The economic effect of lactational antibiotic treatment of chronic subclinical intramammary infections due to Streptococcus uberis or Streptococcus dysgalactiae was explored by means of partial budgeting. Effects at cow level and herd level were modelled, including prevention of clinical mastitis episodes and the prevention of transmission of infections. Input variables for our deterministic model were derived from literature or based on 2002/2003 dairy prices and farming conditions in The Netherlands. Sensitivity analysis was used to examine the effect of uncertainty around input variables or changes in price estimates. On farms where pathogen transmission was prevented through proper udder health management, 3-d antibiotic treatment during lactation resulted in an average net profit of €+11·62 over no treatment while 8-d antibiotic treatment had an average negative net result of €−21·83. Sensitivity analysis showed that profitability depends on the probability of treatment-induced cure, pathogen transmission rates, culling rate, retention pay-off, and costs of antibiotic treatment. Three-day antibiotic treatment of chronic subclinical streptococcal mastitis is economically profitable over a range of input values for cure probabilities, transmission rates and losses due to culling. In contrast, 8-d lactational treatment is only profitable for very valuable animals, on farms where the risk of pathogen transmission is high and/or when the farmer is likely to cull a high percentage of cows with subclinical mastitis. Because bacterial flora, cow characteristics and management differ widely between farms, the economic outcome of lactational treatment of chronic subclinical streptococcal mastitis may be highly farm-dependent.

On most dairy farms teat dips are applied to the teats of cows either before or after milking in order to prevent pathogens from gaining access to the mammary gland via the teat canal. In the present experiments, a natural teat dip was developed using a fermentate containing the live bacterium Lactococcus lactis DPC 3251. This bacterium produces lacticin 3147, a two-component lantibiotic which was previously shown to effectively kill Gram-positive mastitis pathogens. Lacticin 3147 activity in the fermentate was retained at 53% of its original level following storage for 3 weeks at 4°C. In the initial experiments in vitro, 105 colony-forming units/ml (cfu/ml) of either Staphylococcus aureus, Streptococcus dysgalactiae or Streptococcus uberis were introduced into the lacticin-containing fermentate. Neither Staph. aureus nor Str. dysgalactiae could be detected after 30 min or 15 min, respectively, while Str. uberis was reduced approximately 100-fold after 15 min. Following these trials, preliminary experiments were performed in vivo on teats of lactating dairy cows. In these experiments, teats were coated with each of the challenge organisms and then dipped with the lacticin-containing fermented teat dip. Following a dip contact time of 10 min, staphylococci were reduced by 80% when compared with the undipped control teat. Streptococcal challenges were reduced by 97% for Str. dysgalactiae and by 90% for Str. uberis. These trials showed that the teat dip is able to reduce mastitis pathogens on the teats of lactating cows.

A study was undertaken in cattle to evaluate changes in milk L-lactate in relation to mastitis. A healthy, rear quarter of the udder of each of ten cows in mid-lactation was infused with 1000 colony-forming units (cfu) of Streptococcus uberis following an afternoon milking. Foremilk samples were taken at each milking from control and treated quarters and antibiotic treatment was applied following the onset of clinical mastitis or after 72 h. One cow did not become infected. Six quarters showed clinical symptoms of mastitis within 24–40 h and this was associated with a more than 30-fold increase in milk L-lactate (to 3·3 mM) and an increase in somatic cell count (SCC) from 4·5×103 to 1×107 cells/ml. Three cows were subclinical, with cell counts ranging from 1·5×106 to 1×107 cells/ml. In these animals, milk lactate ranged from 0·7 to 1·5 mM in the infected quarters up to 40 h post-infection, compared with less than 0·1 mM in control quarters. Milk was examined from 137 cows in mid-lactation which were known to have mastitis. Foremilk samples were taken aseptically from control and infected quarters of cows on commercial farms. Mean milk L-lactate concentrations and SCC were 0·14±0·02 mM and 1·85±0·3×105 cells/ml, respectively, in control (bacteriologically negative) samples. However, L-lactate concentrations exceeded 2·5 mM in the presence of some types of infection, the level of the lactate response being closely related to the impact of the infection on SCC. L-Lactate concentrations were relatively elevated in milk samples taken post partum, declining from 0·8 to 0·14 mM over the first few days of lactation. In conclusion, milk L-lactate has potential as an indicator of clinical and subclinical mastitis in dairy cows.

