precipitation conditions the particle size distribution could generally be modelled by a normal distribution. The mean particle size generally increased with increasing temperature and pH. The increase in particle size with pH was pronounced at 53 °C, while at 25 and 35 °C particle size varied little with pH. The calcium contents of washed casein curd samples were low at all precipitation pH at a precipitation temperature of 35 °C, but increased markedly above pH 4·4 at precipitation temperatures of 45 and 53 °C.

Physicochemical, organoleptic and microbiological characteristics of semi-hard ewes' milk cheeses, frozen immediately after manufacture under two different conditions at −35 and −80°C and stored at −20°C for 4 months, were studied during subsequent ripening. Frozen storage after either freezing condition did not result in marked alterations in overall composition or rheological and sensory properties of the cheeses after 45 d ripening. Water activity decreased over the ripening period and this decrease was more pronounced in the frozen batches. The water-holding capacities of the protein in the frozen cheese batches were higher than for the control batch. The level of proteolysis, estimated from the level of amino groups, was higher in the previously frozen cheese. Freezing also reduced the viability of the microbial flora in the cheese. The differences in these characteristics for the two freezing conditions were not significant.

This study was conducted to evaluate the development of the mammary gland in Holstein heifers subjected to different dietary metabolisable protein (MP): metabolisable energy (ME) ratios. Twenty-five Holstein heifers (initial body weight (BW) 213±13·5 kg and initial average age 7·8±0·5 months) were divided into five treatments. The treatments were designed to provide MP:ME ratios equal to 33, 38, 43, 48, and 53 g of MP per Mcal of ME. All diets were formulated to have the same energy content (2·6 Mcal ME/kg dry matter). Actual MP:ME ratios were 36·2, 40·2, 46·2, 47·1, and 50·8 g MP/Mcal ME. The experiment was conducted in a randomised block design, while considering initial BW as a blocking factor to evaluate pre- and post-pubertal periods. Block effect was not observed for all variables evaluated; hence it was considered that the diets had the same influence both on pre- and post-pubertal phases. Dry matter and nutrient intake did not change between treatments, excepting protein intake and digestibility. Serum concentrations of insulin-like growth factor 1 increased linearly across treatments. Changes in the pixel brightness of mammary gland ultrasound images, which are associated with lipid content, were significantly influenced by MP:ME ratios in the diet of heifers that were subjected to accelerated growth rates. It is not recommended to use diets of less than 38 g MP/Mcal ME in diets to heifers allowed to gain more than 1 kg/d.

Antimutagenic properties of various dietary components have been investigated in many studies, in order to find compounds protective against the various steps of carcinogenesis. Indeed, cancer is now the principal cause of death in industrialised countries and treatment is still difficult. Thus, research in prevention is of extreme importance. While, the etiology of most cancers has an environmental component, colon or breast cancers are highly linked to dietary habits (up to 50% of colorectal cancers are due to diet; Riboli et al. 1996). In this context, Boutron et al. (1996) showed inverse correlation between consumption of dairy products and colorectal cancer in France.

Skim milks were concentrated by ultrafiltration. Cream was added to the retentates to give cheesemilks standardized to a casein: fat ratio of ∼ 0·74 with protein levels ranging from 30 to 46 g/1. Pasteurized cheesemilks were renneted on a volume basis (22 ml single strength calf rennet/100 1) and converted to Cheddar cheese in 500 1 cheese vats. Set temperatures were reduced from 31 to 28 °C with increasing milk protein level to normalize curd firming rates and prevent curd shattering on cutting the curds. Cheesemaking was otherwise as normal for Cheddar cheese. The proportions of milk fat and protein lost in the cheese whey were not significantly influenced by milk protein level. Moisture-adjusted cheese yields increased with milk protein at a rate similar to that predicted by the Van Slyke cheese yield equation. However, owing to the negative correlation between cheese moisture and milk protein concentration, actual yields increased at a lower rate with respect to milk protein than moisture-adjusted yields. Increasing milk protein levels resulted in significant (P < 0·01–0·001) decreases in the concentrations of moisture, moisture-in-non-fat cheese solids and fat-in-dry matter in the cheese and increases (P < 0·05–0·001) in the levels of protein, salt-in-moisture, Ca and P. While increasing milk protein concentration resulted in significant (P < 0·05–0·01) reductions in the levels of water-soluble N at all stages of the 270d ripening period, it had little influence on the sensory scores awarded for aroma/flavour at 180 or 270d.

Penicillium caseicolum has been shown to completely synthesize styrene. A medium was developed to test the capacity of different strains for this synthesis. In a synthetic medium, styrene production began only after the glucose was entirely consumed. This production depended on storage temperature and occurred simultaneously with 1-octene-3-ol formation.

Although milk may be considered to be the normal habitat of the lactic streptococci, their adaptation to this environment must have followed the domestication of mammals, for these organisms are not pathogenic and do not normally occur in the udder. If this reasoning is accepted, then the small biological age of these organisms logically follows, and possibly they are the youngest members of this genus.

