1. After a preliminary trial with Shorthorn cows in Berkshire, some 461 Friesians were measured in Minnesota, U.S.A., and an attempt was made to correlate 19 measurements with milk yields.

2. Significant coefficients of correlations were obtained for:

Length from withers to hooks and milk yields;

Height at hooks and milk yield; Height at pins and milk yield;

Circumference of chest and milk yield;

Circumference of barrel and milk yield;

Area of milk wells and milk yield.

3. Correlation coefficients that were almost significant were obtained for:

Width at barrel and milk yield;

Width at hooks and milk yield.

4. The best producing cows had the largest milk wells. This was not because they were the biggest cows, for there was practically no loss of coefficient of correlation for milk yield and size of milk wells when the partial correlation for area of milk wells and yield was calculated with height at hooks held constant.

5. Evidence is presented which shows that the areas of milk wells do not increase with mere skeletal growth of cows over 4½ years old, but with increased milk production. This fact makes the area of milk wells a still more reliable indicator of milk-producing power.

6. The results obtained confirm the value of some of the points which stockmen have considered in judging dairy cows. They emphasise the necessity for considering all the points together, but indicate that certain points deserve special consideration.

The protein requirements for maintenance and milk production are based on the well-known investigations of Kellner, Armsby, Haecker, Savage and others, who recommend feeding standards varying from 0·5 to 0·;8 lb. digestible crude protein per 1000 lb. live weight for maintenance, and from 0·52 to 0·63 lb. digestible crude protein per 10 lb. milk for milk production. A detailed study of the work of these investigations shows that in many instances nitrogen equilibrium has been obtained on considerably lower planes of protein intake: but the figures have been arbitrarily raised, partly to provide a sufficient safeguard against underfeeding, and partly on the assumption that the excess food protein could exert a stimulating effect on mammary secretion. Recent investigations, particularly those of Hills and his associates (l), Perkins (2), Buschmann(3) and Savage and Harrison (4) indicate that the existing protein standards could, in fact, be considerably reduced. The above investigations have, however, been limited to a study of the quantity of protein required for maintenance and milk production, and no account has been taken of the possible effect of variations in the quality of proteins on their utilisation.

1. The production in milk of an aroma resembling that of amyl alcohol was due to the growth of white and orange micrococci, similar to those described as M. caseolyticus by Evans(2).

2. The taint was observed when the cows were housed, but disappeared when they were put out to grass.

3. The source of the causal micrococci was found to be the floor of the cowshed. The taint disappeared when the latter was washed and disinfected.

4. The aroma of amyl alcohol was produced in media containing leucine as the sole organic compound.

1. A study has been made of the degree of inbreeding in the Ayrshire breed of cattle.

2. The coefficient of inbreeding for the whole breed, as calculated by Wright's “Approximate (or Short) Method,” showed a progressive increase from nil in 1877 to a mean value of 5·3 in 1927.

3. No difference was found in the coefficient of inbreeding as between registered bulls and cows.

4. A large proportion of the inbreeding was traced to two foundation sires, Burnhouses (8) and Hover-a-Blink of Drumjoan (892).

5. Using Wright's “Long Method,” it was found that high milk-yielding cows showed a markedly lower coefficient of inbreeding than the breed average. On the other hand, when the coefficient of inbreeding of high milk-yielding cows (over 1000 gallons) was compared with that of cows giving average yields (under 800 gallons) it appeared that inbreeding itself had no detrimental effect on milk yield.

6. In 1923, 39 per cent, of the inbreeding ties of high milk-yielding cows were traced to the Drumjoan herd, as against the next highest herd which had only 6·37 per cent, of ties. Of the total coefficient of inbreeding the Drumjoan herd was responsible for 18·36 per cent., whereas the next highest herd was only responsible for 8·35 per cent. The 1928 results also demonstrated the marked influence of the Drumjoan herd. Practically 50 percent, of these ties were traced to animals related to the foundation sire, Hover-a-Blink of Drumjoan. These results demonstrate the profound influence which one herd, and indeed one bull, may exert in the genetic construction of a recently established breed.

7. It is pointed out that Wright's “Long Method,” when applied to breeds of relatively recent origin, gives far more reliable results than his “Short Method.”

The work herein reported has shown that more milk and fat were produced per hour during 9-, 12- and 15-hour night intervals than during intervals of the same length during the day.

The milk increment was, however, greater than the fat increment.

With midday and midnight milking hours more milk and fat were produced per hour from midnight to midday than from midday to midnight.

In this case the fat increment was the greater.

The lactose-fermenting coliform organisms in milk and dung have been investigated.

A large proportion of those recovered from raw milk by direct plating proved to be of the Bact. aerogenes type and a number of “intermediates” was also present.

In dung faecal Bact. coli largely predominated, the proportion of Bact. aerogenes being very small.

If the implication of these experiments be accepted it is possible that many of the coliform types found in milk are derived, not from faeces, in which the proportion of aerogenes is small, but from external sources, such as contaminated utensils, and from food-stuffs.

