Bovine and caprine milks have a similar overall gross composition, but vary considerably in the ratios of their casein components. These differences cause significant changes in the ability of caseins to bind and stabilize calcium (Ca). It might be expected that these in vitro variations, which are thought to be due to differences in casein phosphopeptides (CPP) content, could lead to in vivo differences in the digestion and absorption of Ca. To test this hypothesis three milks with different casein ratios [bovine (B), caprine high in αs1-casein (CH) and caprine low in αs1-casein (CL)] were compared with regard to Ca absorption and deposition in growing male rats. For comparison, each milk was Ca-fortified (BCa-milk, CHCa-milk, and CLCa-milk) and CPP, prepared by enzymatic hydrolysis from the respective caseins (extrinsic CPP), were added to both native and Ca-milks. The effects of added CPP (extrinsic) could then be compared with intrinsic CPP released from the gastrointestinal digestion of caseins. Total gastric Ca was sampled at 15, 30 and 60 min after ingestion. No differences were found among the native milks with or without CPP, but the Ca from all Ca-milks (regardless of casein type) appeared to clear the stomach more rapidly and this was enhanced by the extrinsic CPP. The total intestinal Ca was not different among the native milks±CPP, however, it rose more rapidly with Ca fortification, and was higher at 30 min for all CPP-Ca-milks. At 60 min the total intestinal Ca level fell for the CPP-Ca-milks while all others continued to rise. These observations suggest that the CPP in Ca-milks enhance gastric clearance and uptake from the intestine. Ca availability from BCa-milk, CHCa-milk, and CLCa-milk with and without CPP was estimated by both plasma and femur uptake of 45Ca. Ca availability was enhanced at 5 h in the plasma in each case by added CPP. In all cases CPP stimulated Ca availability in the femur, but the CL-CPP was higher (P<0·05) than that of either CH-CPP or B-CPP (extrinsic CPP). Based on the results of this study we can conclude that the addition of CPP will have beneficial effect on the absorption of Ca in growing rats from CaCO3 added to bovine and caprine milks.

Age thickening is a well known phenomenon within the dairy industry, where the apparent viscosity of concentrated dairy solutions increases with storage time under low shear. The objective of the paper is to develop new tools to analyse several aspects of age thickening, including the increases in shear thinning, the degree of thixotropy and the rate of structural build up with time, as well as irreversible structural changes and gelation. The build up of the dispersed phase structure during storage, was captured by a snap shot technique, where concentrated milk samples were stored, and aliquots were taken at periodic intervals and subjected to shear sweep tests to collect flow curves. Rheological modelling using the Herschel-Bulkley model showed an increase in yield stress and consistency, indicating a build up in structure during age thickening. The trend in apparent viscosity with storage time showed two-phases, a slow and steady increase followed by a sharp rise, which could be used to identify the onset of firm gelation. The extrapolated viscosity at infinite shear rate increased with storage time, indicating the build up in irreversible structural components during age thickening.

Recombinant bovine lactoferrin N-terminal polypeptide (rbLF-N) Escherichia coli expression system was constructed and the rbLF-N antimicrobial activity was displayed by enzymatic proteolysis in this study. A 162 bp 5′-terminal fragment of bovine lactoferrin (bLF) gene from bovine liver gDNA was amplified by PCR. The DNA fragment containing exon-2 of the bLF gene was cloned into the expression vector pGEX-4T1 and the glutathione-S-transferase–rbLF-N (GST-rbLF-N) fusion protein was obtained by over-expression in Esch. coli BL21(DE3). After thrombin/pepsin digestion, the rbLF-N was released from the fusion protein. The recombinant peptide was separated and identified by SDS-PAGE, HPLC and LC-MS/MS analysis. A very strong anti-food-born microbial pathogen activity of the rbLF-N peptides was displayed through bio- and kinetic-assays in vitro. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the rbLF-N peptide for bacterial pathogens Staphylococcus aureus, Streptococcus mutans, Esch. coli and Klebsiella pneumoniae were 11·7, 11·7, 11·7, 23·4 μg and 23·4, 11·7, 11·7, 46·4 μg, respectively. This study created a new route for exploring lactoferrin peptide application in food science.

