bluuebunny/crossref_metadata_2025_split huggingface dataset:
A note on the lactation performance of twin-bearing cows
Authors: Broster William H. , Clements A. June , Hill Randolph E. 
Published: June 2009

SummarySeven pairs of cows were chosen at parturition. In each pair, 1 member had had a twin pregnancy (T) and the other was a comparable cow with a single calf pregnancy (S). All cows were offered the same amount of feed over the first 28 weeks of lactation. In early lactation, intakes were equal; in mid-lactation the T group ate more. The T cows had a lower peak yield of milk than the S cows, but rates of decline in yield in mid-lactation were equal for the 2 groups. Lactose concentrations in the milk were equal throughout lactation, but the fat and protein concentrations were greater for the T group in early lactation. The T group yielded smaller amounts of milk solids. The T group lost less weight in early lactation and gained more weight subsequently. Three of the T group, but only 1 of the S group, did not conceive during the test lactation.
Serum lipoprotein stimulation of lipolysis and its relevance to free fatty acid development in bovine milk
Authors: Anderson Malcolm , Needs Eric C. 
Published: June 2009

SummaryThe role of blood serum lipoproteins in stimulating milk lipolysis was investigated by adding blood serum and heparin to the milk of normal cows and cows in which elevated somatic cell counts were induced by intramammary infusion ofEscherichia coliendotoxin andStaphylococcus aureus. There was considerable variation between individual milks in the extent to which lipolysis was stimulated. In some milks there was almost no response. For values obtained from 29 cows during the first 6 months of lactation a relationship was observed between free fatty acid (FFA) levels in the untreated and serum-stimulated samples (r= 0·776). FFA values were higher after 18 h at 4 °C in milks from infused quarters than in those from control quarters, but this difference was not entirely due to higher values from the infused quarters at 0 h. Both blood serum and heparin stimulated lipolysis in high cell count milks and control milks. The response to heparin was greater than that to blood serum, but the response to both was highly correlated with FFA levels in the untreated milks. There were no differences in the ability of skim-milks prepared from infused and control quarters to promote lipolysis in recombined milks containing sterilized homogenized milk fat globules as a source of substrate. Incubation of blood serum with 2 μg/ml trypsin for 1 h at 37 °C reduced the ability of the serum to promote lipolysis. The importance of lipase activation by blood serum lipoproteins in relation to milk lipolysis is discussed.
Coagulation of renneted bovine casein micelles: dependence on temperature, calcium ion concentration and ionic strength
Authors: Dalgleish Douglas G. 
Published: June 2009

SummaryThe rates of coagulation of completely renneted casein micelles have been measured as functions of ionic strength, temperature, and concentration of Ca2+. At 25 °C and below, the rate constants for the coagulation were found to be low, but increased with temperature so that at 60 °C the particles were coagulating at almost maximum rate permitted by diffusion. This maximal rate at 60 °C was achieved at nearly all of the ionic strengths and concentrations of Ca2+ used. At lower temperatures the rate constant decreased with increasing ionic strength, the dependence being more marked at lower temperatures. Increasing concentration of Ca2+ also increased the rate at low and moderate temperatures. The implications of these results are discussed in terms of specific and non-specific ionic interactions and of hydrophobic bond formation.
Effect of calcium on the hydration of casein. I. Water vapour sorption and fine structure of calcium caseinates compared with sodium caseinates in the pH range 4·6–8·0
Authors: Rüegg Max , Moor Ursula 
Published: June 2009

SummaryHydration of Ca and Na caseinates which were prepared from whole casein at different pH levels (range 4·7–8·0) was determined by means of water vapour sorption measurements in the water activity (aw) range 0·58–0·95. Water uptake of Ca caseinates was systematically lower than that of Na caseinates prepared at equal pH, the differences increasing with increasing pH and aw. Plots of the water content ν. the amount of added hydroxide at constant aw revealed a linear relationship between water uptake and cation content, suggesting that the increase in water uptake is mainly determined by the amount and type of cations associated with the caseins. In the aw range tested, Ca2+ adsorbed about 2–7 and Na+ 3–18 mol water/mol of cation. This implies that replacement of one mol of casein-bound Na+ by Ca2+ is accompanied by a displacement of 1–11 mol water at aw 0·58–0·95. The loss of water is a consequence of conformational changes induced by the chelating and cross-linking effects of Ca2+, which also lead to micelle formation.
N-acetyl-β-D-glucosaminidase (NAGase) levels in bulk herd milk
Authors: Kitchen Barry J. , Middleton Gordon , Kwee W. Seng , Andrews R. Jeffrey 
Published: June 2009

