A feeding trial of the relative value for milk production of National Cattle Food No. 1 and National Cattle Food No. 6 is reported; forty-two first calvers were employed.

The two foods were shown to be of very similar feeding value for heifers giving two to four gallons daily, the difference between them being slightly in favour of the N.C.F. 1. Each pound of this food produced 0·109 lb. more milk than the same amount of N.C.F. 6, but this difference was statistically without significance.

The relationship between live weight and lactation production was examined; records from ninety-nine animals, daughters of seven bulls, were used.

A positive relationship was found to exist within each of the seven groups and within the entire population.

The relationship did not exist between the mean values of the group.

No correlation was found between the live weights at calving of forty-seven dam/daughter pairs; the daughters were the offspring of six bulls.

It was shown that a herd breeding policy which selected animals according to their size would fail, except by chance, to improve the production of the herd.

At the end of normal machine milking some milk, which cannot be removed unaided even by the most efficient milking machine, remains in the udder sinus. This milk, often some 10% of the total yield depending upon the age of the cow, udder shape, partial vacuum of the milking machine and teat-cup liner design, was formerly most frequently removed by hand. As a result of advice and encouragement farmers are rapidly changing to manipulation of the teat-cups, known as machine stripping. This practice has renewed interestin the old controversy about the effect of the method of stripping on udder health.

Using an electronic pressure recording system, pressure changes in the sow's mammary gland in response to injections of oxytocin and whole pituitrin have been recorded. The results suggest that an injection of oxytocin within physiological range may pass round the circulatory system twice, resulting in a small secondary pulse of pressure. Slow injections over periods of the order of 8–16 sec. are shown to produce a double rise in pressure, the two phases of which are of the same order of magnitude, suggesting a contraction followed by a period of relaxation and a further contraction.

Using a differential staining technique, total and differential cell counts were carried out on over 5000 milk samples.

It was found that the cells in both normal and abnormal milk fell into three groups:

(1) Granular leucocytes, including polymorphs, eosinophils and probably basophils.

(2) Lymphocytes.

(3) Epithelial cells (vacuolated and non-vacuolated).

The findings of some earlier workers are discussed.

1. Of a number of farm milks examined, two have been found to develop a positive phosphatase reaction following pasteurization at 161° F. in a small H.T.S.T. plant. This phosphatase was not of bacterial origin but was reactivated milk phosphatase.

2. Considerable variation in reactivation following pasteurization at 161° F. was found to occur using individual churns of the above farm milk from any one milking. Individual cow samples also showed similar variation when tested by the capillary method. No explanation of this variation is offered.

3. Commercial bulk raw milk from road or rail tanks did not develop a positive phosphatase reaction after pasteurization at 161° F. on this plant.

4. Cold storage of pasteurized milk susceptible to reactivation results in less reactivation, and some evidence was obtained that cold storage of the corresponding raw milk also results in less reactivation. No such effect has been observed either using the capillary method or with samples of Uperized milk.

5. Pasteurizing at 170 and 180° F. usually resulted in increased reactivation as compared with that obtained after pasteurization at 161° F. Shortening the holding time at these two higher temperatures sometimes led to a further increase in reactivation.

6. It is shown that no clear relationship exists between the results obtained by plant pasteurization and the capillary method.

7. It is suggested that many of the reported cases of pasteurized cream developing a positive phosphatase reaction on storage can be attributed to reactivation of the enzyme.

8. Practical implications of reactivation in relation to pasteurized milk are discussed.

An examination of the fat-globule size distribution pattern has been made throughout the lactation for one quarter of one cow, samples being taken at different stages in the milking process using a normal milking machine with sampling device attached.

1. The composition has been studied of the milk of forty-four sows in the course of sixty-eight lactations. The milk was obtained by machine milking following intravenous injection of oxytocin.

2. Definite lactational trends have been observed for all the major constituents, and the third week seems a critical stage for most of the milk components.

3. The mean values for the milk, based on the analyses of over 450 samples from the seventh to fifty-sixth day of the lactation were: fat 9·58 %, protein 6·11 %, lactose 4·62 %, ash 0·92%. Such figures are considered to be rather meaningless for most practical purposes, in view of the marked changes over the course of lactation.

4. The day-to-day variation in the composition of sow's milk has been studied. Whereas the fat value changes considerably, the non-fat constituents show a less marked variation. Difficulties in securing a representative sample of the weekly milk have been overcome by preparing a composite sample from three milMngs within the week.

5. Some preliminary work has been done on variation in the composition during the process of milking. Sequential samples show an erratic fat content, especially during the early part of the lactation. When calculated on a fat-free basis, the protein, lactose and ash contents are relatively constant during the process of milking.

