The rate of destruction of Bacillus subtilis spores by sodium hydroxide solutions in the range of atmospheric temperatures 34—82 °F was studied: (a) to provide information which might be used in practice for immersion cleaning of dairy utensils in sodium hydroxide solutions at low atmospheric temperatures, and (b) to examine the nature of the disinfection curves by slowing down the rate of disinfection. The results expressed as a three-dimensional graph showed that an increase in temperature from 34 to 82 °F had a more marked effect on spore destruction than an increase in concentration of sodium hydroxide from 1·5 to 5·0%. The overall effect could be expressed as

where t = time in hours for the 99% destruction of B. subtilis spores, C = concentration of NaOH (%, w/v) and θ = temperature, °F. Since the time for the 99% destruction of B. subtilis spores by a 2% NaOH solution at 34 °F is 5 times that of a 5% solution, immersion cleaning in cold climates might be assisted by increasing the concentration of NaOH from the normal 2–3 to 5%. Results in disinfection tests at low temperatures were more variable than had been observed in previous work at higher temperatures. These surprising results prevented a careful study of the nature of the disinfection curves and confirmed previous conclusions that such curves are basically sigmoid.

The results of 2 experiments indicated that casein whey powder can successfully constitute a relatively high proportion of an all-meal diet for growing pigs. Pigs given a diet consisting of a basal meal allowance per day of ½ lb meat meal and 1½ lb barley meal plus increasing amounts of casein whey powder took significantly less time and required significantly less food to grow from 50 lb to 120—140 lb liveweight, than either the control pigs or those given diets containing smaller basal meal allowances but correspondingly more whey powder. In the best diet whey powder comprised approximately 40% of the total food consumed. In one experiment, diets containing more whey powder than this resulted in slower growth rates, relative to that of the controls, from 110 lb liveweight onwards.

There was a little more scouring on the diets containing the greater amounts of whey powder; but even where whey powder formed approximately 83% of the total food consumed, the incidence of scouring was not of great practical importance. Moreover, there was considerable variation among animals within treatment groups in this respect.

From 50 to 140 lb liveweight pigs were given mixtures containing 25 or 50% of either un-neutralized or neutralized lactic casein whey powders in partial replacement of barley meal in a control ration.

Those animals that were given rations containing 25 and 50% un-neutralized whey powder and 25% neutralized whey grew significantly faster and more efficiently up to 110 lb liveweight than the controls and those given the rations containing 50% neutralized whey powder. For the overall trial period, only differences between the last-named group and each of the 3 other groups that received whey powder were statistically significant.

Water intake increased with level of whey powder in the diet and was significantly greater at both levels with the mixtures containing the neutralized powder than with the other diets.

Carcass measurements did not indicate any significant difference in treatment.

Both whey powders were sticky and unpleasant to handle, the neutralized material being worst in this respect.

As determined by gas-liquid chromatography, the mean fatty acid composition (weight percentages of total fatty acids) of milk fat from sows fed a diet to meet U.S. N.R.C. nutrient requirements was: oleic, 35·3; palmitic, 30·3; linoleic, 13·0; palmitoleic, 9·9; stearic, 4·0; myristic, 3·3; linolenic, 2·5; unidentified 0·7 and 0·5, presumably n-odd chain and branched fatty acids; lauric, 0·3; and capric, 0·2. The corresponding fatty acid composition of colostrum fat was: oleic, 41·7; palmitic, 22·5; linoleic, 20·9; palmitoleic, 5·0; stearic, 5·7; myristic, 1·4; linolenic, 2·4; and unidentified acids, 0·3 and 0·1. Dietary fat increased fat levels in the milk and influenced fatty acid composition of the milk fat. Backfat resembled colostrum fat more than milk fat.

A strain of Streptococcus lactis, C10, known to be resistant to lactenins, was found to be composed of 47% resistant cells, 10% cells sensitive to lactoperoxidase and 43% cells sensitive to both agglutinins and lactoperoxidase. By subculturing a strain composed of 100% resistant cells in different conditions of medium, temperature and incubation time, it was possible to obtain cultures composed of resistant and sensitive cells in various proportions. These findings help to explain how, after numerous subculturings in autoclaved milk, a resistant strain may become sensitive to the natural inhibitors of milk.

