bluuebunny/crossref_metadata_2025 huggingface dataset:
677. The effect of variations in nutrient intake upon the yield and composition of milk: I. Variations in the amount and type of concentrates fed in winter rations
Authors: Burt A. W. A.
Published: June 2009

1. A series of five experiments on the effects of variation in the concentrate ration of cows receiving normal diets of hay and grass silage are described.

2. Responses in milk yield to the feeding of additional concentrates occurred in all five experiments and were statistically significant in three of them.

3. Mean responses in four experiments with adequate statistical control ranged from 0·7 to 1·0 lb. milk/lb. additional S.E. at levels of feeding from 90 to 120% of the Woodman standard, and were not economic at prices ruling during the winter of 1955–56.

4. There were indications that the responses varied with the yield of the cow, and in two experiments there was clear evidence that the response to a second addition of 20% in the production ration was approximately half of that to the first.

5. The response to additional S.E. was appreciably reduced when normal protein standards were not maintained in the additional concentrates.

6. A limited substitution of hay for concentrates, which did not alter S.E. intakes appreciably, had no appreciable effect on milk yield.

7. Significant responses of solids-not-fat percentage to the feeding of concentrates above the normal standards occurred in two experiments, but not in two others where the control percentages were lower. The importance of factors other than energy intake in influencing this quantity was emphasized.
679. The relationship between milking rate and milk yield
Authors: Sandvik Öystein
Published: June 2009

This paper deals with an investigation on the influence of milking characteristics on lactation yield, maximum daily yield, and persistency carried out at the Institute of Animal Breeding and Genetics at the Agricultural College of Norway.

Data used for the analyses were collected from 57 heifers of Norwegian Red Poll and 111 heifers of Norwegian Red and White Cattle. The Red Polls were recorded at the Hafslund Progeny Testing Station, while the recording of the Reds and Whites were carried out by field control.

When the effect of the milk yield at the recorded milkings on the observed milking characteristics was eliminated, the milking character had no significant effect on the lactation yield, the maximum daily yield, or the persistency. This was the case when the effect of the milk yield at the recorded milkings was eliminated by correction as well as by using only those observations of milking characteristics that were taken when the milk yield was between 6·1 and 7·0 kg. Slow-milking cows are not, therefore, necessarily poor milk producers.
686. The fatty acids of butterfat and the volatile acids formed on oxidation
Authors: Hawke J. C.
Published: June 2009

1. Despite the presence of appreciable quantities of steam volatile fatty acids as glycerides in butterfat, no short-chain fatty acids with odd carbon number have been detected by gas-liquid chromatography of the acids.

2. Mild oxidation of butterfat for short periods of time produces steam volatile fatty acids with odd carbon number. A large proportion of these acids was formic, with smaller proportions of propionic, valeric and nonanoic acids.

3. The relative ease with which short-chain fatty acids are produced on oxidation of fats, points to the danger of contaminating naturally occurring fatty acids with extraneous acids.

4. A total analysis of the fatty acids of New Zealand butterfat by gas-liquid chromatography compared well with similar analyses carried out by previous workers by means of esterfractionation analysis.
733. Lactobacilli in Cheddar cheese: III. The source of lactobacilli in cheese
Authors: Naylor Jill , Sharpe M. Elisabeth
Published: June 2009

Lactobacilli occur in large numbers in cheese (1,2,3,4) and may be responsible for or influence the formation of flavour. It is therefore desirable to find the source of the lactobacilli and the route by which they enter the cheese, so that the cheese flora may be controlled
737. The heat coagulation of milk: II. variations in sensitivity of casein to calcium ions
Authors: Pyne G. T.
Published: June 2009

1. The sensitivity to calcium of the caseinate-phosphate complex of milk heated at 120°C., increases to an early maximum and thereafter steadily declines, apparently in consequence of parallel changes in the sensitivity of its caseinate constituent.

2. A simultaneously developed capacity of the heated complex to bind additional colloidal phosphate appears to be unrelated to these changes in casein sensitivity.

3. Colloidal phosphate content is confirmed as a factor in the heat coagulation of milk.

4. Heat-developed acidity contributes to the heat coagulation of milk primarily by increasing hydrogen-ion concentration and only slightly, if at all, through release of calcium ions from insoluble combinations.

5. Neither serum proteins nor protein-lactose combinations play any significant part in the heat coagulation of milk.

6. The bearing of these results on the heat coagulation of milk in general and on the operation of certain high-temperature stabilization treatments is discussed.
739. The effect of heat treatment and temperature of storage on the yield, quality and chemical composition of karish cheese
Authors: El-Sadek G. M. , Motteleb L. Abd El
Published: June 2009

1. Four batches of soft (Karish) cheese were made from raw and from heat-treated milk containing 1·5% fat and 7% added salt. The cheeses were sealed in tins in contact with their own whey and examined after storage for 1 month and 2 months at room temperature and at 4—6°C.

2. Cheese stored at room temperature lost weight throughout the 2 months, but cheese stored at the low temperature gained weight after 1 month and lost weight after 2 months. Parallel changes occurred in the moisture content and salt content of the cheese.

