Male dairy calves may be transported from their farm of origin at a young age. This process may involve an extended period off feed and indirect consignment through an intermediate facility, prompting potential welfare concerns. To assess the impact of transport, 59 male Holstein-Friesian dairy calves (5–9 d old) were either (1) held in situ on farm (control); (2) transported for 6 h; (3) transported for 12 h; or (4) transported for 1 h to a holding facility where they were kept for 6 h and then transported for 5 h. All treatments included a 30-h period of feed (milk) withdrawal, and calf responses were measured over time from before their last feed until the completion of the study after the transport and feed withdrawal periods. Apart from increases in serum creatine kinase in calves transported for 12 h, transported calves generally did not differ in blood concentrations of glucose, beta-hydroxybutyrate, lactate, total protein or in packed cell volume, compared with controls (P>0·05). Calf responses to the indirect consignment treatment did not differ from those of other transported calves. Withdrawal of feed for 30 h caused calves to lose 6% of body weight; blood glucose varied from 3·96 mmol/l immediately before daily feeding to 5·46 mmol/l at 3 h post feeding, and then declined to 3·43 mmol/l at 30 h. Calves lay down for 22–32% of the time during transport, and did not show a rebound effect in lying behaviour post arrival in comparison with controls. Best practice transport of 6–12 h duration, including indirect consignment via a holding facility, did not significantly affect calf blood biochemistry and metabolism in comparison with untransported animals. However, extending the time off feed beyond the daily feeding interval resulted in reduced blood glucose concentrations, suggesting that time off feed needs to be carefully managed in young transported dairy calves.

The pH-dependent behaviour of soluble protein aggregates produced by the pre-heating of reconstituted skim milk at 90 °C for 10 min was studied, in order to understand the role of these aggregates in acid gelation of heated milk. The following milk samples were prepared: (1) control (unheated reconstituted milk, pH 6·5); (2) milk heat-treated at pH 6·5 (mHtd6·5) and (3) milk heat-treated at pH 7·2 (mHtd7·2). They were centrifuged and the supernatants (SPNT 1) pH-adjusted to yield a series of pH values ranging from 6·5 or 7·2 to 4·6 using HCl at 20 °C or GDL at 20 and 38 °C. pH-Adjusted SPNTs 1 were re-centrifuged. The resulting supernatants (SPNTs 2) were analysed by OD (at 600 and 280 nm) and SDS-PAGE in order to characterise proteins still soluble as a function of pH. Particle size in SPNTs 1 was analysed by Steric Exclusion Chromatography. The OD600 nm revealed that during acidification soluble casein in both control and heat-treated samples exhibits variations in its optical properties or size as previously shown with micellar casein. In heat-treated samples, soluble casein and heat-induced covalent soluble aggregates precipitate at the same pH value. A progressive acidification of the soluble phase did not separate them. Increasing the temperature of acidification from 20 to 38 °C resulted in an increase in the precipitation pH of the proteins. However choice of acidifier did not have a significant effect on OD profiles. The soluble covalent aggregates from mHtd7·2 were smaller, more numerous, and had a higher content of κ-casein than mHtd6·5. Both types of aggregates began to precipitate at the same pH value but precipitation occurred over a narrower pH-range for soluble aggregates prepared from mHtd7·2. This may explain the higher gelation pH of mHtd7·2 compared with mHtd6·5.

1. The biological value of proteins at an 8% level of protein intake measured on rats by the method of Mitchell (7, 10) was 52 for white bread of 73% extraction, 76 for Cheddar cheese, 75 for a mixture of both foods when each supplied 50% of the protein, and 67 when the two sources of protein were given on alternate days. The true digestibilities were, respectively, 99, 100, 98 and 99.

2. Similar experiments with dried skim milk and dried cooked potatoes yielded biological values of 71 for potato, 89 for milk, 86 for the mixture and 81 for the substances fed separately on alternate days. The true digestibilities were, respectively, 82, 90, 82 and 87.

3. An attempt to carry out experiments of the same type with dried whey and dried potato failed because of deaths of some rats receiving the whey diet, probably because of its high content of lactose. A biological value of 76 was obtained for the potato proteins and of 70 for a mixture of whey and potato in which whey supplied 25% of the protein. The true digestibilities were, respectively, 82 and 68.