The frequency distribution of aggregates of casein micelles was determined inelectron micrographs of rennet-treated skim-milk. The average degree of aggregation was constant until after 60% of the coagulation time, then increased linearly to 100% of the coagulation time and subsequently rose more slowly. The observations indicated that the rate of aggregation of casein micelles was determined by the random collision of particles, with no preference for the formation or reaction of aggregates of any particular size. The linking together of micelles was not rate-determining.

Ivermectin (IVM) and moxidectin (MXD) are broad-spectrum endectocides belonging to the avermectin/milbemycin class of antiparasitic drugs not approved for use in dairy sheep. However, these compounds are widely used extra-label to control endo- and ecto-parasites in lactating dairy sheep. Effects of the route of administration on the pattern of IVM and MXD excretion in milk were comparatively characterized in lactating dairy sheep. The relationship between the milk and plasma disposition kinetics after subcutaneous (s.c.) and oral administration at 200 μg/kg body weight was also evaluated. IVM and MXD concentration profiles were measured in milk and plasma using a specific HPLC-based methodology. IVM and MXD were extensively distributed from the bloodstream to the mammary gland and large quantities, particularly for MXD, were excreted in milk. Residual concentrations of IVM were recovered in milk up to 11 d (oral treatment) or 25 d (s.c. treatment) post treatment. However, high MXD concentrations were detected in milk between 1 h and 35 d after its oral and subcutaneous administration. MXD concentrations as high as 3·77 ng/ml (oral) and 30·3 ng/ml (s.c.) were measured in milk at day 35 post administration. A higher MXD excretion in milk, compared with that of IVM, was obtained for both administration routes. An extensive plasma to milk distribution pattern was observed, being the area under the concentration-time curve of MXD obtained in milk up to 14-fold higher than that measured in the bloodstream. The total fraction of the administered dose excreted in milk for MXD was significantly higher than that for IVM, which agrees with the well known higher MXD lipophilicity. The long persistence of milk residual concentrations of MXD and IVM in lactating dairy sheep should be seriously considered before their extra-label use is recommended.

Lactic acid bacteria (LAB) can be isolated from different sources such as milk and cheese, and the lipolytic, proteolytic and glycolytic enzymes of LAB are important in cheese preservation and in flavour production. Moreover, LAB produce several antimicrobial compounds which make these bacteria interesting for food biopreservation. These characteristics stimulate the search of new strains with technological potential. From 156 milk and cheese samples from cow, buffalo and goat, 815 isolates were obtained on selective agars for LAB. Pure cultures were evaluated for antimicrobial activities by agar antagonism tests and for proteolytic activity on milk proteins by cultivation on agar plates. The most proteolytic isolates were also tested by cultivation in skim milk followed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the fermented milk. Among the 815 tested isolates, three of them identified as Streptococcus uberis (strains FT86, FT126 and FT190) were bacteriocin producers, whereas four other ones identified as Weissella confusa FT424, W. hellenica FT476, Leuconostoc citreum FT671 and Lactobacillus plantarum FT723 showed high antifungal activity in preliminary assays. Complementary analyses showed that the most antifungal strain was L. plantarum FT723 that inhibited Penicillium expansum in modified MRS agar (De Man, Rogosa, Sharpe, without acetate) and fermented milk model, however no inhibition was observed against Yarrowia lipolytica. The proteolytic capacities of three highly proteolytic isolates identified as Enterococcus faecalis (strains FT132 and FT522) and Lactobacillus paracasei FT700 were confirmed by SDS–PAGE, as visualized by the digestion of caseins and whey proteins (β-lactoglobulin and α-lactalbumin). These results suggest potential applications of these isolates or their activities (proteolytic activity or production of antimicrobials) in dairy foods production.

Changes with time in the distribution of milk between different storage regions of the mammary gland were studied in goats. Milk was allowed to drain from the gland through a catheter (catheter milk); the gland was then milked by hand, before (hand milk) and after the administration of oxytocin (alveolar or residual milk). The hand-milk fraction was of negligible volume. There was an essentially linear increase in the catheter- plus hand-milk fraction from 0 to 16 h. The alveolar fraction increased up to 6 h, but thereafter remained constant to 16 h. There was considerable but consistent variation between animals in the alveolar fraction as a proportion of total milk volume. The proportion of residual milk was inversely related to milk secretory rate per unit weight of mammary tissue. The hourly administration of oxytocin without milking had no apparent effect on the distribution of milk in the gland 1 h later.

