The copper-binding protein, caeruloplasmin, has been detected in bovine blood serum, colostrum and normal milk using immuno-diffusion techniques by comparison with a precipitating oxidase-positive system of human caeruloplasmin and anti-caeruloplasmin. The possible importance of this copper-binding protein of milk in the oxidative deterioration of milk and dairy products is discussed.

The changes in the yield and composition of the mammary gland secretion in the first 16 days of the dry period have been investigated in 6 cows. The quantity of secretion, lactose, potassium, casein, α-lactalbumin, β-lactoglobulin and fat present in the gland decreased rapidly. A decrease was also observed for sodium, chloride, residual albumin and proteose-peptone + globulin but was much less marked. Changes in composition were qualitatively similar to those normally occurring at the end of lactation but they were much more pronounced. Within 8 days after drying-off the concentrations in the secretion of sodium, chloride and potassium were similar to those of blood. There were differences between, animals in the rate at which the changes developed. As the secretory activity of the gland ceased, the constituents of the mammary gland secretion appeared to be resorbed.

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 quantities of acetaldehyde and diacetyl produced in skim-milk and MRS media are reported for strains of Streptococcus lactis, Str. cremoris, Str. diacetilactis, Str. faecalis and Str. thermophilus obtained from culture collections or freshly isolated from natural milk cultures used in cheese manufacture. The diacetyl: acetaldehyde ratio in skim-milk medium was found to be approximately 0·1:1 for Str. lactis and Str. cremoris, 0·5:1 for Str. diacetilactis (5:1 for Str. diacetilactis PIM 13 and K.2 strains) and for Str. thermophilus 0·3:1, in skim-milk medium, and 0·8:1, in MRS medium; in the latter species cultured in MRS medium the ratio varied from 3·5:1 to 0·04:1 and when cultured in milk from 1·2:1 to 0·03:1.

In both media all strains of Str. thermophilus formed more acetaldehyde and diacetyl than other homofermentative lactic streptococci.

The ratio diacetyl: acetaldehyde in 9 strains of Str. diacetilactis was found to be unsuitable for a good culture flavour.

A study was made of the destructive effects of repeated heat processing of milk on its content of vitamin B6, vitamin B12, thiamine and folic acid. Losses of thiamine and vitamin B6 were cumulative, and increased with frequency and severity of heating.

With folic acid, the first heat treatment potentiated the destructive effect of subsequent treatments; in contrast, the loss of vitamin B12 during in-bottle sterilization was markedly reduced by preliminary HTST pasteurization. These anomalous effects are possibly related to a specific interaction of ascorbic acid with each of these 2 vitamins.

The changes in yield and composition of mammary gland secretion throughout the whole of the dry period have been investigated in 6 cows. The yields of lactose, potassium, fat and casein decreased to very low values for the greater part of the dry period but then increased slightly just before parturition. Similar trends were observed for sodium and chloride but they were much less marked. During the middle of the dry period the concentrations of sodium, potassium and chloride tended towards those of blood serum while the concentrations of fat and lactose decreased to < 1%.

The measurement by gas chromatography of pregnanediol in the urine of normal and ketosed cows in the first 3 months of lactation is described. Mean pregnanediol levels, corrected for recovery losses, are reported for 3 groups of cows, namely: normal lactating cows 30·7 μg/1 urine; experimentally induced ketosed cows 22·3 μg/1 urine; and primary spontaneously ketosed cows, 31·4 μg/1 urine. No significant differences between the 3 groups of animals were found.

The effects, on the yield and composition of the milk of the cow, of additions to the diet of the calcium salts of acetic, propionic, butyric or lactic acids were determined in 3 change-over experiments. In all cases yield of milk was increased slightly and milk fat content was reduced; solids-not-fat (SNF) percentage was depressed by acetate and butyrate. The effects of these treatments differed markedly from those observed previously when dilute solutions of the corresponding acids were infused into the rumen, but the relative effects of the calcium salts were similar to those of the free acids. It was concluded that the specific effects of the acids were overshadowed by a more marked general effect arising from their addition to the diet as calcium salts. This was confirmed in a subsequent experiment with fistulated cows, in which the effect of an infusion of propionic acid into the rumen was compared with that of an infusion of calcium propionate and of calcium propionate given with the diet. The effect of the addition to the diet of calcium in the form of carbonate differed from that of calcium salts of the fatty acids. It was concluded that the salts were not likely to find practical use.

The identification and approximate quantitative determination of methyl esters of fatty acids from commercial butterfat was obtained with a combined gaschromatograph-mass spectrometer instrument. Fifty-two components, straight chain saturated and unsaturated, as well as branched chain compounds, were identified. Seven monomethyl saturated fatty acid methyl ester isomers were identified for both C15 and C17, i.e. with chain lengths of 14 and 16 carbon atoms, respectively. Multibranched fatty acids with molecular weights of 326 and 368 were found. The results were obtained in one day.

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.