SummaryN-acetyl-β-D-glucosaminidase (NAGase) levels and somatic cell counts (SCC) were determined monthly for 6 months in the bulk milk of 181 suppliers (1063 samples). A highly significant correlation (r = 0·74; P < 0·001) was found between supplier's bulk herd milk geometric mean NAGase activity and SCC. Monthly trends which grouped suppliers into various categories defined by different NAGase and SCC thresholds showed that a similar overall pattern was obtained with both SCC and NAGase. However, further analysis indicated that 18% of the bulk milk which had SCC < 500 × 103/ml had NAGase levels > 25 units. Also, 34% of samples with SCC > 500 × 103/ml had NAGase levels < 25 units. Overall, 24% of all samples did not have corresponding NAGase and SCC results. When the bulk milk of 2 commercial dairy herds was tested monthly over 12–18 months whilst the infection status of all quarters in the herds was regularly monitored, those herds with low incidence of mastitis (5% quarters infected) had significantly lower bulk milk SCC and NAGase levels than those with a high incidence of mastitis (22% of quarters infected). This suggests that NAGase measurement on bulk herd milk would be a simple means of monitoring infection status of dairy herds and of rapidly classifying a supplier's milk as being of low, medium or high SCC status. The possible combined use of SCC and NAGase levels in bulk milk monitoring schemes is discussed.
Viscosity and heat capacity of whey retentates from sheep's milk cheese
Authors: Fernández-Martín Fernando 
Published: June 2009

SummaryDifferent concentrates from sheep's milk cheese whey, with up to 26·5% solids, were prepared in the laboratory by reverse osmosis, and their viscosities and heat capacities determined over the temperature range 5–80 °C. These products behaved like other liquid milk concentrates previously studied, so that similar analytical expressions could be used to predict these physical properties in cheese whey as a function of the temperature and solid content. A nomogram is also given for an easier computation of each property. The water in liquid dairy products and their concentrates up to 40% solid content appears to behave as pure, free water with respect to its partial contribution to the heat capacity of these products, its apparent heat capacity being 4·208±0·016 kJ. kg-1°C-1.
Effect of heat induced interaction between β-lactoglobulin and κ-casein on syneresis
Authors: Pearse Martin J. , Linklater Peter M. , Hall Robert J. , Mackinlay Antony G. 
Published: June 2009

SUMMARYThe effect of preheating skim milk and artificial micelle milk on curd syneresis was studied. The inhibition of syneresis caused by heat was dependent on the presence of β-lactoglobulin (β-lg) and to a lesser extent α-lactalbumin. The degree of inhibition increased with increasing amounts of added β-lg and preheating temperature. This agrees with the hypothesis that the detrimental effect of preheating on syneresis is due to complex formation between β-lg and κ-casein. This complex appeared to be mediated via thiol–disulphide exchange and its formation appeared to interfere with the micelle–micelle interactions responsible for syneresis.
Heat stability of plasmin (milk proteinase) and plasminogen
Authors: Alichanidis Efstathios , Wrathall Julia H. M. , Andrews Anthony T. 
Published: June 2009

