bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual milk in Friesland sheep and the galactopoietic effect associated with oxytocin treatment
Authors: Heap R. Brian , Fleet Ivan R. , Proudfoot Robert , Walters D. Eurof 
Published: June 2009

SUMMARYMature lactating Friesland ewes had a mean lactation yield of 293 ± 26 kg during a lactation period of 35 ± 2 weeks giving an average daily milk yield of 1·2 kg/d. Ewes were injected intravenously after normal milking with either saline (sham) or oxytocin and then remilked to determine the volume of residual (alveolar) milk. After a long milking interval of 16 h oxytocin treatment gave a significantly greater total daily milk yield than the sham treatment (oxytocin minus saline, morning milking, 0·199±0·038 kg, mean ±s.e.m., P < 0·01). Oxytocin had a small significant reverse effect after a short milking interval of 8 h (afternoon milking, –0·065±0·022 kg, P <0·05). The average increase in total daily yield over four stages of lactation was 0·133±0·029 kg (P < 0·01), or 11% of the average daily milk yield. The galactopoietic effect of oxytocin was associated with the efficient removal of residual (alveolar) milk. Residual milk accounted for 7·4 and 27·2% of the total daily milk yield in ewes treated with saline or oxytocin respectively. Residual milk expressed as a proportion of daily total milk yield remained steady in ewes studied between April and July, but declined in September when yields were less than 1 kg/d.
Seasonal changes in the fat composition and concentration of citrate and related metabolites in cows' milk
Authors: Faulkner Anne , Brechany Elizabeth Y. , Mabon Richard M. , Pollock Helen T. 
Published: June 2009

SUMMARYSeasonal variations were observed in the proportion of long-chain (C18and over) and medium-chain (C6–14) fatty acids (FA) in milk fat. Long-chain FA were proportionately higher during the period June to October. Changes were also observed in the concentrations of citrate, isocitrate and 2-oxoglutarate in milk. Changes in [isocitrate]: [2-oxoglutarate] correlated positively with changes in the proportion of long-chain FA in milk fat and negatively with the proportion of medium-chain FA.
Influence of calcium chloride on the chymosin-initiated coagulation of casein micelles
Authors: Bringe Neal A. , Kinsella John E. 
Published: June 2009

SUMMARYCoagulation of para-casein micelles was monitored using a Platelet Aggregometer at 37·8 °C and pH 6·7. The macropeptide released by chymosin was determined quantitatively with fluorescamine. The aggregatability of para-casein micelles integrated over the complete hydrolysis of κ-casein was calculated from the amount of κ-casein hydrolysed during the clotting time (Tc). Low concentrations of CaCl2 enhanced the rate of κ-casein hydrolysis but increases in CaCl2 concentration above 8 mM caused marked decreases in this rate. Calcium chloride enhanced the ability of para-casein micelles to aggregate. Little aggregation of para-casein micelles occurred at 0·6 mM-CaCl2 even after all of the κ-casein was hydrolysed. As the concentration of CaCl2 was increased from 3 to 60 mM, aggregation of para-casein micelles took place at progressively lower levels of κ-casein hydrolysis and the percentage hydrolysis at the Tc decreased markedly from 71±7% to 26±8%. The combined influence of CaCl2 on the velocity of the chymosin-catalysed reaction and on para-casein micelle aggregatability accounted for its effect on the average rate of coagulation (calculated by the reciprocal of the Tc). Results are consistent with the hypothesis that electrostatic repulsions and ionic bonding are involved in the interaction between chymosin and κ-casein.
Studies on the heat stability of milk: I. Behaviour of divalent cations and phosphate in milks heated in a stainless steel system
Authors: Dalgleish Douglas G. , Pouliot Yves , Paquin Paul 
Published: June 2009

SummarySkim milk was heated rapidly to 130 °C in stainless steel tubing, and was then held at this temperature for periods of up to 1 h in a stainless steel holding vessel. Samples taken at intervals during the holding period were analysed for cations, inorganic and organic phosphate and protein in the total sample and in the supernatant after centrifugation at 60 500g. The cation and total phosphate (organic+inorganic) contents of the sedimentable material remained constant throughout the heating, although the caseins became extensively dephosphorylated. Dephosphorylated protein dissociated from the casein micelles during the first 20 min of heating, after which its concentration in the serum began to decrease, perhaps indicating the onset of the heat coagulation reaction.
Metabolism of the lactating cow: II. Digestive elements of a mechanistic model
Authors: Baldwin R. Lee , Thornley John H. M. , Beever David E. 
Published: June 2009