3. The fat-in-dry-matter content of the cheese increased with room temperature storage, but at 4—6°C. it decreased after 1 month and increased after 2 months.

4. Pasteurization of the milk increased the yield of cheese and the flavour, body and texture were better than that of raw milk cheese stored at the same temperature. The effect of low-temperature storage was, however, greater than that of pasteurization.

5. The total nitrogen content of the cheese decreased throughout storage, particularly at room temperature. The decrease was smaller with pasteurized milk cheese which ripened more slowly. The total nitrogen content of the whey increased throughout storage at room temperature, but at 4—6°C. it increased after one month and decreased slightly after 2 months. The increases were greatest at room temperature and in wheys from raw milk cheese.

6. The initial acidities and also the subsequent rates of increase were higher in wheys from raw milk cheese.

7. The results are discussed in detail.
The reaction of lactose with anthrone and its application to the estimation of lactose in casein and other dairy products
Authors: Richards E. L.
Published: June 2009

Lactose was estimated accurately and rapidly in casein by use of anthrone reagent on the clear filtrate from precipitation of a sodium bicarbonate solution of the casein with 0·1 n-sulphuric acid. The reagent consists of 0·15% (w/v) anthrone in 70% (v/v) sulphuric acid. The ice-cold anthrone solution (10 ml.) was added, with cooling, to 1 ml. of the ice-cold solution containing 0–100 µg. of lactose. The mixture was heated at 100° C. for 6 min. and cooled for 30 min. The optical density of the coloured solution was then measured at 625 mµ
Microscopical observations on Cheddar cheese and curd
Authors: Dean Marion R. , Berridge N. J. , Mabbitt L. A.
Published: June 2009

1. It is possible to study the structure of cheese curd and the disposition of microorganisms therein by microscopical observation of sections cut on the freezing microtome after fixation in formalin.

2. In the small number of cheese examined bacterial colonies were found only in crevices.

3. As ripening proceeded the finer protein structures tended to disappear.

4. The distribution of bacteria in cheese curd is markedly uneven.
Citric acid content of milk in Manitoba
Authors: Reinart A. , Nesbitt J. M.
Published: June 2009

The citric acid content of 440 samples of milk has been determined. The average citric acid content of bulk milk of an estimated 10,000 cows was 0·172%. The average citric acid content of the mixed milk of a Holstein herd of 35 cows was 0·168%, and the average citric acid content of the milk of individual cows was 0·171–0·189%. The coefficients of variation of the citric acid content were: in bulk milk 3·49, in mixed herd milk 7·74 and in the milk of individual cows 10·6–13·5. The citric acid content of the milk of individual cows may differ significantly. The citric acid content of milk in the grazing season was slightly lower and more variable than in the housing season. The stage of lactation had no significant effect on the citric acid content of milk. The time of day of the milking had no influence on the citric acid content of milk. Marked differences may occur in the citric acid content of milk from two successive milkings of an individual cow, and in this study differences up to 0·034% or 23·6% of the lowest value have been found.
Some observations on slow and fast acid-producing variants of strains of Streptococcus cremoris and Str. lactis used as cheese starters
Authors: Garvie Ellen I.
Published: June 2009

Improved growth of Streptococcus cremoris 924 was obtained in the presence of CO2.

When fast and slow acid-producing variants of Str. cremoris 924 were mixed and the mixture subcultured daily the resulting cultures were all active acid producers, irrespective of the initial ratio of fast to slow cells. A balance is established between the two types of cell; probably this will vary with the cultural conditions and vary between strains of Str. cremoris and Str. lactis for any particular conditions of maintenance.

Providing the strains are correctly selected, single-strain starter cultures can be maintained by daily subculture in litmus milk, apparently indefinitely. Activity varies with the present method within wide limits and this variation seems to be a function of the culture.

Freeze drying is a satisfactory method of maintaining active single-strain starters.

The author wishes to thank Miss Shelagh Gibbs for technical assistance, Miss H. R. Chapman for making the cheese, and Messrs. Cow and Gate, Ltd., for supplying the dried milk powder for these experiments.
A quantitative evaluation of some factors affecting the non-fatty solids of cow's milk
Authors: Alexander W. H. , Leech F. B.
Published: June 2009

Ten farms in the county of Durham took part in a field study of the effects of feeding and of udder disease on the level of non-fatty solids (s.n.f.) in milk. Statistical analysis of the resulting data showed that age, pregnancy, season of the year, and total cell count affected the percentage of s.n.f. and that these effects were additive and independent of each other. No effect associated with nutritional changes could be demonstrated.

The principal effects of the factors, each one freed from effects of other factors, were as follows:

Herds in which s.n.f. had been consistently low over a period of years were compared with herds in which s.n.f. had been satisfactory. Analysis of the data showed that about 70% of the difference in s.n.f. between these groups could be accounted for by differences in age of cow, stage of lactation, cell count and breed.

There was some evidence of a residual effect following clinical mastitis that could not be accounted for by residual high cell counts.