During a 12-month longitudinal study, bulk-tank milk was collected from organic (n=17) and conventional (n=19) dairy farms in the UK. Milk samples were analysed for vitamin A (retinol), vitamin E (α-tocopherol) and β-carotene content. The farming system type, herd production level and nutritional factors affecting the milk fat vitamin content were investigated by use of mixed model analyses. Conventionally produced milk fat had a higher mean content of vitamin A than organically produced milk fat, although there were no significant differences in the vitamin E or β-carotene contents between the two types of milk fat. Apart from farming system, other key factors that affected milk fat vitamin content were season, herd yield and concentrate feeding level. Milk vitamin content increased in the summer months and in association with increased concentrate feeding, whilst higher-yielding herds had a lower milk vitamin E and β-carotene content. Thus, conventional dairy farms in the UK produced milk with a higher vitamin A content, possibly owing to increased vitamin A supplementation in concentrate feeds. However, knowledge of the effects of season, access to fresh grazing or specific silage types and herd production level may also be used by all producers and processors to enhance the vitamin content in milk.

We investigated the effects of a probiotic fermented milk and inulin on gastrointestinal function and microecology. The study was double-blinded and comprised 66 healthy adults (22 male, 44 female), mean age 40 years (range, 22–60 years). After a 12-d baseline period the subjects were randomized to consume, for 3 weeks, 3×200 ml daily of either (1) a fermented milk with probiotics (Bifidobacterium longum BB536, Bifidobacterium spp. 420 and Lactobacillus acidophilus 145), (2) a fermented milk with the same probiotics plus 4 g inulin, or (3) a control fermented milk. During the last 7 d of the baseline and the intervention periods, the subjects kept a record of their defaecation frequency and gastrointestinal symptoms, and collected all their faeces. Intestinal transit time, stool weight and faecal enzyme activities were measured. Thirty-nine subjects were randomized to give faecal samples for analysis of pH and microbes, including lactobacilli, bifidobacteria, coliforms, Escherichia coli, Bacteroides and Clostridium perfringens. Consumption of fermented milk with probiotics or with probiotics and inulin increased the faecal number of lactobacilli (P=0·009, P=0·003) and bifidobacteria (P=0·046, P=0·038) compared with the baseline. Compared with the control fermented milk, both active products increased lactobacilli (P=0·005, ANCOVA). Subjects consuming fermented milk with probiotics and inulin suffered from gastrointestinal symptoms, especially flatulence, more than the others (P<0·001). In conclusion, the probiotic fermented milk product had a positive effect by increasing the number of lactobacilli and bifidobacteria in the colon. Inulin did not alter this effect but it increased gastrointestinal symptoms.

The objective was to characterize the antibody isotype responses to vaccination with a commercial Staphylococcus aureus bacterin in dairy heifers. Twenty-five Holstein-Friesian dairy heifers were assigned at random to one of two groups, vaccinates (n=14) or controls (n=11). Vaccinates received two 5-ml doses of Lysigin 28 d apart in late gestation. Both groups were challenged with a heterologous serotype 5 strain of Staph. aureus by aseptic intramammary infusion on days 6, 7 and 8 of lactation. Samples for serum antibody isotype (IgG, IgG1, IgG2 and IgM) determinations were taken before each vaccination, immediately prior to challenge (6 d post-calving) and at the end of the study (28 d post-calving). Samples for milk antibody isotype determinations were taken immediately prior to challenge and at the end of the study. Antibody isotype sample-to-positive ratios (S[ratio ]P ratio=(mean test sample OD−mean within-plate negative control OD)/(mean within-plate positive control OD−mean within-plate negative control OD)) were determined in milk and serum using a series of ELISAs coated with different strains of Staph. aureus belonging to capsular polysaccharide (CP) serotype 5 or 8 or surface polysaccharide (SP) serotype 336. Vaccinates had higher mean serum IgG1 and IgG2 S[ratio ]P ratios than controls against all three strains of Staph. aureus (P[les ]0·023). Vaccinates had higher mean milk IgG S[ratio ]P ratios than controls against CP8 and SP336 strains of Staph. aureus (P[les ]0·030). Hence, a humoural immune response to the vaccine was detected in serum and milk, but responses varied according to strain and antibody isotype tested.