4. The biological value and the true digestibility of the proteins of a sample of edible soya-bean flour were, respectively, 73 and 90.

5. It is concluded that there is a marked supplementary relationship between the proteins of milk and potato and those of bread and cheese when the members of each pair supply equal amounts of protein and when they are given together. No supplementary relationship is exhibited when the sources of protein are given separately on alternate days.

The thermal resistance of the lactococcal bacteriophage P008 was investigated between 55 and 80 °C. Inactivation kinetics revealed an order of reaction above 1 and could be determined by a non-1st-order regression model. Phage inactivation was influenced by the medium (milk and Ca-M17-broth). Within the investigated temperature range, milk had a protective effect on phage P008. This was reflected in the rate constant and in the activation energy. Thermal phage inactivation studies reported in literature were re-analysed using non-1st-order regression. The obtained kinetic parameters showed that phage P008 belongs to the most heat resistant lactococcal phages investigated so far.

The effects of a daily supplement of 300 ml fish oil and 20 g rumen-protected methionine, alone or in combination, were investigated in mid-lactation cows receiving a maize silage-based diet ad lib. Fish oil significantly decreased feed intake, increased milk yield, decreased protein and casein concentrations, and especially fat concentration (by 13·1 g/kg) and output. Fat concentration decreased more in primiparous than in multiparous cows. Methionine supplementation increased protein and casein concentrations and outputs. No significant interaction between oil and methionine supplementation was found on milk composition. Treatments did not modify live weight or body condition changes, or lactose and non-casein nitrogenous compounds in milk. Oil plus methionine supplementation made it possible to decrease milk fat content without changing protein content.

Twenty-five strains of lactobacilli isolated from dairy products, including Lactobacillus casei, Lactobacillus plantarum and Lactobacillus brevis species, were grown in semi-defined media and examined for their ability to ferment citrate and produce formate. Of 7 strains of L. casei, all utilized citrate to varying extents, as did 9 of 10 strains of L. plantarum and 3 of 8 strains of L. brevis. L. casei produced 19–35% of the theoretical yield of formate from the citrate utilized, L. plantarum 0–11% and L. brevis 0–28%. Of 2 strains of L. casei tested for their abilities to ferment citrate in the presence of 2% lactose, strain C 5 was unaffected by lactose whereas strain C 2 showed a 45% decrease in the citrate utilized. However, lactose used at 2% concentration greatly reduced formate production by L. casei C 5, which produced 62% of the theoretical yield of formate from citrate after 35 days in the absence of lactose and only 8% in its presence. The yield of diacetyl produced by L. casei C 5 from citrate plus lactose (both at 2% concentration) was 145 times that produced from citrate alone, and 800 times that from lactose alone.

The effect of giving yogurt supplements to Balb/c mice on the various gut-associated lymphoid cells was studied. Animals were fed for 2, 5, 7 and 10 consecutive days. The different lymphoid cell types were identified and counted by haematoxylin–eosin staining of histological slices. The numbers of cells secreting IgA, IgG and IgM and the numbers of T lymphocytes were determined by direct immunofluorescence. The degree of activation of the intestinal macrophages in the small intestine was assessed by measuring the β-glucuronidase (EC 3.2.1.31) released into the intestinal fluid, and also by a histochemical method. Throughout the feeding period, there were no histological alterations in the gut, but there was marked cell infiltration, mainly of plasma cells and lymphocytes. The number of macrophages on the small intestine increased significantly after feeding for 2 d, while the β-glucuronidase activity was only slightly higher that of the controls. After a 7 d feeding period, the number of IgA secreting cells increased, while the values for cells secreting IgM and IgG and for T lymphocytes remained similar to those of the controls. The effect of giving yogurt on lymphoid cells associated with the large intestine was mainly on the numbers of IgA secreting B cells and T lymphocytes, with a marked increase during the whole feeding period in the latter type of cell. Since giving yogurt mainly enhanced the IgA secreting B cells in both small and large intestines, this increase would strengthen the host's defence mechanisms in the intestinal mucosa. Although the number of macrophages was increased, there was no enhancement in their activity, which might have harmed the host by producing an inflammatory response.