The within-cow regression of s.n.f. on log cell count calculated from the Durham data and from van Rensburg's data was on both occasions negative.

The implications of these findings are discussed, particularly in relation to advisory work.
Incorporation of [1-14C] and [3-14C] butyrate into milk constituents by the perfused cow's udder
Authors: Lauryssens Monique , Verbeke R. , Peeters G. , Reinards M.-Thérèse
Published: June 2009

One half-udder from a lactating cow was perfused for 110 min with blood containing 1 mc of [1-14C]butyrate. Inactive sodium butyrate was added at the eightieth minute. The volume of milk collected was 320 ml. One half-udder from another cow was perfused for 120 min in the presence of 0·5 mc [3-14C]butyrate, inactive sodium acetate being added at the sixtieth minute. The volume of milk collected was 150 ml.

The total amount of14CO2recovered was 5·7% of the [1-14C]butyrate given and 7·6% of the [3-14C]butyrate given. In both instances casein, followed by the volatile fatty acids, showed the highest specific activity of the constituents isolated from the milk. The glyceride fatty acids in the udder were fifty times as active as those in the milk. With [3-14C]butyrate the activity of the total fatty acids amounted to 24% and that of total lactose to 0·38% of the added14C. Butyrate did not appear to be used for glycogenesis in the perfused gland. The specific activity of the lower fatty acids of both the udder and the milk increased stepwise with increasing chain length to reach a maximum at C10. A satisfactory explanation for this peculiar14C distribution cannot be given at the present time. There was no evidence of direct esterification of butyrate. Most of the activity of casein was due to labelled glutamic and aspartic acids, the activity of the former being four times as high as that of the latter. The acids of the Krebs cycle isolated from the udder tissue when [3-14C]butyrate was given showed very high activity. No striking differences were observed between the results of the two experiments. It is concluded that butyrate is split into two C2components which behave identically. These are utilized for fatty acid synthesis and take part in the Krebs cycle. The relative14C distribution between the components isolated from milk and those from tissue may be a reflexion of the secretory processes in the udder cells, synthesized fat tending to be secreted in the alveoli after the other constituents.
The effect of various sampling intervals on the estimation of lactation milk yield and composition
Authors: O'Connor L. K. , Lipton S.
Published: June 2009

A study was made of the effect of various sampling intervals on the accuracy of estimating lactation milk yield, fat yield, solids-not-fat (S.N.F) yield, fat percentage and S.N.F. percentage. The basic data consisited of daily milk, fat and S.N.F. yields for eighteen lactations made by twelve Dairy Shorthorn cows. Estimates of the lactation yields and quality were obtained using sampling intervals of 7, 14, 28, 42, 56 and 63 days, and were expressed as differences from the actual values. Only in the case of milk yield was there any effective bias in the estimates. This bias increased with increasing sampling interval.

The distributions of differences between estimated and actual values are presented. The error of estimation increased with increasing sampling interval. Keeping in mind the comparatively small-sized sample used in the investigation, the results are discussed in the light of the purposes for which records are kept.
Haematin compounds and tallowy discoloration in Cheddar cheese
Authors: Rammell C. G.
Published: June 2009

Evidence linking a Cheddar cheese defect, known as ‘tallowy discoloration’, with a haematin-catalysed oxidation of the fat is presented. The defect has been produced experimentally by incorporating blood in the cheese-milk. The possibility that excessive amounts of blood in the cheese-milk may be a prime cause of tallowy discoloration is discussed.
The effect of root feeding on the intake and production of dairy cows
Authors: Castle M. E. , Drysdale A. D. , Waite R.
Published: June 2009

Since grassland conservation crops are normally bulky fibrous feeds and often limit the appetite and nutrient intake of dairy cows, a feeding trial was made in which a basal ration of hay and grass silage was compared with similar rations containing roots. Three rations were compared in a 12–week winter feeding trial using twelve Ayrshire cows. Ration A consisted of 8 lb of hay and 65 lb of grass silage daily, whilst rations B and C contained 30 and 60 lb of fodder-beet, respectively, in addition. With all three rations concentrates were given at 3½ lb per 10 lb of milk. The total weights of dry matter consumed per day were 29·1, 32·5 and 35·4 lb, respectively, for rations A, B and C and were significantly different. For every 1 lb of additional fodder-beet dry matter eaten the decline in the amount of basal feeds consumed was 0·45 lb. The largest effect was on the silage which fell from 10·8 lb of silage dry matter per day for ration A to 8·8 lb for ration B and 6·8 lb for ration C.

The weight of starch equivalent (S.E.) given per day increased significantly from 18·1 lb for treatment A to 22·2 lb for treatment C, whilst at the same time the total weight of crude fibre and lignin eaten decreased significantly in the rations containing fodder-beet.

The mean daily milk yields for rations A, B and C were 37·4, 39·2 and 38·5 lb, respectively, with a response of 0·9 lb milk per 1 lb of extra S.E. given between rations A and B but no further response between rations B and C. The fat percentages of the milk were not significantly different for the three rations whereas the solidsnot-fat (S.N.F.) varied significantly from 8·58% for ration A to 8·77% for ration C— a response of 0·05% S.N.F. for each additional 1 lb of S.E. The change in the S.N.F. was mainly in the protein fraction of the milk. The cows were significantly heavier when on ration C than when on ration A.