In the course of routine bacteriological examinations of milk carried out at one of the United Dairies pasteurising depots during the past three years, a remarkable lack of constant relationship between the numbers of colonies reported on the 1/10, 1/100 and 1/1000 dilution plates, when standard agar (the Ministry of Health formula) was used, has been observed. When, however, standard agar, enriched with 0·5 per cent, milk, has been used as a plating medium, many of the discrepancies between different dilutions of the same milk have disappeared.

An analysis of the data collected at the Agricultural Research Institute for Northern Ireland, Hillsborough, County Down, was undertaken to find if the system of milk recording practised in Northern Ireland is satisfactory.

The standard deviations of the errors in the calculated milk yields, on a weekly and 2-weekly basis, of 24 cows were found. It is shown that weekly weighings give results which approximate closely to the true milk yield.

By basing the calculated butterfat yields on tests made at intervals of from 1 to 8 weeks, the standard deviations of the errors in the calculated butterfat percentages for each interval, as well as the maxmium errors, were found. It is shown that as the interval between the tests is lengthened, the errors increase. With tests made at intervals of 6 weeks, most of the errors in the calculated butterfat percentages will be less than 8-5 per cent., but in some cases the calculated butterfat percentage may differ from the true butterfat percentage by over 12 per cent.

In order to ensure that the errors in calculated butterfat percentages do not exceed 10 per cent., the interval between butterfat tests should not exceed 1 month.

During the past two years, discoloration, owing to its prevalence in Cheddar cheese, has been the subject of much investigation by the New Zealand Dairy Division, and in the present paper are incorporated details of the observations made in this laboratory and in cheese stores in New Zealand and England, together with short reports on the same subject from English laboratories.

To avoid confusion it must be emphasised that the defects dealt with are “bleached,” “pink” and “muddy” discolorations only. The observations do not apply to “black spot” (due to lead or other metallic contamination), nor to “red spots” (due to faulty annatto), nor to “acid cut” bleaching which seems to follow the outline of the original pieces of curd. Muddy or dark discoloration occurs in white and in coloured cheese, but the bleaching and pink discoloration dealt with here are confined to coloured cheese.

An investigation of the milk of a typical herd of Shorthorn cows kept under south of England conditions has been carried out.

The results of the first three years of the investigation are now recorded. The plan of the experiment, the history of the cows during the period, the management, feeding, milking, and milk yields are described and illustrated in Tables I and II.

The evidence of pH and catalase tests confirms the view that mould growth is closely associated with the production of discoloration in cheese.

The pink discoloration appears to be the result of acids acting upon the annatto colour.

Evidence available from observations and other sources, suggests that the bleaching is chemically a reduction in which changes in the fat play a part.

The muddy or dark discoloration appears to be produced by enzymes (including possibly tyrosinase) which diffuse into the cheese from centres of mould growth and act upon chemical substances present in mature cheese.

1. Colon bacilli grown in milk for from 3 to 16 hours partially inhibit the subsequent formation of acid by lactic streptococci.

2. The inhibition is not entirely accounted for by the increased hydrogenion concentration nor by the lactic acid produced by the colon bacilli. Other substances which have a retarding influence on the streptococci are evidently formed in milk cultures of colon bacilli. The action of these substances is not significantly modified by heating at 75°C. for one hour.

3. The possible practical significance of the phenomenon is discussed.

1. Records of the percentages of fat and solids-not-fat in the milk supplies received at twelve depots in the counties of Cheshire, Staffordshire, Derbyshire and Leicestershire during the period 1923–31 have been analysed and the results of analysis given in the form of graphs.

2. The yearly averages for the whole area and for the three sections of the area are illustrated and compared with graphs based upon meteorological data (rainfall and temperature) recorded at stations in, or adjacent to, the area.

3. The monthly average figures for the whole period are shown in the form of graphs and compared with graphs based upon data recorded by Richmond.

4. The data upon which this paper is based indicate a positive correlation between rainfall and average composition of milk for each year

1. The true lactic acid bacteria cannot grow in a medium in which the sole source of nitrogen is an amino acid mixture or an ammonium salt.

2. The presence of growth factors (yeast extract, marmite and peptones) does not permit the utilisation of this “simple” nitrogen.

3. The streptococci grow fastest with those peptones containing the greatest amount of the higher fractions, Bactoproteose being superior to the other peptones tested; the lactobacilli, however, show a considerably greater fermentation rate with those peptones containing most amino nitrogen, Fairchild's being the best. Similarly, the streptococci thrive best upon a peptic casein digest which is about 15 days old, further digestion impoverishing the growth; the lactobacilli, however, grow better the longer the digestion. The significance of these observations is discussed from the aspects of bacterial metabolism, the sequence of flora in ripening cheese, and the preparation of casein digest media.