The aim of this research was to enhance the nutritional quality of ewe milk fat by increasing potentially healthy fatty acids (FA) through diet supplementation with unprotected oil rich in linoleic acid, and without detrimental effects on animal performance. Twenty-four ewes were assigned to two high concentrate diets, control or supplemented with 6% sunflower oil (SO), for 4 weeks. No differences between treatments were found in milk production and dry matter intake. Although the SO diet increased milk fat percentage and tended to reduce milk protein concentration, it did not affect milk fat, protein or total solid yield. Most of the modifications in milk FA composition were addressed toward a potentially healthier profile: a decrease in C12:0 to C16:0 and a remarkable increase in the contents of cis-9 trans-11 C18:2 (from 0·94 to 3·60 g/100 g total FA) and trans-11 C18:1 (from 2·23 to 8·61 g/100 g total FA). Furthermore, the levels reached were maintained throughout the period monitored. However, the SO diet increased other trans C18:1 isomer percentages, too. The lack of differences between treatments in the in vitro ruminal fermentation parameters, studied with batch cultures of rumen microorganisms, would indicate no negative effects on ruminal fermentation.

The study was carried out in a commercial flock on 286 Churra breed ewes (566 half-udders) assigned to three lots depending on the type of antibiotic dry therapy received in the lactation previous to the one studied. One-hundred-and-four ewes were given complete therapy in all udders, 103 received selective therapy of infected half-udders, and 79 received no therapy at all. Half-udders of all animals were sampled for bacteriological study at ≤72 h (lambing), 60 d, 120 d, and 155 d (drying-off) post partum. Dry therapy, parity number, lactation stage and therapy×parity interaction contributed significantly to variation in intramammary infection prevalence. Antibiotic dry therapy had the most significant effect. Prevalence during the whole of the subsequent lactation was significantly lower in lots receiving complete (18·8%) and selective (15·6%) dry therapy than in the untreated control lot (48·3%). Coagulase-negative staphylococci and streptococci (in particular Streptococcus agalactiae) were the organisms most significantly affected by dry therapy. In untreated ewes, prevalence increased noticeably from the 2nd to the 6th and subsequent lactations, but no significant changes were observed in the treated lots. Milk yield in the dry treated lots was 6·9% higher that in the untreated one. It was concluded that complete and selective treatments of ewes at drying-off were efficient and comparable methods of reducing the intramammary infection prevalence, improving bacteriological quality of milk, and increasing milk yield.

A study has been made of the effect of udder infections on the proportionate yield and composition of the milk of individual quarters of over 100 cows, and the data from eleven of these cows have been presented.

Typical examples have been given showing that subclinical Streptococcus and haemolytic Staphylococcus infections may persist for months and either cause a gradual reduction in the proportionate yield, and solids-not-fat percentage of a quarter or have no measurable effect, and that both types of reaction may occur simultaneously in the same udder.

Examples also show that following penicillin treatment of clinical cases caused by streptococci and staphylococci there is little recovery in the proportionate yield of the treated quarter until the following lactation, when recovery may be complete.

Chemical and physical changes that occur in Na caseinate (at 1 or 2% in water, pH 7·0) on heating in the range 120–150 °C were investigated by polyacrylamide gel electrophoresis, ion-exchange and gel-permeation chromatography, light scattering, u.v. spectroscopy, amino acid analysis, and the formation of pH 4·6 and 12% TCA-soluble N and 12% TCA-soluble P. The electropherograms of heated samples were smeared and indistinct suggesting intermolecular aggregation which was not reversed by 6 M-urea or SDS and indicating covalent bond formation; αs2-casein was especially sensitive. Aggregation was confirmed by ion-exchange chromatography and light scattering. Fragmentation of the caseins also occurred on heating, as indicated by the formation of pH 4·6 and 12% TCA-soluble N and by gel filtration. Formation of soluble N and dephosphorylation followed first-order kinetics. Concentrations of available lysine and available methionine were reduced by 10–15% on heating at 140 °C for 30min; chemical assays for arginine and tryptophan indicated increases, suggesting interference. Ultraviolet spectroscopy indicated a slight apparent increase in aromatic residues after heating at 140 °C for up to 60 min.