Swabs taken from the rectum and vulva of 14 dairy cows on 7 occasions at approximately weekly intervals revealed a pattern of isolations of Streptococcus uberis which were not random. Two of the 14 cows were responsible for 80 and 40% respectively of the swabs of the rectum and vulva which were found to be positive. It is suggested that these patterns are consistent with these 2 cows being intestinally colonized with Str. uberis. The implications of this work are discussed with reference to the sources of Str. uberis in the dairy herd.

Milk production intensification has led to several unwanted aspects, such as sustainability issues and environmental pollution. Among these, increased milk outputs that have been achieved over the last 70 years have led to several health and pathophysiological conditions in high yielding dairy animals, including metabolic diseases that were uncommon in the past. Increased occurrence of diverse metabolic diseases in cattle and other domestic animals is a key feature of domestication that not only affects the animals' health and productivity, but also may have important and adverse health impacts on human consumers through the elevated use of drugs and antibiotics. These aspects will influence economical and ethical aspects in the near future. Therefore, finding and establishing proper biomarkers for early detection of metabolic diseases is of great interest. In the present review, recent work on the discovery of fitness, stress and welfare biomarkers in dairy cows is presented, focusing in particular on possible biomarkers of energy balance and oxidative stress in plasma and milk, and biomarkers of production-related diseases and decreased fertility.

α-Adrenergic mimetics inhibit milk removal whereas β-adrenergic mimetics have a favourable effect upon milk removal in dairy cows. This work aimed to relate these effects to the milk ejection reflex mechanism and/or milk flow from the cisternal cavities only. The α-adrenergic agonist phenylephrine and the β-adrenergic agonist isoproterenol were injected prior to and after milk ejection. Applied after milk ejection, the phenylephrine treatment reduced intramammary pressure (IMP) and milk yield markedly. Phenylephrine application before milk ejection prevented IMP from rising during teat stimulation or after oxytocin injection. Milking produced small amounts of milk at minimal milk flow rates. The very different responses to phenylephrine application prior to and after milk ejection indicate separate adrenergic inhibitory mechanisms for milk ejection and milk flow. The application of the β-adrenergic agonist isoproterenol did not alter the IMP. Nevertheless, this compound improved milk removal by increasing milk flow. The observation of bimodal milk flow at milkings without preceding teat stimulation indicates a delayed milk ejection. Isoproterenol injection without teat stimulation enhanced milk flow rates, but the bimodality remained unchanged. We conclude that isoproterenol enhances milk flow without affectiiig milk ejection.

The ability of Mozzarella cheese to stretch and form long fibres was evaluated by two simple instrumental tests. The first test, which was basically a tensile test, resembled the way the consumer assesses the stretchability of cheese as a pizza topping. The extensibility measurements of the test correlated well with the sensory stringiness scores. The second, fundamental test was a compressive elongation of the melted cheese. The elongational viscosity of the melted cheese was calculated; this could be used as an index of the ability of the cheese to form strings when it is stretched.

1. A method is described for following the intensity of reduction (or oxidation-reduction potential) at different levels in the interior of ripening Cheddar cheese.

2. Variations in this potential throughout the course of ripening are described and mean values assessed.

3. Cheese are shown to be not homogeneous throughout their mass; outer zones of more highly oxidised condition exist near the surface of the cheese and round cracks and borings. The depth of these zones increases with the age of the cheese.

4. The values obtained can be correlated with the known bacteriological data for Cheddar cheese.

5. The significance of the data obtained in relation to cheese faults is discussed.

Explants from lactating bovine mammary gland were cultured in vitro in serum-free medium through 1–9 d. Casein synthesis was determined by [32P] incorporation into newly synthesized Ca rennin precipitable fraction. High correlation (γ = 0·98) was found between incorporation of [32P] and [3H]amino acids in explants cultured under different hormonal regimes, thus indicating that post-translational phosphorylation is not a rate-limiting step in casein synthesis.

Hormonal effects on casein synthesis were studied by supplementing the incubating medium with insulin (I), prolactin (PRL), cortisol (F), thyroxine (T4) and triiodothyronine (T3). It was found that both PRL and I were required absolutely for maximal synthesis and almost maximal effect was achieved with 50 ng/ml. The effect of F was less clear, but some increase was achieved at the 200–1000 ng/ml range. T4 and T3 did not affect casein synthesis at a range of 10-11–10-7M while a significant inhibition was observed at 2 × 10-5 M. A time-course study of casein synthesis further substantiated the dominant role of PRL in maintenance or even elevation of the initial rate of casein synthesis in the explants, through the first 4 d of incubation.

A method for detection of proteolysis in milk was evaluated. Amino acids and peptides soluble in trichloroacetic acid were estimated by the Lowry–Folin procedure with expression of results in terms of colour yield equivalent to that of tyrosine (the ‘tyrosine value’ (TV)). Some variables and alternatives in the method of estimation were investigated.