Cholesterol and phospholipid concentrations in serum lipoproteins, plasma activities of lecithin:cholesterol acyltransferase (LCAT) and phospholipid transfer protein (PLTP) and lipoprotein lipase (LPL) activity in adipose tissue biopsies were measured ante and post partum in dairy cows given either free or restricted access to feed during the dry period. After parturition, all cows were fed ad libitum. The purpose of this study was to try to understand the earlier observed marked drop post partum in plasma triacylglycerol (TAG) in terms of lipoprotein metabolism in cows developing fatty liver post partum. As would be expected, free access to feed during the dry period induced a rise of hepatic TAG concentrations post partum associated with a decrease in plasma TAG levels. Total and free cholesterol concentrations in the VLDL, IDL, LDL and HDL2 fractions fell immediately after parturition. VLDL and IDL cholesterol concentrations remained at a constant, low level during the entire sampling period post partum, whereas the drop in LDL and HDL2 cholesterol post partum was followed by a rebound rise. Plasma LCAT and PLTP activities decreased by on average 19% and 33%, respectively, after parturition and then rose to values seen before parturition, but there was no effect of feeding regimen during the dry period. Activities of LCAT and PLTP were significantly correlated with cholesterol and phospholipid concentrations in LDL and HDL2. Plasma LCAT activity, as measured with exogenous substrate, and PLTP activity were both positively correlated with HDL3 phospholipid levels. LPL activity in adipose tissue dropped after parturition, the drop being smaller after feeding ad libitum during the dry period. It is concluded that the drop in adipose tissue LPL activity post partum is at variance with the simultaneous fall in plasma TAG. Possibly, the decrease in adipose tissue LPL activity helps to channel fatty acids away from adipose tissue into the udder. The post-partum changes in lipid transfer proteins in the blood are in line with the changes observed in the levels of the lipoproteins.

The objective was to utilize data from modern US dairy cattle to determine the effect of days dry on fat and protein yield, fat and protein percentages, days open, and somatic cell score in the subsequent lactation. Field data collected through the dairy herd improvement association from January 1997 to December 2003 and extracted from the Animal Improvement Programs Laboratory national database were used for analysis. Actual lactation records calculated from test-day yields using the test-interval method were used in this study. The model for analyses included herd-year of calving, year-state-month of calving, previous lactation record, age at calving, and days dry as a categorical variable. Fat and protein yield was maximized in the subsequent lactation with a 60-d dry period. Dry periods of 20 d or less resulted in substantial losses in fat and protein yield in the subsequent lactation. In contrast to yields, a short dry period was beneficial for fat and protein percentages. Short dry periods also resulted in fewer days open in the subsequent lactation; however, this was entirely due to the lower milk yield associated with shortened dry period. When adjusted for milk yield, short dry periods actually resulted in poorer fertility in the subsequent lactation. Long days dry improved somatic cell score in the subsequent lactation. Herds with mastitis problems should be cautious in shortening days dry because short dry periods led to higher cell scores in the subsequent lactation compared with 60-d dry.

The response of dairy cows to once a day (OAD) milking was investigated in four trials. Two trials involved Friesians (F) and Jersey cows selected for high (HP) or low (LP) milk protein concentration. Trial 1 compared 74 HP, LP and F cows milked either OAD or twice daily (TAD) for 2 weeks in both mid and late lactation. Trial 2 compared 98 HP, LP and F cows milked OAD or TAD for 12 weeks in early lactation. Trial 3 investigated the repeatability of production loss by milking identical twin cows either OAD or TAD during three 1 week periods. Trial 4 compared the time course of milk production in 32 cows milked every 12 or 24 h for 72 h. Cows milked OAD produced 10–28% less milk and milk solids in early to mid lactation and 9–13% less in late lactation than cows milked TAD. Losses in fat and protein yield were slightly lower than those of milk. HP, LP and F cows did not differ in percentage loss in milk and milk solids in Trial 1, except for loss in protein yield which was lower for HP than LP and F cows. In Trial 2 the losses in milk and milk solids were lower for HP cows than for F cows but the other differences were not significant. Milk storage ability of the udder (hours worth of secretion) was higher and productivity of the udder was lower for HP cows than F cows. Levels of residual milk did not differ among groups. The loss in udder capacity during lactation was greater for cows milked OAD than for those milked TAD. The correlations for repeated estimates of percentage losses in yields of milk and milk solids between successive OAD periods ranged from 0·29 to 0·49. Secretion rate of cows milked OAD was lower during the second 12 h than the first 12 h during each 24 h milking interval. Prediction of OAD performance based on milk composition and udder characteristics was poor. A high level of residual milk was the factor most consistently associated with high loss on OAD milking.