In extensive pastoral dairy farming systems herds graze 12 months of the year with the majority fed a near-100% pasture or conserved pasture diet. The viability of automatic milking in these systems will depend partly upon the amount of supplementary feed necessary to encourage cows to walk from the pasture to the milking unit but also on the efficient use of the automatic milking system (AMS). This paper describes a study to determine the importance of offering concentrate in the milking unit and the effect of minimum milking interval on cow movement and milking performance in a pasture-based AMS. The effects of feeding rate (FR0=0 kg or FR1=1 kg crushed barley/d) and minimum milking interval (MM6=6 h or MM12=12 h) on cow movement and behaviour during milking were studied in a multi-factorial cross-over (feeding level only, 4 weeks per treatment) experiment involving 27 mixed-breed cows milked through a single AMS. Feeding 1 kg barley in the milking unit resulted in a higher visiting frequency to the pre-selection unit (FR0=4·6 visits/d, FR1=5·4 visits/d, sed=0·35, P<0·05) and a higher yield (FR0=22·5 kg/d, FR1=23·6 kg/d, sed=0·385, P<0·01) but had no effect on milking frequency (FR0=1·6 milkings/d, FR1=1·7 milkings/d, sed=0·04, NS). Minimum milking interval was the major factor influencing milking frequency (MM6=1·9, MM12=1·4 milkings/d, sed=0·15, P<0·01). The absence of feeding in the milking unit had no negative effect on behaviour during milking or the number of cows that had to be manually driven from the paddock. The results show that automatic milking can be combined with a near-100% pasture diet and that milking interval is an important determinant for maximizing milk harvested per AMS.

This work investigated the combined effect of solids content, heating and storage temperatures on the rheological behaviour of reconstituted whole milk concentrates. The powder was reconstituted at 35 °C in a custom built recombination rig to various total solids content (TS) from 10–48% TS. The concentrates were then heated to 45–85 °C and stored at the heating temperature. The rheological behaviour shifter from Newtonian behaviour (below 30% TS) to power law (below 40% TS), with the yield stress observed from 40% TS upwards and time-dependent behaviour was noticed above 44% TS. Higher heating temperatures tend to promote non-Newtonian behaviour at lower solids content. The viscosity-solid content curve showed an exponential relationship, while the viscosity-temperature curve exhibited a minimum at 65–75 °C above 46% TS. During age thickening, the yield stress and the consistency coefficient increased, while the flow behaviour index decreased with storage time. This indicated that the milk concentrates deviated away from Newtonian behaviour during age thickening.

Dubert-Ferrandon A, Niranjan K and Grandison AS 2006 A novel technique for differentiation of proteins in the development of acid gel structure from control and heat treated milk using confocal scanning laser microscopy. Journal of Dairy Research73(4) 423–430

For correspondence; e-mail: a.s.grandison@reading.ac.uk

α1-Acid glycoprotein (AGP) is a lipocalin that is produced mainly by the liver and secreted into plasma in response to infections and injuries. In this study, we evaluated AGP isoforms that can be detected in bovine milk. We found that milk-AGP content is made up of at least two isoform groups, a low MW group (44 kDa) that is produced in the mammary gland (MG-AGP), and a higher MW group (55–70 kDa), that is produced by somatic cells (SC-AGP). Identical SC-AGP isoforms can be found both in milk and blood PMN cells. Analysis of the mammary tissue cDNA showed that the sequence of the MG-AGP isoform is identical to that of plasma AGP. Each group contains several proteins with different MWs and different isoelectric points, as shown by 2D-electrophoresis. The glycosylation patterns of these isoforms were analysed by means of specific lectin binding, to evaluate the degree of sialylation, fucosylation and branching. The MG-AGP glycan pattern was identical to plasma AGP produced by the liver. Several differences were detected, however, between plasma and SC-AGP isoforms, the most evident being the strong degree of fucosylation and the elevated number of di-antennary glycans in SC-AGP. Immunohistochemistry showed that AGP is found in all tissues that make up the mammary gland, but that it is most likely produced for the main part by the alveoli.

The bovine's long generation interval results in a delay of several years when evaluating mammary specific transgenes in genetically engineered animals. This experiment was conducted to evaluate the feasibility of reducing that waiting period. Lactation was induced in prepubertal bull and heifer calves as a means of predicting transgene behaviour during subsequent post-parturient lactations in the heifers themselves, and in daughters sired by the bulls. The animals carry a lactation-specific transgene encoding lysostaphin, an antimicrobial protein that kills Staphlococcus aureus, a mastitis-causing pathogen. Oestrogen, progesterone and dexamethasone were administered as previously described (Ball et al. 2000) to nine heifers (five transgenics) ranging in weight from 80 to 145 kg. Eight bull calves (seven transgenics) weighing 81–178 kg received additional oestrogen and progesterone injection prior to dexamethasone treatment. All nine heifers responded to the milk induction scheme yielding between 19 ml and 4·5 l over 5 d. Milk volume from the four responding males (30 μl to 2·5 ml) was significantly less than that harvested from females (P=0·025). Only bull calves >117 kg had a positive response. Lysostaphin was detected in all transgenic prepubertal heifers and in two transgenic prepubertal bull calves induced. A positive relationship was observed between lysostaphin's stapholytic activity in the two types of lactations (r2=0·907, P<0·001) thus providing a useful means of predicting subsequent lysostaphin production in post-partum milk.