The plating method of estimating the bacterial content of milk is the most important means of determining the number of living organisms present, and is the one most frequently employed. It is well recognised, however, that accurate counts cannot be obtained by this method, since considerable errors may be involved through the difficulty of ensuring the separation of chains and clusters of organisms so that each organism is represented by a separate colony, through the inability of some classes of bacteria to grow on the medium employed, and through the fact that the presence of one group of organisms may inhibit the growth of others—particularly on crowded plates. It appears that the difficulties in obtaining uniformity of counts for duplicate tests may be increased in the case of milk because this fluid is heterogeneous in nature, and the bacterial contaminants are liable to occur not only as groups or individuals freely dispersed in the liquid but also in association with matter in suspension, especially the clusters of fat globules. Consequently the bacterial counts are likely to vary with the extent to which the clusters of fat globules are broken up or aggregated by the manipulations.

Small amounts of heavy metal are distributed between cream and separated milk in proportion to the curd nitrogen, but on completely centrifuging the fat a higher concentration of metal occurs in the cream, showing adsorption of complex proteinate at the fat-globule surface.

The heavy metal entering into butter from cream of different acidities is not affected by the acidity but by the curd-nitrogen content of the butter, but the copper associated with the curd in butter is roughly twice that associated with the protein nitrogen of the buttermilk. This is explained by adsorption of heavy metal on the fat-globule surface, which holds alike in water in oil as well as oil in water emulsion.

The entry of heavy metal into the fat phase in the absence of protein is greatest at neutrality but decreases with increasing acidity. The presence of protein increases slightly the amount of heavy metal entering into the fat owing to adsorptive and buffering effects of the protein at the oil-water interface in the emulsion.

The amount of diffusible heavy metal increases directly with the acidity and runs parallel with the diffusion of hydrogen ions.

The concentration of the ionic form of heavy metal in milk is of a low order, but increase in acidity causes more ionic metal to form. Evidence from potentiometric measurements in milk containing known amounts of heavy metal, or from the addition of milk to a standard copper solution at various acidities, confirms this finding.

In the previous paper(1) it was shown that the heat treatment to which a milk powder is subjected during manufacture may result in the production of two distinct types of protein insolubility, namely insolubility due to denaturation of the protein while still in solution, and insolubility caused by over-heating the milk powder while in a dry state. The insolubility due to denaturation was shown to be independent of the temperature of reconstitution of the milk powder. On the other hand the insolubility due to dry heating was found to vary with the temperature of reconstitution, the protein being relatively insoluble when reconstituted in water held at 20° C, but completely soluble when mechanically stirred for 30 min. in water held at 90° C. It was suggested that this latter type of insolubility might be due to the removal of water of imbibition from the protein particles, since such an explanation would account for the effect of hot water in restoring the solubility of the protein. In the previous paper, however, observations on the effect of temperature of reconstitution were limited to the two extreme temperatures, i.e. 20 and 90° C.

It has been shown that neither lactose, nor other sugars tested, casein peptone, nor yeast extract can satisfactorily replace milk as a means of correcting discrepancies which are frequently observed between the plate counts of the 1/100 c.c. and 1/1000 c.c. dilutions of milir on standard agar. Experiments are in progress by which it is hoped that the objections to the addition of milk to standard agar either at the time of making or at the time of plating will be removed, and a medium be evolved which will combine the ease of making and the transparency of standard agar with the efficiency of the medium enriched with milk.

Casein nitrogen has been shown to account for roughly 76 per cent, of the total nitrogen in over 200 samples of normal milk. Samples low in solids-notfat have shown a casein nitrogen percentage below this figure, and by assuming a 76 per cent, level of casein nitrogen as standard, it is suggested that milk may be considered as made up of two fractions, (a) a true-milk fraction and (b) an isotonic diluent. From the distribution of the nitrogen in whole-milk samples it has been possible to calculate on this basis the amount of dilution and the nitrogen distribution in the diluent. Results are given for 38 samples of milk. The chloride content of the diluent has also been approximately arrived at and is approximately isotonic with a hypothetical non-lactosecontaining milk.

The similarity in composition of the diluent either to a modified blood serum or lymph serum or a casein- and lactose-free lacteal secretion has been discussed. Its high chloride content favours its similarity either to lymph serum or a “transudate” or “exudate” closely allied in composition to lymph serum from pathological secretory tissue. The possibility of after-effects of attacks of mastitis causing a chronic catarrhal condition of the udder being the cause of the secretion of this diluent is also discussed.

No reliable information is at present available with regard to the effect of process of manufacture on the solubility of the protein of milk powders. Hunziker(1), it is true, gives a very well-balanced discussion of the subject, but it is apparent from his summary of the views of other workers that these are seldom based on adequate experimental evidence. In fact the only points on which there is general agreement among workers in this field are that the proteins of spray-dried powders are, on the whole, extremely soluble, while those of roller-dried powders are relatively insoluble. Moreover, even where experimental data are available, there remain many unexplained points. For example, Hunziker shows that the solubility of the proteins of a milk powder may vary according to the temperature at which the powder is reconstituted—a higher temperature giving a greater solubility. Such an observation cannot at present be brought into line with current theories regarding the properties of denatured proteins.