SummaryThe structure and characteristics of a model suitable for estimating digestion within the rumen and rates and patterns of nutrient entry in lactating cows are presented. The model consists of 12 state variables comprising a large particle pool, small particle pools representing insoluble dietary nutrients, soluble pools representing soluble dietary nutrients, and fermentation intermediates and end products. The model was constructed assuming continuous feeding, using Michaelis–Menten or mass action kinetics. The computer program was written in ACSL to run on a VAX computer. A fourth-order Runge–Kutta procedure was used for numerical integration.Sensitivity and behavioural analysis demonstrated that overall stability and sensitivity of the model to individual parameters was generally satisfactory, but the need to improve the description and parameterization of aspects such as particle size in relation to availability, rate and affinity constants for amino acid degradation and rate constants for particle outflow from the rumen was established. Adjustments of the model to examine discontinuous feeding regimes were undertaken and initial results with respect to changes in fermentation rates, rumen acetate levels and microbial metabolism were considered realistic.Comparisons with experimental data were considered satisfactory on forage-based and medium concentrate-containing diets, but with diets comprising 90% cereal, some inconsistencies, especially with respect to predictions of volatile fatty acid production rates, were observed. Reasons for this are put forward and suggestions for improvements in the model are discussed.
Purification of goats' milk casein by reversed-phase high-performance liquid chromatography and identification of αs1-casein
Authors: Mikkelsen Jan , Højrup Peter , Knudsen Jens 
Published: June 2009

SummaryGoats’ milk caseins were separated into four components in a single run using reversed-phase gradient high-performance liquid chromatography. The purity of the isolated components was checked by sodium dodecyl sulphate polyacrylamide gel electrophoresis, amino acid analysis and determination of the N-terminal residue. By a comparison with previously published results for goats’ milk caseins the four peaks were identified as κ-, αs1-, αs2- and β-casein. In order to confirm the existence of αsl-casein in goats’ milk, this component was sequenced for 44 steps, revealing a sequence homologous to bovine αsl-casein and almost identical to the N-terminal sequence previously published by Boulangeret al.(1984).
Heat stable proteinase fromPseudomonas fluorescensAH-70: purification by affinity chromatography on cyclopeptide antibiotics
Authors: Azcona Juan I. , Martín Rosario , Asensio Miguel A. , Hernández Pablo E. , Sanz Bernabé 
Published: June 2009

SummaryA heat stable extracellular proteinase from the psychrotrophPseudomonas fluorescensAH-70 was purified to electrophoretic homogeneity by affinity chromatography on a gramicidin S–Sepharose-4B column. Bacitracin linked to Sepharose-4B was unable to retain any proteolytic activity, whereas the same antibiotic bound to AH-Sepharose-4B retained ~ 25% of the total activity. The purification procedure on the gramicidin S–Sepharose-4B column was easy to perform, fast and reproducible; it resulted in a 207-fold increase in the specific activity and a yield of 41% of the original activity. The purified enzyme was a monomer with a mol. wt of 33000. The enzyme hydrolysed whole casein and its fractions whereas no activity was observed against bovine serum albumin. The enzyme was a metalloproteinase. It was heat stable, havingD-values at 121, 135 and 150 °C of 3·8, 1·9 and 0·6 min respectively.
Increased secretion of insulin-like growth factor I into milk of cows treated with recombinantly derived bovine growth hormone
Authors: Prosser Colin G. , Fleet Ivan R. , Corps Anthony N. 
Published: June 2009

