1. With the assistance of the Central Council of Milk Recording Societies of England and Wales and its affiliated Societies, particulars were obtained of the calf losses, pre-natal and post-natal, sustained in 1936–7 by 315 herds situated in different counties of England and Wales. Further data were collected from twenty private owners in England and from forty-seven herds in a limited area in Scotland.

2. The herds in England and Wales were chosen in such a way as to give a fair representation of the geographical distribution of the cow population throughout the country. It is obvious, however, that they are a selected sample in which a relatively high standard of husbandry might be expected to prevail and their rates of mortality, therefore, will probably be below that of the general run of herds.

3. Owing to the early disposal of bull calves the losses of males after the first week of life are likely to be considerably understated. It is, therefore, wise to confine attention mainly to the figures for females.

4. In the 335 herds of England and Wales 12,544 female calves were born and of these 693, or 5°5 %, died before the age of 6 months.

5. Of 26,440 total births reported in England and Wales, 1231, or 4°4 %, were of stillborn animals.

Connecting the trend of the different parts of the lactation curve with what is believed to be the underlying hormonal mechanism, it has been pointed out that any analysis of the curve must deal separately with three parts. The central portion, lying between the peak of daily production and the rapid decline (drying off) has been the object of investigations in an inbred Ayrshire herd. Coefficients of persistency were obtained by fitting exponential curves to this central portion. When first lactations were excluded and correction for month of calving applied, the coefficients (P) were found to be reasonably consistent for different lactations of the same cow. Month of calving accounted in this herd for about one-third of the variance of P. Of the remaining variance approximately one-half is attributed to differences among cows. A possible physiological explanation of the cause of the well-known negative correlation between maximum yield and persistency has been suggested. No conclusions can be drawn from this material on the relative importance of heredity and environment in determining persistency.

1. The concentration of carotene and of vitamin A in colostrum and colostral fat and the total daily yield of these substances in successive milkings has been studied for four shorthorn cows and nine heifers.

2. The concentration of vitamin A in the first colostrum ranged from 8160 to 820 Moore blue units per 100 g. and that of carotene from 2026 to 411 Moore yellow units per 100 g.

3. The highest and lowest concentrations and yields of vitamin A and carotene respectively in samples of colostrum and later milk were in the ratios: per g. of colostrum (milk) 35:1 and 65:1; per g. of fat 27:1 and 34:1; calculated on daily yield 31:1 and 65:1. This last calculation favours colostrum.

4. Access to pasture before calving appeared to have no effect on the secretion of vitamin A in colostrum but increased the output of carotene.

Our best thanks are due to Mr A. G. Cotton who supervised the collection of the samples of colostrum and to Miss D. V. Dearden for churning the butters.

1. The microflora of A.I.V. silage consists mainly of lactic acid bacteria—lactobacilli, streptococci, micrococci and sarcinae. Some samples also contain yeasts and yeast-like organisms.

2. Among the lactobacilli, both homo- and heterofermentative types are represented. The former include strains of Lactobacillus plantarum (Orla- Jensen) Bergey et. al.; in the heterofermentative group L. brevis (Orla-Jensen) Bergey et al. has been found.

3. Cultures of a motile homofermentative lactobacillus were isolated; this appears to be a new type. Among the unidentified heterofermentative lactobacilli, forms which may prove to be similar to the inactive group of Pederson were encountered.

4. The homofermentative streptococci were found to belong to the Streptococcus lactis group; the heterofermentative forms were identified with Leuconostoc mesenteroides (Cienkowski) van Tieghem.

5. Strains of unidentified homofermentative micrococci and sarcinae were isolated and shown to possess characteristics not usually associated with organisms of these types.

6. Streptococci, micrococci and motile lactobacilli were found mainly in fodder recently ensiled; the majority of the lactobacilli and sarcinae were associated with the older samples.

7. The characteristics which proved to be most valuable for the differentiations of the organisms were ability to produce carbon dioxide, percentage of lactic acid formed and lactic-acetic acid ratio.

Data have been given of the variations in the calcium ion, ultrafiltrable calcium complex, non-ultrafiltrable calcium complex and protein-bound calcium at normal parturition in the dairy cow, and an interpretation of the results has been presented. The variations observed have been shown to be consistent for all the animals studied.

