1. In a winter feeding trial, using eight Ayrshire cows, two concentrates with digestible crude protein contents of 15% and starch equivalents of 63 and 79 were each fed at 2·6 and 4·6 lb./gal. of milk.

2. The basal ration was hay, silage, dried grass and fodder-beet.

3. Milk yield was significantly increased from 30·9 to 34·7 lb./day when the amount of concentrate fed increased from 2·6 to 4·6 lb./gal., but the average milk yields when the concentrates low in starch equivalent were fed did not differ significantly from those obtained when the concentrates high in starch equivalent were fed at the same levels.

4. The fat content of the milk was similar on all four rations with an average value of 3·84%, whereas the solids-not-fat varied from 8·53% on the low starch concentrate fed at the lower rate to 8·77% on the high starch concentrate fed at the higher rate.

5. The cows which were fed at the rate of 4·6 lb./gal. were significantly heavier by an average of 33 lb./cow than the ones fed at the rate of 2·6 lb./gal. The two different qualities of concentrate did not cause differences in live weight.

6. The weight of dry matter in the basal ration consumed per day was similar on all four treatments.

7. A comparison of feeding costs and the value of the milk showed that the largest margin was obtained with the low starch equivalent concentrate fed at the rate of 2·6 lb./gal.

8. It was concluded that because of the loss in live weight on the lowest level of feeding, and because the quality of the concentrate gave no improvement in milk yield or liveweight and little improvement in milk composition, the optimal level of feeding in this experiment was 4·6 lb./gal. of the low starch equivalent concentrate.

The use of an autogenous vaccine/toxoid in the prophylaxis of clinical and subclinical staphylococcal udder infections in a dairy herd is described. Mainly first calving cows were included in the trial, and the results are given on 25 vaccinated and 18 uninoculated control animals. Four injections of vaccine at weekly intervals were given and every 6 months a further inoculation was given with a view to reinforcing immunity.

Observations were made over a period of 2½ years and there was a significant difference in the number of heavy staphylococcal infections and clinical cases in treated and control groups during the first 18 months, only one clinical case occurring in the treated group compared with 9 in the controls. Major infections totalled 8·1% during this period compared with 1·9% in the treated cattle, total staphylococcal infections being 16·2% compared with 7% in the respective groups.

In the last 12 months of the experiment eight clinical cases occurred in the treated group compared with five in the controls. It is clear from these results compared with those for the first 18 months that the reinforcing doses of vaccine/toxoid every 6 months were insufficient to maintain immunity. Subclinical infections, however, remained at a lower level in the treated group than in the control animals.

The significance of subclinical staphylococcal infections in relation to Whiteside tests is discussed, also the possible relationship of toxoid and bacterial vaccination to actual immunity produced. Some evidence is given that the presence of blood serum antitoxin is not necessarily associated with immunity.

The melting dilation of butterfat between 10° and 30° C. has been determined from results obtained for the thermal expansion of solid and liquid butterfat. Measurement of the solid fat percentages obtained with different cooling treatments showed that at higher rates of cooling there was an increase in the solid fat content, which is in accordance with the theory of mixed crystal formation. A cooling rate existed beyond which no further increase in solid fat content took place, since butterfat cooled by immersion in a 5° C. water-bath had practically the same solids content as it had when cooled in a 0° C. water-bath. Differences in cooling rate changed the solid fat content mainly in the region of lower melting-point glycerides. Seasonal variations in solid fat content indicated relatively large differences in the content of higher melting glycerides. There is an indication that not only the quantity of solid fat, but also the composition of the crystals is important as a factor influencing the hardness of butter. It was possible to recrystallize mixed crystals in butterfat at 22·5° C. and thereby lower the solid fat content of the butterfat.

1. Measurements, by means of a continuous vaporization equilibrium still, of vapour/liquid equilibrium relationships in the steam distillation of dilute aqueous solutions showed that for mesityl oxide the relationship was linear, equilibrium coefficient (CV/CL)= 74.

2. For acetylpropionyl it was linear over the concentration range l–10 p.p.m. in the liquid, CV/CL=51, and above a concentration of 20 p.p.m. it was again approximately linear. At 20 and 50 p.p.m. in the liquid the values found for CV/CL were 34 and 21·5 respectively.

3. For acetyl-iso-butyryl it was not linear even at very low concentrations, of the order of 1–3 p.p.m. in the liquid, but there was an approach to linearity at concentrations 0–1 p.p.m., CV/CL=240. At concentrations above 1 p.p.m. in the liquid there was a steady fall in the value for the equilibrium coefficient.

