1. Five Dairy Shorthorn male calves born in February and March 1953 and three groups of four born in each of the months February, March and April 1954 were placed out of doors on permanent pasture at birth.

2. Each calf received 6 or 8 pt. colostrum followed by approximately 45 gal. whole milk during the first 8 weeks of life, and thereafter, except for a small amount of dried grass given in Exp. 1, pasture grass comprised the sole item of diet until 6 months of age.

3. Mean growth rates for each month of life and from birth to 6 months are presented. After the first month of life, good progress was made, and it is considered that the live weights at 6 months of age are similar to those obtained with conventional methods of rearing.

4. There was a significant effect of birth weight on live-weight gain. After adjustment for birth weight, there were no significant differences in live-weight gain between February, March and April-born groups of calves.

5. Weather conditions seemed to have little effect on the incidence of scouring during the first 3 weeks of life.

6. On leys, greater weight gains were obtained than on permanent pasture.

7. No lungworm larvae were detected in faeces samples examined. In many cases there was a high level of infestation with stomach and intestinal worms as indicated by the number of trichostrongyle eggs/g. faeces. Some aspects of this infestation are discussed.

8. Satisfactory growth to 18 months of age was obtained with silage during the 6-month winter period and at grass during the following spring and summer.

9. Details of behaviour of the five calves in Exp. 1 studied at approximately monthly intervals to 6 months of age are presented.

1. Two Shorthorn cows with rumen fistulas were used to investigate the effect of diets high in concentrates and low in hay on the physical and biochemical processes of the reticulo-rumen.

2. During the initial control period of the investigation the cows received daily 16 lb. hay and 20 lb. concentrates (flaked maize 50%, weatings 35%, decorticated ground-nut cake 15%) and during the final control period 18 lb. hay and 10 lb. concentrates. There were three intervening experimental periods, in each of which the cows received 2 lb. hay daily. In the first experimental period they received, in addition to the hay, 24 lb. concentrates; in the second, 20 lb. concentrates and 5 lb. of dried delignified straw pulp in a finely macerated form; and in the third, 20 lb. concentrates. The experiment lasted 27 weeks.

3. In the experimental periods the mean milk-fat percentage remained below 2·0 for 10 weeks, whereas the mean value for the control periods was about 3·5. Addition of the straw pulp to the diet low in hay brought about no recovery in milk-fat percentage. It is calculated that in the two cows the losses in the yield of fat were 62·2 and 51·2% in the first experimental period and 62·5 and 58·7% in the second. In the experimental periods there were increases in the milk solids-not-fat percentage amounting in the two cows to upwards of 0·75 and 0·40 respectively. The composition of the butterfat was influenced by the diets low in hay, the main changes being a marked fall in the Reichert value, and a rise in the iodine value.

4. Digestibility trials showed that in the initial control period and the first and second experimental periods the mean daily intake of digestible crudefibrewas 2·6,0·6 and 3·0 lb. respectively. A tentative estimate of the extent of digestion in the reticulo-rumen, based on the lignin-ratio method, showed that a marked depression in values for the digestibility of the cellulosic constituents of the diet given during the first experimental period took place in the reticulo-rumen. In all experimental periods, even the first, the digestion of starch in the reticulo-rumen was virtually complete, only traces passing undigested to the remainder of the gut. In these three periods the mean daily intake of ether extract remained at 0·4·0·5 lb.

Using an electrical pressure-recording system simultaneous pressure records have been made in both the milked and unmilked quarters of a dairy cow. The unmilked quarters showed a very slow fall in pressure, while, as would be expected, the milked quarter showed a steady pressure fall. Re-stimulation some time after the beginning of the experiment resulted in a rise and fall in pressure within the milked quarters, but no change when the quarter was not milked.

The effect of ‘hold’ and ‘H.T.S.T.’ heat treatment on cream was a 97–100% reduction in the tributyrinolytic flora. There was no significant difference between the two methods in this respect. The tributyrin-splitting organisms have been tested for their ‘true’ lipolytic effect upon triolein; of 967 organisms tested 55 % attacked triolein. In raw cream the most numerous lipolytic organisms were of the Micrococci and Pseudomonads groups, whereas in heated cream the former were by far the predominant lipolytic organisms.