The effect of feeding roots on the appetite of the cow and on the resulting milk quality, and the problems of growing roots on intensively managed grassland farms are briefly discussed.
A comparison of the hydrometric and gravimetric methods for the determination of solids-not-fat when applied to the milk of individual cows in a single herd
Authors: Edwards R. A.
Published: June 2009

Five hundred and sixty-nine individual cow milk samples from forty-five cows in a single herd were analyzed for fat by the Gerber method, and solids-not-fat by a standard gravimetric method and by the two commonly used British hydrometric techniques. Three hundred and four of the samples were analyzed also for lactose, protein and ash. Large differences between the total solids values obtained by the hydrometric and gravimetric methods were recorded. The magnitude of the differences from the gravimetric values varied with the season of the year and the stage of lactation. The main factor affecting the differences was the protein content of the milk, and equations for the calculation of total solids content incorporating a protein correction factor are given for use if the protein content be known. The hydrometric methods are considered to be of limited use when applied to milks of individual cows.
Viscometric measurements of the activities of commercial rennets using sodium caseinate as substrate
Authors: Blair G. W. Scott , Oosthuizen J. C.
Published: June 2009

The considerable falls in viscosity of sodium caseinate solutions under the action of rennet are shown to be due to changes in volume and shape (or either alone) of loosely coiled long chain molecules, resulting from the discharge of ionization (‘Third-type electro-viscous effects’). This reduction may be as well effected by small amounts of NaCl or by the separated decomposition products of the rennin-caseinate reaction. Even at the highest practicable caseinate concentrations (9–10% by weight) the solutions are truly fluid over the range of shear-rate of the Ostwald viscometers used

The initial rate of fall of viscosity is found to be proportional to the maximum (initial) specific viscosity, leading to an equation Xk1 = 1/τ where X the proportional viscosity loss, varies with the source of caseinate but is constant for all normal rennets; k1, the first-order reaction constant, varies with the rennet but is independent of the source of casein over a wide range; and τ, which has the dimensions of time, varies with both caseinate and rennet.

The parameter k1 may be found either from the exponential viscosity fall or calculated from the asymptotic initial slope and has been shown to serve as a useful index of rennet activity. This method of rennet testing does not depend on the keeping qualities of rennins, rennets, milks or caseinates. Details of the preparation of caseinates and of the methods for practical testing of commercial rennets are given.
A simple spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes
Authors: Goulden J. D. S. , Sherman P.
Published: June 2009

A rapid spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes using a simple filter absorptiometer has been devised. Turbidities are measured at two different wavelengths to allow for changes in the degree of homogenization. The standard deviation of the differences from the values obtained by the Werner-Schmid method was found to be 2·5% of the mean fat content value. The method also enables the mean fat globule diameter to be determined.
Studies on the properties of New Zealand butterfat: VII. Effect of the stage of maturity of ryegrass fed to cows on the characteristics of butterfat and its carotene and vitamin A contents
Authors: McDowall F. H. , McGillivray W. A.
Published: June 2009

In two outdoor feeding trials with monozygotic twin cows during the spring and early summer months the effects of mature and immature H1 short rotation ryegrass on the composition of the butterfat produced and on the carotene and vitamin A contents of the butterfat and the blood were compared. In both trials the characteristics investigated were markedly affected by the stage of maturity of the grass. The butterfat from cows receiving immature ryegrass was more unsaturated and had higher carotene and vitamin A contents than that from cows receiving mature ryegrass. The blood of cows fed immature ryegrass also contained more carotene than the blood of cows fed mature ryegrass.

It is suggested that variation in the stage of maturity of New Zealand dairy pastures throughout the year is an important factor contributing to the seasonal variations in the characteristics and the carotene and vitamin A contents of commercial butterfat. The influence of stage of maturity is probably associated with the quantity and nature of the pasture lipids.
The effect of preparative conditions on the composition of the k-casein complex
Authors: Hill R. D. , Hansen Raione R.
Published: June 2009

The effects of changes in the conditions of preparation on the composition of the k-casein complex have been studied and a method of preparation is suggested which embodies the optimal conditions. The varied conditions include temperature of precipitation of the acid casein, the pH, temperature, CaCl2 concentration and duration of the CaCl2 treatment, and the conditions of centrifuging. Changes in composition caused by alcohol fractionation are reported and the results are discussed from the point of view of k-casein as a complex of three or more proteins.
The effect of pre-partum feeding of heifers on milk composition
Authors: Foot A. S. , Line C. , Rowland S. J.
Published: June 2009

The effect of the level of pre-partum feeding of Friesian heifers on the yields and composition of the milk in the subsequent lactation has been investigated using 23 heifers on each of 2 treatments. For 1 treatment, over a period of 6 weeks before calving, generous grazing on good pasture was supplemented with 8 lb/cow daily of concentrates, and for the other only restricted grazing of an already sparse sward was allowed.

