Seven changeover experiments were conducted to examine the effect of giving restricted amounts of concentrates on the voluntary intake of different roughages by non-lactating dairy cows. The addition of up to 6 kg concentrates daily to the diet of cows receiving roughage ad lib. caused little change in the intake of hay and a small increase in the intake of barley straw. Larger amounts of concentrates of 6 and 8 kg daily reduced hay intake by between 0·2 and 0·4 kg dry matter/kg concentrate dry matter given. When concentrates were given to the cows the rate of decline in intake of hay tended to be greatest with the hays of highest digestibility. The daily addition of up to 8 kg concentrates to the diet of cows offered silage ad lib. caused only small depressions in the intake of silage. The results are discussed in relation to recent work on this subject with cattle and sheep.

Three rations were compared in a 15-week winter feeding experiment using 12 Ayrshire cows. All the cows received silage 3 times a day and concentrates; ration A contained no sugar-beet pulp whilst ration B contained 6 lb of pulp and ration C 12 lb.

The total weights of dry matter consumed were 29·7, 32·3 and 33·4 lb/day, respectively, on treatments A, B and C. For every 1 lb of extra sugar-beet pulp dry matter eaten the decline in the dry weight of the other feeds consumed was 0·50 lb on treatment B and 0·55 lb on treatment C. The main decrease was in the silage part of the ration. The weights of starch equivalent (S.E.) consumed daily were 18·0, 19·8 and 20·7 lb on rations A, B and C, respectively, with mean daily milk yields of 38·2, 39·3 and 39·7 lb, giving a response of 0·55 lb milk/lb extra S.E. between rations A and C. The corresponding fat percentages of the milks did not differ significantly from each other but the solids-not-fat (SNF) percentages increased significantly from 8·76% on ration A to 8·88% on ration C. The average response per lb extra S.E. was 0·044% SNF and the increase was in the protein fraction of the milk. The cows were significantly heavier on rations B and C than on ration A. The inclusion of beet pulp in rations B and C had no adverse effect on the taste of the milk.

The viscosity of cream increased with increasing fat content, and higher values were obtained if the cream was separated at 38–43 °C rather than above 55 °C, and if the cream was cooled to below 15 °C before storage at 20 °C. The ‘type’ of viscosity varied with cooling and storage conditions; for example, cream cooled below 20 °C and stored at 20 °C gave increased viscosity readings with increased rates of shear due to churning of the cream, while the behaviour of cream cooled only to 20 °C was Newtonian.

Cream stability as measured by free fat content decreased with increasing fat content above about 42%, with low temperature separation (38–45 °C), with cooling to below 15 °C before storage at 20 °C, and with increased pressure at temperatures below 15 °C.

Dilatometric study of the amount of fat crystallization indicated that larger amounts of crystallization resulted in higher final viscosity and free fat content.

Two experiments were conducted with non-lactating cows to examine the effect of adding concentrates to a diet of hay on the rate of disappearance of digesta from the alimentary tract. The addition of large amounts of concentrates to the diet of cows offered hay ad lib. decreased the voluntary intake of hay, increased slightly the digestibility of the organic matter and decreased markedly the digestibility of the crude fibre of the diet. Also, the addition of concentrates increased the mean time of retention of stained hay residues in the alimentary tract and increased the time/kg hay the cows spent ruminating. At the end of a meal the amount of digesta in the reticulo-rumen of the cows offered hay ad lib. with restricted amounts of concentrates was about the same as that found when offered hay ad lib. as the only food. The results are discussed in relation to the regulation of the voluntary intake of hay by the cow.

Milks of the closely related species ox, buffalo, goat and sheep were differentiated by the precipitin test using antisera to blood serum proteins. The antisera were made specific for the homologous species by absorption. The component of milk tested was the lactalbumin–lactoglobulin fraction present in whey. Fraudulent sale of diluted buffalo's milk, cow's milk–buffalo's milk–water mixtures and reconstituted whole and skim-milk powders as genuine cow's milk was detected. Of 270 milks serologically tested, 233 were cow, 26 buffalo, 1 goat, 3 cow–buffalo mixtures, 2 reconstituted whole-milk powders and 5 reconstituted skim-milk powders. Of the samples serologically identified as cow, 135 had analytical figures for fat and solid-not-fat (SNF) only just outside or within the buffalo range.

Milk from any one species was detected in a concentration of 5% (v/v) in milk of a related species. Species identification was made of human milk stains in 2 medicolegal cases. Fresh cow's milk, reconstituted whole-milk powder and reconstituted skim-milk powder were differentiated.

The fatty acid composition of colostral and milk fat samples representative of the total secretion of the nursing mammae of each of 3 sows was determined by gas-liquid chromatography. In both colostral and milk fats, acids of chain length C16 and C18 accounted for more than 90% of the total fatty acids present; colostral fat contained a higher proportion of oleic acid and linoleic acid and less palmitic acid and palmitoleic acid than normal milk fat. Structural studies on milk triglycerides showed that, as in pig depot fat, palmitic acid is preferentially esterified to the secondary alcoholic group (2-position) of the glycerol molecules with the C18 acids (stearic, oleic and linoleic acids) being present for the most part in the 1- and 3- positions.