The result of storing cream at 8–11° C. for 24 hr. was an 8- to 13-fold increase in tributy-rinolytic organisms, mostly of Gram-negative rods many of which attacked triolein. The effect of heat treatment nullified this increase and the lipolytic flora of heated cream was much the same whether or not the cream was stored before heating.

The triolein media incorporated two new indicator dye combinations which were successful but a third, nile blue, was found to be strongly inhibitory to the majority of triolein-splitting organisms.

Methods are given for calculating the degree of taint removal from systems in which steam is bubbled through the liquid, and systems in which the liquid is boiled. The reverse procedure of obtaining equilibrium curve data from results of batch experiments is also shown. Examples are given for experimental values for removal of diacetyl and acetoin from solution by boiling.

The rate of removal of a dissolved tainting substance from cream by steam-distillation treatment is dependent in part on the relative volatility (or boiling point) of the pure substance, in part on the temperature of steam distillation, and in part on the influence of water on the vapour pressure of the tainting substance in dilute solution (i.e. on the activity coefficient, γ).

The application of Raoult's law and Henry's law to the problem of removal of taints from cream is discussed. For the dilute solutions commonly encountered in cream Henry's law can be expected to apply.

The equilibrium relationships for diacetyl and acetoin used as reference substances in investigations on cream-deodorizing equipment have been determined. The equilibrium coefficient for diacetyl in water at concentrations up to 50 p.p.m. in the liquid, as measured by the continuous equilibrium vaporization method, is 39·3. With rise in concentration above 50 p.p.m. in the liquid the coefficient decreases. At 100 p.p.m. it is 32 and at 1000 p.p.m. it is 20. The coefficient for acetoin in water at all concentrations up to 1·2% in the liquid is constant at 1·29. The activity coefficient for diacetyl in concentrations up to 50 p.p.m. was found to be 26·4 and for acetoin at concentrations up to 1·2%, 5·4.

For diacetyl the solubility partition coefficient as between butterfat and water rises from 0·47 at 100° F. to 0·74 at 180° F. For acetoin the partition coefficient remains constant at 0·18–0·19 over this range of temperatures. Correspondingly diacetyl is removed equally easily from butterfat and from water, whereas acetoin steam-distils much more readily from butterfat than from water.

The freshly formed surface of milk or cream obtained by overflowing in a double funnel is nearly free from microscopically visible fat.

When this surface is disturbed, either by repeated touching with a platinum ring or by allowing air bubbles to burst there, the fat globules and clumps are brought on to the surface, appearing there as such, or being stretched to lenses, or being spread as patches.

The amount of fat brought onto the surface increases with the extent of disturbance, viz. the number of touches with a platinum ring or the number of air bubbles burst, and with the fat percentage of cream.

Ageing of milk or cream slightly promotes the transfer of fat globules onto the surface.

At 30° C. the bursting of about 10–15 air bubbles is enough to cover the milk surface in the overflow outfit with an almost continuous fat blanket, while at 20° C. the globules and clumps occur separately.

The fat globules rendered hydrophobic by mechanical treatment of the milk surface, as well as the fat patches on the surface, are likely to be accessible to the action of lipase. This may explain the agitation activation of lipolysis in raw milk during certain stages in machine milking and during transportation.

The Gerber method (B.S. 696:1936) and the Röse Gottlieb method (B.S. 1741:1951) for the determination of the fat content of milk have been compared on 208 samples of milk covering the range of 2·5–6·0% fat. The following relationship was found between the Gerber percentage (G) and the Röse Gottlieb percentage (RG):G = 1·036 RG – 0·097. Thus, for milks containing 3·0, 4·0, 5·0 and 6·0% fat, as determined by the gravimetric Röse Gottlieb method, the Gerber test gave results which were higher, on the average, by 0·01, 0·05, 0·08 and 0·12% fat respectively.