For the period 3—8 weeks from calving the heifers fed at the high plane pre-partum produced significantly more milk than those fed at the low plane (36·8 compared with 31·9 lb/cow daily). The solids-not-fat (S.N.F.) and fat contents of their milk were also significantly higher (8·71 compared with 8·47%, and 3·72 compared with 3·38%, respectively). For the period 3—14 weeks from calving the effect of milk yield was slightly greater but the effect on composition was less. For the period 3—30 weeks from calving the difference in milk yield remained significant (31·3 compared with 26·1 lb/cow daily), but the average differences in S.N.F. and fat contents over this period (8·63 compared with 8·51%, and 3·75 compared with 3·59%, respectively) were not significant.

The heifers fed at the higher plane increased in liveweight before calving at a rate which was highly significantly greater than that of the heifers fed at the low plane. After calving, the heifers which had been on the higher plane remained almost constant in weight during the first 12 weeks whilst the others regained some of their losses, a difference which was highly significant. This recovery was apparently made at the expense of milk yield and composition.
The effect of concentrates on the voluntary intake of roughages by cows
Authors: Campling R. C. , Murdoch J. C.
Published: June 2009

Seven changeover experiments were conducted to examine the effect of giving restricted amounts of concentrates on the voluntary intake of different roughages by non-lactating dairy cows. The addition of up to 6 kg concentrates daily to the diet of cows receiving roughage ad lib. caused little change in the intake of hay and a small increase in the intake of barley straw. Larger amounts of concentrates of 6 and 8 kg daily reduced hay intake by between 0·2 and 0·4 kg dry matter/kg concentrate dry matter given. When concentrates were given to the cows the rate of decline in intake of hay tended to be greatest with the hays of highest digestibility. The daily addition of up to 8 kg concentrates to the diet of cows offered silage ad lib. caused only small depressions in the intake of silage. The results are discussed in relation to recent work on this subject with cattle and sheep.
The effect of mammary gland denervation on the fatty acid composition of goat's milk
Authors: Ward P. F. V. , Huskisson N. S.
Published: June 2009

Milk was analysed from twin Saanen goats. In one of the goats one mammary gland was transplanted to the neck. The milk yields and fat content from each gland were recorded and the composition of the fat examined using gas-liquid chromatography. The yield and fat content of the milk from all the glands fell within the normal range. With the operated goat, the milk from the transplanted gland differed little in fatty acid composition from that from the non-transplanted gland. Milk from either gland differed little in this respect from milk from the normal goat.
A note on the estimation of D(–) lactic acid using lactic dehydrogenase
Authors: Garvie Ellen I.
Published: June 2009

Van den Hamer & Elias (1958) described a method of estimating D(–) lactic acid using lactic dehydrogenase and a Warburg technique. The enzyme was obtained as an acetone preparation ofEscherichia coligrown on a medium containing lactate as energy source.
The stability of milk protein to heat: I. Subjective measurement of heat stability of milk
Authors: Davies D. T. , White J. C. D.
Published: June 2009

A subjective test for the determination of the stability of milk protein to heat is described. In the test, the time required for particles of coagulated protein to become visible throughout a 2·5-ml sample of separated milk maintained at 135°C in a glass tube rocking at 8 c/min is taken as a measure of stability. The precision of the test was such that single determinations were generally adequate.

Coagulation time decreased by about 12% as rocking speed was increased over the range 4–12 c/min and increased by a factor of about 3 for a decrease in heating temperature of 10 degC over the range 140–105 °C; with some milks the Q10°C value increased to 5–8 a temperature decreased. As sample volume was increased over the range 1–3 ml coagulation time increased, especially With milks whose coagulation was poor (initial clots small). This volume effect appeared to be a consequence of the accompanying decrease in the proportion of headspace oxygen to volume of milk.
Serological differentiation of cow's, buffalo's, goat's and sheep's milks
Authors: Pinto F. C.
Published: June 2009

Milks of the closely related species ox, buffalo, goat and sheep were differentiated by the precipitin test using antisera to blood serum proteins. The antisera were made specific for the homologous species by absorption. The component of milk tested was the lactalbumin–lactoglobulin fraction present in whey. Fraudulent sale of diluted buffalo's milk, cow's milk–buffalo's milk–water mixtures and reconstituted whole and skim-milk powders as genuine cow's milk was detected. Of 270 milks serologically tested, 233 were cow, 26 buffalo, 1 goat, 3 cow–buffalo mixtures, 2 reconstituted whole-milk powders and 5 reconstituted skim-milk powders. Of the samples serologically identified as cow, 135 had analytical figures for fat and solid-not-fat (SNF) only just outside or within the buffalo range.