The chemical composition and rennet coagulation properties at pH 6·4 of milks from 2 commercial herds of Friesian cows were monitored during the change from winter diet to spring grazing. There was considerable variation both in composition and in coagulation properties during this period. There were significant trends for increasing concentrations of casein, Na and lactose, and decreasing concentrations of fat, citrate, K and Mg following the change. Many correlations occurred between concentrations of components, some of which may have physiological significance. Coagulum strength increased after the change to spring grazing and was related to the concentrations of casein, citrate and some of the minerals. Syneresis time did not follow any trend during this period, but was significantly related to concentrations of fat, Na and K. Rennet clotting time did not follow a significant trend immediately after the dietary change, but tended to increase as the summer progressed; it was significantly related to concentrations of Ca, Pi Na and K, as well as to the original pH of the milk. When the concentration of lactose in milk was adjusted, variations in lactose concentration did not affect the coagulation properties of milk.

The dry period plays an important role in maintenance of udder health. Cows are most susceptible to intramammary infections (IMI) after dry-off and near parturition and drying-off procedures may affect the likelihood of IMI at calving. The objective of this study was to evaluate the association of milk yield and infection status at dry-off with the likelihood of IMI at calving by examining different drying-off methods. Cows (n=112) at the Ohio State University Waterman Dairy Teaching and Research Herd were randomly assigned to either an intermittent or a standard, twice-daily milking group 1 week prior to dry-off. All quarters of all cows in the herd were treated with an antibiotic dry-cow product after the last milking. Milk samples were collected 1 week prior to dry-off (pre-dry), on the day of dry-off, and within 3 d of parturition to determine infection status of the quarters. Association between IMI at calving and cumulative milk yield for the final week of lactation and drying-off method was examined using generalized estimation equations with logic link, accounting for potential confounders, such as pre-dry and dry-off infection status, and for the correlated data structure due to quarters clustered within cows. Intermittent milking significantly reduced milk yield at the end of lactation. Increasing cumulative milk yield during the last week of lactation was significantly associated with a greater probability of IMI at calving for quarters that were uninfected prior to dry-off: uninfected quarters of cows producing more than 115 kg during the last week of lactation were 7·1-times more likely to be infected at calving (P=0·0081) than uninfected quarters of cows producing less than 75 kg. Even though the overall cure rate over the dry period was relatively high at 84%, the odds of a quarter being infected at calving was 7·6- and 3·3-times higher if it was infected at dry-off with major pathogens (P<0·0001) or minor pathogens (P=0·028), respectively, compared with an uninfected quarter at dry-off. The results suggest that decreasing milk yield prior to dry-off may serve as an effective means to maintain good udder health in a herd.

The objective of this study was to investigate whether there is a difference in chemical composition and particularly in fatty acid (FA) profile, with emphasis on cis-9, trans-11 CLA, of milk obtained from conventional and organic dairy sheep and goats farms under the farming conditions practiced in Greece. Four dairy sheep and four dairy goat farms, representing common conventional production systems and another four dairy sheep and four dairy goat farms, organically certified, representing organic production and feeding systems were selected from all over Greece. One hundred and sixty two individual milk samples were collected from those farms in January–February 2009, about three months after parturition. The milk samples were analyzed for their main chemical constituents and their FA profile. The results showed that the production system affected milk chemical composition: in particular fat content was lower in the organic sheep and goats milk compared with the corresponding conventional. Milk from organic sheep had higher content in MUFA, PUFA, α-LNA, cis-9, trans-11 CLA, and ω-3 FA, whereas in milk from organic goats α-LNA and ω-3 FA content was higher than that in conventional one. These differences are, mainly, attributed to different feeding practices used by the two production systems. The results of this study show that the organic milk produced under the farming conditions practiced in Greece has higher nutritional value, due to its FA profile, compared with the respective conventional milk.