A survey was undertaken to update and extend available information on the vitamin content of pasteurized milk as produced at processing dairies in mainland UK and to investigate regional, seasonal and breed effects. The concentration of total retinol in milk from non-Channel Island (NCI) breeds averaged 61·9 βg/100g in summer and 41·2 βg/100g in winter. Concentrations of β-carotene were 31·5 and 10·5 βg/100g in summer and winter respectively. Concentrations of retinol in milk from Channel Island (CI) breeds were similar, but concentrations of β-carotene were on average 3 times higher. The concentration of vitamin D3 in milk from NCI breeds was 0·033 βg/100g in summer and 0·026 βg/100g in winter. There was no marked seasonal variation in the mean concentration of total vitamin C (14·5 βg/ml). Values for the concentration of B vitamins (βg/ml) were: folic acid 0·060, vitamin B12 0·0042, riboflavin 1·78, nicotinic acid 0·71, pantothenic acid 3·60, biotin 0·020, thiamin 0·46 and vitamin B6 0·61. Seasonal variation in the concentration was most marked for folic acid (c.v. 17·4%) and to a lesser extent for vitamin B12 (c.v. 10·3%). The only breed differences in the B vitamin content were for riboflavin and folic acid, the mean values obtained for milk from CI breeds being respectively 20 and 10 % higher than those from NCI breeds.

We examined the relationship between physicochemical indicators and somatic cells in the milk of dairy cows during experimentally induced mastitis and their significance as indicators for use in controlling udder health. We were concerned particularly with the effect of alveolar milk ejection on the sensitivity of these indicators. In Expt 1, Escherichia coli lipopolysaccharide (Esch. coli LPS) was injected into the left rear quarter to induce an inflammatory reaction in one quarter in each of six cows. The contralateral control quarter was injected with a solution of NaCl (9 g/l). Nine milk samples were taken from both quarters until 60 h after injection. In Expt 2, repeated milk samples were taken every 20 s from one quarter during a 120-s teat stimulation in 20 cows with different somatic cell counts (SCC). Quarters were clustered for low (<5·0 log cells/ml), mid (5·0–5·7 log cells/ml) and high (>5·7 log cells/ml) SCC of the sample taken at t=0 s. Samples were analysed for SCC, electrical conductivity (EC) and Na+ and Cl− concentrations. During the experimental inflammation SCC, EC, Na+ and Cl− peaked at 12 h from LPS administration and values in treated quarters (T) at this time were elevated to 7900, 157, 501 and 169% of the values in untreated quarters, respectively. In Expt 2, SCC, EC, Na+ and Cl− in high SCC quarters were 2520, 121, 283 and 141% of low SCC quarters at the start of stimulation (t=0 s), respectively. Highly significant (P<0·001) differences in EC, Na+ and Cl− between high and low SCC quarters disappeared owing to the onset of alveolar milk ejection 100 s after the first contact with the teat. In conclusion, SCC in cows' milk provided the strongest amplitude in the case of an intramammary inflammation. EC, Na+ or Cl− were useful tools only if the measurements were performed in cisternal milk before the start of alveolar milk ejection.

An examination was made of the effect of varying the protein, lactose and total serum ion content of milk on the rate of production of heat-induced acidity (as measured by pH decrease), on heat stability (as measured by coagulation time), on the relationship between coagulation time and initial pH of milk (as measured by coagulation time-pH curves) and on the interrelationship of these parameters. In addition, the effect on these parameters and their interrelationship of varying the composition and volume of the headspace atmosphere in contact with the milk was investigated. Explanations are proposed for the observed effects on heat stability of varying the composition of milk and the heating conditions, with special reference to the influence of heat-induced acidity.

A method is described for the quantitative determination of phosphatase in raw milk. Using this method, it has been found that phosphatase is sufficiently thermolabile to be destroyed completely by pasteurisation if this process is properly carried out. The absence of phosphatase from a sample of milk or cream indicates with a fair degree of certainty that the milk or cream has been heated sufficiently to destroy such pathogenic organisms as were originally present, though it is of course no guarantee that the product is free from these organisms at the time of testing.

A simple, qualitative test-tube method is described which may be used for differentiating between raw and heated milk, or between raw and heated cream, and which with slight modifications may also be used for distinguishing between butters made from raw or from heated cream.