SUMMARYThe effect of heating on plasmin activity in various media, including phosphate buffer pH 7·0, skim milk, blood plasma, solutions of casein and solutions of whey proteins were investigated. Plots of log residual activity υ. heating time were linear at all temperatures from 63 to 143 °C. In buffer solutions the presence of casein led to substantial substrate protection, the Arrhenius plots being linear both in the presence and absence of casein. The activation energy, Ea, for the inactivation reaction, was 62·4 kJ/mol in buffer alone and 58·4 kJ/mol with casein present at 25 mg/ml. In skim milk, despite the presence of casein at a similar concentration, plasmin was no more stable to heat than in buffer alone, and a curved Arrhenius plot was obtained indicating a more complex inactivation mechanism. Heating in the presence of proteins having free -SH groups accelerated the inactivation of plasmin. The role of -SH groups was confirmed by experiments with added α-lactalbumin, in which no free -SH groups occur, and reduced carboxymethylated β-lactoglobulin, both of which were without effect. In blood plasma, plasmin was less stable to heat than in buffer (pH 7·0) or in skim milk. Plasminogen behaved very similarly to plasmin either when activated to plasmin with urokinase before heating or when activated afterwards. A hypothesis is presented to describe the heat inactivation and denaturation of plasmin. Technologically important findings are that in skim milk plasmin was largely unaffected by pasteurization conditions and 30–40% of its activity remained even after ultra high temperature processing conditions.
Radioimmunoassay for measurement of bovine α-lactalbumin in serum, milk and tissue culture media
Authors: Akers R. Michael , McFadden Thomas B. , Beal W. E. , Guidry Albert J. , Farrell Harold M. 
Published: June 2009

SUMMARYA 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.
Effect of different neutralizing treatments on the efficiency of an anaerobic digester fed with deproteinated cheese whey
Authors: Haast Johannes De , Britz Trevor J. , Novello Johannes C. 
Published: June 2009

SUMMARYDeproteinated whey, prepared from sweet whey powder, was digested anaerobically in a downflow fixed-bed reactor at 35 °C. Different pH control treatments were applied over a period of 210 d. Initially NaOH was added at a concentration of 68 mequiv. l-1 substrate. This was successfully replaced by 80 mequiv. Na2CO3l-1 which resulted in a 15·5% increase in biogas production and a 6·7% increase in CH4 production. A decrease in the quantity of Na2C03l-1 added led to signs of instability and a drop in CH4 production. The stepwise addition of urea restored the stability, and a further increase of urea, to a level of about 20 mequiv. l-1, made it possible to replace Na2C03 completely. When all pH control measures were omitted, complete failure resulted within 10 d. Methane yields, under stable conditions, varied between 0·321 and 0·272 m3 kg-1 chemical oxygen demand (COD) removed which corresponds to 92 and 78% of the theoretical yields. Carbon balances indicated that between 60·8 and 68·5% of the carbon fed was converted to biogas. No toxicity was observed at a carbon: nitrogen (C/N) ratio of 7·7. This was in contrast to previous results where toxicity had occurred at the same C/N ratio but at a higher concentration of Na.
Effect of breed of cow (Friesian and Montbéliarde) on spontaneous and induced lipolysis in milk
Authors: Chazal Marie-Paule , Chilliard Yves 
Published: June 2009

SummaryLevels of free fatty acids (FFA) were determined immediately after milking (initial FFA), and after 22 h storage at 4 °C, either without (FFA-22) or with a mechanical induction of lipolysis (FFA-22I), in milk from Friesian and Montbéliarde cows in the same herd, at identical stages of lactation and pregnancy and receiving the same feeding regimes. There was no difference between the two breeds in initial FFA and FFA-22 contents whatever the lactation period. This was also true during late lactation when lipolysis was further increased after feeding a poor quality grass silage. The observation that milk FFA-22I content from the Montbéliarde cows was higher than that from Friesian cows in summer, but not in winter, requires cautious interpretation as the activation treatments were not comparable, owing to the different ambient temperatures during activation in these two periods.
Microbiological assay of blood serum for the vitamin B12status of dairy cows
Authors: Carlos Gerard M. , Telfer Stewart B. , Johnson C. Lewis , Givens D. Ian , Wilkins Roger J. , Newberry Robert D. 
Published: June 2009