SummarySix lactating, non-pregnant Jersey cows were given subcutaneous injections of recombinantly derived bovine growth hormone for 7 d. Milk yield was increased by 4·5 kg/d on d 7, compared with the average yield of 10·7 ± 0·4 kg/d (mean ± s. e. m.) for the 7d preceding treatment. Concentrations of insulin-like growth factor I (IGF-I) in the milk increased from 0·44 ± 0·04 nmol/1 (mean ± s. e. m.) during the 7 d preceding treatment to 1·6 ± 0·2 nmol/1 on d 7 of treatment. Taking the increase in milk yield into account the total increase in the secretion of IGF-I into milk of one udder half was 6-fold. Plasma concentrations of total IGF-I rose from 15·5 + 1·3 nmol/1 (mean ± s. e. m.) on the day preceding treatment to 56·9 ± 3·6 nmol/1 (mean ± s. e. m.) on d 7 of treatment. Mammary plasma flow increased from 1·6 ± 0·09 to 2·2 ± 0·06 1/min udder half over the same time. Estimates of the amount of IGF-I that reached the mammary gland gave values of 24 and 116 nmol/min udder half before and during treatment respectively. IGF-I in milk of treated cows was associated predominantly with proteins ranging from 40000 to 150000 mol. wt, but a significant proportion (19%) of the total IGF-I was present in the free unbound form. IGF-I crosslinking studies revealed the presence in milk of one specifically labelled band at 31000 mol. wt.
Anaerobic digestion of deproteinated cheese whey in an Upflow Sludge Blanket reactor
Authors: Schröder Emilige W. , De Haast Johannes 
Published: June 2009

SummaryTwo l·9 1 Upflow Anaerobic Sludge Blanket (USAB) reactors, operated at 35 °C, were used for the digestion of deproteinated cheese whey substrate. The C/N ratio was 19, and the alkalinity requirements of the two reactors were satisfied by adding Ca(OH)2 and Na2CO3 in two different ratios respectively. Gas and effluent parameters indicated that reactor 1 (receiving a higher level of calcium) was superior and eventually a loading rate of 7·1 kg COD m−3 d−1 could be obtained in this reactor, compared to a loading rate of 5 kg COD m−3 d−1 which was obtained in reactor 2. Pellets with good settling abilities formed in reactor 1, while the sludge in reactor 2 developed a granular slimy appearance and settled poorly. Investigation of the ultrastructure of the sludge particles revealed a difference in the types of bacteria present in the granules.
Compensatory milk production within the bovine udder: effects of short-term non-milking of single quarters
Authors: Hamann Jörn , Reichmuth Joachim 
Published: June 2009

SummaryDaily quarter-milk yields of eight high-yielding cows (24–28 kg/d) and eight heifers (14–24 kg/d) were measured to examine compensatory changes in milk production between quarters within an udder. Either one, two or three quarters per cow were left unmilked for 12 d, in early or late lactation, and then all quarters of all cows were milked normally for a further period of 12 d. Concentrate feeding levels were constant throughout the experiment.The mean daily yield per cow fell to 26, 59 and 75% during the period of milking either one, two or three quarters respectively. Twelve days after resumption of normal milking the total daily yield per cow was the same for cows continuously milked in two, three or all four quarters. Daily yield in cows with only one quarter milked continuously recovered to only 78% of the level of the pretreatment period.During the treatment period, the mean daily yield of the continuously milked quarters increased by almost 14% for cows milked in one quarter only, by more than 10% for two quarters milked, and by 4% per quarter if three quarters were milked. Milk yields of these quarters remained above their pretreatment levels when milking was resumed in the adjacent quarters.There was no difference in the compensatory effect between cows and heifers in early lactation, but the compensatory effects were lower in late lactation heifers.
Repression ofPseudomonas fluorescensextracellular lipase secretion by arginine
Authors: Fernandez Leonides , San Jose Carmen , McKellar Robin C. 
Published: June 2009

SummaryThe effect of arginine on the production of extracellular lipase byPseudomonas fluorescens32A was studied. Arginine repressed lipase production when N was supplied partially or totally as arginine. Proteinase production was unaffected under the same conditions. Arginine did not repress lipase secretion when cells were pregrown in an arginine-containing medium; however, repression was found with uninduced cells. Several arginine-analogues were tested for the ability to repress lipase secretion and. of these, L-homoarginine and L-canavanine were the most effective. D-Arginine, L-arginine methyl ester, and L-ornithine did not cause repression. With the exception of glutamic acid and methionine, those amino acids that supplied N but not C for growth were found to repress lipase secretion. It is suggested that the accumulation of metabolic intermediate(s) may cause repression of lipase production.
Proline-specific peptidases ofStreptococcus cremorisAM2
Authors: Booth Mary , Donnelly William J. , Fhaoláin Ide Ni , Jennings P. Vincent , O'Cuinn Gerard 
Published: June 2009