4. For acetylvaleryl it was curvilinear even over the concentration range 0·1–4·0 p.p.m. in the liquid. At 0·5–1·0 p.p.m. in the liquid the equilibrium coefficient was of the order of 240. Above a concentration of 4 p.p.m. in the liquid the relationship was linear.

5. For acetylcaproyl it was approximately linear only over the concentration 0·1–0·4 p.p.m. in the liquid, CV/CL=180. At 4 and 8 p.p.m. in the liquid the coefficients were 90 and 70 respectively.

6. For acetylbenzoyl it was curvilinear at low concentrations, i.e. 0·1–0·5 p.p.m. in the liquid, CV/CL=30 decreasing to 16. Above this concentration there was a gradual fall in the equilibrium coefficient to 11·5 at 70 p.p.m. in the liquid.

7. Of the substances investigated only diacetyl and acetylpropionyl and, within limits, acetylbenzoyl were considered to be of suitable properties for use as reference substances in detailed investigations on cream deodorization equipment.

1. The effect of 4·5% lactose in solution on the vapour/liquid equilibrium relationship for acetylpropionyl, acetyl-iso-butyryl, acetylvaleryl, acetylcaproyl and acetylbenzoyl has been investigated.

2. There was no appreciable effect on the relationship for acetylpropionyl and acetylbenzoyl.

3. For acetyl-iso-butyryl there was a lowering of the coefficient at low concentration of diketone in the liquid, but at concentrations above 4 p.p.m. there was no appreciable effect.

4. For acetylvaleryl at low concentrations in the liquid the coefficient was lowered, and at concentrations above 3·0 p.p.m. in the liquid it was increased.

5. For acetylcaproyl the coefficient was lowered by presence of 4·5% lactose in the solution.

6. Change in concentration of lactose over the range 0·5—10% had little effect on the vapour/liquid equilibrium coefficient for acetylpropionyl and acetylbenzoyl, but it caused a progressively increased reduction in the coefficient for acetyl-iso-butyryl, acetylvaleryl and acetylcaproyl.

1. Coefficients of distribution for acetoin, diacetyl and acetylpropionyl between butterfat and skim-milk were measured over a range of temperatures up to 190° F. by passing preheated milk containing the reference substance through an hermetic cream separator and analysing the cream and skim-milk obtained.

2. The coefficients increased with rise in temperature, and the relationship between change in coefficient and change in temperature was linear for all three substances.

3. Coefficients of distribution for acetyl-iso-butyryl, acetylvaleryl, acetylcaproyl and acetylbenzoyl between butterfat and 4·5% lactose solution were measured at 40° and 60° C. by direct separation after equilibration, followed by estimation of the diketone in the lactose solution.

4. Coefficients of distribution at 100° C., obtained by linear extrapolation from these results, were: acetoin, 0·255; diacetyl, 1·27; acetylpropionyl, 5·9; acetyl-iso-butyryl, 20; acetylvaleryl, 23; acetylcaproyl, 152; acetylbenzoyl, 48.

5. The coefficients of distribution for diacetyl and acetylpropionyl between butterfat and 4·5% lactose solution were not affected by change in concentration of the diketone in the lactose solution.

1. The relationship between vapour/liquid equilibrium coefficient for a tainting substance in cream (mc) as compared with the coefficient for the substance in skim-milk (ms) at 100° C. is given by the formula

where F is the percentage fat content of the cream, and k is the butterfat/skim-milk distribution coefficient at 100° C.

2. The values for the vapour/liquid equilibrium coefficients for acetoin, diacetyl, acetylpropionyl, acetyl-iso-butyryl, acetylvaleryl, acetylcaproyl and acetylbenzoyl in cream, computed by the formula from the equilibrium coefficients for the substances in 4·5% lactose solutions and the distribution ratios at 100° C, were in good agreement with the experimental results for these substances in cream.

3. It was shown that high solubility of a substance in butterfat relative to solubility in skim-milk greatly reduces the steam volatility of the substance from cream.

4. It was concluded that steam volatility of a substance from cream may be affected by temperature of deodorization because of the effect of temperature on the butterfat'skim-milk distribution coefficient.

Lactose was estimated accurately and rapidly in casein by use of anthrone reagent on the clear filtrate from precipitation of a sodium bicarbonate solution of the casein with 0·1 n-sulphuric acid. The reagent consists of 0·15% (w/v) anthrone in 70% (v/v) sulphuric acid. The ice-cold anthrone solution (10 ml.) was added, with cooling, to 1 ml. of the ice-cold solution containing 0–100 µg. of lactose. The mixture was heated at 100° C. for 6 min. and cooled for 30 min. The optical density of the coloured solution was then measured at 625 mµ

1. Under carefully standardized conditions, the increase in the over-all rigidity modulus of curd when the time after rennetting is doubled, varies inversely as the cube root of the rennet concentration. The intercepts of the extrapolated setting curves on the time axis and the observed coagulation times vary inversely as the concentration.