1. The variation in the time required for the coagulation of milk by rennet and the relationship between milk composition and renneting time were examined.

2. The renneting times of herd bulk milks varied over the relatively narrow range of 3·2–5·4 min., whereas the renneting times of milks from individual cows varied from 1·4 to 12·9 min. and two did not coagulate.

3. In general, milk quick to coagulate gave a firm curd (early lactation milk) and milk slow to coagulate gave a soft curd (late lactation and subclinical mastitis milk).

4. The renneting time of milk was related to the stage of lactation of the cow. In early lactation, renneting times were short and as lactation advanced there was a progressive increase in renneting time; the increase became more pronounced towards the end of lactation.

5. The property of milk most closely related to renneting time was acidity. As pH increased from 6·4 to 7·2, there was a curvilinear increase in renneting time from 1·5 to 13 min. Titratable acidity was related to renneting time in the opposite way to pH.

6. Although milk containing a relatively high concentration of ionized calcium coagulated quickly with rennet, the renneting time of milks containing average, or less than average, amounts of ionized calcium was not related to their content of this constituent.

7. Weak relationships between the concentrations of other milk constituents and renneting time could be attributed to the interrelations of the concentrations of these constituents and pH.

The blue cheese nitrogenous fractions soluble in water and in 5% phosphotungstic acid (PTA) were analysed by HPLC after 3–180 d ripening. In the water-soluble fraction, in addition to four or five major peaks corresponding to amino acids, there were many minor peaks, which increased during ripening. The low molecular mass peptides, soluble in 5% PTA, showed ripening-induced increments. A method combining precipitation with 5% PTA, gel permeation and subsequent HPLC was used to isolate some peptides of cheese. Four peptides containing between seven and ten residues were isolated and their amino acid composition and N-terminal residues determined.

An agar diffusion slide assay using a thin layer of calcium caseinate has been developed as a micro-method for the quantitative study of calf rennet and other proteolytic enzymes. The number and width of the precipitation zones formed as a result of proteolytic activity depended upon the enzyme used, the concentration of calcium ion, pH and temperature. The assay was highly reproducible and particularly suitable for the measurement of large numbers of samples. It was considerably more sensitive than the milk clotting technique and, in general, more sensitive than other standard methods for measuring proteolytic activity.

The variation in deposit formation from milk of 2 herds was measured over a period of more than 12 months using a hot-wire laboratory apparatus. A marked minimum was found in May–June, with high deposit levels between September and April. There was a difference of 2 to 1 between maximum and minimum levels. The amount of deposit was not positively correlated with the mineral or protein contents of the milk, but was strongly positively correlated with fat content. It is suggested that the controlling factor is closely associated with fat content and varies with it.

Methods for measuring the reflectance of milk are described. The effect of heating is to reduce the reflectance of whole and separated milk progressively towards the blue end of the visible spectrum. The reflectance of cream is almost unaffected. The measurement of reflectance at the blue end of the visible spectrum is shown to be a useful method for the determination of the brownness of milk. The variation of rate of browning with temperature and with pH and the effect of storage on brownness are given.

1. A diffusion cup technique using Micrococcus lysodeikticus has been found suitable for lysozyme estimation. By this method raw milk gave only small zones of inhibition. The inhibitory substance of milk was shown not to be lysozyme.

2. Dose-response curves (dilution v. pH) were obtained with Streptococcus pyogenes as the test organism. They indicated that the effect of milk on this organism was the result of the interaction of one stimulatory and at least two inhibitory substances.

3. The existence of two inhibitory substances was confirmed by dilution assays, one, L1, occurring mainly in colostrum, the other, L2, occurring mainly in milk. The inhibition is greatest when L1 and L2 act simultaneously.

4. The pH and heat stabilities of the two substances are slightly different. L1 is most stable at pH 6−6·5, 90% being destroyed at 68° C. L2 is most stable at pH 7 and 95% is destroyed at 74°C.