SummaryThe present study identifies proline-specific peptidases found inStreptococcus cremorisAM2. These activities were present prcdominantly in the cytoplasmic fraction of the cells with minor amounts in cell membrane fraction. No evidence vvas found for such activities in either the extracellular fluid used to grow the cells, in the wash fraction or in the cell wall fraction. The involvement of these enzymes in release of free proline from proline-containing peptides is considered.
Effects of added salts on the heat stability of recombined concentrated milk
Authors: Augustin Mary-Ann , Clarke Phillip T. 
Published: June 2009

SummaryChanges in heat stability and Ca2+activity of recombined concentrated milk (18% solids non-fat:8% fat) induced by the additions of 0·011–0·217 mol phosphate/kg skim milk solids (SMS), 0·022–0·217 mol citrate/kg SMS, 0·011–0·022 mol Ca/kg SMS and 0·016–0·067 mol EDTA/kg SMS were evaluated. Heat stability was assessed using an objective method which involved determination of viscosity after heating under controlled conditions. Low levels of added phosphate and citrate generally effected an acid shift of the viscosity–pH profile, while higher levels caused a broadening of the profile. Addition of CaCl2at a level of 0·011 mol/kg SMS resulted in a narrowing of the viscosity–pH curve; additions of higher levels resulted in a non-heat stable recombined milk concentrate. EDTA also caused a narrowing of the viscosity–pH curve. The results highlight the importance of pH control for effective stabilization of recombined milk concentrates by additions of phosphate and citrate.
Firmness values of three-phase, milk fat-based table spreads as determined by composition and temperature
Authors: Foley John , Moran Michael A. , Cooney Cornelius M. 
Published: June 2009

SummaryPhysical properties of aerated, high moisture and low calorie table spreads are considerably influenced by the phase volumes of the mix components. Using a statistical approach developed for mixture experiments, the firmness values of milk fat-based table spreads at three different temperatures were quantified in terms of the phase volumes of the fat, water and gas present. A simple equation was found which related changes in relative firmness values with composition at any temperature. Absolute firmness values may be obtained from relative values by multiplying by a factor, F, which is the firmness value of the similarly treated milk fat. This factor is related to the solid fat content by the formula F = 10ks+c, where F is the firmness value in kg cm–2 of milk fat having a percentage solids content, s, k is the slope of a semi-logarithmic plot and c is a constant.
Effect of pre-milking teat dipping on clinical mastitis on dairy farms in England
Authors: Hillerton J. Eric , Shearn Martin F. H. , Teverson Rachel M. , Langridge Susan , Booth James M. 
Published: June 2009

SummaryTwo trials were conducted to investigate the effect of pre-milking teat dipping (PMTD) on mastitis caused by environmentally associated pathogens. The first trial showed considerable variation in effect between herds, so a second, larger trial was conducted. In this second trial a comparison of the rate of clinical mastitis was made between nine matched pairs of dairy herds over 24 weeks of the winter housed period. All herds were near the national average incidence of mastitis before the trial. One member of each pair used their normal method of udder preparation throughout the trial and disinfected all teats after milking with an iodophor disinfectant. In the other nine herds the preparation of all teats, at all milkings, included dipping in a 0·25% available iodine disinfectant, which was left on the teat for 30 s. Every teat was then wiped with a paper towel before cluster attachment. There was no difference in the overall rate of mastitis or the incidence of mastitis caused by any particular type or group of pathogens between the trial groups of herds. Both groups showed a reduction in mastitis compared with the previous winter. Although there were apparent benefits in some pairs of herds there was no overall benefit. In comparison with the previous winter the control herds reported a greater reduction in mastitis than the PMTD herds. The effect of trial supervision on normal practice gave a benefit which overwhelmed any effect of PMTD. There appeared to be no effect of PMTD on the total bacterial count, cell count or iodine content of bulk tank milk. There appears to be no justification for wholesale use of PMTD although most farms and risk groups could benefit from better attention to conventional mastitis control.
Changes in milk on heating: viscosity measurements
Authors: Jeurnink Theo J. M. , De Kruif Kees G. 
Published: June 2009