In studies where regular analyses of sow's milk are being made in an effort to evaluate the total energy content of the milk from sows at different dietary levels, once the composition trends of the milk have been assessed, the number of analyses can be considerably reduced and a greater number of samples handled. Satisfactory calorific values can be obtained from the estimated composition requiring analyses for fat and total solids only.

1. Measurements of hardness and ‘free-oil’ content of samples of butter from cream held at various temperatures before churning were made before and after storage. Hardness was determined by the sectility method, while free-oil content was estimated from the weight of oil exuding from thin slices of butter sandwiched between filter-papers and held at 64–4° F. (18° C).

2. Butter from cream held at 60° F. and churned at 45° F. was much softer and contained more free oil than butter from cream held and churned at 45° F.

3. If the cream was precooled to 45° F. before being held at 60° F. the butter was very slightly softer than that from cream held at 60° F. without precooling, but the difference disappeared after storage. It contained rather less free oil, but the softening point of the oil was lower. Fat losses in churning which were high where cream was held at 60° F. were reduced almost to normal when cream was precooled before being held at 60° F.

4. Cream slowly cooled to 45° F. yielded butter which was softer and contained more free oil than that from cream cooled rapidly to 45° F. and held at that temperature. The butter, however, was not so soft as that from cream held at 60° F.

5. Butter from cream held at a temperature below that at which it was to be churned did not differ significantly in hardness or free-oil content from that produced from cream held at the churning temperature.

6. Present commercial methods of cream treatment in New Zealand (rapid cooling to churning temperature and holding at that temperature) give butter of almost maximum hardness for the type of fat involved at each stage of the season.

7. More uniform consistency of butter throughout the season could be achieved only by reducing the hardness of the firmer butter and not by increasing the firmness of the ofter butter.

Cream samples (200–500 ml.) are churned in about 1 min. in a covered beaker by an agitator directly coupled to a ¼ h.p. electric motor. The beater sweeps the whole of the enclosed space so as to prevent thickened cream from collecting in places where it can escape agitation.

1. The vitamin D potency of three samples of south Indian butter has been determined in prophylactic tests with rats.

2. Two samples of butter from Bangalore contained 0·56 and 0·41 i.u. vitamin D/g. fat, a sample from Coimbatore contained 0·29 i.u./g. fat.

Coat formation in Stilton cheese is started 5–10 days after manufacture by scraping the surface to fill in crevices and to smooth the coat. Normally the cheese, when ready for scraping, is firm at the surface, greasy to the touch and smells like ripe pears. In some dairies, however, an abnormal condition known as “slip-coat” may be apparent at the scraping stage. The cheese is not firm to the exterior, but has a layer of softened material ½–¾ in deep resembling a partially drained cream cheese. The texture is flaky, whereas in the scrapings from the surface of a normal cheese the texture is granular. Patches of grey, or, less commonly, yellow or brown discoloration, may be formed at the surface of slip-coat cheese.

Severe losses are caused in some types of cheese by the growth of spore-forming anaerobes. The species most commonly involved is Clostridium butyricum and its variants, but other clostridia such as Cl. sporogenes (Bacillus putrificus of Dorner (1)) may also be concerned. Existing methods for the study of the properties of these organisms are inadequate, a fact on which Rosenberger(2) has commented. This work has been particularly concerned with devising a medium suitable for all clostridia, which is clear, simple to prepare, and which requires no special anaerobic precautions in its use.

1. Many single-strain lactic streptococci used as cheese starters exhibited a difference in susceptibility to an inhibitory substance present in raw and H.T.S.T. pasteurized milk, some being markedly affected whilst others were completely resistant to this inhibitory aubstance.

2. The inhibitory effect of raw or partially heated milk on ‘susceptible’ strains of starter streptococci appears to be a widespread phenomenon. It can be said that the inhibitory substance is normally present in all milk supplies throughout the year. It occurs in milk freshly drawn from the udder aseptically.

3. Heating the milk to boiling-point for variable periods or autoclaving the milk destroys the inhibitory effect of the milk on ‘susceptible’ cultures.

4. The inhibitory substance is closely associated with the fat globules in milk and can exert a marked effect owing to the large surface area exposed.

5. Growth-stimulating substances prepared from extracts of fowl liver, separator slime, and yeast were able to overcome the inhibitory effect when added to raw milk. However, the effect of these substances were markedly depressed on the addition of small amounts of freshly separated cream to the cultures.

6. It is suggested that the above growth-stimulating substances contain a common growth factor which enters into competition with an inhibitory substance closely associated with the fat globule.

7. The inhibitory substance appears to be bacteriostatic in its effect and not bactericidal.

8. Owing to the heat lability of the inhibitory substance and its presence in close association with the fat globule, it is suggested that it may be enzymic in nature.