2. With the same (normal) rennet concentration, some rheological parameters increase or decrease progressively as temperature is increased from 21° to 41° C.; others pass through maxima or minima, all between 29° and 35° C.

3. Long-term ‘creep’ experiments have been done over the above temperature range, creep and slow recovery increasing progressively with temperature. Relaxation experiments, though showing the simplest distribution of relaxation times at about 32° C., are too greatly influenced by unavoidable differences in firmness at the different temperatures for it to be possible, at this stage, to draw conclusions about their temperature dependence.

4. A comparison of some of these results with data published by a few other workers is attempted.

1. Results are reported of an experiment with fattening pigs carried out under commercial conditions, to obtain further information on the comparison of all-meal feeding with meal plus unrestricted amounts of whey. In addition, the effect of omitting the antibiotic, oxytetracycline, from the diet during the latter half of the fattening period was investigated.

2. There were four treatments. (i) Meal only ad lib. up to a daily maximum of 6 lb./pig, with oxytetracycline included in the diet for the whole fattening period. (ii) As (i) but oxytetracycline included in the diet only up to an average pen live weight of 130 lb. (iii) 3 lb. meal reduced to 2 lb./pig/day by 13 weeks of age plus unrestricted amounts of whey with oxytetracycline included in the basal meal for the whole fattening period. (iv) As (iii) but oxytetracycline included in the diet only up to an average pen live weight of 130 lb.

There were five pens of nine group-fed pigs on each treatment, involving a total of 180 pigs. The pigs were on experiment from approximately 8 weeks of age to bacon weight. Comprehensive carcass measurements were made on all pigs.

3. The meal plus whey-fed pigs grew significantly slower and utilized their food significantly less efficiently than those fed meal only. They also had a significantly lower dressing percentage, but longer and less fat carcasses than the all-meal fed animals. The results are discussed in relation to those obtained in earlier experiments completed under similar conditions at the Cow and Gate farm.

4. Comparison of the efficiency of food utilization results of the all-meal and meal plus whey-fed pigs showed that 1 gal. of whey replaced approximately 0·7 lb. of meal.

5. The results showed that omission of antibiotic from the diet of either the all-meal or meal plus whey-fed pigs after they reached 130 lb. live weight, had no significant effect on growth rate, efficiency of food utilization or any carcass measurements of the pigs.

We wish to thank the Director of Messrs C. and G. Prideaux, Ltd., Bacon Curers, Motcombe, Shaftesbury, Dorset, for permission to take carcass measurements of the experimental pigs, and we are greatly indebted to Messrs K. Lawrence and P. Prideaux who most conscientiously took these measurements.

The heat resistance of strains of lactobacilli previously isolated from Cheddar cheese was determined using a laboratory pasteurization test and a commercial pasteurizer.

The laboratory tests showed variations in heat resistance at 140° F. for 10 sec. which were not correlated with species, but at 150° F. for 10 sec., an average of 99·55% destruction occurred with all strains.

With the commercial pasteurizer, heating at 155° F. for 17 sec. caused a 99·99999–100% destruction, whilst heating at 160° F. for 17 sec. destroyed 100% of all strains of lactobacilli tested in every case.

We wish to thank Miss H. R. Chapman and Miss A. J. W. Harrison for operating the pasteurizer.

1. It is possible to study the structure of cheese curd and the disposition of microorganisms therein by microscopical observation of sections cut on the freezing microtome after fixation in formalin.

2. In the small number of cheese examined bacterial colonies were found only in crevices.

3. As ripening proceeded the finer protein structures tended to disappear.

4. The distribution of bacteria in cheese curd is markedly uneven.

The accuracy of the method specified in B.S. 734:1937 for the estimation of the total solids and solids-not-fat contents of milk from the density and fat content has been assessed by direct comparisons with the gravimetric method. A total of 2425 samples of milk, mostly from single herds, were examined in five series over different years.

The percentages of solids estimated by the density method were lower, by an average of 0·06, than those determined gravimetrically. To correct for this error, and to compensate for the lower, more accurate fat percentages arising from the recent reduction in the capacity of the Gerber milk pipette, it was proposed that the density formulae be modified to T=0·25D+l·22F+0·72 and S.N.F.=0·25D+0·22F+0·72.

These formulae were adopted in October 1957 in an amendment to the B.S. 734 published in 1955.