SummarySkim milk was heated at 85 °C for different holding times. As a result of such heating, whey proteins, in particular β-lactoglobulin, denatured and associated with casein micelles. This led to an increase in size of the casein micelles but also to a different interaction between them. Both these changes could be described by using a quantitative model which was developed for the viscosity of so-called adhesive hard spheres. We applied the model successfully to skim milk and were able to describe on a quantitative basis the changes due to the heat treatment of milk. It was shown that after heating the casein micelles became larger and acquired a mutual attraction. The unfolding of the whey proteins and their subsequent association with the casein micelles appeared to be responsible for these changes. How this reaction influences the fouling of heat exchangers is discussed.
Influence of processing on the molecular modifications of milk proteins in the course of enzymic coagulation
Authors: Iametti Stefania , Giangiacomo Roberto , Messina Giorgio , Bonomi Francesco 
Published: June 2009

SummaryThe formation of hydrophobic sites on the surface of casein micelles as a consequence of enzymic coagulation of industrially heat-treated milk was studied by following the distribution of a fluorescent hydrophobic probe between a free and an aggregated protein fraction. Results were compared with those obtained when coagulation of the same milk samples was followed rheologically in a Gelograph apparatus and by tristimulus colorimetry. Thermal treatment of milk appeared to affect the accessibility of casein to enzyme action, while homogenization influenced the rate of cooperative aggregation of casein subjected to proteolysis.
Neutral volatile compounds in the raw milks from different species
Authors: Moio Luigi , Dekimpe Jocelyne , Etievant Patrick , Addeo Francesco 
Published: June 2009

SummaryA comparative study was carried out on the flavour constituents of bovine, ovine, caprine and water buffalo fresh raw milks. The volatiles were isolated from milks by means of vacuum distillation and liquid–liquid extraction. Eighty neutral volatile compounds were identified using high resolution gas chromatography (HRGC) and HRGC-mass spectrometry. About 30 of these components have not been detected previously in milk. The volatiles in milk were similar for the four species, although several quantitative differences might explain the different odours. The volatiles consisted mainly of ethyl esters, especially those derived from butyric and hexanoic acids. Dimethylsulphone alone comprised ~ 25% of the volatile components in bovine, caprine and ovine milk, but only 4% in buffalo milk. Among the aldehydes, pentanal and nonanal were the most representative. Other aldehydes were present selectively: 3-methylbutanal was found only in buffalo milk; phenylacetaldehyde and benzaldehyde were present in large quantities in caprine milk, and in trace amounts in the other milks. The content of ketones, mainly 2-methylketones, was higher in buffalo milk than in the other three types. Alcohols varied between species, from 1·5% (bovine) to 5% (buffalo). Among these, 1-octen-3-ol and phenylethanol could be particularly important for the aroma of milk. The level of l-octen-3-ol in the milks was: buffalo > ewe > goat ≫ cow. Phenylethanol was not found in ewes' and goats' milk and its concentration in buffalo milk was 100 times higher than in bovine milk. Finally, indole and 4-methylphenol, interesting because of their odorant properties, were present in higher quantities in buffalo, ewes' and goats' milks than in cows' milk.
Purification and some properties of proteinase fromPseudomonas fluorescensNo. 33
Authors: Kumura Haruto , Mikawa Katsuhiko , Saito Zenichi 
Published: June 2009

SummaryThe extracellular proteinase fromPseudomonas fluorescensNo. 33 was purified to electrophoretic homogeneity by a procedure including precipitation with HC1 and (NH4)2SO4, and column chromatography. The enzyme was purified 170-fold giving a yield of 7 % of the original activity. The molecular mass of the purified enzyme was 48000 by SDS-PAGE. The optimum pH and temperature for the hydrolysis of casein were 8·0–9·8 and 30–35 °C respectively. The enzyme was more thermostable in synthetic milk salts solution than in 0·1 M-sodium phosphate buffer, but was heat-labile at 50 °C in both buffer Systems. The activity was inhibited byo−phenanthroline, Hg2+, Cu2+, Fe2+and, to a lesser extent, Ni2+. Caseins were susceptible to the proteinase, but degradation patterns were dependent on the form of the casein.