Serum phosphatase did not show any consistent changes at the time of parturition.

1. In a large-scale experiment, using about 500 cows, half the cows were fed a production ration consisting of decorticated ground-nut cake, maize meal, wheat offals and molasses supplying about 0.6 lb. protein equivalent per 10 lb. milk produced, and the remaining half were fed a production ration containing the same constituent foods in different proportions supplying a similar starch equivalent, but only two-thirds the amount of protein. No measurable difference was observed in the fatness, handling properties of the skin, hair on the body and percentage of fat and solids-not-fat in the milk.

The milk yields showed no difference during the winter feeding period of about 20 weeks, but during the succeeding period when all the cows were allowed ample grass the milk yield response of the cows previously given the low-protein ration was significantly greater than that of the corresponding cows previously given the high-protein ration.

The experiment was repeated the following winter, using about 600 cows, and confirmatory results were obtained.

2. Another experiment similarly planned, using 300 cows, compared highwith low-protein production rations consisting of the constituents noted above together with soya-bean meal and rice bran. No significant differences were observed between the effect of the two rations on milk yield or composition, fatness of the cows, etc. There was, however, an indication (not statistically significant) that the low-protein ration which contained a relatively high proportion of rice bran depressed the milkfat percentage.

3. A small but more completely controlled experiment confirmed the findings of the large-scale experiments.

1. The influence of temperature, oxygen tension, yeast autolysate and chalk on the production of by-products and the ratios of by-products formed to sugar utilized and lactic acid produced in milk by the lactobacilli has been investigated.

2. The total production of lactic acid is increased by the presence of chalk and “growth factors” but is not affected by temperature or oxygen tension. The ratio of lactic acid produced to sugar utilized is decreased at lower temperatures and increased by chalk but yeast autolysate and variation in oxygen tension give variable results.

3. The total production of acetic acid is increased by the presence of chalk, and “growth factors” and by anaerobic conditions. The ratios of acetic acid produced to sugar utilized and lactic acid formed are decreased by chalk and anaerobic conditions and there is a tendency for the ratios to be decreased by the presence of yeast and increased at lower temperatures.

4. The total production of alcohol is increased by anaerobiosis and also by the presence of chalk and yeast in the medium. The ratios of alcohol formed to sugar utilized and lactic acid produced is increased by anaerobic conditions, and chalk also tends to increase the relative amount of alcohol. Temperature and yeast autolysate have little effect.

5. Chalk is effective in maintaining the pH at a higher level during growth, but the influence of chalk on the ratios of by-products formed to sugar utilized is probably not entirely a pS. effect since the addition of talc to the medium has an equally strong influence in altering the relative production of lactic acid and alcohol.

6. It was previously shown for the heterofermentative streptococci that the Pasteur effect (suppression of alcoholic fermentation by respiration) is slight; similar results have been obtained with the heterofermentative lactobacilli.

The question whether the tomato pigment, lycopene, an isomer of carotene, can pass from food into milk in the cow has been submitted to direct test by feeding three different cows with tomato purée and examining the resulting milk fats separately for lycopene. No evidence of the presence of lycopene has been detected in the unsaponifiable matter of the butter fat when this was subjected to careful chromatographic adsorption and it is concluded that, although the cow normally absorbs α- and β-carotene and certain oxidation products of these substances from its food it completely excludes the isomeric and very similar lycopene which has been found in the faeces in considerable quantity after tomato feeding. The mechanism of this selective absorption of one isomer only is quite obscure.

2. Adsorption of the carotenoids of several colostrum fats gave no indication of the presence of lycopene but the adsorption columns contained two small zones above that of β-carotene due to traces of pigments having absorption maxima at 452 and 425 mμ. (petroleum ether b.p. 70–80°). These may be due to oxidation products of β-carotene.

The following average fractionation of serum calcium in the dairy cow has been reported:

Part I

1. A method for the estimation of vitamin B1 in milk by a modified Jansen test involving takaphosphatase treatment is described in detail.

Part II

2. It is shown by ultra-filtration experiments, by treatment with pepsin and takaphosphatase, with trichloroacetic acid and with fuller's earth that vitamin Bx is present in milk unesterified and phosphorylated and that both forms may be freely diffusible or combined with protein either loosely or by firmer bonds.