SummaryFour vitamin B12assays were compared using blood sera from Friesian cows on winter diets or grazing. In herd 1, ten animals were blood-sampled three times at monthly intervals and the vitamin B12concentration of the sera determined by thePoteriochromonas malhamensisandLactobacillus delbrueckiiassays. At all three sampling dates the results produced by theP. malhamensisassay were significantly greater than those produced by theL. delbrueckiiassay. Cows in herd 2 were divided into two groups, each of 30 animals. One group was given a soluble glass bolus releasing cobalt and the other was unsupplemented. Milk yields were recorded throughout the experimental period and herbage samples were taken at intervals for cobalt determinations. Blood samples were taken at intervals from January to September 1983 and the vitamin B12concentration of the sera determined by four different assay methods: theP. malhamensisandL. delbrueckiimicrobiological assays and the Becton Dickinson and RIA Products ‘No-boil’ radioassays. The last of these failed to detect vitamin B12in any sample. There was a significant difference between the results obtained by the three other assays, with the Becton Dickinson radioassay consistently producing the lowest result and theP. malhamensisassay the highest result of the three. There was no significant effect of cobalt supplementation on milk yield.
Influence of somatic cell count on the whipping properties of cream
Authors: Needs Eric C. , Anderson Malcolm , Kirby Simon 
Published: June 2009

SummaryCows were infused with Escherichia coli endotoxin to provide a pool of milks with high somatic cell counts (SCC). This was mixed with bulk tank milk obtained from either of two Institute herds, producing a range of milks containing 0, 10, 20, 30 and 100% high SCC (HCC) milk. Creams containing 38% fat were produced from these milks on nine separate occasions; five times from winter milks and four times from summer milks. The SCC of the milks, the free fatty acid concentration of the unwhipped creams and the whipping time, stiffness and overrun of the whipped cream were measured. Whipping time and stiffness increased and overrun (volume increase) decreased as the proportion of HCC milk in the mixture increased. However, these changes were statistically significant only when comparing the 100% HCC milk with the other treatments containing lower levels of HCC milk. Creams produced in the summer took less time to whip and were less stiff than winter creams but there was no change in overrun. The source of bulk milk supply affected the stiffness and overrun of the whipped creams. Free fatty acid concentration appeared to have no direct effect on whipping characteristics.
Factors influencing the concentrations and yields of milk constituents and their interrelationships
Authors: Sharaby Mahmoud Abdelalim 
Published: June 2009

SummaryMilk samples from 250 Jersey and Friesian cows were collected and used to investigate the pattern of interrelationships between milk constituents and to test the effects of breed, sire, parity, stage of lactation, season of calving and milking time on them. Breed and sire effects were significant for all constituents. Overall Jersey cows produced significantly higher milk constituent concentrations except lactose, but the test-day yields in Friesians were significantly higher. Milk constituents had varying responses to parity, days in milk and season of calving. Correlation between different constituents and their regression on each other suggested antagonistic relationships. The pattern of association between constituent concentrations in Friesian cows was similar to that between test-day yields, indicating an equilibrium between volume and content of milk.
Lack of correlation between milk glucose concentrations and rates of milk production in the rat
Authors: Grigor Murray R. , Carrington Janet M. , Arthur Peter G. , Hartmann Peter E. 
Published: June 2009

SummaryConcentrations of lactose, α-lactalbumin (α-la), glucose and glucose-6-phosphate were measured in milk obtained from rats under conditions where the rates of milk production varied from 0 to 2·6 g/h. In the milk from rats fed a low protein diet where milk production was 0·9 g/h, the concentration of α-la was 1·5 mg/ml, being significantly lower than that in the milk of control rats at 2·9 mg/ml and where the rate of milk production was 2·6 g/h. No differences were detected in the glucose concentrations. When rats were fed restricted amounts of the control diet and where milk production varied from 0 to 1·7 g/h during the course of the day, no differences in the concentrations of either α-la or glucose were detected. These results suggest that considerable caution must be used in interpreting the significance of milk glucose in the rat.
Precision conductometry in milk renneting
Authors: Dejmek Petr 
Published: June 2009

SummaryOn renneting, the electrical conductivity of milk decreased as viscosity increased. The sigmoidal time course of the decrease resembled the time course of shear modulus, but was more rapid. The total amount of change was independent of the amount of rennet and proportional to milk conductivity and its casein content. The conductivity change was interpreted as a change in the way casein micelles obstructed the path of the charge-carrying ions.
Ultrafiltration of reconstituted skim milk
Authors: El-Salam Mohamed H. Abd , Shahein Nadia 
Published: June 2009