Coagulase-negative staphyloccoci were isolated regularly over a period of 39 weeks from quarter milk samples of 18 cows belonging to one herd. They did not produce a leucocytosis in the milk or high anti-haemolysin titres in the blood of these cows, but such responses occurred in 2 cows infected with pathogenic staphylococci. The coagulase-negative variety was found to colonize the teat duct and surface of the teat in preference to the milk and possessed greater resistance than pathogenic staphylococci to certain long-chain fatty acids. Infection with coagulase-negative staphylococci was thought to antagonize the colonization of the udder by a pathogenic variety present in the herd; 23% of the coagulase-negative strains were found to elaborate an antibiotic substance inhibitory to the growth of a coagulase-positive staphylococcus. Coagulase-negative strains were characterized by the production of ɛ-toxin and could be divided into 3 main groups according to their effect on gelatin, mannitol and phenolphthalein diphosphate as substrates.

Bacteriological examination of 15 pairs of Cheddar cheeses, of which one of each pair was made aseptically, showed that there was a relationship between the development of rancid flavour and the numbers of Clostridium tyrobutyricum present. Other species of clostridia, Cl. beijerinkii, Cl. sporogenes and Cl. perfringens, were also present but occurred only as spores. Conditions for the growth of Cl. tyrobutyricum appeared to be more favourable in the aseptically made cheese; it is suggested that the adventitious bacterial flora of the non-aseptically made cheese, which gains access during cheesemaking, has some inhibitory effect on the growth of this organism.

Dry butterfat occasionally develops a greenish colour when stored for at least 1½ years at −12°C whereas samples of the same fat kept for 2 years at +2 or +15°C do not show this colour defect. Spectrophotometrical measurements have shown that the defect is accompanied by a chemical change of the carotene. Its absorption maxima are shifted towards the shorter wavelengths, and a new absorption is observed at 400–410, 430–435 and 450–460 mm. The possible involvement of oxidation products of carotene, such as isomeric diepoxides or furanoid oxides is discussed. The colour defect can be observed before any change in flavour is noticed.

Washed rennet curd releases significant quantities of calcium phosphate and relatively small quantities of calcium para-caseinate when shaken with water. Treatment with small quantities of sodium chloride in aqueous solution similarly differentiates between these 2 components, but larger quantities attack both phosphate and para-caseinate with equal severity. A more extensive release of Ca and inorganic Poccurs when the curd is treated with lactic acid solutions; the comparative ease with which Mg is removed under these conditions suggests that Mg is present as magnesium citrate.

The C1,2,5–8 n-alkan-1-ols were identified from oxidized butter prepared from cream treated with cupric chloride and ascorbic acid. The six n-alkan-1-ols occurred in approximately equimolar amounts and in concentrations of approximately 1 μmole/kg, the same order of magnitude as that of the C6–9 n-alkanals. The amounts increased rapidly during the first 4 weeks of storage, but only slowly during the succeeding 4–20 weeks. Only insignificant amounts of the C3–8 alkanols formed in the untreated samples. It is suggested that C1–8 alkanols are formed by the oxidation of unsaturated fatty acids according to the theory of Farmer, Koch & Sutton (1943) from primary alkoxy radicals resulting from the decomposition of lipid hydroperoxides.

An antibiotic produced by coagulase-negative staphylococci isolated from the bovine udder was examined by deferred antagonism tests and its inhibitory properties compared with those of other staphylococci. While inhibiting the growth of representative phage types of bovine pathogenic staphylococci, its activity against corynebacteria was more restricted than that of Staphylococcus aureus NCTC 6507 and 8004. Only minimal amounts of inhibitory substance were produced in liquid media, larger amounts were produced on solid media and the incorporation of a blood plasma factor further increased production. The inhibitory substance resisted treatment with pepsin and trypsin and withstood boiling for 30 min. Its characters in relation to inhibitory substances produced by other staphylococci are discussed.

The effect of 6-, 12-, 18-, 24-, 30- and 36-h milking intervals on milk secretion has been investigated. The effect of the previous milking intervals was eliminated by interposing a recovery period consisting of 12-h milking intervals between the experimental intervals. Bias due to the carry-over of residual milk was reduced by removing the residual milk at the end of each milking, after an injection of oxytocin.

The rate of secretion of milk and of the individual constituents decreased curvilinearly, with duration of the interval, but the degree of curvilinearity differed between constituents. The rates of decrease were in the following increasing order: sodium, chloride, fat, whey proteins, casein N, water, non-protein N, lactose and potassium. The effects of the treatments persisted for some time after the end of the experimental intervals, but the original rates of secretion were regained by the end of the recovery period. The differing effects on the secretion of individual constituents resulted in increases in the concentrations of sodium, chloride and whey proteins in the milk and decreases in those of lactose and potassium.