Part III

3. The effect of the stage of lactation on the amounts and partition of vitamin B1 in milk has been studied. Samples of colostrum and early milk were found to contain large amounts of cocarboxylase (up to 80 % of the total). Hardly any cocarboxylase was present in mid or late lactation milks. The total vitamin B1 content was 60–100μg./100 ml. for colostrum, up to 60μg./100 ml. for early milk and 30–40μg./100 ml. for mid and late lactation.

4. A marked negative correlation exists between the cocarboxylase content of cow's and goat's milk and their alkaline phosphomonoesterase titre. As this enzyme cannot dephosphorylate cocarboxylase it is probably accompanied in milk by other enzymes more suited to this process.

5. The suggestion is put forward that the vitamin B1 of milk is mostly derived not directly from the blood but from the secretory cells of the mammary gland.

1. A review of the literature shows that the destruction of living microorganisms by heat is a complex process, and that the problem is particularly difficult when it is applied to the heat resistance of spores.

2. The problems involved in the method of heating and in the choice of a container for the inoculated substrate for heat-resistance tests are discussed, with special reference to the difficulties encountered at high temperatures such as are used in studies with spores of aerobic bacteria. Four different types of containers, namely, (a) glass capillary tubes, (b) glass ampoules or bulbs, (c) glass Pasteur pipettes and (d) corked test tubes, have been tested, and the latter were found to fulfil the necessary requirements.

3. A trial test of the heat resistance was conducted on nearly forty strains of aerobic sporeformers isolated from canned milk products, in order to obtain general information regarding the difficulties which might be expected in later and more detailed studies. Many of the strains were found to be exceedingly heat resistant. No dormancy was apparent when the spores were heated and subsequently incubated in milk products. “Skips” were only observed to any great extent among strains of B. licheniformis.

4. Special studies of the heat resistance of three strains of B. subtilis which had produced bitterness and thinning in canned cream were made. Details are given of the methods of preparing spore suspensions for these tests and of preparing the substrates for subsequent inoculation in such a way that equal concentrations of spores are present in the final subsamples.

5. The effect of the reaction of the substrate on the destruction of two of these strains of B. subtilis by heat has been examined, but over the narrow range of pH. tested the results, which have been expressed as survival percentages, lack consistency.

1. Three Shorthorn cows were grazed on the best available permanent pasture when the growth of grass was vigorous, and three other cows of similar lactational history continued to be stall-fed. At the time of the experiment they had been on winter rations for 6 months.

2. By suitable blending of morning and evening milkings the fat content of the milk from both groups of cows was adjusted daily to a common level. A part of each milk was then holder-pasteurized.

3. Four groups of specially prepared litter-mate male rats were fed ad lib., for a period of 8 weeks, on raw and pasteurized milks, both being supplemented with minerals. There were no differences in appetite or gain in weight.

4. In similar experiments sugar was added to the milks to double their caloric value. Again the growth and appetite of the animals were the same on the raw summer and “winter” milks. Pasteurization did not alter significantly the value of the milks, but the summer milk, whether raw or pasteurized, was superior to the pasteurized “winter” milk.

5. Guinea-pigs receiving the raw mineralized milks alone or with sugar died within a comparatively short time. There was no difference in growth performance or time of survival between the summer and “winter” milk groups.

6. These experiments give no indication of the presence of a specific new appetite or growth factor in pasture milk.

1. A description is given of a weakly haemolytic organism, which first appeared as a contaminant, in the form of pin-point colonies, in agar plates inoculated with dilutions of a cream which had been subjected to partial processing in a butter churn.

2. Though it resembled in many respects certain strains of Str. bovis recently isolated from pasteurized milk in America, it is concluded that the majority of its characteristics showed it to be a resistant strain of Str. thermophilus which had adapted itself to contaminate a churn.

3. That the churn was responsible for the spread and maintenance of this heat resistant contaminant is regarded as significant and indicates that efficient pasteurization must be followed by storing and processing in sanitary equipment.

I am indebted to Dr M. Grimes for his help and suggestions in the course of this work.

Since publication (1) the apparatus previously described by the authors has been altered and improved. The alterations have been concerned mainly with excluding draughts and securing a better form of support. In using the apparatus we have found that the absence of vibration is important for the agreement of duplicates. It would seem that vibration tends to break the cohesion between the curd and the surface of cylinder A. For this reason a part of the laboratory as free as possible from vibrational disturbances was chosen and the support fixed to the wall.