TVs for milk freshly drawn from individual cows were extremely varied (0·31–0·92 mg/ml). TVs for samples of refrigerated milk from daily supply farms were in the range 0·40–0·58 mg/ml; no relationships between TV and bacterial counts were evident with these samples. With bulk refrigerated raw milk supplied to Brisbane for liquid consumption from country depots and local farms equipped with bulk vats, significant positive relationships were found between TV and total bacterial count (TBC) for supplies from some sources, but in no instance was a significant relationship found between TV and psychrotroph or proteolytic psychrotroph count. Significant positive relationships were found between TV of bulk milk supplies from some sources and atmospheric temperature, and between TBC of the supplies and atmospheric temperature. The significance of these various relationships for bulk milks is discussed.

Natural variation in TV imposed limitations on reliability of the method to provide an index of proteolysis; in general the results indicated that its application was restricted to bulk milk cold-stored for at least 3 days.

The prevalence of intramammary infection in 4 commercial goat herds was studied in conjunction with electronic somatic cell count and volume analysis, determined using a Coulter Counter and volume analyser.

Neither streptococci nor mycoplasma were isolated from any half and the prevalence of intramammary infection with Staphylococcus aureus ranged from 0 to 3% between herds. For coagulase-negative staphylococci the range for infected halves was 36–71%. There was no significant difference between the mean total microscopic somatic cell count for halves infected with coagulase-negative staphylococci and those free from infection. A similar trend was observed for electronic somatic cell counts although the mean electronic cell count was greater than the mean total microscopic count on the 2 occasions that they were compared. The correlation coefficients between the 2 cell counting methods were 0·86 and 0·94. Between herds there were significant differences in mean electronic somatic cell count, with herd means ranging from 438×103 to 1684×103 cells/ml. In 2 of the 4 herds studied, milk samples from halves infected with coagulase-negative staphylococci had a significantly higher prevalence of cell volume distributions with a modal cell volume between 65 µ3 and 100 µ3. This was attributed to a higher proportion of polymorphonuclear neutrophils.

Use of electronic somatic cell count and cell volume analysis were considered of little value in predicting infection caused by coagulase-negative staphylococci as there was a high proportion of false negative and false positive predictions.

British Saanen dairy goats (n = 10) were treated with bromocriptine or vehicle from day 147 of pregnancy to day 4 post partum, a treatment duration of 8·8±1·7 d (mean ± SEM). The periparturient prolactin surge was abolished by this treatment, but there were no significant effects on plasma growth hormone or insulin concentrations. Lactogenesis was delayed in the bromocriptine-treated goats, milk yields being significantly depressed (P < 0·01) for the first week of lactation. Yields had recovered to control values by day 10 when prolactin concentrations were still significantly depressed. Mammary gland biopsies were taken on day 4 post partum from five animals in each group. Using this tissue, no significant differences could be shown in mammary morphology or DNA synthesis, but the RNA:DNA ratio was significantly reduced (P < 0·05). After week 1, there were no significant differences between bromocriptine-treated and control goats in milk yield, milk composition, udder volume, time of peak yield or persistence. The goats given short-term bromocriptine treatment at parturition showed prolonged effects on prolactin secretion, their seasonal prolactin rise being severely blunted (P < 0·001). A normal lactation is therefore not prevented in goats by a delay in lactogenesis, suppression of prolactin at parturition or the resulting prolonged depression of circulating prolactin. Goats in established lactation given bromocriptine for 8 d showed, by contrast, a rapid recovery of plasma prolactin concentrations within 5 d post treatment. Milk yield declined significantly (P < 0·03) compared with pretreatment values during and for 1 week after bromocriptine but then began to recover, with no significant change in vehicle-treated goats.

A method for measuring the increasing rigidity moduli and internal viscosities of milk during rennet setting is described. Curves are given showing the degree of reproducibility on replicate samples of dried and liquid milks, and of the effects of changes in calcium levels in the case of the former.

A tentative interpretation of the shape of the main part of the setting curve is proposed. The upper part of the curve generally becomes erratic with the onset of syneresis, but some dried milks do not show this behaviour.

Some curious phenomena concerning the production of syneretic liquid (whey) are described and methods for obviating the disturbing effects of syneresis are discussed.

Flow separation and cavitation effects in a simple homogenizing valve have been studied visually and recorded photographically. The degree of separation depended upon the profile of the seating inlet boundary, the pressure loading and several other interdependent factors. Cavitation did not occur independently of separation; conditions would be suitable for microscale cavitation to occur within the separated flow itself, but this was not discerned with certainty. The suppression of separation and any cavitation, assessed visually, did not influence the homogenizing characteristics of the valve. It was concluded that hydrodynamic forces of cavitation are not responsible for fat globule disintegration in drop-and-lift or poppet types of high-pressure homogenizing valve.