Casein derived from the micelles of milk by removing the calcium has been subjected to partition and counter current distribution between phases containing polyethylene glycol and dextran. The results show that at least 2 kinds of casein complex exist which differ in structure, in size or in both. There are also differences in composition with respect to minor components, though both types contain predominantly α- and β-casein.

Lactose could not be detected in the urine of non-lactating cows but was invariably found, though usually in low concentration, in the urine of lactating cows; the highest values were observed with cows of high lactation number. Towards the end of an extended milking interval of 39 h, the lactose concentration in the blood and the excretion of lactose in urine increased markedly, but on milking there was a rapid return to original values. Lactosuria was observed in pregnant cows from about 20 days before parturition, and at parturition there was a temporary, marked increase in the excretion of lactose in urine.

Injections of l-thyroxine into normal dairy cows at the beginning of lactation resulted in animals fed on a high protein diet becoming ketotic. Some of the symptoms observed in the induced ketotic cows showed many similarities when compared with those associated with the spontaneous condition.

In most cases the levels of the constituents estimated in the blood of the induced ketotic cows were similar to those measured in blood from spontaneous cases. A histological examination of the liver from an induced ketotic cow showed a considerable increase in the fat content, particularly in the centrilobular regions. The fat content of this tissue amounted to 26% with a concomitant depression of liver glycogen to only 10% of the normal level.

Diet was found to play an important role in the susceptibility of cattle to the induced ketosis, since animals fed on rations containing a lower level of protein were more resistant. Attempts to induce ketosis in cows 6—8 months after calving were completely unsuccessful.

The part played by the thyroxine and the diet in the induction of ketosis is discussed.

The milk flowing during a single pulsation cycle was collected in a circle of contiguous cups which rotated in a chamber at 1 rev/pulsation cycle just below the end of the teatcup liner. The mean flow rate during the time taken for each collecting cup to pass under the milk stream was calculated and the flow-rate curve for the milkflow period of the pulsation cycle plotted. Flow rates were measured at 130, 97, 65, 32 and 16 c/min, and also after the pulsator had been stopped with the liner open for 0·5 min (0 pulsation).

It was concluded from the series of flow-rate curves at the different pulsation rates that flow rate from the teat increased in about 0·05 sec to a steady value which continued for 0·5 sec or so, and then declined over a period of about 1·5 sec to a new constant value approximately equal to that shown after milk had flowed continuously from the teat for 0·5 min.

These results suggest that once the pressure difference across the streak canal during milking forces the teat sphincter open a considerable time elapses before the muscle control system responds, and that a further much longer period elapses before the full closing force of the sphincter is exerted. Thus, it would appear that at pulsation rates of about 50 c/min and above, the streak canal is closed by pressure exerted on the teat by the closing liner, the sphincter muscle playing no active part because its response rate is slow compared with the pulsation rate. At lower pulsation rates the flow rate declines during each cycle because the sphincter muscle has time to exert a closing force to a greater or lesser extent depending on the duration of the milkflow period.

Milk was analysed from twin Saanen goats. In one of the goats one mammary gland was transplanted to the neck. The milk yields and fat content from each gland were recorded and the composition of the fat examined using gas-liquid chromatography. The yield and fat content of the milk from all the glands fell within the normal range. With the operated goat, the milk from the transplanted gland differed little in fatty acid composition from that from the non-transplanted gland. Milk from either gland differed little in this respect from milk from the normal goat.

Strains of Lactobacillus bulgaricus and Streptococcus thermophilus isolated from yoghurt culture were used to study the cause of the synergistic effect on acid production by mixtures of the 2 cultures. The beneficial effect was essentially limited to the gradual accumulation of factors in the L. bulgaricus cultures that promoted more rapid acid production by Str. thermophilus. The active factors were identified as glycine and histidine.

Total and differential cell counts were obtained for approximately 38000 fore-milk samples taken from cows of the Institute herd during a period of 12 years.

For most of the period of the experiment the incidence of subclinical mastitis associated with coagulase-positive staphylococci was about 5% of all the quarters in milk, but for a period of about 12 months in the 7th and 8th year of the experiment the herd was free from infection with coagulase-positive staphylococci.

The average cell count for cows in each lactation up to the 7th was calculated, and in addition each lactation was divided into 4 equal periods, and the average cell count for each period determined.

It was found that the average total cell count increased from one lactation to the next, and that this rise was due mainly to an increase in the number of polymorphs in the samples, the counts of cells other than polymorphs remaining relatively constant.

It was also found that the average total cell count rose during the course of any one lactation; but this was due to an increase in both the number of polymorphs and the number of cells other than polymorphs.

During the period when the herd was free from infection with coagulase-positive staphylococci the average lactation age of the cows was 4·3 lactations, and the average total cell count was 0·30 million cells/ml, a figure which was the same as that obtained throughout the experiment for animals in their 1st lactation.

Possible relationships between the rise in cell counts and the pathology of mastitis are discussed.