A sensitive, specific radioimmunoassay for bovine α-lactalbumin (α-la) suitable for measurement of serum, tissue culture media and milk was developed. α-La was not detected in serum from prepubertal male or female cattle, but was detected as early as 60 d of gestation in nulliparous Holstein heifers, the level being greatly increased during the last one third of gestation. Serum from cross bred beef heifers contained less α-la and it was not detected until late gestation. Concentrations of α-la in serum samples from pregnant multiparous Holstein cows decreased at drying-off and subsequently increased just before parturition. Secretion of α-la by mammary tissue explants from steroid-primed prepubertal Holstein heifers was induced by the addition of bovine prolactin, ovine prolactin or human growth hormone to tissue culture media.

Four multiparous Holstein cows, each equipped with a duodenal cannula and an ultrasonic mammary blood flow probe, were assigned to a 4×4 Latin square to measure the effects of duodenal infusions of Leu (0, 40, 80 and 120 g/d) on lactational responses and mammary metabolism of nutrients. Cows were fed a diet of 67·0% corn silage, 5·3% grass hay, 14·2% peas, 7·8% maize starch, 1·0% each of molasses, urea, and sodium bicarbonate and 2·4% minerals and vitamins. Requirements of the remaining 9 essential amino acids were met by infusing into the duodenum 323 g/d of a mixture of amino acids including, Ile, Val, Met, Lys, Trp, Phe, His, Thr, Arg, Tyr and Glu. Milk protein content and yield were highest with 40 g/d of Leu and then progressively declined. Milk fat content and yield were significantly decreased over the entire range of Leu infusions. Arterial concentrations of Leu increased linearly and corresponding mammary arterio-venous differences increased to a plateau with 80 g/d of Leu. As Leu infusions increased, extraction rates of Leu decreased linearly, whereas those of Ile, Val, Lys, Arg, Thr and Tyr were significantly increased. Leu was taken up by the mammary gland according to milk output with 0 and 40 g/d of Leu infused and then largely in excess. Based on responses of protein yield and mammary uptake to milk output ratio, Leu concentration in total amino acids absorbed in the small intestine needs to be close to 8·9% for optimal milk protein synthesis.

Dairy cattle in the Alps are traditionally maintained on high altitude pastures during summer. In recent decades, however, many farmers prefer to maintain the cows always indoor with a hay-based diet. Many authors have shown that the forage type is able to modify the characteristics of milk and cheese. Recently the product specification of PDO Montasio allowed differentiation between mountain cheeses and other products. Aim of this trial is to study the effect of rearing system on the characteristics of milk and cheese produced in this context. One hundred and twenty Simmental dairy cows were considered, 60 grazed on high altitude pasture, and 60 kept indoor and fed a hay-based diet. Cheese production was repeated in two periods (early July and late August) and ripened two and six months. Pasture-derived milk and cheese presented higher fat and lower protein content than hay-derived ones. Rearing systems also affected cheese colour. Textural parameters, hardness, gumminess and chewiness were found to be higher in pasture-derived cheese. In addition, it showed lower level of total saturated fatty acids, and higher level of mono and polyunsaturated fatty acids than hay-derived cheeses. Consumers perceived the difference of cheeses in terms of colour and holes, but they express a similar overall liking. More limited effects of period and ripening time were observed.

The objective was to identify predisposing factors for increased risk of involuntary culling in adult Holstein–Friesian dairy cows. Data were sourced from Scotland's Rural College (SRUC) Dairy Research Centre. Between September 2003 and August 2010 175 cows were culled, a herd culling rate of 33·7%. The major reasons for involuntary culling were fertility (27·4%) and udder problems (26·9%). In the analysis, the culled cows were matched with their cohorts that survived to a later lactation. To identify predisposing factors, a binary logistic model was applied. Cows with higher than average body condition score (BCS) at last service were five times [Odds Ratio (OR) = 4·8] more likely to be culled due to infertility. Cows with low protein yield on day 60 ± 5 in lactation were ten times less likely (OR = 0·1) to be culled. In first lactation heifers, only BCS at last service increased the risk of involuntary culling due to infertility (OR = 13·0). A high milk yield acceleration was a significant (P = 0·04) factor in increasing the risk, five times (OR = 5·2) more, of culling cows due to udder problems. In conclusion, a high BCS at last service, high milk protein yield at around day 60 in lactation and acceleration of milk yield after calving exposed cows to a risk of being culled involuntarily. In practice, monitoring of traits that indicate metabolic imbalance could assist identifying cows at high risk of being culled and contribute to reducing the associated risk through a more effective timely decision.