If the capacity of the Gerber milk pipette were reduced from 11·04 ml. of water, as specified at present, to 10·94 ml., the average results obtained by the two methods would be in agreement for milks with a fat content around 3·6%, the average for milk in England and Wales, and the difference between the results by the two methods would, for most purposes, be negligible over the normal range of fat content.

Tables are given, for the 11·04 and 10·94 ml. milk pipettes, showing the average differences between the results by the two methods for various values of Gerber fat percentage.

The contributions of lactose and chloride to the total freezing-point depression of milk have been measured by an incremental procedure. Successive additions of these substances to watered milk have enabled direct determination of the partial freezing-point depression to be made in a medium substantially the same as the original.

The C6–C11 2,4–dienals have been identified in distillates from skim milk with oxidized flavour. The C4–C11 2–enals were isolated from the same distillates in a previous investigation. The most abundant individual compounds in the two groups were 2–octenal, 2–nonenal, 2–4–heptadienal and 2,4–nonadienal. These compounds when flavour–tested in skim milk in dilutions of 10–7–10–9 closely resembled oxidized (cardboard) flavour. It is concluded that they are the main constituents of this flavour defect and that they originate from the oxidation of the more highly unsaturated fatty acids in milk lipids.

Butterfat oxidation occurred in both salted and unsalted butters during storage at 14° F. Butterfat oxidation values, after storage, were much lower in unsalted and in highly salted butters than in butters of normal salt content.

Butterfat oxidation in salted butters during storage was retarded by treatment with antioxidants. These included fat-soluble and water-soluble substances, surface-active agents and copper-complexing compounds.

Unsalted butter, salted butter and salted butter treated with antioxidants all developed ‘storage’ flavour during storage for eight months.

Many of the antioxidants added to salted butter were effective in retarding further fat oxidation and further increase in intensity of storage flavour when the butters were transferred to a temperature of 60–65° F. after storage.

Cheese has been successfully made from raw and pasteurized milk by a process similar to that employed for Cheddar or Cheshire-type cheese but omitting the starter inoculum.

In the preferred method gluconic acid lactone was used as the acidifying agent during the setting of the curd and after milling.

The flavour of the best products was acceptable to a number of people not necessarily experienced in cheese-tasting, but it was different from that of normal Cheddar.

No improvement in flavour was achieved by inoculation of the cheese milk with a strain of L. casei and L. brevis.

Further detailed investigation is needed to perfect the process and to determine whether its use in industry is justified or desirable.

Lactobacilli are found in large numbers in cheeses of many varieties, and it is therefore believed that they are concerned with the development of flavour. In investigating this, Mabbitt(1) made cheese without starter, adding strains of lactobacilli to the cheese millr to determine whether flavour would then develop. The serological types of the lactobacilli were known, and the present paper describes the serological methods of identifying the strains of lactobacilli which were recovered from the cheese with those which were added.

1. The serum prepared by subjecting Cheddar cheese to pressure becomes inhibitory to the growth of lactobacilli as the cheese ripens.

2. One factor responsible for the inhibitory phenomena is the increasing osmotic pressure of the serum due mainly to the increasing amounts of amino-acids present.

3. Observations made during the ripening of a normal Cheddar cheese suggest that other factors, e.g. amino-acid imbalance, are also important.

Kizer, Hankin, Speck & Aurand(1) have observed that the impurities associated with proteolytic enzymes are stimulating to lactic acid bacteria, and they have suggested that these substances may accelerate the ripening of dairy products. In view of these observations and suggestions an experiment begun in March 1954, on the preparation of cheese with crystalline rennin, is reported below. The results are in agreement with the suggestions of Kizer et al.

A variability study of ball-compressor readings on the upper faces of 10 Cheddar cheeses has shown that:

1. Percentage elasticity readings were generally less discriminating than total deformation readings.

2. As measured by the total deformation, there were firmness gradients across the faces of the cheeses, which tended to increase in firmness from the centre outwards.

Further experimentation to determine consistent firmness differences on cheeses has been recommended and meanwhile, from preliminary examination of firmness discrimination, it is suggested that four total deformation readings may give sufficient accuracy for many routine purposes.