Milk from any one species was detected in a concentration of 5% (v/v) in milk of a related species. Species identification was made of human milk stains in 2 medicolegal cases. Fresh cow's milk, reconstituted whole-milk powder and reconstituted skim-milk powder were differentiated.
Occurrence of milk proteins in the urine of cows during an extended milking interval
Authors: Lyster R. L. J. , Wheelock J. V.
Published: June 2009

Immunological methods have been used to test samples of urine from 5 cows for the presence of milk proteins. None could be detected when the cows were milked twice daily at the usual intervals, but during an extended milking interval α-lactalbumin was found in the urine of all 5 cows and β-lactoglobulin in the urine of 2 cows. The urine of one cow during and after a milking interval of 39 h contained 1·63 g α-lactalbumin, 1·12 g β-lactoglobulin and a small amount of casein. One of the factors affecting the transfer of these milk constituents from the udder to the urine appears to be their molecular weight.
Seasonal variation in deposit formation from whole milk on a heated surface
Authors: Burton H.
Published: June 2009

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.
Some skin characteristics in British Friesian pedigree bulls and their correlation with relative breeding value
Authors: Nay T. , Johnson Helen
Published: June 2009

A possible relationship between the Relative Breeding Value (R.B.V.) and some skin characteristics has been investigated in 89 British Friesian pedigree bulls made available by the Milk Marketing Board of England and Wales.

It was found that there was a statistically significant correlation between the R.B.V. and the follicle diameter. There was also a correlation between the thickness of the papillary layer and the R.B.V. The possible value of the results for selection purposes is discussed.
The action of rennet on whole milk
Authors: Wheelock J. V. , Knight Dorothy J.
Published: June 2009

The release, by the action of rennet, of peptides which are soluble in trichloroacetic acid (TCA) has been studied using milk samples from individual cows. This release showed an initial marked increase with time of rennet action. After the milk clotted there was no further increase for at least 30 min. There was considerable variation in the total amount of N and of sialic acid released from milk samples taken from individual animals at different times during the lactation.

For a given milk sample treated with rennet, the amount of sialic acid in the filtrate obtained after precipitation with 2% TCA was similar to that obtained with 10% TCA, whereas the amount of nitrogen was much greater with the 2 % TCA. It appeared that the peptides containing sialic acid were released at a slower rate.

On average, about half the total sialic acid in the casein was recovered in the TCA filtrate after rennet action, which suggests that either a proportion of the κ-casein was not accessible to enzyme action or the technique used did not permit full recovery of the sialic acid-containing peptides.
Metabolism of [U-14C]D-fructose by the isolated perfused udder
Authors: Verbeke R. , Massart-Leën Anne-Marie , Peeters G.
Published: June 2009

A lactating mammary gland of a sheep and a goat were perfused for several hours in the presence of [U-14C]D-fructose and received adequate quantities of acetate, glucose and amino acids.

In both experiments, there was a small incorporation of14C in the expired CO2. Smaller radioactivities were measured in milk citric acid, lactose, casein and fat, the activities decreasing in that order. The specific activities of the amino acids from one casein hydrolysate were determined. The highest radioactivities were found in alanine and serine; methionine, glutamic acid and aspartic acid showed a smaller incorporation of14C.

These results indicate that fructose is metabolized only to a very limited extent by the mammary gland. The relative distribution of14C observed among the different substances isolated may be explained by a direct splitting of fructose into two C3-fragments, glycolysis and metabolism via the Krebs cycle.
Section G. General. Nitrogen metabolism and the rumen
Authors: Smith R. H.
Published: June 2009

The fact that rumen micro-organisms have a modifying effect on the utilization of food nitrogen by ruminants has been recognized for very many years (references to early work are given in Hungate, 1966) but until about 1947, when this subject was reviewed by McNaught & Smith (1947), many of the processes involved were not well understood. Since that time a large amount of work has been done in this field and more recent reviews (Chalmers & Synge, 1954; Blackburn, 1965; Hungate, 1966; Waldo, 1968) present a much clearer picture. Most of the work covered by these authors will be mentioned only briefly in the present review and attention will be directed mainly to developments reported in the last few years. Few references to work published before about 1964 will be given as they may readily be found in later publications.
The winter decline in the solids-not-fat content of herd bulk-milk supplies
Authors: Wright J. A. , Rook J. A. F. , Panes J. J.
Published: June 2009

(1) A survey of the composition of the milk of individual cows in 4 commercial herds in the West Riding of Yorkshire was undertaken from October 1967 to May 1968.

(2) In 3 of the 4 herds there was a decline in solids-not-fat (SNF) content throughout the winter feeding period. Milk protein content was at a minimum in January–February but in all 3 herds lactose content also declined and in 2 of the herds this was the major cause of the fall in SNF content.

(3) The decline in lactose content was the result partly of the characteristic effect of an advance in lactation, partly of an increase in the incidence of mastitis throughout the winter period. In all herds there was a significant inverse relationship between lactose content and cell count in the bulked milk of individual cows.