The manufacture of Domiati cheese by ultrafiltration (UF) processing of recombined milk bas been described in several reports (El-Shibinyet al.1982; Bogaard, 1986). This method has several potential advantages in areas short in milk production. In Egypt, a new plant has been established recently for the manufacture of Domiati cheese on the basis of this technology.The behaviour of fresh pasteurized skim milk during UF has been described (Glover, 1971; Setti & Peri, 1976; Patel & Reuter, 1985; Chiang & Cheryan, 1986). Similar studies are lacking for reconstituted skim milk or recombined milk. Skim milk powder is usually subjected to variable heat treatments during processing which are known to affect its properties. These heat treatments have been used as a basis for classification of skim milk powders. Therefore, studies on UF of reconstituted milks previously subjected to different heat treatments would be important in the adaptation of this technology to cheese manufacture.We describe here results obtained for permeation rates of reconstituted skim milk during UF compared with fresh pasteurized skim milk.
Changes in the concentration of metabolites in milk from cows fed on diets supplemented with soyabean oil or fatty acids
Authors: Faulkner Anne , Pollock Helen T. 
Published: June 2009

SummaryCows were fed on diets supplemented with soyabean oil or soyabean fatty acids which in some cases were protected from rumen hydrogenation. The fat-containing diets reduced the output of short- and medium-chain fatty acids in milk. Associated with this fall in short- and medium-chain fatty acids was a decrease in the concentration of 2-oxoglutarate and an increase in that of isocitrate and citrate. Protection of polyunsaturated fat from rumen hydrogenation had no significant effect. Milk yields were unaffected by diet, but the variation in milk yield among cows correlated positively with the concentration of glucose in milk.
A study of surface hydrophobicity of milk proteins during enzymic coagulation and curd hardening
Authors: Peri Claudio , Pagliarini Ella , Iametti Stefania , Bonomi Franco 
Published: June 2009

SummaryThe formation of hydrophobic sites on the surface of casein micelles as a consequence of rennet action has been followed through the binding rate of a fluorescent probe and its distribution between a free and an ‘aggregated’ protein fraction. The variation of this parameter has been related to clotting time and curd hardening kinetics.Results show that a first aggregation of casein through hydrophobic sites interaction began as soon as rennet was added to milk. At the natural pH of milk, the sol-gel transition occurred when all the casein micelles were already involved in large aggregates. This was not the case with slightly acidified milk (pH 6·5 and 6·3) where clotting occurred well before the first aggregation step had been completed. The surface hydrophobicity of casein continued to increase in the curd due to continuing enzymic action and structural rearrangements. When this process has been completed the hardening of curd proceeds at an accelerated pace until it reached its maximum asymptotic value.
Titration – a rapid method for the determination of proteolysis in cheese
Authors: Ollikainen Pia 
Published: June 2009

Titration is an old method used for the determination of acidic and basic groups of a molecule. Several metabolic end-products in cheese are compounds with acidic or basic groups, e.g. propionic, acetic and lactic acids, amino acids, amines and ammonia. A number of colorimetric and fluorometric methods have been used to study proteolysis in cheese; some are time-consuming with several steps, and certain of the reagents are hazardous.We have used acid-base titration for analysis of the products of proteolysis in Swiss-type cheese. The titration system was that originally developed for use in silage analysis (Moisio & Heikonen, 1989) and applied to cheese it has proved to be useful, easy and rapid with an accuracy similar to that achieved by colorimetry.
Influence of static and dynamic teat characteristics and milking time on udder health in Norwegian Red Cattle
Authors: Rønningen Odd , Reitan Arne Dagfinn 
Published: June 2009

SummaryA field survey with 70 cows in 15 herds was carried out to find a possible correlation between the depth of teat penetration into the teatcup liner during milking, and udder health. The investigation showed that the depth of penetration into the liner of fore teats was positively correlated with the fore teat end hardness (P < 0·01), and with the frequency of clinical mastitis for the whole udder (P < 0·1). The investigation also showed that the teat end height above the floor was negatively correlated with mean cell count for the previous year (P < 0·001), and with the prevalence of subclinical mastitis in rear quarters (P < 0·05).