Pent-1-en-3-ol and pent-l-en-3-one were isolated in approximately equal amounts from buttermilk obtained from oxidized cream. The two vinyl compounds were identified by combined gas chromatography and mass spectrometry. The flavour of pent-1-en-3-ol is comparatively mild being detectable in water, skim-milk, butter oil and butter at 3 pts in 106, 3 pts in 106, 1 pt in 105 and 1 pt in 105, respectively. The flavour of pent-1-en-3-one is approximately 1000 times stronger being detectable in water, skim-milk, butter oil and butter at 1 pt in 109, 3 pts in 109, 5 pts in 109 and 5 pts in 109, respectively: these concentrations are of the same order of magnitude as for the compound responsible for metallic flavour, oct-1-en-3-one.

The formation of pent-1-en-3-ol and pent-1-en-3-one is discussed.

An analysis of variance was applied to the ‘within herd’ variance of milk total solids in order to find the contribution due to sampling, testing and biological variances on a balanced 8 × 8 two factor (herds and days) experiment with replicate sampling and testing. Testing samples from every consignment from 10 herds over a 12-month period showed that the mean monthy ‘within herd’ variance was 0·039 and the yearly ‘within herd’ variance was 0·085. A formula is given showing how the variance of the mean for compositional quality testing can be obtained and on which the design of testing schemes can be based.

A study of the production of L(+) and D(−) lactic acid in cultures of DL forming lactic acid bacteria has shown that they can be divided into 2 groups. The first includes the thermobacteria and Pediococcus cerevisiae in which the percentage of L(+) lactic acid is high initially but decreases as the cultures grow. The second includes Lactobacillus plantarum and the heterofermentative lactobacilli and in cultures of these species the percentage of L(+) acid changes little during growth and is generally below 50% of the total.

In a strain of Lactobacillus acidophilus it has been found that if the pH is kept constant during growth the proportion of L(+) lactic acid decreased. However, when acid production stopped the proportion of total acid which is the L(+) isomer is greater than the proportion at the same stage of development in cultures where the pH was not adjusted. Cells harvested from young cultures formed more L(+) acid than cells harvested from older cultures.

There is some evidence that the composition of the medium can affect the ratio of L(+):D(−) lactic acid.

The following compounds were isolated from best-quality Australian butter oil by high vacuum degassing, and identified by the combination of gas chromatography and mass spectrometry: the C3,5,7,9 alkan-2-ones, the C2,4,6,8,10,12 n-alkanoic acids, the C6,8,10 5-lactones (or their hydroxyacids), dimethyl sulphone, all isolated in amounts above 1 pt in 108 of butter oil, and butanone, undecan-2-one, 5-dodecalactone, diacetyl, n-nonanoic acid, a decenoic acid, methyl n-decanoate, toluene, o-methoxyphenol, a cresol, phenol, benzaldehyde, methyl benzoate and benzothiazole, all isolated in amounts between 1 pt in 1011 and 1 pt in 108 of butter oil.

No compound was isolated in an amount greater than flavour threshold, in fact most compounds were below one-tenth threshold level. However, the distillate obtained by degassing produced a very attractive creamy flavour when added to bland non-cultured butter.

1082 drip samples of fresh milk were taken at a creamery over a period of 3 years and tested for total solids by the current gravimetric method (British Standards Institution, 1963) and the hydrometric method with the fat in the liquid state (British Standards Institution, 1959). On average, the hydrometric method overestimated the total solids by 0·096. It is suggested that the formula which applied before 1 October 1957 is correct and should replace the present formula.

In suitable media the relationship between the citrate content and the acetoin formed by the growth of Streptococcus lactis var. diacetilactis NCDO 1007 is linear. An assay method for citrate is described which is based on this relationship. It has been used to assay the residual citrate in cultures of lactic acid bacteria and, therefore, to assess the ability of these bacteria to dissimilate citrate. Some suitable media for the test are described.

A milking parlour and milking equipment are described which have been found suitable for experimental work on the nutrition and the physiology of lactating ewes.

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.

A series of experiments has been carried out in order to develop antibiotic preparations which, when infused into the udder at drying-off, eliminate established infection and prevent new infection from occurring in the dry period. It has been shown that the persistence of antibiotic in the dry udder is affected by the solubility of the antibiotic salt, the quantity of antibiotic infused and the base in which it is formulated. Whereas 0.2 g cloxacillin as the sodium salt infused in a 3% aluminium monostearate in mineral oil base after the last milking of lactation persisted for less than 1 week, 0.5 and 1.0 g cloxacillin in the form of the benzathine salt, in a similar base, usually persisted for 3 weeks.

Secretions removed from the udders of dry cows inhibited the growth of Bacillus subtilis and Sarcina lutea but not 2 strains of staphylococci.

Clean spores suspensions of 3 strains of Clostridium tyrobutyricum were prepared after culture in dialysis sacs. The survivor curves of the spores heated at 90 °C in 0·033 M phosphate buffer (pH 7·0) or in skim-milk were logarithmic. From the thermal-death-time curves the following values were calculated: D at 121 °C = 0·003−0·012 min and z = 8·4−10 °C when spores were heated in phosphate buffer; D at 121 °C = 0·006−0·008 and z = 9·5−9·9 °C when spores were heated in milk.

When clean spores of 2 strains of Clostridium butyricum were heated at 85 °C in 0·005 M phosphate buffer (pH 7·0) the survivor curves were logarithmic, but ‘tails’ were observed after heating in skim-milk. The value of D at 85 °C was lower than that obtained with spores of C. tyrobutyricum.