(4) In 3 of the herds autumn-calving (October–December) animals showed a pronounced fall in milk protein content in the early months of lactation which was not observed in summer-calving (July–September) animals. There was no response in SNF or protein content to supplementary concentrates offered towards the end of the winter-feeding period, whereas with the commencement of grazing in the spring there was an immediate increase in both protein and SNF contents.
Milk-clotting and proteolytic activities of rennet, and of bovine pepsin and porcine pepsin
Authors: Fox P. F.
Published: June 2009

The milk-clotting and proteolytic activities of rennet, bovine pepsin and porcine pepsin were compared. The milk-clotting activity of porcine pepsin was extremely pH-dependent around pH 6·6 and coagulation did not occur above pH 6·68. The clotting activity of bovine pepsin was slightly more dependent on pH than that of rennet but no rapid drop-off in activity occurred as with porcine pepsin. Temperature influenced the clotting activity of rennet and bovine pepsin similarly but the behaviour of porcine pepsin was markedly different.

For equal milk-clotting activity, the proteolytic activities of rennet and bovine pepsin were approximately equal and substantially lower than that of porcine pepsin. Electrophoretic examination showed that the proteolysis products of rennet and bovine pepsin were similar and quite different from those produced by porcine pepsin.

The suitability of bovine pepsin as a rennet substitute is discussed.
Studies on the mechanism of the whiteside mastitis test reaction
Authors: Nageswararao G. , Derbyshire J. B.
Published: June 2009

The contribution of certain components of leucocytes and milk to the viscosity and precipitate which develop in the Whiteside mastitis test was studied to obtain information on the mechanism of the reaction. The viscosity obtained in the Whiteside test reaction was considerably less than that in the California mastitis test reaction and the Whiteside test was found to be more dependent on precipitation than increased viscosity.

Leucocyte nuclei were mainly responsible for the formation of the precipitate in the Whiteside reaction and CaCl2 dispersed the precipitate formed by the leucocyte nuclei into small clumps. Leucocyte protein and fibrinogen increased the amount of precipitate formed by the leucocyte nuclei. Fat globules also increased the amount of precipitate, probably by being trapped in the precipitate.

The addition of non-gelable or gelable nuclei resulted in the formation of similar amounts of precipitate in the modified Whiteside reaction. Furthermore, storage of milk for 5 days did not decrease the amount of precipitate formed, indicating that the DNA-protein complex of the leucocyte nuclei need not be present in the native form to contribute to the precipitate in this reaction.
The pattern of release of free fatty acids from milk fat under the action of intrinsic and added lipases
Authors: Hemingway E. B. , Smith G. H. , Rook J. A. F.
Published: June 2009

(1) The rate of release of fatty acids from milk by porcine pancreatic lipase was studied as a model system for the development of lipase taint. The rate was low initially but then increased logarithmically and later declined. Addition of milk which had been subjected to the action of lipase and then boiled to inactivate the enzyme enhanced fatty acid release. An extract containing monoglycerides from lipolysed milk had a similar action whereas an extract of free fatty acids had an effect mainly in the early stages, increasing the initial rate. Addition of Ca2+, which accelerated lipolysis of fresh milk, enhanced the action of fatty acids and depressed that of monoglycerides.

(2) In the early stages of lipolysis there was a preferential release of short-chain fatty acids and a high proportion of these passed into the aqueous phase. These effects were more pronounced at low temperature and at acid to neutral pH. At alkaline pH a greater proportion of the short-chain acids was present in the aqueous phase but the total release of these acids was less.

(3) Fresh milks differed in their response to ‘aeration’ and storage at 4°C. In those in which taint was induced there was a considerable release of fatty acids in response to aeration, and a further release and also a redistribution between the aqueous and fat phases during storage. No relationship was apparent between the amount of fatty acids released and the initial fatty acid content.

(4) The findings are discussed in relation to the development of lipase taint in commercial milks.
Structure of the casein micelle. A proposed model
Authors: Garnier J. , Dumas B. Ribadeau
Published: June 2009

On the basis of complete permeability by high molecular weight reagents of casein micelles in milk and a uniform distribution of the 3 different casein subunits, a model of the micelle structure is proposed. It is composed of an average repeating unit of 1 κ-, 2 αs1;- and β-casein subunits assembled in a 3-dimensional network or branched polymer made of 130–130000 monomers, in which the trimers of κ-casein occupy the nodes and the copolymers of αs1;- and β-caseins make up the branches. All the associations between subunits are through non-covalent bonds. The chemical composition varies with the number of αs1;- and β;-casein subunits in the branches. This proposed structure is strongly supported by evidence from electron microscopy and a scale model has been made. It leads to an understanding of the role of κ-casein in micelle formation and opens new perspectives in explaining some properties of the caseins. It offers an interesting example of a new type of quaternary structure of protein subunits.
The determination of vitamin C in evaporated and fortified sterilized milks
Authors: Toothill Joyce , Thompson S. Y. , Hill W. B.
Published: June 2009

A study has been made of the use of 2,6-dichlorophenolindophenol (DCP) and also of 2,4-dinitrophenylhydrazine (DNPH) with and without chromatography of the DNPH derivatives, for the determination of ascorbic acid (AA) and dehydroascorbic acid (DHA) in evaporated milks, and of AA in AA-fortified sterilized milks.

In the DNPH method, when interfering compounds were removed by the chromatographic separation of the DNPH derivatives, absorption curves typical of the pure DHA derivative were obtained.