Transduction experiments were carried out using recipient strain Streptococcus lactis C2Ss (streptomycin-sensitive) and virulent phages prepared on donor strain Str. lactis C2Sr (streptomycin-resistant). At a high multiplicity of infection of 10, transduction to streptomycin resistance occurred at a frequency approximately 1 in 30 surviving cells and the recombinant character exhibited a delayed expression. Transduction did not occur when phages propagated on Str. lactis C2Ss were used or when phage antiserum was added to the transducing phage suspension. The transducing phage manifested an altered lytic cycle following passage through the Str. lactis C2Sr donor which rendered it incapable of reinfecting the donor but did not alter its virulence for the Str. lactis C2Ss recipient.

The volatile components of milk have been isolated in a form suitable for application to a gas chromatograph, using the simple rapid technique of entraining them in a gas stream and trapping in a syringe barrel cooled in liquid nitrogen.

The souring process in milk which occurred during incubation at 22 °C was followed by observing the differences between chromatograms of samples taken at intervals. Onset of souring was detected with a sensitivity similar to that obtained by measurement of pH, but the chromatographic method had the advantage of being independent of the initial pH and buffering power of the milk.

With suitable chromatographic apparatus the total analysis time including the preparation of the sample could be about 3 min. Modifications are discussed which would increase the speed of analysis, and thus form a basis for the development of a practical method of assessing the odour of milk before processing.

Cheeses collected monthly for 6 months from 6 factories in the same district were stored for a period of 12 months. At intervals the cheeses were sampled and the fats extracted for oxidation tests. There was no increase in peroxide value, no decrease in induction period and only a slight increase in free fat acidity during storage of the cheeses.

The effects of changes in the conditions of preparation on the composition of the k-casein complex have been studied and a method of preparation is suggested which embodies the optimal conditions. The varied conditions include temperature of precipitation of the acid casein, the pH, temperature, CaCl2 concentration and duration of the CaCl2 treatment, and the conditions of centrifuging. Changes in composition caused by alcohol fractionation are reported and the results are discussed from the point of view of k-casein as a complex of three or more proteins.

An apparatus is described which measures at 10—15 sec intervals the viscosity of rennetted milk taken from a cheese vat. The first signs of an increase in this viscosity mark what is at present the earliest measurable stage in the process of coagulation. Coagulation times so determined agreed fairly closely with the observations of a skilled cheese-maker and, for a given milk, were inversely proportional to rennet concentration over quite a wide range. Clotting times obtained by the method of Berridge (1952) for standardizing rennets came 2 or 3 min after those determined by the new method and were linearly related but not proportional to inverse rennet concentration.

In a series of 3 trials there was little or no difference in milk yield when cows were fed the same quantity of dry matter in the form of well-preserved hay or silage from the same sward.

A higher milk yield was obtained from silage made from grass at an early stage of maturity than from silage or hay made from the same crop 5 weeks later.

In 2 trials when hay or silage was fed ad lib. the dry-matter intakes of the cows were higher with hay than with silage, and there was a consequent increase in milk yield and S.N.F. content in favour of hay.

Some of the results indicated that with certain silages a depression in the S.N.F. content of the milk, due to a decrease in the casein content, could occur, although this was not associated with an inadequate energy intake.

Dissolved oxygen in anhydrous milk fat is reacted with an aqueous manganous-ferrous hydroxide suspension at 50 °C. The mixture is acidified and after separation into two layers the amount of ferric iron in the aqueous layer is estimated by iodometric titration. The procedure is relatively simple and is suitable for routine testing of milk fat.

The effect of the level of pre-partum feeding of Friesian heifers on the yields and composition of the milk in the subsequent lactation has been investigated using 23 heifers on each of 2 treatments. For 1 treatment, over a period of 6 weeks before calving, generous grazing on good pasture was supplemented with 8 lb/cow daily of concentrates, and for the other only restricted grazing of an already sparse sward was allowed.

For the period 3—8 weeks from calving the heifers fed at the high plane pre-partum produced significantly more milk than those fed at the low plane (36·8 compared with 31·9 lb/cow daily). The solids-not-fat (S.N.F.) and fat contents of their milk were also significantly higher (8·71 compared with 8·47%, and 3·72 compared with 3·38%, respectively). For the period 3—14 weeks from calving the effect of milk yield was slightly greater but the effect on composition was less. For the period 3—30 weeks from calving the difference in milk yield remained significant (31·3 compared with 26·1 lb/cow daily), but the average differences in S.N.F. and fat contents over this period (8·63 compared with 8·51%, and 3·75 compared with 3·59%, respectively) were not significant.

The heifers fed at the higher plane increased in liveweight before calving at a rate which was highly significantly greater than that of the heifers fed at the low plane. After calving, the heifers which had been on the higher plane remained almost constant in weight during the first 12 weeks whilst the others regained some of their losses, a difference which was highly significant. This recovery was apparently made at the expense of milk yield and composition.