A comparison of the value of various milk sera for the determination of the soluble phosphate and calcium of milk, using dialysis at 0–5° C. as a standard method, gave the following results:

(i) Rennet whey was the most satisfactory; with fresh milk it yields fairly accurate values for calcium, slightly low (average 5 %) for phosphate. With increasing acidity of the milk both sets of values tend to rise somewhat relatively to those of the dialysate, phosphate approaching the true value and calcium rising slightly above it.

(ii) Mercuric chloride borax serum gives high results for the soluble phosphate of fresh milk With increasing acidity of the milk, the results fall steadily.

(iii) Papain whey gives somewhat low results for both the phosphate and calcium of raw and pasteurized milk, with the same tendency as rennet whey to yield higher and improved results as the acidity of the milk: increases. With boiled milk it gives abnormally high results for both constituents. The additional phosphate and calcium appear to arise from the solution of colloidal calcium phosphate.

Milk of normal appearance from cows having a latent infection with Str. agalactiae yielded definitely less cheese than that from normal cows. Milk from cows free from “agalactiae” infection, yet classed as “abnormal”, behaved similarly. The lowered yield appeared to result from the lower casein and solids-not-fat contents of these “mastitis” milks.

With a single exception, the cheese made from these “mastitis” milks were not inferior in quality to those made from normal milks.

1. A method is described for measuring the consistency of cheese curd during the scalding process which has been found satisfactory with Cheddar, Cheshire, Leicester, Double Gloucester, Caerphilly, Kingston and Derby cheese and is probably applicable to some other varieties.

2. The property (W/h), taken as a criterion of consistency, can be measured within less than 1 min. and is highly correlated with moisture content except when abnormal scalding conditions produce an uneven distribution of moisture in the curd. The size of cut does not affect this correlation within wide limits, though both moisture content and W/h are regularly affected by size of cut until the curd is approximately ready to pitch, at which point both properties show unique values independent of size of cut.

3. When the curd is nearing the pitching point, W/h measures the extent to which a standard cylinder of curd loses whey, the liquid being replaced in the solid structure by air. At an earlier stage in the scalding process the capacity of the curd to retain its shape under the force of gravity also affects W/h.

4. Although the cheese-maker judges the consistency of curd suitable for pitching by a complex mixture of properties, it is believed that Wjh will serve as an effective single-value criterion of consistency, suitable for judging pitching time if the acidity is also known.

In order to compare the old and the modified methods of the methyleneblue reduction test, 185 samples of raw milk were examined. We followed Wilson's method absolutely, but included two tubes in each test, one of which was inverted and the other not.

The results obtained and their interpretation agreed with the theoretical expectations given in our previous paper, and briefly outlined at the beginning of the present paper.

It is found that the deviations in the reduction time, corresponding to a given initial number of cells, are smaller by the modified than by the old method, and that the average time of reduction is shorter.

The smaller variation in the reduction time corresponding to a given number of cells at the beginning of the test is due probably to a more uniform distribution of the bacteria in the milk following the inversion of the tube. Wilson's suggestion that the shortening of the reduction time in the modified method is due to the stimulation of bacterial growth proves to be entirely correct. We obtained the average coefficients of multiplication in the old method of 0·660, and in the modified of 0·885.

Our results confirm on the whole the positive value of the modification of the methylene-blue reduction test as suggested and worked out by Wilson.

The pH of cheese at 14 days old appears to be the most useful means of measuring the extent of acid development in the cheese, and shows a very fair agreement with the observations of graders on mature cheese. Cheese with a pH value close to 4°90 at 14 days gained the highest average score at maturity.

Measurements of titratable acidity either on the aqueous extract of the cheese or directly on a paste of the cheese, readily distinguish cheese which are insufficiently acid, but do not clearly distinguish over-acid cheese or cheese of low pH value: The direct method of acidity titration has the disadvantage that the results are affected to such an extent by the colour of the cheese as to make impossible the comparison of results on cheese of different colour intensities.

pH or titratable acidity values for mature cheese are less useful indicators of the quality of the mature cheese than the values at 14 days.