The DCP method gave erroneously high values for the AA and DHA content, and the lower values obtained by the DNPH method with chromatography of the DNPH derivatives were judged correct. Thus for an evaporated milk, the values for vitamin C content (AA + DHA) were, in mg/100ml reconstituted milk, 0·88 (DCP method), 0·66 (DNPH method without chromatography), and 0·48 (DNPH method combined with chromatography). The AA contents (mg/100 ml) of the 2 fortified sterilized milks were 3·63 and 5·78 (DCP method); 3·01 and 4·28 (DNPH method combined with chromatography).

The AA contents of the 5 different evaporated milks, determined by chromatography of the DNPH derivatives, ranged from 0·07 to 0·63 mg/100 ml reconstituted milk. The DHA content was negligible.

As judged by the shape of the absorption curves after chromatography of the DNPH derivatives, it is concluded that this method is the most reliable of those studied.
Bovine milk protease
Authors: Dulley J. R.
Published: June 2009

Milk protease, the naturally occurring proteolytic enzyme from fresh raw bovine milk, was purified 629-fold. Purification methods are described which included acid precipitation, ion-exchange and gel chromatography and ammonium sulphate fractionation. It was necessary to use a large-scale purification as the amounts of enzyme in milk are very low.

The basic properties of the enzyme were elucidated from experiments on this partially purified fraction. Under the conditions of assay these showed a wide pH optimum from 6·5 to 9·0 and a temperature optimum of 37°C. The protease was fairly heat stable, the stability being pH dependent.

The source of the enzyme appeared to be the mammary gland, where the enzyme was also detected.
A procedure for the partial fractionation of the αs-casein complex
Authors: Fox P. F. , Guiney J.
Published: June 2009

A method for the partial fractionation of the αs-casein complex is described. It involves removal of κ-casein from iso-electric casein by the method of Zittle & Custer (1963) followed by fractionating the residue (αs- and β-casein) by the urea procedure of Hipp et al. (1952). αs0- and αs1-caseins precipitate from 3·3 M urea at pH 4·6, but much of the αs2-, αs3- and αs4-casein remains in solution and co-precipitates with β-casein from 1·7 M urea at pH 4·9. Chromatography on DEAE cellulose clearly separates β-casein from the αs2-, αs3- and αs4-caseins, which are not resolved by the conditions employed. The method is suitable for the fractionation of iso-electric casein into all its major components (i) κ-casein; (ii) αs0- and αs1-caseins; (iii) αs2-, αs3- and αs4-caseins; (iv) β-casein; (v) γ-casein.
The susceptibility of milked and unmilked udder quarters to intra-mammary infection
Authors: Thomas Carol L. , Neave F. K. , Dodd F. H. , Higgs T. M.
Published: June 2009

The teats of quarters which were milked, and those in which milking had ceased, of 16 cows were exposed to bacteria twice daily for 2 weeks by dipping them in a suspension of streptococci and staphylococci.

Of 32 quarters in which milking had ceased 22 became infected in this period. Eighteen infections were with Streptococcus dysgalactiae, 2 with Streptococcus uberis, 1 with Staphylococcus aureus and 2 with organisms not used in the culture. Only 3 of 32 milked quarters became infected in the experimental period: 2 infections were with Str. aureus and 1 with an organism not used in the culture. Animals differed in their susceptibility to infection.

Quarters which had been unmilked for 2 weeks were as susceptible to new infectionas those in which milking had just ceased.

In this experiment, factors such as intramammary pressure, leakage of milk, concentration of bacterial inhibitors, composition of secretion and cell counts of the secretion did not appear to influence the rate of infection. Yield at drying-off, milking rates and teat patency were not related to the differences in susceptibility between animals. It is suggested that the main reason for the lower new infection rate in the milked quarters is that pathogens entering the streak canal or teat sinus are usually flushed out with the secretion during milking and do not cause infection.
Changes in proteins of Domiati cheese during pickling
Authors: Abd El-Salam M. H. , El-Shibiny Safinaz
Published: June 2009

Domiati cheese from homogenized and unhomogenized pasteurized milk was pickled for 4 months at room temperature. During pickling, the soluble tyrosine and tryptophan contents of the cheese gradually increased, indicating progressive proteolysis.

Gel filtration of cheese extract on Sephadex G-25 revealed the presence of nitrogenous substances of various molecular weights. The maximum formation of amino acids and related substances was observed after 15 days storage.

The changes in the electrophoretic patterns of proteins in the cheese during pickling indicated that both αs- and β-caseins were attacked. β-Casein, however, was much less affected.

Homogenization was found to affect the formation of soluble nitrogenous substances, but was without effect on the electrophoretic pattern of the protein in the cheese.
The temperature coefficient of electrolytic conductivity of milk
Authors: Prentice J. H.
Published: June 2009

The temperature coefficient of electrolytic conductivity of normal milk decreased with temperature from 0·0241 ± 0·0003/°C at 15 °C to 0·0173 ±0·0003/°C at 40 °C. The temperature coefficient for a sample of mastitic milk lay within this range.