As a member of Committees of the Empire Marketing Board and subsequently of the British Standards Institution, the author has had experience in methods of milk testing which has led to the discovery of a simplified test for butterfat, which may be of value in filling some of the gaps in the application of the present known methods.

Milk was obtained simultaneously from cows on early pasture and from stall-fed cows receiving winter rations. By suitable blending of the morning's and evening's milkings of each milk the fat content of the two milks was equalized daily. A part of each milk was then pasteurized in the laboratory by a “holder” method. The total nutritive value of the milk was measured on rats in two separate experiments. In one the milks, supplemented with iron, copper and manganese, were fed as an exclusive diet. The four types of milk were given to twelve groups of litter-mate male rats, the intake being equalized within each group. The experiment lasted 8 weeks, and at the end no difference was found in gain in weight, body length, general appearance of the rats or composition of the carcasses. The palatability of the milks as gauged by the refusals of the rats was investigated by various statistical methods, which showed that summer milk was probably more palatable than “winter” milk, but that pasteurization had no effect.

In the second experiment the intake of milk was limited to 20 ml. daily, but the rats were given in addition unlimited access to a basal diet of casein, sugar and salts. This experiment was also carried out on groups of four litter mates (four groups of does and seven groups of bucks). After 8 weeks 5% brewer's yeast was added to the basal diet, resulting in a marked increase of the growth rate of all the groups. At the end of the 8 weeks, the gains in weight, intakes of basal diet, and gains per gram of solids ingested were compared. The only statistically significant differences were in favour of pasteurized summer milk when compared with summer raw and with “winter” pasteurized.

In an ad libitum feeding experiment the greater growth of a group of animals may be due either to superior availability or to superior palatability of their diet. To distinguish between these two factors it is necessary to eliminate the effect of superior palatability by equalizing the food intake of corresponding animals. If the quantity offered is so small that it is always consumed entirely, the range of application of the experiment is restricted to conditions of substarvation, and at the same time the possibility of obtaining from the results any evidence of difference of palatability is sacrificed. The ration plan must therefore be designed to be as liberal as possible subject to the conditions that the aggregate food intakes are equalized in pairs (or larger groups), while at the same time the animal with the smallest appetite of each pair (or group) is always on the border-line of refusing a little of its portion. In the first set of experiments described in the preceding paper (1) a system of this kind is employed.

1. Bull calves from tuberculin-tested Ayrshire herds were fed on raw or commercially pasteurized milk up to 12 weeks of age, in amounts strictly in relation to their body weight. This diet was supplemented from the eighth week by hay at the rate of 2/3 lb. per head per day.

The milk used was mixed milk from untested herds, the raw and pasteurized milk being derived from the same bulk sample. The quality of the milk was controlled by daily butterfat and phosphatase tests and by inoculation of grouped daily aliquots twice weekly into duplicate guinea-pigs.

2. The total number of calves used in the experiment was ninety-two. Of these, forty-two received pasteurized milk and fifty raw milk. Nineteen calves died before completion of the experiment, five in the pasteurized milk-fed group and fourteen in the raw milk-fed group. The mean ages of these calves at death were 44 and 27 days respectively.

Seventy-three calves completed the full 12 weeks of the experimental feeding. Of these, thirty-seven received pasteurized milk and thirty-six raw milk. The former group showed a mean percentage gain in live weight of 80·2 ± 3·1, the corresponding figure for the latter group being 74·5 ± 2·7. The difference, i.e. 5·7 + 4·1, was not significant. Reasons are given for the relatively low growth rate observed.

3. No appreciable differences were noted in the skeletal growth of the two groups. Marks awarded by experienced stock judges showed consistent differences in favour of the pasteurized milk-fed group, although the significance of such differences cannot be assessed.

4. Inoculations of grouped daily aliquots of raw milk twice weekly into duplicate guinea-pigs resulted in finding viable tubercle bacilli in 70% of the samples and Br. abortus in 38% of them. The pasteurized milk samples were uniformly negative to both tests.

The differences in tuberculous infection of the two types of milk were reflected in the results of tuberculin tests and post-mortem examinations on the calves at the conclusion of the experiment. Twenty-four out of thirty-six calves fed on raw milk reacted to the test, and the presence of tuberculous lesions was confirmed in twenty-three by post-mortem examination. One calf in the pasteurized milk-fed group reacted to the test, but exhaustive post-mortem examination and inoculation of glandular material into guineapigs failed to confirm the presence of any tuberculosis.

5. This work has failed to show any significant differences in the nutritive value of raw and of pasteurized milk for the rearing of young calves. The use of pasteurized milk, however, had a clear advantage in that it preserved the animals from infection through drinking milk containing living tubercle bacillli.

A Preliminary investigation of certain defects and the results of the short time storage of experimentally processed batches of cream have been reported in a previous communication(1). The results of further storage of these batches and of additional batches utilizing different stabilizing agents are now presented. It is thought that a complete picture of the corrosion phenomena and the main factors influencing them have now been obtained.

1. Three organisms have been isolated from defective commercially-canned cream which, on inoculation into normal cream, cause bitterness and thinning.

2. These organisms are described and are shown to be strains of B. subtilis. Their spores are capable of withstanding temperatures up to 120°C. for as long as 40 min.

3. The rate of development of bitterness and thinning in experimentally inoculated cans is shown to vary with the culture used and with the temperature of incubation.

4. Both bitterness and thinning are associated with the breakdown of protein, as indicated by determinations of the non-protein nitrogen and of the peptone and subpeptone fractions.

5. The alterations in viscosity do not appear to be due to any fundamental change in the structure of the cream, nor to differences in the degree of clumping of the fat globules.

6. The applications of the results in commercial practice are discussed.

The paper embodies an examination of the possibility of sex-linked genes affecting the transmission of milk yield. To reduce environmental effect the study was restricted to three herds of the English Dairy Shorthorn breed, and each herd was considered as a unit. Fisher's Squared Difference method was used.

The lumped results confirm previous work to the effect that the paternal grandsire has a lesser effect than the maternal grandsire. In this respect the figures for one herd did not agree with the other two.

The largest herd (which showed this difference) was divided into two sections, high and low yielders. These sections did not show any difference in the relative effect of the two grandsires. The implications of this are discussed, and it is tentatively suggested that if sex-linkage operates it has a considerable effect of some 250 gallons on an average yield of 600 gallons.